# Converting Minimag (2AA version)



## remuen (Dec 5, 2001)

Hi folks
It is really great how you all are sharing your knowledge and experience with others!







I already learned a lot!

Even I'm a newbie in this board I started already my second thread. The reason is: I noticed that there are a lot of threats starting on a specific topic but after a few posts changed the topic. You have to get through the whole board to get the informations.








For example I've found several threads with some more or less complete informations on how to convert minimag's but none which has this as a specific topic. So it would be great to keep this single topic in such an own thread and not to change to how to convert a Maglite 3D or something else. I think converting a Minimag (this is the one with 2 AA cells and the little bulb) is a specific topic. (Sorry for such hard words from a newbie









. I'll try to make it better in future!)

I made my first convertion with the Minimag a few weeks ago. It was very simple: Just replacing the bulb with a white Nichia LED and the 2 AA cells with 3 N cells. The result is also very simple that means not satisfying. Its a poor light for such a housing. An ARC AAA as a great tiny little thing is brighter. I own a few of these Minimags and like this housing. Why not making a great LED flashlight out from it?

So what I am searching for: A convertion for the Minimag either with 3 - 6 LED's using the original 2 AA cells or a bulb replacement eg. like the Versaluc PR-2 for bigger flashlights. Of course for the first solution one has to have a step up converter which fits into the head of the Minimag. 

My problem is that I'm (better I was) an engineer twenty years ago but completly out of practice. So I wouldn't be able to build my own step up converter even one could find some very good informations on this (eg see here http://mikro.e-technik.uni-ulm.de/persons/lares/LED_flashlight.html#V2 ).

Today I got a great tip in another thread on how to convert bigger flashlights with the Versalux Utility Module. Is there something similar available for converting the Minimag or can someone tell me how a beginner like me (as far as I learned there are a lot more guys like me in this forum) can convert the Minimag much better than I did it?





Thanks a lot for your help!


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## mikep (Dec 5, 2001)

this is a 7 led conversion thread (though it used N cells): http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=000367


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## php_44 (Dec 5, 2001)

I did a conversion for a 2-AA aluminum flashlight that uses 2-AA's. I wanted the AA's over N's for excellent battery life. The conversion has been running great for half a year. I used the non-alkaline heavy duty cells for the first set of batteries and they lasted a good 30+ hours of intemittent run time. You could use the same circuit to power 2-3 LEDs. I chose a flashlight with a push button switch so that I'd have a little extra room for circuitry inside the flashlight - and not disturb the reflector assembly. Here's the details:

Craftsman 2-AA conversion


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## remuen (Dec 5, 2001)

Oh guys

I see you want me to be a real flashaholic which builds his own step up converter. Give me a few days to think about this. 

I've also something for you guys to think about: You could become very very rich making such a conversion set and selling it. Imagine how many Minimags are spread all over the world. Of course all Minimag owners would immediatly buy your conversion set!!!


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## The_LED_Museum (Dec 6, 2001)

I won't force a step-up converter down your throat. In fact, I've never built one myself, yet I have more than 200 flashlights.
Does this mean I'm still not a flashaholic?


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## remuen (Dec 6, 2001)

Hey Stingmon

I'm happy that you looked into the thread of such a newbie like me!

Your homepage was one of the first I visited when I got into the LED matter. It's a great site. Because of your review in the punishment zone I bought up to now already 10 ARC AAA for me and my friends (Peter Gransee, do you see what these guys are doing for you?)! Thanks for all you are doing for us!


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## lightlover (Dec 6, 2001)

True, Stingmon's greatness is a grace to any topic. 
(In fact, I hope to benefit from his wisdom on another matter, quite soon. Must post those questions ...... )

He tends towards the helpful, he's knowledgeable, and he gets things right.
Whether you're a "new chap" or an Expert, he will discuss away, and/or advise as necessary. 

Don't you agree, Doug ?

lightlover

Oh, and welcome aboard remuen !


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## Quickbeam (Dec 6, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Don't you agree, Doug ?<HR></BLOCKQUOTE>

Ummmmmm... Which Doug? I think there's at least 4 of us here



!

But if you were referring to me, I agree! Stingmon is definately a "Hoopy Frood" (in the words of Ford Prefect - HHGTTG). 

(that's a "really cool guy" for those uninitiated souls out there



)


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## mikep (Dec 6, 2001)

Another conversion, since it appears a luxeon star led can be pretty bright with 3v (or slightly more with Li AAs), is described here: http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=000696


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## papasan (Dec 6, 2001)

here's a circuit board i drew up based on the zetex ZXSC3x0 IC...this is all theoretical right now, i've never even attempted to build it...but i will after christmas and we'll see what happens...it's 14mm accross and meant to just pull the reflector and bulb out of the mag and drop this in...i don't see why it couldn't be as bright as any other 3 LED overdriven light...


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## **DONOTDELETE** (Dec 6, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*It was the target of this thread to gather all the information about converting Minimags. It seems that exactly this happens. So me and all other newbies (and mayby you cracks too) don't have to search through the whole board which costs a lot of time. If you have some more informations and links please place them here.*

If you're suggesting someone else do all the searching and re-posting for you, that's a lot to ask, isn't it?

*Does someone know how bright a Minimag is whith such a Luxeon Star? Are there somewhere pics of the beam?*

Yes. Search all the threads that contain "luxeon" and I think you will find some beam photos.
<HR></BLOCKQUOTE>

As you can see, there's a lot of interest in coming up with a board that will fit inside a MiniMag and drive a Luxeon Star. Once we do, you'll be able to obtain the bare board, a board with all the parts, or even a completely soldered board where all you have to do is hook up the LS.


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## remuen (Dec 6, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*As you can see, there's a lot of interest in coming up with a board that will fit inside a MiniMag and drive a Luxeon Star. Once we do, you'll be able to obtain the bare board, a board with all the parts, or even a completely soldered board where all you have to do is hook up the LS.*<HR></BLOCKQUOTE>

The longer the more I like the idea with a step-up/DC-DC-converter because one could squeeze the batteries much more and with a bright light almost until the batteries are dead. I made a test with my ARC AAA. It is astonishing how bright the light still is with a battery that made only a little glue in one of my Maglites Solitaire.


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## napalm-2002 (Dec 6, 2001)

papasan i want one if you ever make it!


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## remuen (Dec 7, 2001)

Great, you're providing more information than I can "swallow" at the moment, because I'm working 10, 12 or more hours a day in the last few weeks. I will try to review all your posts during christmas holydays.

It was the target of this thread to gather all the information about converting Minimags. It seems that exactly this happens. So me and all other newbies (and mayby you cracks too) don't have to search through the whole board which costs a lot of time. If you have some more informations and links please place them here. 

Does someone know how bright a Minimag is whith such a Luxeon Star? Are there somewhere pics of the beam?


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## sunspot (Dec 7, 2001)

I also would love to convert a 2AA to a 7 led array with a dc/dc converter for max light over the life of the batteries. Now this is where I would need help. I am somewhat mechanically skilled but electronically challenged. I have taken courses in electricity and am now taking a course in basic eletronics, so I'm on the way. I(and maybe other newbies) would, like~need~politely request, any mods that have a parts list, PCB layout, schematic and maybe a photo posted. I have followed theads on mods but cannot grasp enough to do a mod myself. Anyone?


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## jeff1500 (Dec 7, 2001)

http://mikro.e-technik.uni-ulm.de/persons/lares/LED_flashlight.html#V2 

The guy from Ulm posted here once. He even said he had a couple boards to give away. I was going to ask for one but I think he gave them to someone else.

Maybe if someone writes to him he'll come and visit us and help out.


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## remuen (Dec 8, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
* This is a method for soldering small surface mount ICs. http://www.seattlerobotics.org/encoder/200006/oven_art.htm 
Here's a little tiny MAX1701 IC with a schematic http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=1830 

Here's a larger MAX757 IC that's easier to make connections. http://dbserv.maxim-ic.com/quick_view2.cfm?qv_pk=1167 

I'm in the process of hooking up the MAX757 just to experiment. *<HR></BLOCKQUOTE>

Jeff1500, you sent me this post in another thread. Can you tell me whats the real difference between the IC's MAX1701, MAX757 IC and the Zetex ZXSC3x0 IC on which a special thread is running? Papasan is also working on a conversion with the Zetc IC (see his earlier post in this thread).

By the way: I found a conversion with LED's in a tailcap. It's not the way I want to convert my Minimag's but if someone is interested here is the link http://electriclights.tripod.com/flashlights/outtec.htm


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## jeff1500 (Dec 9, 2001)

That's a very interesting conversion module. And I too would like to have a converted AA Mag light. Here's the ideas I have:

1. What's the difference between the chips? 

a) Size is a big deal. Too small and it's very difficult to hook up to. Too big and it won't fit. The MAX1701 does a lot of great things and as I recall it will take quite a bit of current flow, but it's just too small with too many connections. It has 16 pins.

b) The MAX757 is a pDIP chip, that's plastic dual inline package. This is a comfortable size to work with. It's an older chip with a lower, but I think, still respectable efficiency. It has 8 pins.

c) Here's a very nice application of a small surface mount MAX867, also with 8 pins. It's in Czech language but you can look at the photos and the schematic.

Click to see very nice Czech Light

He's only using one led and one battery, but two batteries and more leds would work too. He shows two circuits, one with transistors, and one with an IC for higher efficiency.

d) The Maxim chips seem to have a lower minimum starting voltage. Other chips I've seen people reference are LT1302, LT1073, LT1070, but I don't seem to like them as much as the Max chips. 

e) Today, and it might change tommorrow, my favorite picks are MAX757 because it's big and I can work with it easily, and MAX867 for a smaller smaller surface mount one since I've seen it working.

f) I've been watching the Zetex discussion a little. I think they're trying to modify it to do more.

g) I think a few of the components on the IC schematics could be eliminated. LEDs don't need the kind of pure power that a computer does. I suspect the famous manufacturers chop the schematic significantly to save space.

2) Mag light size. I've always wondered how hard it would be to machine a short sleeve, to thread in between the end cap and the barrel to make more room for circuitry.

3) Change the rules to make things easier.

a) All this electronic stuff is just to jump up the voltage enough to make the white Nichia leds work. There are other colors that work at lower voltages that might solve the problem. 

Click here for Other Color LEDs

This one for example:
8000 mcd
5mm YELLOW LED
Mfg. - TOSHIBA
Mfg. # TLYH180P(U2)
Operates on 2.1 - 2.5 VDC @ 20 mA
8000 mcd typical luminosity
T1-3/4 (5mm), colorless, transparent
Super ultra bright, lights yellow beam
Brightest 5mm LED available


Three yellow or green or blue leds might work very well in a AA Mag light and you wouldn't need complicated circuitry. And a little bit of cloudy tape makes a good beam diffuser.

b) Leds really do like a resistor in series with them. Without it, the current ramps up quickly. It wastes power and burns up the LED without giving off hardly any more light. But lots of designs get away without it. I think the leds will take quite a beating and still keep going.

c) Some leds have good beam patterns. Others do not. I wish I could see the beam patterns for the LEDs at the link above. Can anyone suggest a model number for colored leds with good beam patterns?

d) MCD, milli-candelas is a brightness measurement. It's very deceiving. A small hotspot in the beam will give a high MCD value but that doesn't mean it's proportionatly more light. I wish they'd also list lumens. That's quantity of light. I have a couple 23,000 mcd yellow leds. I don't really like them. Bad beam pattern. I suspect there are other yellow ones that are much better.

Here's my easy AA Maglight conversion for two batteries:

1) Throw away plastic reflector.
2) Solder three 1/4 watt resistors (maybe smaller) and three 5 mm colored leds onto a circuit board disk. Forget about etching the board, just use small wires.
3) Plug the board into where the bulb used to be.


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## remuen (Dec 9, 2001)

jeff1500

I just looked into the thread of the Uni Ulm which is mentioned in two earlier posts. They use the DC-DC converter LT1307B and the IC MAX1759. I think both versions are not very efficient (65 - 77%) and one gets only 100mA output current.

A few weeks ago I made a simple convertion for my son in which I used one white Nichia LED (white one) with a resistor. It sucks about 38 mA on a 4.5 volts with getting only a little bit warm (without any heatsink mesurements) and has about the same brightness as an ARC LE. I think 35 - 40mA is about the right current for a good brightness.

Therefor for such a conversion one should have a DC-DC converter with at least 200mA output current to use 5 white LED's what is the minimum of LED's I want to have in my Minimag. Better would be 7 LED's what should be possible in this diameter. 

1. Which of the DC-DC Converters would you use? 

2. You wrote that a few of the components could be eliminated. Which ones?

3. I know that that some other color LED would need less volts. But my prefered colors white and turquoise need the higher voltage.

4. In your easy conversion you remove the plastic reflector. How do you switch on or better off the Maglight? In the normal state the reflector is doing it. Do have a tailcap switch? And where is such a switch available?


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## jeff1500 (Dec 9, 2001)

1. Which chip. Let's see. If it's going to fit inside an AA mag light it's got to be small. (I still like the idea of making a barrel extension sleeve.)

The max757 is good for as much as 200 mA (100 mA for best efficiency) and 727 mW but it is kind of big, so that takes us to the max867.

First thing is to decide how many mA per led. You want as much light as possible without making much waste heat.

Looking here
LED caving light

Let's say 30 mA per led or P = .030 * 3.6 = 108 mW 

Max power for the max867 looks like 471 mW, but the data sheet
max867
looks like the output current limit isn't much. Maybe only 10 mA optimum.

max867 summary

I guess that one's no good for multiple leds.

Here are all the max step-up chips:

Go here and click on step-up

I'll try to print it out and study it one day at lunch time. See if you can find one you like and we can talk about it here. I'm studying this too. I want to get something working on my breadboard and just let it run for a while. 

So far I'm thinking about 8/PDIP but maybe the 8/SO.15 which is half the size would work too. They make a small breadboard adapter called a surf board that you solder it too. You need a really thin soldering iron and a magnifying glass or maybe that self-aligning solder paste stuff in the link above. That's why I like 8/PDIP.

2. Eliminate components. A little while ago we made a two transistor step up circuit. It works well. It's the one in the brinkman light.

Two transistor circuit

Based on experiments from there, I'll bet you could get rid of 1) the input filter capacitor, 2) the output filter capacitor and diode together, and 3) maybe the reference voltage capactor. The feedback resistors and inductor are needed. This would be a good breadboard experiment.

3. Do you have any turquoise leds? What does the beam pattern look like? How do they compare to the Nichia whites?

4. Mag light switch. I'm working from memory. I don't have a mag light here with me, but I think just the silver plastic reflector comes out and leaves the switch and head still fucntional. Like this:
Mag AA lens view with 2 leds

It's a journey.

Other idea. An energizer four AA double barrel #D420BP will work with 2 AA batteries and then you can use the other barrel to hold circuitry or a third battery. Some day I may get one of those and take it apart. Other people here seem to like them for conversions. The head is good for plugging leds into and you can modify the switch somehow.


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## jeff1500 (Dec 10, 2001)

I took a look at all the MAX step up ICs at lunchtime today. The table displays better with Explorer that it does with Netscape. 

Today my favorite is the MAX757. It comes in two packages. 1) a larger 8/PDIP that's good for 727 mW and 2) a smaller 8/SO.150 that's good for 471 mW.

So I'd say that on a good day you could make a 2AA Maglight conversion with 3 or 4 leds.

I'd set it up on a breadboard and try to eliminate the filter capacitors and the diode. If there's an output capacitor then I'll bet the diode is needed. They work as a set. Either both or neither.

Then try to stuff it into the flashlight head with surface mount parts and an etched board. I don't know how boards are etched but I think there's a way to do it with a photocopy machine. Other people here are soldering surface mount parts by hand so I guess it can be done if you're careful. They make a magnifying glass with clips to hold things in place for not too much money.

Maybe instead of all the trouble to etch a board you could make the connections with wire and then coat them with something for insulation.


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## remuen (Dec 10, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*3. Do you have any turquoise leds? What does the beam pattern look like? How do they compare to the Nichia whites?

4. Mag light switch. ...

Other idea. An energizer four AA double barrel #D420BP will work with 2 AA batteries and then you can use the other barrel to hold circuitry or a third battery. Some day I may get one of those and take it apart. Other people here seem to like them for conversions. The head is good for plugging leds into and you can modify the switch somehow.*<HR></BLOCKQUOTE>
I had no time to look into the other points because today I was in a training course for our new ERP (Enterprise Resource Planning) system. 

- No, I don't have any turquoise leds for the moment. But the beam is wider than the one from the wide ones. In a fex days I'll get 2 ARC AAA with this turquoise led. Then I'll know more.

- the Minimag has no switch to press. It switches on and off with the reflector which is pressing the bulb holder back so the negative contact can or cannot touch the housing. That is one of the problems when converting Minimags.

- I looked also at the Energizer 4 AA lamp. Would be an interesting thing. But I like the body of the Minimag much more - that's why I own 4 of these Maglites. It's very handy, it is almost indestructible, and adjusted to only a spot it is good. But if you use a good illumination - means a broader beam - it is terrible. And of course it's a yellow light which gets the longer the more red when the battery gets toward its end. And the bulb doesn't like to get old ....

Will come back on the other topics tomorrow (here in Central Europe it is now 11:30 PM).

-----

I had just an idea before going to bed: I will discuss this matter with an R&D engineer in our company. He's specialiced on power supplies. I know that he has made some experiments with LED's I gave him. Will try to convince him to join us.


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## jeff1500 (Dec 10, 2001)

Today I got my MAX757 PDIP working. Some of the parts are not as optimum as I would like, but it's working. It's running two leds right now.

Input:
2.83v x 85 mA = 240.6 mW

Output:
2 leds x 25 mA x 3.45v = 172.5 mW

efficiency = 172.5 / 240.6 = .717

That's not bad considering I'm using a hand wound 40 turn inductor. These were quick measurements. I should let it run for a while for more stability, but I want to try to get a real inductor first. I'm nervous at the moment because I don't want to burn anything up.

The led current and voltage stays just about the same for two new batteries (v=2.83), two old batteries (v=2.64), and about 3 mA less per led for one old battery.

Click for Circuit Diagram


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## remuen (Dec 11, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
Do you have any turquoise leds? What does the beam pattern look like? How do they compare to the Nichia whites? *<HR></BLOCKQUOTE>

I just got the turquoise ARC's. Here my first impressions:

1. The color of the turquoise leds is in my eyes not at all turquoise - it is green like the color of traffic signal lights.

2. The turquoise leds have a completly different beam pattern. The white led's have a smoth beam with a much brighter spot in the middle. The turquoise ones have a wider beam without that center spot and not such a smooth beam but some rings. 

3. Even it is very difficult to compare (because of the comletly different beam) the turquoise (= green) leds are very very bright.

Jeff, I'll come back on the other points concerning the DC-DC converter later on!


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## jeff1500 (Dec 11, 2001)

I experimented with the chip a little. I briefly removed the input filter capacitor and the reference voltage termination capacitor. It seemed to work fine without them. 

I kind of like the output filter capacitor and diode. I don't know what the output wave looks like without it. It might prevent led damage from voltage spikes. But then again maybe it's not really needed, especially since the chip runs a such a high frequency. 

You could probably get rid of the dividing resistors on the leds too. I don't really understand it all that well. Perhaps someone else can comment.

The hand wound inductor seems to work fine too.

It's interesting to hear about the green leds. Maybe they are the same ones that go in traffic lights.

I looked at led lights in a backpacking store. I saw a couple of interesting things. 1) One light had leds with flat tops like someone cut off the dome and then polished them. 2) Another was a dual incandescent and led light. They just drilled a hole in the side of the reflector and stuck the led in from the back next to the regular bulb. That permitted using the space behind the reflector for wires.


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## remuen (Dec 12, 2001)

Jeff, here I am. I had no time to look a bit closer into the matter. But I did two things:

First thing I did: 
I talked to the engineer in our r&d department. He will not be involved into this BB because a) he has not enough time and b) he thinkls his English is not good enough. But he will help us in developping a DC-DC converter. He recently developped such a thing for a complet different application with an input 4 ... 6VDC and an output of 24V to feed a magnetic coil. So I think he knows from what he is speaking. From time to time he will look into this thread and give me his opinion and of course I can ask him everytime. 

Here is a first input for another IC he would use. It is the LT1932 Constant-Current DC/DC LED Driver from Linear Technology. Take a look at the datasheet under http://www.linear-tech.com/prod/datasheet.html?datasheet=771 

In the brief introduction I told him that it should be possible to use 5 - 7 LED's with a switchable current 20 - 40 mA (I think more is dangerous for the LED's). This would be possible with this IC. The minimum input voltage should be 2 or less volts, the maximum is slightly more than 3 volts (with 2 AAA/AA/C/D cells).

Second thing I did:
I looked on how such a converter could be mounted into the Minimag. It's a bit tricky too because of the kind of its switch. The reflector mounted in the head of the lamp is part of this switch. Depending on how you screw the head more or less on the housing it presses against the bulb socket (or releases the socket) which makes the negative contact on the housing.

I've really to study this mechanical thing because the conversion itself should be easy to make and solid.

---------------------
*Added later:*
I've just got another link giving some information on the LT1932 chip: http://www.linear-tech.com/pub/document.html?pub_type=desn&document=295


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## sunspot (Dec 12, 2001)

Rene'. I have in my hand a Nordic brand 2AA torch/light that has a barrel mounted switch. The battery contact, switch and bulb holder are all combined in an easy to remove piece that is simply screwed in between the body and the head. The lens and reflector are also easy to remove. The depth between the switch module and lens is about 13mm. If you can use it for the project, please email me an address and I will post it to you gratis.


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## remuen (Dec 12, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by phred:
*Rene'. I have in my hand a Nordic brand 2AA torch/light that has a barrel mounted switch. The battery contact, switch and bulb holder are all combined in an easy to remove piece that is simply screwed in between the body and the head. The lens and reflector are also easy to remove. The depth between the switch module and lens is about 13mm. If you can use it for the project, please email me an address and I will post it to you gratis.



*<HR></BLOCKQUOTE>

Thanks for your offer! I can not really imagine how this thing looks like and how it could be used. What is your idea looking at this torch?

By the way: Your "thing" takes me just now back to an idea I somewhere read: An mechanical adapter which one could screw e.g. between the tail cap and the housing. But thinking a bit over this I must say:
a) It would not look very nice (different Minimag colors)
b) It would be expensive 
c) It could not be easy produced and especially not from everyone who wants to convert his Minimags
d) And the only positve point I see: It would give some more room for a DC-DC converter and a switch - but which switch (must be waterproof and small and ... and ...)
So I think I will not any longer follow up this idea.

------------
*Added later:
How to switch on/off a converted Minimag?
*
------------

poop, I cannot switch off. This mechanical switch problem is tracking me. 
Looking at the ARC I had just another idea: Removing the original bulb socket (which is also the switch). But then the DC-DC converter must have a contact to the positive contact of the battery (through the hole in which the socket was). The negative contact is either made with the thread (or how do you call this winded connection between body and head of the Minimag in English?) or direct to the body. Then the switch should work like in an ARC AAA. Also not really easy, I think. 

Guys, let me think about this project a bit longer and give me your opinions!


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## sunspot (Dec 12, 2001)

Rene'. I understand your point about the torch being different than Mag's. BUT, because of the cool switch, I think this is what I will base a led conversion on. A somewhat coarse pic can be seen at the bottom of this ebay page.


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## jeff1500 (Dec 12, 2001)

click to see LT1932 dimensions

That is great chip for this application. It's interesting to see the leds in series on the diagram.

I took a mag 2AA apart today. I understand the switch issue. Maybe drilling a few holes in the reflector will work. That would turn it into a skeleton, then maybe the new parts could be woven through the holes while still preserving the switch and electrical configuration. This might also be a good idea for other lights like the Nordic light that you have Phred.

My MAX757 is running nicely over in the corner with 2 leds.

Someone where I work also took an interest in this project. I think tomorrow at lunch we'll place an order for a few parts to experiment with. I'll probably get one of those magnifying glasses with clips to hold small parts for soldering. I think he's going to get a couple of leds to practice with. He has a couple of young sons and this is a good way to learn a few things about electricity.


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## remuen (Dec 12, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*click to see LT1932 dimensions

That is great chip for this application. ...

... I understand the switch issue. Maybe drilling a few holes in the reflector will work. ...

... I think tomorrow at lunch we'll place an order for a few parts to experiment with. ...*<HR></BLOCKQUOTE>

Jeff, on my side I try to convince my friend to make a test circuit with that LT chip.

-------
*Mechanical switch issue*
-------
Firtst I thougt also something in the kind like you mentionod would work. But there are some negative points:
- It's maybe not enough room if the reflector remains in the head
- You have to connect the circuit with wires into the bulb socket. If you turn the head many times to switch on/off after a shorter or longer time the wires will disconnect or possibly break.
This would be a solution but I think not a proper one.
So I'm folling up the idea i had yesterday with a similar switch as in the ARC. Maybe one can make an adaptor from wood instead the bulb socket. 


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by phred:
*
Rene'. I understand your point about the torch being different than Mag's. BUT, because of the cool switch, I think this is what I will base a led conversion on. A somewhat coarse pic can be seen at the bottom of this ebay page.. *<HR></BLOCKQUOTE>

Phred, now I see the point. Thanks again for your offer but you see to target is to convert the Minimag. That's because a lot of people (also flashaholics) have one or more of these Minimags. As I already mentioned in a earlier thread it is not a great light but a lot of people like this body very much.

For your Nordic light you can use the same electrical solution as we are try to make for the Minimag. You have only some minor mechanical problems because your lamp seems to be much more suitable for such a conversion (as a lot of other incandescent flashlight).

So stay connected with us. We do have the same target!

----
_Uuuuff - I had some problems to post this with the layout I wanted. It's too early in the morning ....._


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## remuen (Dec 13, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*click to see LT1932 dimensions

My MAX757 is running nicely over in the corner with 2 leds.

And in another post:
That is great chip for this application. It's interesting to see the leds in series on the diagram.*<HR></BLOCKQUOTE>

First: Great that your DC-DC Converter with the MAX757 is already running!!

Second: This LT1932 is really a tiny little thing. But my friend says it is no problem for him to solder it. He did it with another switcher with the same size he recently used for a project. 

Together with my friend I looked a bit more into the matter. With this chip and the other parts it should be no problem to make a print size of max 1cm2 (= square centimeter, think this is about 0.4 x 0.4''?) or less. So it would be no problem to mount it into a Maglite or almost every other flashlight (writing this I think also on how to convert a headlight, see my other thread).

We'll go to make a test circuit. There is only one minor problem: The Swiss distributor of Linear Technology sells it only in quantities of at least 2000 pieces!?! But samples and smaller quantities can be ordered directly from Linear Technolgy. So I'll order some pieces but I don't know how long they need to ship them to Europe. Therefore it could last a while until we can do it.

By the way: 
*Have you seen the typical application examples in the data sheet? There are examples from 1 LED/1.5V single cell up to 16 LED's/5VDC!!! So this chip could be used for almost every conversion!!!!! *


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## Klaus (Dec 13, 2001)

René,

you might also check out some of the other threads where the guys are working on various LED circuits namely the Zetek3000 thread and others from the same guys.

Badische Grüsse in die Schweiz

Klaus

PS: Es heist "bad" und nicht "worse" in dem Fall


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## remuen (Dec 13, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Klaus:
*René,

you might also check out some of the other threads where the guys are working on various LED circuits namely the Zetek3000 thread and others from the same guys.

Badische Grüsse in die Schweiz

Klaus

PS: Es heist "bad" und nicht "worse" in dem Fall*<HR></BLOCKQUOTE>

I am looking a little bit into this Zetek thread - but I'm not an engineer and cannot follow the whole thing and especially not judge what they are doing there. For me it looks professionally what they do and I think it's great that they are doing this!

*But you're right we should never forget to look around what others are doing.* 

I also try to take a look in other threads. I think Jeff is doing the same. And I know others do it too as for example Papasan which is involved in the Zetek thread and has posted replies in this thread. In earlier posts in this thread we also posted a few links to other threads and also to other homepages dealing with this issue. So we're not competitors. 

But: There are several ways which could lead to a good result. Why not go more than one of them? I can imagine that eventually there are two or more good DC-DC converter circuits available. Could well be that the two or three Converters will not exactly do the same thing so all of them are needed. In this case each one who needs a converter can choose which solution fits best to a specific problem. For example I cannot tell yet if a Converter based on the LT1932 could be used for a Luxeon Star. Maybe the Zetek converter or Jeff's Max757 can be used for this.

What I really hope is that in the end *someone is willing and able to produce one or two converters for all of us * because not all flashaholics are able to do it - eg. I couldn't solder such a tiny LT1932 chip on a board (this seems to be no problem for my friend here in the company). Then all who want to make a good conversion of a flash light could easily do it! That would be great!

_Just for your background information:_
---------------------------------------
The MAX757 ist Jeff's thing and according his last post it is already on a test run. That's a big advantage because until now I didn't find a really working converter in this BB. 

The LT1932 is the idea of my friend here in the company (he is a professional r&d engineer and expert in switcher/DC-DC converters. So I trust him. The LT1932 is very new on the market - why not try it out and look what this new chip can do for as flashaholics?
------

_PS: Danke, ich hab's geändert. Eigentlich hätte ich's auch wissen müssen, aber es schreibt halt des öftern schneller als es denkt. Und eigentlich war's ja ganz gut, da hat jeder gleich gesehen, dass ich mit Englisch so manchmal meine liebe Mühe habe! Schweizerische Grüsse ins Badische!_


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## JollyRoger (Dec 13, 2001)

You might want to contact Wayne Johnson, also here on the CPF. I've been working with him on some projects. He already has good working regulators using the MAX756, MAX757 and numerous other LT and LM chips. Both step up and step down.

He's trying to get the size of these regulators down, too....


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## Klaus (Dec 13, 2001)

René,

no offense in any way - just wanted to let you know and wasn´t shure you looked into it already - also lots of older threads and such which are no longer as high on the radar screen.

And I definetely like the idea of readily available circuits based on CPF projects - I for now am shooting more for brighter is better and regarding LEDs (besides waiting for my first ARC AAA LE) I didn´t went beyond easy mods like the 2 Lithiums in Mag 2AA / 3 2/3AAA NiMhs in Mag 2AAA / 3 LEDs in PR base stuff - just too stupid and unexperienced hands for such tiny items like the Zetek - and no engineer myself as well.

All the best with your circuits

Wo in der Schweiz seid Ihr denn ?

Regards

Klaus


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## JollyRoger (Dec 13, 2001)

A good flashlight for this type of conversion is also the Coleman 2AA aluminum flashlight (found at Walmart and on Coleman's website).
It's not much bigger than a mag (not talking about the "platinum" aluminum flashlight, which *is* much bigger). Plus, the switch is on the tail cap, which eliminates any complexities when you're looking for space near the head for the regulator.

What do you guys think?
http://www.coleman.com/coleman/ColemanCom/prod_Detail.asp?Product_id=5339-701&CategoryID=1190&SourcePage=PROD_CATEGORY_MAIN.ASP&SubmittingPage=Prod_subcategory.asp


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## jeff1500 (Dec 13, 2001)

This is a great topic. I'm especially interested in hearing about soldering results for small chips, and what to solder them too. I'm very new to surface mount soldering.

I also want to experiment with a dimmer. Maybe a digital one. In my long term plan I want to make a white led light that runs on 2 AA cells with a dimmer kind of like the digital volume control on my TV.

Maybe a first step for me is to make a one cell, one led light. Just using one battery will make lots of room for a step-up circuit.


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## remuen (Dec 13, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Klaus:
*René,

no offense in any way - just wanted to let you know and wasn´t shure you looked into it already - also lots of older threads and such which are no longer as high on the radar screen.

And I definetely like the idea of readily available circuits based on CPF projects - I for now am shooting more for brighter is better and regarding LEDs (besides waiting for my first ARC AAA LE) I didn´t went beyond easy mods like the 2 Lithiums in Mag 2AA / 3 2/3AAA NiMhs in Mag 2AAA / 3 LEDs in PR base stuff - just too stupid and unexperienced hands for such tiny items like the Zetek - and no engineer myself as well.

All the best with your circuits

Wo in der Schweiz seid Ihr denn ?

Regards

Klaus*<HR></BLOCKQUOTE>

Sorry if you felt like this. I didn't think it was an attack - and I didn't want to attack you. I only tried to explain why we are doing something similar. I started with easy conversions too but they don't satisfy - at least not me.

_ Ich wohne in Bad Ragaz, das ist ca. 20km nördlich von Chur._

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by roger:
*You might want to contact Wayne Johnson, also here on the CPF. I've been working with him on some projects. He already has good working regulators using the MAX756, MAX757 and numerous other LT and LM chips. Both step up and step down.

He's trying to get the size of these regulators down, too....*<HR></BLOCKQUOTE>

Can you please publish the link to this thread here? As I mentioned in my very first post one of the targets of this thread is collecting all infos about converting Minimags. So such a link would belong to that topic. 

By the way: *Can someone compare these Maxim chips and other ones with that LT 1932 chip and tell us what is the difference (means advantages/disatvantages) between them?* I think it would be wrong to say that one chip is better than another one - but one could be better suited for this and another one better for that.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by roger:
*A good flashlight for this type of conversion is also the Coleman 2AA aluminum flashlight (found at Walmart and on Coleman's website).
*<HR></BLOCKQUOTE>

I just opened this link - it is an interesting flashlight too. 

As I wrote in an earlier post such a converter can be used in various flashlights not just in a Minimag. But the Minimag conversion is the real challange because of the little available room and the mechanical switch problem. If we can do this we can convert a lot of other flashlights. On my side I try also to convert a headlamp ( see under (http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001212&p=3 ) and a twenty years old Varta flash light and I am quite sure later on I will buy some other lamps too just to convert them.

_added later:
--------------
Just a hint (because I think this issue should not be dealed in this topic): There is a Versalux Utility Module available (www.techass.com) which could be used for some flashlight conversions! But it needs to be a very big flashlight._

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*This is a great topic. I'm especially interested in hearing about soldering results for small chips, and what to solder them too. I'm very new to surface mount soldering.

I also want to experiment with a dimmer.*<HR></BLOCKQUOTE>
Hi Jeff, I think the dimmer would be a big challange .... I already thougt about a very simple version of this in "our" DC-DC converter with a little DIP switch on the board which would allow to switch eg in a low (dimmed) and a high (bright) mode.

According to my friend Thomas (the guy in my company) soldering SMD parts is no problem. He seems to have eyes like an eagle because he is soldering his breadbord circuits without using a glass (he uses this later on to check the soldering points). But for soldering SMD parts it is necessary to take a special PCB with soldering points which fit exactly to the SMD parts. I'll try to give you more infos about this.

-------------------------------------
_*added a few hours later:*_
-------------------------------------
Jeff, it's a special laboratory PC board. As source I know only our Swiss distributor. Here's a link so you can at least take a look at this thing and find it at one of your distributors: http://www.distrelec.ch/cgi-bin/supply.storefront/1693577783/Ext/ProductView0 1/010101_abakaaaabu/ 

Concerning soldering SMD parts: I remember that I've seen a link somewhere in the CPF showing to this topic but cannot find it again. Who knows this link?

_*Added 12-17-01:*_
--------------------------------------------
The link showing the laboratory PC board for SMD parts works not correkt. Despite this click on teh link and then choose Search (top right, in German: Suche). In the search form do the following:
under 1: Choose *In allen*
under 2: Choose *Artikelnummer*
under 3: Write *451599* in the field
Then click on *Suche starten*. 
This leads you to the SMD PC board with the article no 451599 and the type RE 437 EP
Sorry, I don't know why but it does not work the other way round!


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## jeff1500 (Dec 14, 2001)

Soldering. I may have read that link you are referring to. I think a needle type soldering iron is what they use with very fine solder.

I also took a look at the data sheet for the Zetex ZXSC300 chip that is generating so much discussion in the other topic. It looks very good for multiple LEDs. I haven't read all that's posted over there for sure, but I think they're trying to use it for a Luxeon Star which requires a much higher current value.

The reason I never paid much attention to it was because I wanted to find a larger size DIP chip for my first experiments. I don't know which is better, ZXSC300 or LT1932.


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## **DONOTDELETE** (Dec 14, 2001)

Here are some things to look for when choosing a DC/DC converter chip.

<UL TYPE=SQUARE><LI>Size. The smaller the chip, the smaller the circuit board, and the more applications it can satisfy. However, small chips are more difficult to solder.

<LI>Number of pins. The more pins a chip has, the more versatile the circuit is. However, a lot of pins close together are hard to solder, and a large number of pins often means a large number of components.

<LI>Price and availability. You want a chip that's readily available in small quantities at a reasonable price.

<LI>Number of components. Some chips require complicated circuits which may result in bigger size and lowered efficiency.

<LI>Component size. For example, some chip circuits recommend large inductors, while others recommend smaller ones. Smaller ones are more readily available, usually cheaper, and... smaller.

<LI>Common components. For example, avoid circuits that call for uncommon resistor values such as 0.01 ohm, as they are often hard to find and expensive.

<LI>Input voltage. Make sure the chip will work properly and efficiently when the batteries are fresh, but also when they start to run down.

<LI>Output power. Circuits that are designed for a single small LED can be made smaller and usually less expensively than circuits that need to power multiple LEDs, or large ones such as the Luxeon Star.

<LI>Features. Some chips offer features like shutdown and regulation, which can be either be useful or unnecessary depending on your application. The more features you use, the more complicated the circuit will be.

<LI>Efficiency. Important in some applications, but usually not critical. If a set of batteries lasts 3 hours at 100% efficiency, you still get almost 2.5 hours at 80% efficiency. However, lower efficiency means more heat.

<LI>Documentation & Support. Some chips come with extensive documentation and accurate performance data, whereas others don't. Look for manufacturers or distributors that reply to email.

<LI>State of the Art. Chips that have been around for several years may not continue to be available, or may not be as efficient as newer ones. However, they may be cheap and easy to solder![/list]


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## **DONOTDELETE** (Dec 14, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*I also took a look at the data sheet for the Zetex ZXSC300 chip that is generating so much discussion in the other topic. It looks very good for multiple LEDs. I haven't read all that's posted over there for sure, but I think they're trying to use it for a Luxeon Star which requires a much higher current value. I don't know which is better, ZXSC300 or LT1932.*<HR></BLOCKQUOTE>

The LT1932 is limited to 40mA, so it won't power a Luxeon Star which requires 350mA.

In the Zetex thread, we are looking at components that can handle that kind of current, which is overkill for powering conventional LEDs, especially in series.

I like the LT1932's regulation and shutdown feature, and it uses some really tiny inductors and capacitors and doesn't need an external transistor, so it can fit in some pretty tight places.

If you're looking to buy one, you can get it directly from http://www.linear-tech.com/prod/datasheet.html?datasheet=771 by clicking on the blue Buy Now button. Not sure about international shipping though.


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## remuen (Dec 15, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Soldering. I may have read that link you are referring to. I think a needle type soldering iron is what they use with very fine solder.

The reason I never paid much attention to it was because I wanted to find a larger size DIP chip for my first experiments. I don't know which is better, ZXSC300 or LT1932.*<HR></BLOCKQUOTE>

Jeff, concerning soldering: Thomas uses as far as I've seen a Weller soldering iron with a very fine tip (or how is this called in English?). And of course it needs some soldering training (and good eys!). For this training it's the best to take some cheap SMD parts like resistors because the chip does not really like to much heat.

Concerning the chip: Looking at Duggg's very interesting post I think we're on the right way. 

The "Zetec guys" make a real power converter which - as Duggg wrote - would be an overkill for the conversion of flashlights like the Minimag. I think it would not fit in a Minimag.

We on our side concentrate on a smaller DC-DC converter for a conventional LED's. IMO (I have just learned in another thread what this means and hope I use it correct) it is also right going two ways for this. The Max757 chip you are working with will be a good solution for most of us CPF members because it's easier to use (soldering?) as a tiny chip like the LT1932. I think you should work with this furtheron and bring it to a final solution we all can use. By the way: Have you already looked after the thread in which Wayne Johnson is working with the Max chips (see Roger's post above)?

On my side I - or better Thomas in the background - try to realize a DC-DC converter with the LT1932. 
I cannot say when we can do it because I wanted to order a few of these chips from LT but they wanted me first to make a price request. I didn't get an answer till now. Maybe this chip is still not available?

The possibility to make such a small converter with the LT1932 brought me on an idea: For a safer flashlight (eg if one uses the flashlight in critical situations) one could use two converters in one single flashlight, each one for a part of the LED's. If one DC-DC converter does not work the other one could deliver still some light even it's dimmer. 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*The LT1932 is limited to 40mA, so it won't power a Luxeon Star which requires 350mA.

In the Zetex thread, we are looking at components that can handle that kind of current, which is overkill for powering conventional LEDs, especially in series.

I like the LT1932's regulation and shutdown feature, and it uses some really tiny inductors and capacitors and doesn't need an external transistor, so it can fit in some pretty tight places.
*<HR></BLOCKQUOTE>

Duggg, thank you very much for your explanations! Now I understand the whole thing much better. 

It's the first time I participate in a BB and it's great that all help all. Of course there are some of us like me which can take out more profit of it than we can give back. I'll do my best to give what I can give.


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## remuen (Dec 15, 2001)

Jeff, I've searched for the threads Wayne is involved. It looks like he is working with different chips like some of Maxim but also with LT and LM chips (beside the Zetec). Here are some links to threads he's discussing about this issue (lead you direct to the according pages):
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=000983&p=7 
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=000911 
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001043 
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001110 
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001206 
http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001269


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## **DONOTDELETE** (Dec 15, 2001)

When hooking LEDs in series, don't skimp when it comes to the working voltage of the output capacitor. It should be at least double, if not triple, the combined LED voltage.

For example, to run four white LEDs (each 3.5 volts), multiply 4 x 3.5 x 3 = 42 volts, so a 50 WVDC capacitor is recommended.

The drawback is, the larger the WVDC, the more massive the capacitor is.


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## remuen (Dec 15, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*When hooking LEDs in series, don't skimp when it comes to the working voltage of the output capacitor. It should be at least double, if not triple, the combined LED voltage.
*<HR></BLOCKQUOTE>





Why that, Duggg? Do the LED react like an inductivity when switching on/off? I didn't read that in the LT1932 datasheet. Did you make any bad experiences with LED's in series?


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## InTheDark (Dec 15, 2001)

remuen,
I'm working on a Mini-mag mod and had the same problems you had fitting all the components in. Also, someone mentioned in another thread that it's not possible to put the step-up converter in series with the batteries because the converter needs to be connected to the positive and negative end of the battery, and the positive and negative of the LED's. So far, the only way I can figure out how to make it work is to remove the switch all together to make room for the converter. this is what I plan on doing

1. Drill a hole in the tailcap, mount a touch switch (I got one from a car alarm remote control) I'll have to isolate the spring from the negative end of the battery, so the switch would work between the two, but that won't be that hard, I'll probably use a spacer or something.

2. With the switch at the bottom, I can remove the switch at the top of the light, and I'll be able to mount my step up in there. I can wire the positive terminal of the step up to the original switch contact point, and the negative to the body of the light. I'll still be using most of the original switch, but now I can glue it in there permanently and not have to worry about how to switch it on and off. I can also cut out most of the innard to make more room for the step-up.

I'm still waiting for my LS to arrive, hopefully it'll be finished by christmas.


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## **DONOTDELETE** (Dec 15, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*



Why that, Duggg? Do the LED react like an inductivity when switching on/off? I didn't read that in the LT1932 datasheet. Did you make any bad experiences with LED's in series?*<HR></BLOCKQUOTE>

Most DC/DC converters use an inductor and voltage spikes should be anticipated.

Small tantalum capacitors are especially vulnerable to overvoltage damage.


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## remuen (Dec 15, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*remuen,
I'm working on a Mini-mag mod and had the same problems you had fitting all the components in. Also, someone mentioned in another thread that it's not possible to put the step-up converter in series with the batteries because the converter needs to be connected to the positive and negative end of the battery, and the positive and negative of the LED's. So far, the only way I can figure out how to make it work is to remove the switch all together to make room for the converter. this is what I plan on doing
.....
*<HR></BLOCKQUOTE>

InTheDark, I will come back to this (I'm a little short in time now). After a first (and very fast) reading of your post I didn't see how it really works. I will study it more carefully later because this switch issue is not really easy to solve.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*Most DC/DC converters use an inductor and voltage spikes should be anticipated.

Small tantalum capacitors are especially vulnerable to overvoltage damage.*<HR></BLOCKQUOTE>

Thanks Dugg! I will keep that in mind when we start to make the converter (as soon as we have the LT1932).


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## remuen (Dec 16, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*remuen,
I'm working on a Mini-mag mod and had the same problems you had fitting all the components in.*<HR></BLOCKQUOTE>

Now I see what you meen! Sorry, but I've to read English much more carefully to understand ....

I think the room in the Minimag head will not be a problem especially not wiht a small converter like one could build with the LT1932 IC.

The more critical point is what you are working on: The switch issue! With a tailcap switch I think you are going a good way. This makes things easier than any other solution and IMO this solution works for sure.

Coherence made a 2 AA Mini Maglight -> Luxeon Star (LS) conversion in which he used such a tailcap switch from Brightguy. Here is the link: http://www.brightguy.com/detail.tpl?cart=10079523572784&sku=KROAM2A666 

I've two other solutions in my head but don't know wether I can bring them to work or not. With both solutions you'll switch on/off by turning the Minimag head as usually (one solution should be similar to the one in the ARC AAA). Hope that I can try them out in my christmas holidays. If they work I'll tell you here how to do.


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## remuen (Dec 17, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*... I also want to experiment with a dimmer. Maybe a digital one. In my long term plan I want to make a white led light that runs on 2 AA cells with a dimmer kind of like the digital volume control on my TV.
.... *<HR></BLOCKQUOTE>

Jeff, yesterday I studied the datasheet of the LT1932 a bit closer and found out that there is a posibility to dimm the light. And this morning I found by chance this thread 8 Led Dimmable Driver Schematic

Concerning SMD soldering: Take a look at this side: SMD Tips. I think it's the one we looked for.


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## ElektroLumens (Dec 17, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Today I got my MAX757 PDIP working. Some of the parts are not as optimum as I would like, but it's working. It's running two leds right now.

Input:
2.83v x 85 mA = 240.6 mW

Output:
2 leds x 25 mA x 3.45v = 172.5 mW

efficiency = 172.5 / 240.6 = .717

That's not bad considering I'm using a hand wound 40 turn inductor. These were quick measurements. I should let it run for a while for more stability, but I want to try to get a real inductor first. I'm nervous at the moment because I don't want to burn anything up.

The led current and voltage stays just about the same for two new batteries (v=2.83), two old batteries (v=2.64), and about 3 mA less per led for one old battery.

Click for Circuit Diagram*<HR></BLOCKQUOTE>

Hey jeff1500,

I finally got around to reading this thread. i didn't realize what you guys were doing here. The LT1932 circuit looks real interesting, I'll have to try this one.

I didn't realize anyone else had been working with the MAX757 chip. I have been fiddling around with this chip for some time. I manage to get more current from it by using a 150uH inductor, and 150uF caps. Recently I have tried the small surface mount caps and inductor, and managed to design a circuit that is ony 1" in diameter. So far this is with the MAX756 circuit, and I hope to do the same with the MAX757, but it adds a few parts so requires a little more space.

I finally got ahold of some .01 ohm resistors, and plan to test efficiency. I have bee driving one Luxeon Star in a 2 'D' cell flashlight, quite successfully. I have been thinking how great it would be to convert a Mini Mag, but because of the small size, haven't been to serious about it. But reading this thread is very interesting and encouaging, to do this mod. 

I'm still working on reading all the posts here in this tread.


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## jeff1500 (Dec 17, 2001)

I'm very happy with the max757 chip. It seems like I can put just about anything into it; one battery, two, old battery, new, and a nice stable voltage and current flow come out the other end. One of these days I'
ll try to solder a surface mount chip but I need a few more tools and things to do it.

My next step is to make a dimmer that will vary the output voltage in a predetermined range of around 3 to 3.8 volts. I want to be able to turn it on at night after my eyes have adjusted to the darkness.

My tantalum filter capacitors are 10 volts. That's 10 / 4 = 2.5 so I guess I'm in the range mentioned above. That was the factory spec. voltage rating. The next step up was 16 volts.


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## ElektroLumens (Dec 17, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*I'm very happy with the max757 chip. It seems like I can put just about anything into it; one battery, two, old battery, new, and a nice stable voltage and current flow come out the other end. One of these days I'
ll try to solder a surface mount chip but I need a few more tools and things to do it.

My next step is to make a dimmer that will vary the output voltage in a predetermined range of around 3 to 3.8 volts. I want to be able to turn it on at night after my eyes have adjusted to the darkness.

My tantalum filter capacitors are 10 volts. That's 10 / 4 = 2.5 so I guess I'm in the range mentioned above. That was the factory spec. voltage rating. The next step up was 16 volts.*<HR></BLOCKQUOTE>

Hello jeff1500,

Yes, I'm happy with this chip as well. Tonight I finally managed to get the MAX756 chip on a one inch disc. I've been working on this for ahwile. I am using surface mount 150uF tantalum capacitors, and a surface mount 100uH inductor. The rest are through hole, so for now some parts are on both sides, until I use all surface mount parts. I am looking into using solder paste for the small SO parts. I want to see if I can get this circuit small enough to fit inside the head of the Mini Mag flashlight head. That will be a challenge.

With just 1.2 volts in, the MAX756 powered the Luxeon around 3.1 to 3.2. With 2 volts in , it powered it at just about 3.3 volts out, and very bright.

I am following this thread. I like the idea of a luxeon in a Mini Mag light.


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## remuen (Dec 17, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*... I want to see if I can get this circuit small enough to fit inside the head of the Mini Mag flashlight head. That will be a challenge. ...

I am following this thread. I like the idea of a luxeon in a Mini Mag light.*<HR></BLOCKQUOTE>

Hi Wayne

I thougt the Luxeon is too big to mount it together with a DC-DC converter into a Minimag. Do you see a real chance doing this?
And what's about the heat and how long would two AA batteries about run with such a Luxeon?

By the way: I didn't get an answer from Linear Technology concerning the LT1932 chip. So we're ar waiting and follow what's about the circuit with the Max757. Looks good to me with this chip!


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## ElektroLumens (Dec 17, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Hi Wayne

I thougt the Luxeon is too big to mount it together with a DC-DC converter into a Minimag. Do you see a real chance doing this?
And what's about the heat and how long would two AA batteries about run with such a Luxeon?

By the way: I didn't get an answer from Linear Technology concerning the LT1932 chip. So we're ar waiting and follow what's about the circuit with the Max757. Looks good to me with this chip!*<HR></BLOCKQUOTE>


remuen,


I think that if a regulator were to fit in a Mini Mag head, it would have to be really small. I am going to order a few MAX756 chips from DIGIKEY, the SO package, which is a very small surface mount chip. If I use this surface mount chip, and all small surface mount parts, there might be a chance?

I also have a few other AA flashlights that look a little more promising: A stainless steel flashlight from Garrity, a Coleman 2 AA cheapo, and I have a Brinkmann 3 AA flashlight, in which I hope to mount a Luxeon emitter, and put the regulator in a AA dummy, to replace one of the 3 batteries.

I think 2 Alkaline AA's should power a Luxeon for 3 or 4 hours at full brightness with the MAX756/MAX757, but I still have not done a test for this.

I looked up the LT1932 chip. It looks interesting, as it regulates current and not voltage like the MAX757. 

The Zetex chip might also be a very viable option when it's final design and components are completed. 

I have been making MAX756/MAX757 boards, at 1" X 2", which is just right for a 'D' cell dummy. I have put these in 3 'D' cell flashlight mods, with both the Luxeon, and with 12 white Nichia's. Works great.


----------



## remuen (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
...I want to see if I can get this circuit small enough to fit inside the head of the Mini Mag flashlight head. That will be a challenge. ....

.... I also have a few other AA flashlights that look a little more promising: A stainless steel flashlight from Garrity, a Coleman 2 AA cheapo, and I have a Brinkmann 3 AA flashlight, in which I hope to mount a Luxeon emitter, and put the regulator in a AA dummy, to replace one of the 3 batteries.

I think 2 Alkaline AA's should power a Luxeon for 3 or 4 hours at full brightness with the MAX756/MAX757, but I still have not done a test for this.

I looked up the LT1932 chip. It looks interesting, as it regulates current and not voltage like the MAX757. 
*<HR></BLOCKQUOTE>

As you wrote converting the Minimag is the real challenge That's the reason why I looked for a chip as small as possible and found the LT1932 (means my friend Thomas found it). As I wrote in an earlier post we think that with this chip and the other SMD parts it should be possible to make a board size of max 1cm2 (= square centimeter, think this is about 0.4 x 0.4''?). 

There is another challenge with the Minimag conversion: The switch issue (see my reply on a post of InTheDark 2 days ago). Maybe you have a good solution for this problem? IMHO the kind of switch like in the ARC AAA seems the one that would work best (personally I don't like the tailcap switch for the Minimag even it would be the easiest one).

Of course I want to convert some other flashlight too eg. a headlamp (LED Headlights and Headlight conversions). Another great flashlight to convert would be the energizer four AA double barrel. 

What I will try to make together with Thomas is a DC-DC converter with the LT1932 which could be used for one single AA up to four AA cells (1.5 - 6V) and 1 to 8 Nichia's. That would cover all applications I have now in my plan. 

For more LED's I think the MAX757 or the Zetek chip would be a better choice (the MAX 757 also has a better efficiency according to the data sheets). For the Luxeon the LT1932 can anyway not be used because the LT1932 is limited to about 40mA and as far as I know the Luxeon sucks up to 350mA.


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## Barbarin (Dec 18, 2001)

As you all know, my english is not very good, and my knowledgments of electronics are even worse; even thought today I have been "studiying" the MAX757 data sheet, and if I am not wrong I have understood that it is not possible to get an estabilized Vout if you want to use NiMH or Alkalines. I want to find an DC-DC that allows me to use both batteries, without any modifications.
I have a bunch of LS w/o, and have found a perfect (dive resistant,anodized aluminium made...)kind of boxes to make a flashlight, and now I would like to know what could be the best converter for that aplication. The number of batteries could be 3/6 AA, or 2/3 C.
Thanks in advance.
By the way , the price of the LS w/o here is 10 Euros (plus 16% IVA)for short quantities


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## remuen (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by barbarin:
*...if I am not wrong I have understood that it is not possible to get an estabilized Vout if you want to use NiMH or Alkalines. 
*<HR></BLOCKQUOTE>
As far as I know with the MAX757 you can use not only alkalines but also NiMH. But I think Jeff1550, Duggg or Wayne Johnson are much more competent to give you an correct answer.


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## ElektroLumens (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*As you wrote converting the Minimag is the real challenge That's the reason why I looked for a chip as small as possible and found the LT1932 (means my friend Thomas found it). As I wrote in an earlier post we think that with this chip and the other SMD parts it should be possible to make a board size of max 1cm2 (= square centimeter, think this is about 0.4 x 0.4''?). 

There is another challenge with the Minimag conversion: The switch issue (see my reply on a post of InTheDark 2 days ago). Maybe you have a good solution for this problem? IMHO the kind of switch like in the ARC AAA seems the one that would work best (personally I don't like the tailcap switch for the Minimag even it would be the easiest one).

Of course I want to convert some other flashlight too eg. a headlamp (LED Headlights and Headlight conversions). Another great flashlight to convert would be the energizer four AA double barrel. 

What I will try to make together with Thomas is a DC-DC converter with the LT1932 which could be used for one single AA up to four AA cells (1.5 - 6V) and 1 to 8 Nichia's. That would cover all applications I have now in my plan. 

For more LED's I think the MAX757 or the Zetek chip would be a better choice (the MAX 757 also has a better efficiency according to the data sheets). For the Luxeon the LT1932 can anyway not be used because the LT1932 is limited to about 40mA and as far as I know the Luxeon sucks up to 350mA.*<HR></BLOCKQUOTE>


remuen,

The LT1932 would work for a Mini Mag conversion, if you can get it that small, it seems to me. According to the specificaitons of this chip, it seems like you could drive up to 5 LED's, with 2 AA's. I'll have to check on that again, but anyway, you could put one or two on for sure.

I have a Mini Mag lite, in which I put a single white Nichia in it, and put 3 'N' batteries. It really lasts a long time, and I like this flashlight a lot. A regulator would be nice because I could then use the 2 AA batteries instead of the 3 'N' cells. I suppose the battery life would be great.

I have a few Luxeon emitters, which I would like to mount on a custom PCB board, and see if it would fit in the Mini Mag. But there doesn't seem to be any room for the regulator in the head, and the heat might affect the regulator. So I just don't know about doing this mod or not. I have a Brinkmann 3 AA flashlight, and I might try this mod with it, and put the regulator in place of one of the 3 batteries.

I have the Energizer 4 AA Double Barrel, and I think that is a very good possibility for the Luxeon mod, and the regultor might fit in the head. I also have the 6 AA Double Barrel, and for sure there is plenty of room in it, but it is a very large flashlight, in which I was considering mounting 20 LED's and a regulator in it. (The MAX757, set at 4.0 to 4.5 volts)

The Luxeon Star will draw 350mA at 3.2 volts, and at 3.4 volts, which I like to drive it at, it will draw 400mA. The MAX757 will drive the Luxeon with 2 AA's at these currents, and with a single AA will drive it at around 3.1 volts (not sure of the current, but probably about 300mA).

I am planning on making a custom flashlight body with copper pipe. I used to do this quite a bit. I want to use a singe 'C' battery, the MAX757 regulator, and a single Luxeon Star. It would be a short and stubby flashlight, and very bright, and last maybe 4 hours at full brightness, or a bit longer, and still fit in a pocket (baggy pants), or a purse.

I have a big clunky flashlight I made, with 8 AA's, a LM2595 step down regulator, and 2 Luxeons. Awesome bright! I have the regulator set at 3.4 volts. I call it the 'Luxeon Double Star'. I also call it the 'Ugly Star', because it is ugly. The head of the flashlight could be removed from the battery pack and put on bicycle handlebars, or on a head light band.


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## ElektroLumens (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by barbarin:
*As you all know, my english is not very good, and my knowledgments of electronics are even worse; even thought today I have been "studiying" the MAX757 data sheet, and if I am not wrong I have understood that it is not possible to get an estabilized Vout if you want to use NiMH or Alkalines. I want to find an DC-DC that allows me to use both batteries, without any modifications.
I have a bunch of LS w/o, and have found a perfect (dive resistant,anodized aluminium made...)kind of boxes to make a flashlight, and now I would like to know what could be the best converter for that aplication. The number of batteries could be 3/6 AA, or 2/3 C.
Thanks in advance.
By the way , the price of the LS w/o here is 10 Euros (plus 16% IVA)for short quantities*<HR></BLOCKQUOTE>


barbarin,

I don't see why it would make any difference what the type of batteries are that are used with a regulator. The larger the battery, the less the internal resistance, so there would be a better current flow. The more amp hours the battery has, the longer the burn time will be.

The MAX757 will drive one single Luxeon just fine. I use a larger inductor than is recomended, a 100uH surface mount inductor. I also use 150uF tantalum surface mount inductors. This pumps it up a bit, and drives a little more current through. I read of a mod for the MAX757 in which the Cout capacitor was changed to be 2 1000uF 16v capacitors, and with 4.5 volts in (3 AA's), will drive 5 volts at 1.5 amps!

If you are using a single Luxeon, the volts in should not exceed 3.2 volts, and for sure not be over 3.4. You will burn it up real quick! I did try putting 2 Luxeons in series, and drove them at 6.8 volts (using a huge heat sink.)

I am not sure of the Euro/US dollar conversion at this time. A Luxeon here costs about $14, and I can get the emitter for $11.50. In larger quantities, the cost can go down a bit.


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## remuen (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
remuen,

The LT1932 would work for a Mini Mag conversion, if you can get it that small ...
According to the specificaitons of this chip, it seems like you could drive up to 5 LED's, with 2 AA's. .....

I have a Mini Mag lite, in which I put a single white Nichia in it, and put 3 'N' batteries. It really lasts a long time, and I like this flashlight a lot. A regulator would be nice because I could then use the 2 AA batteries instead of the 3 'N' cells. I suppose the battery life would be great.

...
The Luxeon Star will draw 350mA at 3.2 volts, and at 3.4 volts, which I like to drive it at, it will draw 400mA. The MAX757 will drive the Luxeon with 2 AA's at these currents, and with a single AA will drive it at around 3.1 volts (not sure of the current, but probably about 300mA).

....I am planning on making a custom flashlight body with copper pipe. I used to do this quite a bit. I want to use a singe 'C' battery, the MAX757 regulator, and a single Luxeon Star. It would be a short and stubby flashlight, and very bright, and last maybe 4 hours at full brightness, or a bit longer, and still fit in a pocket (baggy pants), or a purse.

*<HR></BLOCKQUOTE>

Hi Wayne
We think we can make the LT1932 circuit as small as mentioned. So no problem to put it into a Minimag. But first I must have these chips. 

According Thomas with the LT1932 it should be possible to drive 6 - 8 LED's on 2 AA cells. But let's see how we can bring it to work.

One of my first mod was also a Minimag with one single white Nichia and 3 N cells. The unsatisfying result (wasn't bright enough!) of this easy mod, the dimming of my Petzl Tikka after a short time and an astonishing test with the ARC AAA on a low battery (How an ARC AAA runs on a low battery) brought my to the idea to make a stepup converter.

For the moment I'm a bit afraid of using a Luxeon Star (Current consumption, heat ..). Maybe I'll try the LS later when I've a bit more experience....

Concerning the LS with only one single AA: Driving the Luxeon with 300mA at 3.1V means, that the AA cell has to deliver something between 600 and 700mA! I didn't try it out but to me it seems quite a high current for an AA battery.

Reading about your future copper pipe flashlight I thought: Why not buying an ARC LS? But now I see the point: You're planning to use a C cell. That is exactly what I would like to be available for the ARC LS. With a C cell I think a current of 300 - 350mA for the LS (700 - 750mA on the battery) should also be not a problem. 

And a last thing: Can you publish some pics of the mod's you've made? This would be very intersting.


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## jeff1500 (Dec 18, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by barbarin:
*possible to get an estabilized Vout if you want to use NiMH or Alkalines*<HR></BLOCKQUOTE>

My max757 works well with either type of battery.


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## remuen (Dec 19, 2001)

*Are the white Nichia LED's now brighter?
----------------------------------------*
I buy my Nichia LED's from a traffic light manufacturer. I've just got my last order with twenty white LED's for tests and mods I'll make with DC-DC converters. 

Astonishing for me this time is that according the papers their specification now should be *3.6V 20mA 8000mcd 20 degrees*. 

Does anyone know if this light output is possible?

For your information: 
This manufacturer uses as far as I know only Nichia LED's and the Nichia sales office recommanded this company to me when I was searching for a source. But they use their own article no's so it's difficult to identify the LED's. 

But I found a designation L5W54N bS which could be a Nichia type (the original Nichia type for the white 5mm Led's is NSPW500BS).

By the way: I've seen that on the Nichia homepage the white Nichia LED's NSPW500BS are now specified with 6400mcd. If I'm right it was till now "only" 5600mcd?


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## ElektroLumens (Dec 19, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*



Originally posted by Wayne Johnson:
[qb]
remuen,

The LT1932 would work for a Mini Mag conversion, if you can get it that small ...
According to the specificaitons of this chip, it seems like you could drive up to 5 LED's, with 2 AA's. .....

I have a Mini Mag lite, in which I put a single white Nichia in it, and put 3 'N' batteries. It really lasts a long time, and I like this flashlight a lot. A regulator would be nice because I could then use the 2 AA batteries instead of the 3 'N' cells. I suppose the battery life would be great.

...
The Luxeon Star will draw 350mA at 3.2 volts, and at 3.4 volts, which I like to drive it at, it will draw 400mA. The MAX757 will drive the Luxeon with 2 AA's at these currents, and with a single AA will drive it at around 3.1 volts (not sure of the current, but probably about 300mA).

....I am planning on making a custom flashlight body with copper pipe. I used to do this quite a bit. I want to use a singe 'C' battery, the MAX757 regulator, and a single Luxeon Star. It would be a short and stubby flashlight, and very bright, and last maybe 4 hours at full brightness, or a bit longer, and still fit in a pocket (baggy pants), or a purse.

Click to expand...

*


> <HR></BLOCKQUOTE>
> 
> Hi Wayne
> We think we can make the LT1932 circuit as small as mentioned. So no problem to put it into a Minimag. But first I must have these chips.
> ...




Hello Remuen,

Yes, the LT1932 looks interesting, and should drive several Nichia's fine, and be small enough to use with the Mini Mag. It might be a good choice. Availability of the chip can be a real problem. We might see achip that looks perfect, only to find that all we can get is a few samples, and if you want to purchase it, you need to buy 1,000 of them. If this chip is available, it might be a good choice. I consider availability a major criteria for selecting a chip.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*Concerning the LS with only one single AA: Driving the Luxeon with 300mA at 3.1V means, that the AA cell has to deliver something between 600 and 700mA! I didn't try it out but to me it seems quite a high current for an AA battery.*<HR></BLOCKQUOTE>

I hear what you're saying here. However, all I can say is that I have hooked up the Luxeon star to a single AA battery, using the MAX756 step up board I have, and it is shining at about 3.1 volts, probably about 300mA. If that doesn't add up mathmatically, I don't know what to tell you. I didn't test for burn time, so I don't know how long it will last with 1 AA, but it did indeed work.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> Reading about your future copper pipe flashlight I thought: Why not buying an ARC LS? But now I see the point: You're planning to use a C cell. That is exactly what I would like to be available for the ARC LS. With a C cell I think a current of 300 - 350mA for the LS (700 - 750mA on the battery) should also be not a problem. 
<HR></BLOCKQUOTE>

Well, I am purchasing a ARC LS, as soon as they are available. Now, I can make a little flashlight, using 1" copper pipe, really cheap. It in no way would be anywhere near as nice as the ARC LS. However, it would work, and it is something I myself made. It shows creativity. Anyone can plunk down $100 (if they have it), and just buy a ARC LS, but few people can make their own Luxeon Star flashlight, like we can. 

Also, as you say, the ARC LS, only uses smaller AA batteries, and I can use any size I want.

By the way, right now I am doing a run-time test with the Luxeon Star, a MAX756 one inch regulator board I just put together, and one 'C' battery. Because of the smaller surface mount parts I am using, the voltage only starts at 3.1 volts, as opposed to higher output voltages I have had with different components. Anyway, it's now been shining for over 1 1/2 hours, and the output voltage under load is 2.928 volts, and the input voltage under load is .89 volts. Considering the low input voltage, I think is is doing okay. At 2.9 volts it is not as bright as at higher voltages, but it is not bad. When I have a chance I'll put this Luxeon Star and regulator in a short little flashlight made with the copper pipe, put a little switch on it, and have a neat little home made 'Pocket Star', as I will call it. Perhaps someday I might make a nice aluminum flashlight body?

As regards pictures, I don't have a good digital camera, but I have a little web eye on my computer with which I could take some photos of some of my mods. I don't have a way to poste them, but I could email them to you if you wanted.


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## remuen (Dec 19, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*Availability of the chip can be a real problem. We might see achip that looks perfect, only to find that all we can get is a few samples, and if you want to purchase it, you need to buy 1,000 of them. If this chip is available, it might be a good choice. I consider availability a major criteria for selecting a chip.*<HR></BLOCKQUOTE>

Wayne 

First the positive news: 
The LT1932 is deliverable from stock. And Linear Technology is one of the few manufacturers which delivers also in quantities less than 100 pieces. But you have to order direct from LT.

And the bad news:
The costs for international shipments are a terrible $28.00!




I'm looking for a cheaper way but don't know how.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>* ... and it is shining at about 3.1 volts, probably about 300mA.*<HR></BLOCKQUOTE>


Oh sorry, I missunderstood you, I thougt it was only a calculation and not an result of a test. No doubts in this result!


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*Now, I can make a little flashlight, using 1" copper pipe, really cheap. It in no way would be anywhere near as nice as the ARC LS. However, it would work, and it is something I myself made. It shows creativity. Anyone can plunk down $100 (if they have it), and just buy a ARC LS, but few people can make their own Luxeon Star flashlight, like we can.*<HR></BLOCKQUOTE>


I'm interested in this creation! Maybe I'm going to make also an own flashlight in the future. Let me first finish my planned mod's (3 Minimags, 2 Minimag clones, a headlight, a 20 years old Varta flashlight with 2D).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*By the way, right now I am doing a run-time test with the Luxeon Star, a MAX756 one inch regulator board I just put together, and one 'C' battery. Because of the smaller surface mount parts I am using, the voltage only starts at 3.1 volts, as opposed to higher output voltages I have had with different components. *<HR></BLOCKQUOTE>


Mmmhh, your board becomes smalller - don't compete our future mini board with the LT1932 ...

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*As regards pictures, I don't have a good digital camera, but I have a little web eye on my computer with which I could take some photos of some of my mods. I don't have a way to poste them, but I could email them to you if you wanted.*<HR></BLOCKQUOTE>

Please email the pics. Thanks in advance.
I've also no way to post pictures. But I'm sure some of the flashaholics reading this know how to do and will tell it to us!

*Jeff1500, you have already posted a drawing of your MAX757 circuit. How did you make this?*. And how can I post pictures direct in a reply even I don't hav a homepage or something like this?


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## ElektroLumens (Dec 19, 2001)

Remuen,

Regarding Linear Technology, I forgot, yes, I myself have ordered chips from them. I appreciate their willingness to sell small quantities. Most manufacturers it seems only sell 1,000 pieces or so. The shipping price is a real bummer. That is really high cost. Perhaps you can find a vendor in Europe that will sell the chips you want?

Well, I finished the test with the Luxeon and the MAX756 one inch disc circuit. It started at 3.1 volts in under load, with a almost fresh battery. It lasted basically 5 1/2 hours. I shut it down with .641 volts in, and 2.878 volts out. It is supposed to shut down at .7 volts, so I don't know why it was still shining. I suppose the time would at least double with 2 'C' batteries. This will be my next test. So, perhaps 10 hours with 2 'C' batteries. I do have a 3 'D' cell flashlight, with this same regulator in it. I put the regulator in a 'D' cell dummy in place of one of the batteries. I never did do a test to see how long it will run, but probably 20 hours at full brightness anyway?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>* I'm interested in this creation! Maybe I'm going to make also an own flashlight in the future. Let me first finish my planned mod's (3 Minimags, 2 Minimag clones, a headlight, a 20 years old Varta flashlight with 2D). 
quote: 
*<HR></BLOCKQUOTE>

Sounds like you have a lot of mods on your hands now. 

Recently, after really strugling with the design, I finally managed to come up with a one inch disc design for the MAX756/MAX757. It wasn't easy, but I managed it. When I finally installed the components, it worked right away! I plan to use this new board in several of my flashlight mod plans, and also in a few flashlights I intend to design and possibly market, someday? 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>* Mmmhh, your board becomes smalller - don't compete our future mini board with the LT1932 ... *<HR></BLOCKQUOTE>

Well, sorry if I compete with your mini board design. I think that eventually there 
may be more than a few different boards available.



> * I've also no way to post pictures. But I'm sure some of the flashaholics reading this know how to do and will tell it to us!
> Jeff1500, you have already posted a drawing of your MAX757 circuit. How did you make this?. And how can I post pictures direct in a reply even I don't hav a homepage or something like this?
> *
> 
> ...


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## jeff1500 (Dec 19, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> *Jeff1500, you have already posted a drawing of your MAX757 circuit. How did you make this?. And how can I post pictures direct in a reply even I don't hav a homepage or something like this?
*<HR></BLOCKQUOTE>

1. I use StarOffice. Linux people use it. I think it's a German program. Sun Microsystems bought it and made it open source. They have versions for Linux and Windows all for free at
http://www.sun.com/staroffice/ 

It's about 80 MB so you need a high speed connection, or for a little money I think they'll mail you a disk. I downloaded it for free. It has a drawing program that will save files as .gif or .jpg for web posting. It's a nice set of programs.

2. I use a free web page I got from:
http://www.tripod.lycos.com/ 

They put ads on it but, oh well, it's free and you can get there from any internet connection. To post a single image file you have to put it on an html page like this:
http://edusite10.tripod.com/led3/max757.html

3. Here's the two transistor circuit we made a few weeks ago. It doesn't have voltage regulation but it might be good for high current things like luxeon stars. You could use Nimh batteries. They have an almost flat discharge curve so lack of voltage regulation may not be a problem.

Two transistor circuit based on Brinkman led light via. MrAl


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## remuen (Dec 20, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
Regarding Linear Technology, I forgot, yes, I myself have ordered chips from them. I appreciate their willingness to sell small quantities. Most manufacturers it seems only sell 1,000 pieces or so. The shipping price is a real bummer. That is really high cost. Perhaps you can find a vendor in Europe that will sell the chips you want?*<HR></BLOCKQUOTE>

It seems I've to buy them at their conditions because at least in Germany (and in here in Switzerland) they do not have the LT1932 in stock ....

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*Well, I finished the test with the Luxeon and the MAX756 one inch disc circuit. ... *<HR></BLOCKQUOTE>

Hey superb! Something happens. Your circuit is running, Jeff1500's MAX757 is in a test run and now the news: 

*Thomas made today a first test circuit with a LT1613 chip!!! I've to test it now but it already works fine with 2 LED's in series on a single AAA with about 30mA! And it takes already in this very early state less than 1cm2 on the board!*

Taking this chip was just a short descision of Thomas because we don't have yet the LT1932 (see above) but a few samples of the LT1613.

Some first details to this test circuit: It's mainly the circuit showed as typical application on the first page of the PDF-Datasheet of the LT1632. But instead the resistor R1 there are 1 to xx? LED's in series (max output 36VDC, so possibly 7 - 9 LED's could be used). R2 is adjusted on a voltage of 1.25V over this resistor at 30mA. This means that the whole circuit works - like the LT1932 - as a current controller!

* <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Well, sorry if I compete with your mini board design. I think that eventually there may be more than a few different boards available.*<HR></BLOCKQUOTE>

Sorry, I've forgotten to put this



or this



on my post when I wrote about the competition. Honest: It's great that we soon will have some different circuits (see also my post to Klaus on page 3 of this thread. I hope each one of these circuits will be in a state that others can use it! Perhaps later on someone is going to produce these boards in small series to make them available for the guys which cannot make it on their own.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>* I asked this question, and a few CPFer's answered me. I haven't tried it. If I find the post, I'll let you know where it is. It explains it pretty well.*<HR></BLOCKQUOTE>

Ok, i think I can use it later on to publish our result of the mod!


----------



## remuen (Dec 20, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
* To post a single image file you have to put it on an html page like this:
http://edusite10.tripod.com/led3/max757.html*<HR></BLOCKQUOTE>

Hi Jeff1500

How is this circuit now running? I don't have all the things in my head but it seems to me you have changed some values?

Concerning publishing pics I've to look much more into the matter. Perhaps I'll have a own homepage too (remuen.ch is already reserved). But your solution with the free web site would obviously be much cheaper ...


----------



## jeff1500 (Dec 20, 2001)

This sketch doesn't show the input filter capacitor whereas the max757 data sheet does. I don't know if it does anything useful for this circuit or not. I seems to work fine without it. There also seems to be flexibility in the inductor size. It also still works if I unplug the .1 uF capacitor that terminates the reference voltage pin.

The output filter capacitor and diode work together. It may prevent led damage from voltage spikes so I like to use it. I don't have an oscilloscope to measure the voltage spikes. I don't want to run without it at my current level of understanding, but I'll bet it could be eliminated. People have run the one transistor satcure circuit without an output filter capactor and diode.

SatCure LED driver circuit

Another one transistor circuit with a capacitor and diode.


----------



## remuen (Dec 20, 2001)

Here are the results I've got from my first measurements with the LT1613 test circuit in this very very early state. 

Just for your background information: I'm very poor equiped at home. So I had to use old batteries to get the different voltages (input and output voltage is always under load). And I do not have a digital volt meter so the results may not be really excact.

*With 1 white Nichia LED:*
_U In U Out I Out 
(V) (V) (mA)_
--------------------
0.8 ¦ 0.8 ¦ 0
0.9 ¦ 3.1 ¦ 4
1.05 ¦ 3.5 ¦ 20
1.2 ¦ 3.6 ¦ 21
1.3 ¦ 3.6 ¦ 27
1.4 ¦ 3.6 ¦ 32
1.5 ¦ 3.6 ¦ 33

*With 2 white Nichia LED's:*
_U In U Out I Out 
(V) (V) (mA)_
--------------------
0.8 ¦ ? ¦ 00
0.9 ¦ ? ¦ 1.7
1.05 ¦ ? ¦ 9
1.2 ¦ ? ¦ 12.5
1.3 ¦ ? ¦ 23
1.4 ¦ ? ¦ 26
1.5 ¦ ? ¦ 24 (??)

*With 3 white Nichia LED's:*
_U In U Out I Out 
(V) (V) (mA)_
--------------------
1.5 ¦ 7 (?) ¦ 13

*With 4 white Nichia LED's:*
_U In U Out I Out 
(V) (V) (mA)_
--------------------
1.5 ¦ 13 ¦ 6

*With 5 white Nichia LED's:*
_U In U Out I Out 
(V) (V) (mA)_
--------------------
1.5 ¦ 15 ¦ 2

That's all for the moment!

By the way: Have you ever tried to make such a table here? It didn't work for me!


----------



## ElektroLumens (Dec 20, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Here are the results I've got from my first measurements with the LT1613 test circuit in this very very early state. 
*<HR></BLOCKQUOTE>

Hello remuen,

Hey, good work. I figure anytime I get one of these circuits running, that's a major accomplishment! You got it working, and that's great!


You definately need to get a digital voltage meter. However, for current measurements, you should use a resistor. Get a .1 ohm or a .01 ohm resistor. Connect it in series with the LED. Measure the voltage across the resistor. If you use a .1 resistor, multiply the voltage by 10, or if you use the .01 (that's what I use), multiply it by 100. The number will be your current being used. You need a DMV to do this though, because it's hard to tell with the analog. If you search the Zetex thread, you'll find Duggg and MrAl explaining this to me. 


This is a chip I have completely overlooked. I will order a couple, and try this circuit out. Hey, they even give us a PCB board diagram to use. Well, I always design my own anyway. It says you can design a board at about .2 inches, that's pretty small! I wonder if this chip could be tweaked to run a Luxeon?


----------



## jeff1500 (Dec 20, 2001)

Hurray, it works.

Ya, the resistor trick is a good one. I need to find a .1 or .01 ohm resistor. The current scale on my meter only goes up to 200 mA.

What kind of a circuit board did you and Thomas solder the components too. Did you etch a board? Were you able to buy something?

If I were to collect all the surface mount components, I don't know what I would solder them too.


----------



## remuen (Dec 20, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*However, for current measurements, you should use a resistor. Get a .1 ohm or a .01 ohm resistor. Connect it in series with the LED. Measure the voltage across the resistor. *<HR></BLOCKQUOTE>

I'll do next time with a resistor. I think it's because of the inner resistor of the volt meter? It makes it also a bit easier to measure.

* <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>I wonder if this chip could be tweaked to run a Luxeon?*<HR></BLOCKQUOTE>

I think it should be possible. For 400mA the value of R2 should be only 3.13 Ohms (R = U/I = 1,25/0.4 = 3.13)

*Very important: 
This circuit with the LT1613 is only a stepup converter, not a stepdown regulator!* 
Keep this in mind especially with the Luxeon but also if you're using standard LED^s. For a a input voltage up 3.5V -> minimum 1 LED, for up to 7V - > minimum 2 LED's switchen in serial.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jeff1500:
*
What kind of a circuit board did you and Thomas solder the components too. Did you etch a board? Were you able to buy something?*<HR></BLOCKQUOTE>

First: I didn't yet look into the SatCure LED driver circuit. I'll do it later.

Second: Thomas took a piece of such a laboratory board I mentioned in a earlier thread a few days ago. It's not edged, but the circuit takes about 1.5 x 0.6 cm (not optimized) on this board.

What exactly do you mean by "Were you able to buy something?" 

_Just do inform you early enough: I think the work on this circiut will not proceed over the christmas holidays because our company is then closed. And I think he will not work on it at home. _


----------



## remuen (Dec 20, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
This is a chip I have completely overlooked. I will order a couple, and try this circuit out.*<HR></BLOCKQUOTE>

Just a few more informations about the circuit which i didn't give you in my earlier post:

Thomas took some parts he just had in his drawer. 

L1 = 22uH
C1 and C2 = 10uF
And from SHDN to the positive contact a 100kOhm resistor

Good luck!


----------



## jeff1500 (Dec 22, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen wrote:
*What exactly do you mean by "Were you able to buy something?" 
*<HR></BLOCKQUOTE>

I was trying to say, "Were you able to buy a manufactured adapter board to solder the chip to?" 

I've never seen one, but I think someone makes a small circuit board that's used to adapt small surface mount chips to DIP pin spacing. With such a thing, you solder on the chip and then plug it into a breadboard for testing.


----------



## papasan (Dec 22, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*I've never seen one, but I think someone makes a small circuit board that's used to adapt small surface mount chips to DIP pin spacing. With such a thing, you solder on the chip and then plug it into a breadboard for testing.*<HR></BLOCKQUOTE>

Capitol makes SO to SIP adapters called surfboards, perhaps this is what you mean...i recently ordered a SOT-23-5 adapter to test out some zetex stuff, hopefully i'll get it soon and i can report how well it works...it's a simply thing, i really could have saved myself $2 and made one, just easier this way...


----------



## remuen (Dec 22, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*I've never seen one, but I think someone makes a small circuit board that's used to adapt small surface mount chips to DIP pin spacing. With such a thing, you solder on the chip and then plug it into a breadboard for testing.*<HR></BLOCKQUOTE>

Thomas uses such a special SMD laboratory board I mentioned in an earlier thread. The pins of the chip and all other surface mont components as resistors, capacitors etc. fit exactly on the soldering points of the board or vice versa (poop, I don't know how all these things are called in English!). So it's not an adaptor. I tried to find a better picture than in the mentioned link but didn't find one. 

For this test circuit with the LT1613 Thomas took a small one (maybe it's only a part of a bigger one?), size is about 0.8 x 5 cm (~0.3" x 2"). The whole circuit in this very first version uses only about 0.8 x 1.5 cm (~ 0.3"x 0.6") so you could make about 4 complete circuits on this little board and then edge it. For this test circuit Thomas soldered just 4 wires (for in- and output) direct on the board.

By the way:
Today I ordered some equipment for my home lab as an adjustable laboratory power supply, a digital multimeter and a "helping hand" (such a thing with clips to hold a board and with a glass to see things a bit better). I hope that future test results will be better - in every case I can measure them easier.


----------



## jeff1500 (Dec 23, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Thomas uses such a special SMD laboratory board I mentioned in an earlier thread. The pins of the chip and all other surface mount components as resistors, capacitors etc. fit exactly on the soldering points of the board or vice versa. So it's not an adapter. 

Papasan wrote:
Capitol makes SO to SIP adapters called surfboards, perhaps this is what you mean
*<HR></BLOCKQUOTE>

This is very interesting. Sounds like they're two different things. I wish I could see a picture of each one. I'll look around.


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## papasan (Dec 23, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*This is very interesting. Sounds like they're two different things. I wish I could see a picture of each one. I'll look around.*<HR></BLOCKQUOTE>

digikey sells surfboards, look under prototyping tools...


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## jeff1500 (Dec 23, 2001)

Here's a whole bunch of them.
http://www.capitaladvanced.com/products.htm

with a help file for soldering techniques
http://www.capitaladvanced.com/solderin.htm

and modifying the foil pattern
http://www.capitaladvanced.com/foil.htm


----------



## remuen (Dec 24, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*This is very interesting. Sounds like they're two different things. I wish I could see a picture of each one. I'll look around.*<HR></BLOCKQUOTE>

I've found a bit a better picture of such a board Thomas uses: http://www.conradelektronik-online.de/coel/40/smd_laborkarte.htm 
Click on the hotspot (*Bild gross*) below the picture to enlarge it.

The board is a double sided version and through hole leaded so you can put the components on one side and make some additional wiring on the back side. The size of the board is about 3.75" x 2.1". 

The soldering points (or soldering isle or soldering eyes or whatever they are called) are arranged in a 1/40" raster so SMD components fit exactly on them.

It's a board to make such test circuits. Finally you can edge it whatever size the circuit has.


----------



## jeff1500 (Dec 28, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Fill first the hole in the wax with liquid epoxy and then place the contact ring (eg. such a part you use under a screw - I don't know how it is called in English) <HR></BLOCKQUOTE>

1. Maybe "washer" is the word you're looking for.

2. Where's the switch?

3. Has the length of the flashlight increased?


----------



## remuen (Dec 28, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*1. Maybe "washer" is the word you're looking for. * <HR></BLOCKQUOTE>
That's right (I looked in the dictionary)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*2. Where's the switch? * <HR></BLOCKQUOTE>

The adapter itself is the switch. Because it is fixed in the head (that's the reason for the thread in this adapter) it moves together with the head. So if you screw the Minimag head more on the body the negative contact ring will touch the Minimag body and make the contact close (the positive contact of the adapter is the most time already on the positive contact of the battery because of the spring presure). Unscrewing the head a bit will remove the contact ring of the adapter away from the Minimag body - means the contact is no longer closed - the switch is in its off position. 

It is the similar principle as in the ARC AAA but here the negative contact is switching (instead the positive contact as in the ARC). This works better in the Minimag because switching the positive contact means that you have to lead the negative contact over the thread and this did not work absolutly proper. It seems that the ARC's thread is much more precise and makes a better contact than the one in the Minimag.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*3. Has the length of the flashlight increased? * <HR></BLOCKQUOTE>
No - or yes? The size of the Minimag in its off position is a bit longer because the head
cannot be screwed as close on the body than without the adapter. In the on position it's about the same length depending on the adjustment of the beam with the original Minimag.


----------



## remuen (Dec 28, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
2. Where's the switch?
*<HR></BLOCKQUOTE>

Jeff1500, I've made a drawing of the adapter. Could you publish it on your home page? (I am going to send it to you by email)


----------



## remuen (Dec 29, 2001)

I have made some mechanical experiments on how to modify the Minimag. It was a bit a "try and error approach" but finally it works fine.

I have made an adapter from epoxy to screw into the head. As I can not yet place a drawing on a home page I try to describe it:

*How does this adapter look like:*
--------------------------------
Imagine a empty AA cell housing but take only the upper part of the body with the positive contact. This part of the body is about 10mm long and its diameter about 16mm (like the inner diameter of the Minimag). It has a thread fitting exactly in the inner thread of the Minimag head so one can srew it in the head. The "positive contact" of this battery-like adapter is about 6 mm long.

The top of the "positive contact" of the adapter has a contact plate on it and inside it and is wired to the body inside (this contact will press throug the whole on the positive contact of the battery in the Minimag housing).

On the place where the adapter body begins there is a contact ring. (this contact ring will be pressed on the Minimag body). There is also a wire connection from the contact ring to the inner part of the adapter body.

If you use a small DC-DC converter like we are talking about in this thread (eg with a LT1632 chip) you now can place it in the empty part of the adapter body and connect it to the positive and negative contact (with the wires described before). On top of the adapter you can place a board with the LED's (max. 7 LED's will fit into the Minimag head!).


*How does the adapter work:*
--------------------------
1. First you have to remove the reflector in the Minimag head and the bulb socket on the Minimag body (without the original tool from Maglite the socket will breake!!). Then scratch the top of the body (the part which was covered by the bulb socket) completley blank. 

2. Now screw the adapter with the converter and the LED board into the Minimag. Obviously the positive contact of this adapter has to show to the Minimag body. You can use about the front half of the inner thread of the Minimag head because in the rear half you have to screw the Minimag body. 

The poitive contact of the adapter has to go through the hole in the Minimag body (where the bulb socket was) and should press a little bit on the positive contact of the battery.

3. It now needs a bit of adjustment to bring the whole thing to work.
(The very first part of this adjustment is the right length of the positive contact of this adapter - see below under How did I make this adapter.)

First thing: The O-ring of the Minimag body must be completly in the head so it is tight sealed.
Second thing: If you screw the head closer on the body the contacts should be closed means the positive contact of the adapter should press on the positive contact of the battery (should press it into the spring in the tail cap) and the described contact ring for the negative pole should press tight on the blank top of the Minimag housing. If everything is correct the LED's now should give light.

If you unscrew the Minimag head a bit the contact ring of the adapter will be removed from the Minimag housing and the light should be switched off - but the O-ring should still seal the whole! 

*Added 01/01/2002:*
-----------------------
A pictures says more than 1000 words .... Jeff1500 was so kind to publish my drawing on his homepage. Here the link: http://edusite10.tripod.com/remuen/adapter.html 

*How did I make this adapter:*
----------------------------
1. Unscrew the Minimag head and remove the reflector. 
2. Put the head on its smaller end on a paper
3. Fill it from top with liquid wax up to about the half of the inner thread and let the wax cool down
4. Make a hole in the center of the wax with a diameter of about 5mm
and about 10mm deep /eg. with a screw). This will give the positive contact of the adapter. 
5. Take same vaseline and treat the rest of the inner head part (also the visible part of the thread!!) thouroghly with vaseline. Without this vaseline (or another grease) you cannot later on remove the epoxy adapter!!! 
6. Fill first the hole in the wax with liquid epoxy and then place the contact ring (eg. such a part you use under a screw - I don't know how it is called in English) and put it on the wax in the Minimag head. Important: This (negative) contact has to be a ring so the epoxy (the positive contact of the adapter) is really connected through the hole of this ring!
7. Fill in some more liquid epoxy into the Minimag head (about 1 cm higher than the wax) and let it dry.

When the epoxy is almost hard it's the best time to remove the adapter from the head. Remove first the wax in the Minimag head (scratch it away or heat the head a bit). Then screw the body from the rear site (where the wax was) into the head. With the help of the Minimag body you now should be able to screw the adapter out from the head. A tip: When the epoxy is still not hardend put a screwdriver deep in the top side of the epoxy. So you can use the screwdriver too to remove the adapter.

Now you have adjust the length of the adaptor's positive contact. If the contact ring presses tight on the top of the Minimag body the positive contact should press strong enough on the battery (through the hole where the bulb socket was) to make a good contact.

Finally you have to empty the body of this epoxy adapter. I drilled it out. Then drill a small hole from the top of the adaptors positive contact to the empty room in the body. As contact piece you can use the positive contact of an old battery which is wired through this hole. Then make a hole from the contact ring (negative contact to the empty room and wire it too. Now you can put the DC-DC converter in the empty room and connect it.

So, this describtion was very complicated. somewhen I will make a drawing of the whole thing and also make some pictures and publish them.


----------



## remuen (Dec 30, 2001)

I've made some additional measurements with the LT1613 converter. It is still the very first test circuit Thomas has built with
SMD parts he had in his drawer.

*For those who didn't follow this thread here a short condensation:*
------------------------------------------------------------------
We have made a first sample of a DC-DC converter with a LT1613 chip form Linear Technology. It is basically the typical application circuit shown on the front page of the pdf datasheet http://www.linear-tech.com/prod/datasheet.html?datasheet=490. The main difference is that the resistor R1 is replaced by some LED's switched in series. The values of the SMD components in this very first test circuit are:

R1 = no resistor but the LED's in series
R2 = 390 Ohm
L1 = 22uH
C1 = 10uF
C2 = 10uF
and additional a resistor 100kOhm from SHDN to the positive contact (is not showed in the typical application circuit).

In this circuit the LT1813 chip works as a current controller. The resistor R2 is responsible for the current because the voltage over this resistor is always 1.25V.

*And now the measuring results:*
--------------------------------
I took the below listed configurations (amount of LED's + cells) because for me they will be the most used ones (eg. 5 or 7 LED's on 2 AA cells for the Minimag modification and 10 LED's on 4.5V for a headlamp).

BTW - because I didn't yet receive the ordered ragulated power supply I still had to use a pair of new and used batteries. With the power supply the results should be more exact. (Wayne Johnson: I now have a digital multimeter but no 0.1 or 0.01 Ohm resistor for the suggested kind of measuring the current.) 

*5 white Nichia LED's on 2 AA cells*
---------------------------------
U In | I In | U Out | I Out | P In | P Out |	Eff
2.71V | 179.8mA | 17.1V | 25.1mA | 0487.3mW | 429.2mW | 88.1%
1.48V | 052.4mA | 15.9V | 04.0mA | 0077.6mW | 063.6mW | 82.0%

*7 white Nichia LED's on 2 AA cells*
---------------------------------
U In | I In | U Out | I Out | P In | P Out |	Eff
2.85V | 087.1mA | 23.7V | 10.3mA | 0248.2mW | 244.1mW | 98.3%
2.18V | 032.2mA | 20.9V | 01.4mA | 0070.2mW | 029.3mW | 41.7%

*7 white Nichia LED's on 3 AA cells*
---------------------------------
U In | I In | U Out | I Out | P In | P Out |	Eff
3.75V | 270.0mA | 25.1V | 25.1mA | 1012.5mW | 630.0mW | 62.2%
2.80V | 104.1mA | 23.7V | 10.1mA | 0291.5mW | 239.4mW | 82.1%

*10 white Nichia LED's on 3 AA cells*
---------------------------------
U In | I In | U Out | I Out | P In | P Out |	Eff
4.00V | 105.6mA | 34.4V | 12.1mA | 0422.4mW | 416.2mW | 98.5%
3.60V | 042.5mA | 30.6V	| 02.3mA | 0153.0mW | 070.4mW | 46.0%

As expected (because of the earlier results) this first circuit did not deliver the results I wish it would. So I'm going to ask Thomas for a modification. My target is that the converter delivers an output current of 30 ... 40mA on an input voltage of 1.8 ... 4.5V.

*Has anyone already a good working solution for such a circuit with the LT1613?*

If it is not possible to reach this target we have to wait until I get the LT1932 chip.

*To Wayne Johnson and Jeff1500:*
------------------------------
- Did you make any further progress with the MAX756/Max757 chips? 
- How do your circuits work with 5 ... 10 LED's on an input voltage range of 1.8 ... 4.5V? 
- And could you already make the board smaller?
I am interested on some good news!


----------



## remuen (Dec 31, 2001)

Has anyone already inspected the *VersaLux Utility Light Module* from TechAss and can tell which chip they use or knows the circuit? 

I just looked on their page http://www.techass.com/el/versalux/ulm/ulm.php and I think they must have an excellent converter/regulater because they claim a constant power consumption of 0.84 watts on a input voltage range of 2.2 ... 13.8 volts.

Looking at the picture of this module I think this kind of converter could not be made as small as it is necessary for a Minimag modification but could be intersting for some other modifications where the VersaLux ULM is too big.


----------



## papasan (Dec 31, 2001)

very od how you got efficiencey rating that varied from 41 to 98% from seemingly small input voltage changes...that's a huge window...and looking at the output watts it doesn't seem to be regulating very well...what's the 'history' behind these numbers?...is this a starting and ending type set-up?...i would take one of these set-ups and take more detailed measurements, like every hour...


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## remuen (Dec 31, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*very od how you got efficiencey rating that varied from 41 to 98% from seemingly small input voltage changes...that's a huge window...and looking at the output watts it doesn't seem to be regulating very well...what's the 'history' behind these numbers?...is this a starting and ending type set-up?...i would take one of these set-ups and take more detailed measurements, like every hour...*<HR></BLOCKQUOTE>
You're right, the results are not satisfying. There are some reasons for that:

1. The original plan was to make a current controlled DC-DC converter with the very new LT1932 chip. The LT1613 is not intended to use in this kind but as we do not yet have a LT1932 Thomas (a friend in my company) made this booster in a similar way. 

2. I think the main reason because this converter with the LT1623 does not work as supposed is that the values of the inductivity and the capacitors are not right. Thomas made this first test circuit within a few minutes (during lunch) with SMD parts he had just in his drawer. The circuit has obviously to be optimized!

3. Another reason for the confusing results is also my measurement method. I had to use batteries (new and used ones). I switched the circuit on and measured after about a minute - as soon as the output values were almost stable. The main problem was caused by the used batteries - and you see that the bad effiency results are the ones with these batteries. In a few days I will be equiped much better with a regulated power supply and at least two digital multimeters. I hope I can make some improved measurements also with an improved test circuit. 
4. I noticed another weak point: To measure in- and output current I had to switch on and off what obviously influences the results. Wayne Johnson already suggested to measure the voltage over a 0.1 or better 0.01 ohm resistor in series with the load and then calculate the current. This method would be better especially with two DMM's because input and output current can be measured at the same time.

Another important thing: 
This DC-DC controller with a LT1613 or LT1932 chip is not the only one we are discussing in this thread. Jeff1500 and Wayne Johnson are both working on a circuit with the Max756/757 chips. I don't know how good they already work but I'm conviced that at the end we will at least have one (hopefully two) converters which work fine.


----------



## ElektroLumens (Dec 31, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>

To Wayne Johnson and Jeff1500:
------------------------------
- Did you make any further progress with the MAX756/Max757 chips? 
- How do your circuits work with 5 ... 10 LED's on an input voltage range of 1.8 ... 4.5V? 
- And could you already make the board smaller?
I am interested on some good news!

--------------------

<HR></BLOCKQUOTE>

remuen,

I have had very good success with the MAX756 and the MAX757 circuits. I am making 1 inch diameter circuit boards for both these chips. I have not tried driving Nichia's, as I've been using them with the Luxeon Star. For the white Nichia's, the MAX757 would be best because it has variable voltage output, so it can be set to 3.6 to 4 volts out. It's range is up to 5.5 volts out, but we don't want to set it that high for the Nichia's.

Driving the Luxeon at 3.4 volts, I have gotten up to 79% efficiency, which, considering the heavy load at 400mA, is not too bad.


The MAX757 would work just great with the Nichia's, and I'm sure because of the smaller current drain, the efficiency would be higher. I'll have to do a test with these LED's, next time I have some on hand. I am doing a mod for a friend, putting 20 white Nichia's in a 3 'D' cell flashlight. I'm considering putting the MAX757 in a 'D' cell dummy, and using the 2 'D' cells at 3 volts. Should be interesting. He also wants a similar flashlight with only 12 LED's in it. I prefer the Luxeon Star, but he wanted Nichia's, and it is an easy mod.

The one inch diameter disc is a nice size for modifying various flashlights. It is also only 3/8" tall. It is too big for the Mag Lite, though, but it fits in other flashlights I have just fine.

I am presently working on a 2 Luxeon Star flashlight. I am using a 3 'D' cell flashlight. I am making a step up regulator with a LT1302 chip. It will be 1 1/4 inches in diameter (disc), and will fit in the battery chamber with 3 'D' cells. I will set the voltage to 6.4 to 6.8 volts to drive the 2 Luxeons in series. The MAX757 will only go to 5.5 volts, and for the higher amperage required, I need to run higher voltages, so I needed to use a different chip. I'll let you know how this one works out as well. Two Luxeons at 350mA puts out 36 lumens, which is very bright. I am not sure what the lumens are at 400mA, but it is considerably brighter (and hotter!)


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## ElektroLumens (Dec 31, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*



Originally posted by papasan:
[qb]very od how you got efficiencey rating that varied from 41 to 98% from seemingly small input voltage changes...that's a huge window...and looking at the output watts it doesn't seem to be regulating very well...what's the 'history' behind these numbers?...is this a starting and ending type set-up?...i would take one of these set-ups and take more detailed measurements, like every hour...

Click to expand...

*


> <HR></BLOCKQUOTE>
> You're right, the results are not satisfying. There are some reasons for that:
> 
> 1. The original plan was to make a current controlled DC-DC converter with the very new LT1932 chip. The LT1613 is not intended to use in this kind but as we do not yet have a LT1932 Thomas (a friend in my company) made this booster in a similar way.
> ...




remuen, with this circuit, the LT1932, LT1613, you might want to try larger capacitors. I see you were using 10uF? Try using 100uF. Also you might want to try using a larger inductor, like a 100uH or so? You can also buy a ferite toroid core, and wind one of your own, which also works quite well. The huge variance in results might be because of inductor saturation? Anyway, just a thought. It doesn't hurt too much to go higher in values of inductance and capacitance, but to go under will cause a lot of problems.


I have gotten higher current supplies with the different circuit designs by 'tweaking' the inductance and capacitance. For the step up regulators, the output capacitor's size makes a big difference.


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## jeff1500 (Dec 31, 2001)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Jeff1500, I've made a drawing of the adapter. Could you publish it on your home page? (I am going to send it to you by email)*<HR></BLOCKQUOTE>

Here it is. 

http://edusite10.tripod.com/remuen/adapter.html


Looks like a good idea. I haven't made any circuit changes these last few days. I've been thinking about grinding the top off my leds to make them flat so I get a more even light distribution.


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## remuen (Jan 1, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
... For the white Nichia's, the MAX757 would be best because it has variable voltage output, so it can be set to 3.6 to 4 volts out. It's range is up to 5.5 volts out, but we don't want to set it that high for the Nichia's.

... The MAX757 would work just great with the Nichia's, and I'm sure because of the smaller current drain, the efficiency would be higher. I'll have to do a test with these LED's, next time I have some on hand. I am doing a mod for a friend, putting 20 white Nichia's in a 3 'D' cell flashlight. I'm considering putting the MAX757 in a 'D' cell dummy, and using the 2 'D' cells at 3 volts. Should be interesting. He also wants a similar flashlight with only 12 LED's in it. I prefer the Luxeon Star, but he wanted Nichia's, and it is an easy mod.

The one inch diameter disc is a nice size for modifying various flashlights. It is also only 3/8" tall. It is too big for the Mag Lite, though, but it fits in other flashlights I have just fine.
*<HR></BLOCKQUOTE>

I'm very intersted to see your results with Nichia LED's and your circuit with this MAX757 chip. Because I don't know if I ever will be able to solder SMD parts I'd like to make such a DC-DC converter on my own (in many cases the circuit board must not be as small as for the Minimag). Making such a circuit would give me some experience. 

BTW - am I right that this MAX 757 (and 756) circuit is "only" a stepup converter? How difficult is it to make a stepup/stepdown regulator?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
* 
remuen, with this circuit, the LT1932, LT1613, you might want to try larger capacitors. I see you were using 10uF? Try using 100uF. Also you might want to try using a larger inductor, like a 100uH or so? You can also buy a ferite toroid core, and wind one of your own, which also works quite well. The huge variance in results might be because of inductor saturation? Anyway, just a thought. It doesn't hurt too much to go higher in values of inductance and capacitance, but to go under will cause a lot of problems.

I have gotten higher current supplies with the different circuit designs by 'tweaking' the inductance and capacitance. For the step up regulators, the output capacitor's size makes a big difference. 
*<HR></BLOCKQUOTE>

Like you also Linear Technology suggests larger values especially for the capacitors:
C1 = 15uF
C2 = 22uF
L1 = 4.7uH
I'm not an expert but think the inductor should be larger to reach my targets. With 22uH the inductor Thomas has used is already larger but according your advice maybe a larger one would be necessary. We will try some other values for these parts but first we have to order them. It's a pity that I am not able to work with these SMD parts.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
...I am presently working on a 2 Luxeon Star flashlight. ... 
*<HR></BLOCKQUOTE>

It seems to me that all the experienced guys like you are working with the Luxeon Star. At the present time I am afraid using it because of the higher power consumption, the heat - and the costs if I would send such a LS to the LED nirwana ..... Maybe I'll try it later when I have some more knowhow and experience.


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## remuen (Jan 2, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Here it is. 

http://edusite10.tripod.com/remuen/adapter.html


Looks like a good idea. I haven't made any circuit changes these last few days. I've been thinking about grinding the top off my leds to make them flat so I get a more even light distribution.*<HR></BLOCKQUOTE>

Thanks a lot for "hosting" this drawing




!

BTW - I had really good results with polishing the plastic glass of my Swatch with tooth paste - it got really very clear. Maybe you have to try another tooth paste?


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## remuen (Jan 2, 2002)

---------------------------------

*Improvements on the epoxy adapter*

---------------------------------

After some tests I've made with this adapter - see my earlier post here http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=001221&p=6] and the drawing here http://edusite10.tripod.com/remuen/adapter.html - I had to make the following improvements on its construction: 

1. A week point in my first construction is the positive pole of the epoxy adapter because it can break. So I put a cupper bolt with 3mm diameter in the wax whole for the positive contact before I filled it with epoxy. The positive epoxy pole has now a cupper kernel and will no langer break. And the best thing - I don't have to drill a whole through the length of this positive contact to wire it to the place where the DC-DC convertor will be placed because I can solder the wire on the top end of this cupper bolt.

2. Before I put the washer (the negative contact of the adapter) in the wax shape I soldered a wire on it. With this I can again avoid to drill a whole through the epoxy (for wiring the negative pole).

3. Because of the cupper bolt and the wire it is now impossible to drill out the inside of the adapter to make room for a stepup regulator. So I made the adapter shorter (4 - 5mm). The shorter it is the more room you have for an stepup converter - *but please note point 4!!!*. As housing walls for the stepup convertor I now take a short piece of a plastic tube with very thin walls and with a diameter of about 16mm. 

4. I made the following experience with a Minmag clone which has a finer thread than the original Minimag - but I think it could happen with the Minimag too. 
If one screws the Minimag head on the body of the Minimag two things can happen:
a) the epoxy adapter will be screwed out (what I was afraid that it could happen)
b) If one screws the body to strong into the head the pressure on the epoxy thread is so high that the windings of this thread will not last very long. Not really a very nice thing!



I suppose it's caused because this kind of epoxy thread is not precise enough.

My solution for both problems is: 
After doing all the wiring and adjustments I took the epoxy adapter out again, put a bit of epoxy on its thread and screwed it back into the Minimag head. 

After doing this it is not easy to remove the adapter later (eg to put a improved circuit in it). I suggest to make a few more adapters just for future replacements. Then you can break the adapter to remove it. BTW, heating the adapter and/or the thread of the Minimag head makes it easy to remove the adapter but then the thread will be defect.

--------------------------------------------
_Because of this last weak point a metal adapter (made eg. from an 16mm aluminium tube) would be the best thing - but who can cut the necessary thread into it? And of course you still need some epoxy or whatever else to make the positive contact. _
--------------------------------------------

Finally after making all the above mentioned modifications the adapter works fine. The resistance for the negative contact (between housing and epoxy adapter) is 0 millohms! 

--------------------------------------------
_And last but not least this kînd of simple switch reminds me all the time on the best little flashlights I know: The ARC AAA! It has given me the idea to make the Minimag switch in a similar simple way and avoiding all the problems with wiring the stepup converter to the original bulb socket. And don't forget - the original Minimag switch is not the best one! It causes from time to time contact problems._


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## Daniel Ramsey (Jan 2, 2002)

I hate to look a litle green here but may I ask where I can by this 757 dc/dc controller? I too want very much to use the Luxeons in some future projects and right now I have made 7 circuit boards that fit in the head of a D or C size 3 cell maglight. I have also bought 200 Nichia NSPW500BS LEDs to use for my mods. From what info I am getting 1 Luxeon is about equal to 12 6400 mcd Nichias (the mcd rating is what Nichia rates these) so its an easy mod for 12 LEDs at $2.05 each or the better mod of the Luxeon (about $14-15)with a dc/dc controller ($25 or less on amount bought) and then a smaller flashlight housing like a 2C cell or even a single like the Arc LS. What I plan to do is just make a drop in module for any Maglight per the battery (2-3-4 cells)and just sell these as a replacement to the efficient lighting source also with Lithiums for our extreme cold weather environments here in Alaska.Ideally i want to make an easy drop in mod for the 2AA Mini mag because it fits in a holster. Many many of my friends and coworkers need good long battery life and operations of a flashlight during our long winters when daylight is just a few hours a day.Myself I have to inspect concrete mixers and operations at the batching facility in total darkness for half the day at times and so far I have used a Nightbuster 8X which has already burned out 1 LED, sadly it cannot be replaced without destroying the lens and I do not reccomend these to anyone, I do have a Nightbuster 18X which is hefty in size identical to a 3D maglight, it was $129.00 from Glowbug.com,the light is good and spead out but ideally I want a smaller package hence the MiniMag. Perhaps in a few months I may buy a metal lathe and turn my own housings ( I am a machinist as well) that would be just the right configuration for the dc/dc board,Luxeon,lithium battery.And this light should have a hands free cip as well or bendable gooseneck.


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## ElektroLumens (Jan 2, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*I hate to look a litle green here but may I ask where I can by this 757 dc/dc controller? *<HR></BLOCKQUOTE>

Daniel,

You can get free samples from MAXIM of the MAX757, but you cannot purchase smaller quantities than 1000. The MAX756 can be purchased from DIGIKEY, in any quantity. If you are going to use the regulator with the Luxeon, the MAX756 works okay.

The MAX756/MAX757 also have a cold weather version of the chip, which is what you would need in Alaska.

I also have made a 'D' cell dummy, with the MAX756 and the MAX757. works quite well. With the Mag lite, there is a problem of grounding the regulator as the body is anodized. A wire has to go back to the tailcap and it must be grounded there. Other than this, it works quite well. I did this in a 3 'D' cell MAG LITE, and put a luxeon star in the head. I shortened the relflector and put it in for cosmetics, and also it holds in the Luxeon Star/heat sink. Very very nice mod, and I am sure very long lasting. It seems just a bit brighter than 12 white Nichias being driven at 4.5 volts.

If you want one of my boards, email me. I have a one inch disc MAX757, and I also have a 1" X 2" board (which works fine for a dummy battery.) 

Wayne


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## remuen (Jan 3, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
...I want to see if I can get this circuit small enough to fit inside the head of the Mini Mag flashlight head. That will be a challenge.

...I am following this thread. I like the idea of a luxeon in a Mini Mag light.*<HR></BLOCKQUOTE>

Solving the mechanical issue with the switch/epoxy adapter I thougt already on a Minimag mod with a luxeon. As far as I can remember someone in the CPF has put a Luxeon into the Minimag. Therefore the Luxeon should fit into the head of the Minimag?

Making my adapter I had always the ARC AAA in mind. The ARC brought me again on an idea how to make some more space in the Minimag for placing a stepup convertor in it: 

One could shorten the inner part of the tail cap because after the mod the place for the replacement bulb is no longer needed. The spring could also be shortened so I think one could win about 5 - 8 mm more room in the Minimag body. The problem to solve is only the threat in the tail cap - see below for more about this issue.

Maybe that's already enough space for a little dummy battery with a very small regulator in it? 

If not one could completly open the Minimag body on his top end (where the bulb socket/switch is). With an changed version of my epoxy adapter I think one could get a room of about 10 - 12mm height and 15mm diameter for placing a regulator in the head. Onother thought: Maybe one could put the regulator completly into an epoxy adapter which works like a very short dummy battery?

It now depends on how much more room the Luxeon itself needs compared to the Nichia LED's.

Going this way it would be easy to solve the thread problem with the tail cap because one could glue it. To change the batteries one had to remove the Minimag head (like in the ARC AAA). Maybe with glueing the tail cap one could win 1 - 3 mm more room than without.

Hope these first few ideas will help you to make your Luxeon Minimag dreams come true. I'm also interested in the whole thing (a new target for later: Modifying a modified Minimag



).


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## John N (Jan 3, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Coherence made a 2 AA Mini Maglight -> Luxeon Star (LS) conversion in which he used such a tailcap switch from Brightguy. Here is the link: http://www.brightguy.com/detail.tpl?cart=10079523572784&sku=KROAM2A666 
*<HR></BLOCKQUOTE>

In case anyone wants to know what the tailcap switches from Brightguy look like, I took a few photos:

http://www.navitsky.org:4601/index/minimag/ 

-john


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## remuen (Jan 3, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*

....The LT1932 is limited to 40mA, so it won't power a Luxeon Star which requires 350mA. .....

....When hooking LEDs in series, don't skimp when it comes to the working voltage of the output capacitor. It should be at least double, if not triple, the combined LED voltage.

For example, to run four white LEDs (each 3.5 volts), multiply 4 x 3.5 x 3 = 42 volts, so a 50 WVDC capacitor is recommended.

The drawback is, the larger the WVDC, the more massive the capacitor is.*<HR></BLOCKQUOTE>


Duggg. the last few days I had a bit time to look closer into the LT1932 datasheet where I found the following informations:

- *Switch current limit 780mA *
(so if I understand everything right I think the LT1932 could be used for the Luxeon Star)

- And directly copied from the datasheet:
* Ceramic capacitors do not need to be derated. A 16V ceramic capacitor is good to more than 
16V, unlike a 16V tantalum, which may be good to only 8V when used in certain applications.*


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## Daniel Ramsey (Jan 3, 2002)

Thanks Wayne for that info! I started a sensation yesterday as I was leaving my day job as maintenance supervisor of a large concrete batching facility, first I made a stop at a fleet parts store and showed my friend a current mod of a 3D Maglite with 18 LEDs, well the customers at the counter were so impressed they wanted all the lights turned off in the store so as to see what it looked like. We could have just gone outside you know after all right now sunrise is around 9:45 am and sunset about 4 pm (further north the daylight is even shorter) here then I was asked for business cards and when I was going to sell these. then I stopped off at a Radio Shack for some supplies and again half the store was checking out my latest project! I am actually considering cutting into my day job at $18 an hour just to ramp up an assembly line! whew if there was any place that really needs an LED lighting its here in Alaska in the winter. Course on the other hand we do get over 21 hours of daylight during the summer, go figure. This is a good source of income during my slower winter months and I am really interested in finding some dc/dc controllers so I can used either 2-3-4 cell Maglites and just drop in the light module or sell it as a standalone bulb replacement so as to not cause legal issues with Maglite.Yeah I am going for the free samples and check that out instead of just having 12-24 LEDs without voltage regulation though it does tend to work because of the batteries resistance.A universal voltage sensing input from .6v or so up to 9v (6 cells) and then output of regulated 3.6-4.0v with appropiate ma for a Luxeon (300ma?) its that or individual controllers for 2,3,0r more more battery Maglites.


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## ElektroLumens (Jan 3, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*Thanks Wayne for that info! I started a sensation yesterday as I was leaving my day job as maintenance supervisor of a large concrete batching facility, first I made a stop at a fleet parts store and showed my friend a current mod of a 3D Maglite with 18 LEDs, well the customers at the counter were so impressed they wanted all the lights turned off in the store so as to see what it looked like. . . . *<HR></BLOCKQUOTE>


Daniel,
I guess Alaska is the place that really needs good long lasting flashlights! A 21 hour night? Wow! 

Most people I show my mods to, it's like, ho hum, that's nice. And then you tell them how much it costs to do the mod, and they are incrdulous that a flashlight could cost so much. Twenty LED's is $60, plus $18-20 for the Mag Lite, another $20 for the regulator: $100 for a flashlight!!?? A look of astonishment on their face, and bewilderment that anybody would pay more than $3 for flashlight!

I like the Luxeon Star LED, as it cuts out that huge expense of multiple LED's, anyway. One Luxeon is only $14, and puts out as much light as 18 LED's they say. I say about 15 LED's driven at 4.5 volts. Totally sufficient for walking, whatever.

Here in sunny southern California, flashlights are not a necessity. Even at night, well, in the city, all the street lights and all, who needs a flashlight, except for emergencies. 

I did a mod similar to your Mag conversion, I guess. I mounted 20 LED's in a 4 'D' cell flashlight. No need for resistors, and even without regulation, it lasts forever.

I have a 3 'D' cell Mag I just put a Luxeon in, with a regulator in a dummy cell. This is a very nice mod, and it probably lasts forever on the 2 'D' cells. I suppose if I lived in Alaska, I would be selling these things like hot cakes, huh?

The only thing is the cold weather. Be sure the components you mount on your circuits are rated for that cold weather!

I am currently doing a couple of mods for a friend, mounting 21 LED's in a 3 'D' cell flashlight, and also 12 LED's in a 3 'D' cell flashlight.

I have a homemade flashlight with 2 'C' cells, a MAX757 regulator on a 1 inch disc, and the Luxeon Star. This is my favorite flashlight right now. Just the right size. I have a aquaintance who owns a machine shop, and I'm going to see if he can manufacture me a nice flashlight housing for it.

Regarding Mag Lite patent infringment, maybe I'm wrong, but I don't think there is anything they can do to you for selling retrofit kits, or for buying their flashlights and modifying them and reselling them, as long as you don't claim their flashlight as your own design. ?? You are helping their sales by buying their product and then reselling it (slightly upgraded), right? It might be a good idea to check with a lawyer I suppose, anyway.

Wayne


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## Daniel Ramsey (Jan 3, 2002)

I never thought about the need for modern lighting until I came to these boards, yes on a standpoint about Alaska needing more efficient lighting during the long winter (6 months) and very short daylight hours I forgot to mention the many thousands that live above the Arctic Circle where its totally dark for *months!*(opposit applies in summer) This is becoming more that a personal hobby for me, I am aggressively pursuing the LED flashlight assembly and sales because everywhere I go someone wants one! And price is not an issue because we normally pay more fore everything up here.A persons life is in extreme jeopordy at night when its -40 and and many miles from a township if a vehicle or snowmachine breaks down, I am pushing the lithium batteries for power because they still have max voltage at -40, and LEDs are unaffected.


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## Daniel Ramsey (Jan 3, 2002)

While the general topic here has been about the Minimag I am mostly interested in a dc/dc converter, the MAX756/757 is at a good price but is it easy to work with for a beginner like me? Isnt there another one called a LM261 from National Semiconductor? If I was to use the Luxeon emitter fron Peter (I did order 4 last week) which would be the better or best one to use? I plan for something bigger like a 2 cell c/d Maglite.I would really appreciate some advice and I looked at the pdf file on the 757 and it mentioned an "e" version that indeed is rated for extreme cold just what I want, could you please take a minute and suggest which part number for me to order? Thanks a lot! I would like to add that the Garrity Stainless 2 AA has a nice little twist lock pop out switch on its tailcap that could be cut down and rethreaded just a hair so as to fit the Minimag but consider this first, it uses a 2/AA plastic tube as a battery holder, voila! remove it, you can use a wider battery than the AA=question, what is that? the 123 battery? if so this sounds like an ideal candidate for an LED conversion.


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## TrevorNasko (Jan 3, 2002)

ooh that sounds neat. gotta get one at wally world. describe the tailcap in more detail


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## ElektroLumens (Jan 3, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*While the general topic here has been about the Minimag I am mostly interested in a dc/dc converter, the MAX756/757 is at a good price but is it easy to work with for a beginner like me? Isnt there another one called a LM261 from National Semiconductor? If I was to use the Luxeon emitter fron Peter (I did order 4 last week) which would be the better or best one to use? I plan for something bigger like a 2 cell c/d Maglite.I would really appreciate some advice and I looked at the pdf file on the 757 and it mentioned an "e" version that indeed is rated for extreme cold just what I want, could you please take a minute and suggest which part number for me to order? Thanks a lot! I would like to add that the Garrity Stainless 2 AA has a nice little twist lock pop out switch on its tailcap that could be cut down and rethreaded just a hair so as to fit the Minimag but consider this first, it uses a 2/AA plastic tube as a battery holder, voila! remove it, you can use a wider battery than the AA=question, what is that? the 123 battery? if so this sounds like an ideal candidate for an LED conversion.*<HR></BLOCKQUOTE>

The circuit design for the MAX757 is relatively simple. It's not too hard to figure out. For Alaska, you definately need to go with the epa version, as the regular MAX756/MAX757 chip doesn't do well below 0 degrees centigrade.

It took me a long time to figure out how to get the MAX757 circuit to be small enough to fit on a one inch disc.

I have the Garitty AA flashlight you are speaking of. I just made my own homemade head for it, stuffed a one inch regulator disc in it, and a Luxeon star. I just used electricians tape to tape the new head to the flashlight body, because it is just a test and is temporary. For a permanent mod, the head could be threaded or epoxied on. This is a very nice flashlight. Looks funny, but it is very functional.

I have a LM2621 evaluation board, but I have not tried it with the Luxeon yet. It is small enough to fit in a 'D' cell dummy. Someone has done a mod around here, with a luxeon, and a LM2621 in a dummy, and someone also put the Luxeon in a headlamp, with a LM2621 regulator.

Whatever you do, be sure to really heat sink those Luxeons, it doesn't take much to burn one up. I make really huge heat sinks for the Luxeon. That's how I can run them at the higher voltages.

If I had a good camera, I'd show you the MAG 3 'D' cell mod I did with the Luxeon in it. On my high priority list is a decent digital camera.

I'll have a web page in a few months, and I'll be able to show my work on it. 

Wayne


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## remuen (Jan 4, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*While the general topic here has been about the Minimag I am mostly interested in a dc/dc converter, the MAX756/757 is at a good price but is it easy to work with for a beginner like me? Isnt there another one called a LM261 from National Semiconductor? If I was to use the Luxeon emitter fron Peter (I did order 4 last week) which would be the better or best one to use? .....*<HR></BLOCKQUOTE>

Daniel, here a few threads where they talked altready about the LM2621 and sometimes also about the Luxeon Star:

National Semiconductor LM2621 Evaluation Board  

UKE 2L to Luxeon Star and LM2621 conversion 

How best to go about this conversion?

Luxeon Star & Laser Diode Driver Module

Size of LM2621 Eval Board? 

My first mod (LS headlamp) 

It's sometimes not quite easy to gather all the informations on a specific topic. The CPF search function helps a lot - but then you have to look into each thread (found with this search function) wether the information is relevant ....


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## remuen (Jan 4, 2002)

--------------------------------------------


*Circuit simulator from Linear Technology*


--------------------------------------------

Wayne (and all others interested in making a regulator with LT chips):

I found a software performance simulator with integrated waveform viewer and more on LT's home page to make the development of circuits with different LT switcher chips (eg. LT1613 but not the LT1932) much easier. It is called SwitcherCAD III and you can download it here:

http://www.linear.com/software/


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## ElektroLumens (Jan 4, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Daniel, here a few threads where they talked altready about the LM2621 and sometimes also about the Luxeon Star:
*<HR></BLOCKQUOTE>


remuen,

Hey, thanks for this tip. I have the LM2621 evaluation board, and have been thinking of how I might mod it to be variable. This gave me the idea of using the small SMD potentiometer I have, and mount it on the board in place of R1, and replace R2. I suppose it's time to use this board, and see what it does with the Luxeon.


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## jeff1500 (Jan 4, 2002)

http://www.ResurgentSoftware.com/Perfect_LED_Light.html

Here's an application of the LM2621 idea. It has a lot of good information.

http://mikro.e-technik.uni-ulm.de/persons/lares/LED_flashlight.html#V2

This is the Ulm minimag conversion. I still don't understand how they work with circuit boards and components that small.

max1759 spec sheet with link to package dimensions

Remuen: Do you know how they solder such small connections? How about your friend Thomas. Does he know? Do they do it by hand with a big magnifying glass? How do they make the circuit boards?


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## Daniel Ramsey (Jan 4, 2002)

Here is a reply about the Garrity Stainless 2AA flashlight, well I bought some 123 Duracells this morning and removed the snap cartridge battery holder from the flashlight, it just falls out, I supposed because its stainless they decided on a real thin wall thickness compared to the thicker aluminum Minimag, you may have to slightly fille of a thread burr but the 123 fits very nicely with no rattle. So what I am planning to do is measure the right resistor for now and cut a spacer out of some 5/8 dowell, drill a hole in the center for the resistor, make or solder buttons on both ends and use that because now we have 6v instead of 3v with shorter batteries ( I may cut and rethread tube shorter later) As far as the LEDs there is a moderate amount of room without removing the lense and I think even more room than the Minimag. The tail cap is plastic and the threads are possibly .5 millimeter(.020 or less) larger than the tail end of the Minimag. Since its plastic cutting the threads smaller is no problem.Brownells may have those dies if anyone needs such, I use similar ones to thread for muzzle brakes on my rifles. The details of the switch is to rotate until it pops out (quarter turn, left or right) and then from that point it is push/push on/off, you can then push and turn to lock it in and off so as to put in a holster or pocket, really nice though I wish it was metal. The whole thing retails for $8.95 (Alaska) may be cheaper in the lower 48. I am pursuing this as a 4 and 8 version (Luxeon?) LED to sell, with the extra space using two 123's its very possible to put in a dc/dc regulator. BTW for a tailcap switch check out Brownells for a tactical light switch, since I am also a hunter and gunsmith I seem to recall seeing one there for tactical purposes such as shotguns, if not check out CheaperThanDirt which is a clearing house for law enforcement and sportsman, one more isBhotac Tactical another source that I buy from.


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## Daniel Ramsey (Jan 4, 2002)

And special thanks to Wayne and Renee' for their help here, I have only been here a week I think and about the same time on the LED flashlight idea, its just that so many of us here in Alaska need exactly what we are talking about! Many many homesteads out in the bush (way away from roads and services) have only generators or kerosene lanterns, most must use outhouses and send children to school with moose and bear about,I know because I have had to fire warning shots to scare the moose off to send my kids to school because they lick the road salt from our vehicles, go figure 5 hours of daylight during winter at my latitude and progressively less further north until you get about 200 miles north of Fairbanks where the sun sets in Nov and rises around March, thats farely true and its the opposite of course in the summer. I can go to bed at 11:30pm in june and get up at 4am and both times the sun is still up. Thats Alaska.


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## **DONOTDELETE** (Jan 4, 2002)

If you're looking for something small, efficient, and affordable for driving a Luxeon Star, the Zetex ZXSC300 looks very promising.

Although its small size is an asset in most applications, it is more difficult to solder than the MAX756/757, but not nearly as hard as the LM2621 or similar chips.


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## Daniel Ramsey (Jan 4, 2002)

You have a valid point there Duggg, I just bought another 15 watt soldering iron just for those smaller circuits, I would rather work large for now because I am new at this though I went through a slot machine repair school many years ago in Las Vegas I am just a heavy equipment mechanic right now with model railroading and gunsmithing for my main hobbies. That is why I like the full sized maglites they are excellantly built, have a trademark name and nice feel. And later but soon when I become better I will do smaller dc/dc boards like what Peter has in his Arc LS.that is the push right now, affordable circuit boards to optimize LED drive and extend battery life beyond current low level yields that we have taken for granted many many years. If we can be successfull on a curve the same as the advancements in computers of the last 5 years we should soon have portable lighting that will totally dominate the future of the lighting industry. I see within 5 years LED replacement bulbs on supermarket shelves and lowered use of home or work kilowatts usage that will dramitically chage the landscape of having to buy bulbs once a month, someday soon when a family buys a house the next time they change a light bulb the kids are in 3 grade! 10 year or even longer theoretically if an LED is maintained at a constant voltage. Sorry if I got up on my soapbox but this whole idea of using LEDs is just too new, its like suddenly finding a free transister in your mailbox, and its in the year 1945!


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## remuen (Jan 4, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
Remuen: Do you know how they solder such small connections? How about your friend Thomas. Does he know? Do they do it by hand with a big magnifying glass? How do they make the circuit boards?*<HR></BLOCKQUOTE>

Jeff1500, I'm in the same position as you and asking me all the time how do they do it. 

For your background information: In our company we are only developping our hardware means designing circuits and circuit boards but then we let it produce outside in series up to 1000 pieces. 

But for the development process they have obviously to make some hand made circuit boards. For this Thomas uses such a labor board we already discussed. Then he solders the parts just by hand - without any magnifying glass and without a "third hand" or anything else! I looked him over the shoulder doing it this way. After soldering all he then checks the circuit board with a magnifying glass eg. to avoid short cuts. Thomas (and another guy here in the company) say it's just experience and the right feeling




! Even I saw it with my own eyes I can hardly believe that one can do it this way. 

I cannot imagine that I ever could solder such SMD parts - but it seems there is only one way to find it out: Someday I'll try it with such a test board and some cheap SMD parts because I would like to make my own circuit boards. But one thing is for shure: I will use a third hand and a magnifying glass!


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## **DONOTDELETE** (Jan 5, 2002)

I was soldering a small 3x2.5mm SOT-23 diode this evening using tweezers. Suddenly I had to sneeze, and next thing I knew, the chip wasn't in the tweezers any more!

Took me ten minutes to find it on the carpet on the other side of the room.

I too was intimidated by the small size of SMD technology---until I got a soldering iron with the right tip. Now it's a piece of cake! The right tools make all the difference.


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## remuen (Jan 5, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*I too was intimidated by the small size of SMD technology---until I got a soldering iron with the right tip. Now it's a piece of cake! The right tools make all the difference.*<HR></BLOCKQUOTE>
Hi Duggg
Thomas (the electrical engineer in my company) uses only a standard soldering iron with a thin tip. But in our company we have also a special soldering iron. They use it when they solder a first small series of the circuit boards for field tests. But this one is very expensive (I think more than $1000.00) and as far as I'm informed this special soldering tip (it looks like a very small spoon) is patented and available only for this SMD soldering iron.

I can hardly imagine that you payed such a lot of money for your soldering iron. Therefore my question: Which soldering iron did you buy and how much did you pay for it?


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## Daniel Ramsey (Jan 5, 2002)

That almost sounds like a small spot inductive weld similar to what I use with a MIG welder but on a much smaller scale, in my other hobby collecting brass HO locomotives there is some nice soldering tools including the inductive types (its called resistance soldering) where a small current is place through the tip of the iron while the back circuit tab is grounded, the amperage creates a spot weld and if the tab was pretinned I think this would work, then a layer of epoxy like Devcon 2 Ton or 5 minute would then secure the SMD tab and also seal the connection. Check out the tools at Micromark I have been using tools like this when I build my own trains for years. there is an article at Luxeon about assembly of the Luxeon Stars that is close to what I am talking about.


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## jeff1500 (Jan 5, 2002)

I went to Walmart today and got a Dorcy 4AA flashlight on sale for $3. It's not very graceful but it sure has lots of empty space for experiments. 

I want multiple leds with a dimmer. I'm thinking this will be good for prototype experiments with big clunky components. I'll work on elegant later.
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> posted by Duggg:
Suddenly I had to sneeze, and next thing I knew, the chip wasn't in the tweezers any more!<HR></BLOCKQUOTE>

That's a good story.


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## Daniel Ramsey (Jan 5, 2002)

Why not install a pot type of switch that would click say for 3,4 different outputs? I am working on such for use on a headlamp for dog mushers so they have low LED flood, high wide flood and a tight focussed long range beam. It would have a big enough knob or a lever so heavy mittens can move it easily.


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## **DONOTDELETE** (Jan 5, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen asks,
*Which soldering iron did you buy and how much did you pay for it?*<HR></BLOCKQUOTE>

I found a new 20-watt Weller WP25P on Ebay for $14.51 delivered. That model isn't made any more, but you can probably find the current WP25 for around $25.

The secret is to replace the standard tip with an ST6 or ST7 tip.


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## jeff1500 (Jan 6, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*Why not install a pot type of switch that would click say for 3,4 different outputs.*<HR></BLOCKQUOTE>

Ya, something like that. Gotta look around for something that's not too big.


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## remuen (Jan 6, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*I found a new 20-watt Weller WP25P on Ebay for $14.51 delivered. That model isn't made any more, but you can probably find the current WP25 for around $25.

The secret is to replace the standard tip with an ST6 or ST7 tip.*<HR></BLOCKQUOTE>

Thanks Duggg for this info. I've an old Weller TCP24 (electromagnetical). I just sent a email to our local distributor asking if there is a tip according the ST6 or ST7 available for my soldering iron.


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## remuen (Jan 7, 2002)

*Test result with the improved epoxy adapter:
-------------------------------------------- *

I've testet the improved epoxy adapter I described in a earlier post in a easy modified Minimag clone (3 Nichia LED on 3 N cells, but no regulator) for a few days and switched this Minmag many hundred times on and off. I've also tried to break the adapter or especially its thread by screwing the Minimag head very strong on the body. The conclusion: *The epoxy adapter works perfectly*! No mechanical problems, contact resistance is still 0 milliohm - exactly what I have expected because of the contact pressure which is much higher than the original switch has and the self cleaning effect of the new contact.


*How to make the epoxy adapter easier
-------------------------------------*

I've improved the 'production' of this adapter. The first adapters I made directly in the Minimag head what causes some problems to remove the epoxy adapter after hardening. Now I make them in a wax shape. 

For this fill a small water glass with hot wax and let it get cold. To make the necessary shape remove the Minimag head, the bulb and the bulb socket/switch from the Minimag body (things what you have to do anyway if you want to modify your Minmag with such an adapter). Take a piece of round wood and prepare it in the way that you can put it from behind through the top end of the body. The wood should stick about 8 mm out of the top end (this will give the shape for the positive contact of the epoxy adapter) and somehow be fixed in the Minimag body. This prepared Minimag body is the positive shape you use to make the negative shape in the wax.

Now take the glass with the wax and a hot soldering iron (with an old tip) and smelt a bit of wax in the glass - about in the shape you need for the adapter. Then put the top end of the prepared Minimag body into this smelted wax. Important: Only about The O-ring should not be in the wax - only about half the thrThen either keep the body very quiet until the wax hardens (not easy to do) or fix the body with a ribbon, a wire or what ever else so that you get a very exact negative shape of the top end of the Minimag body. 

After the wax is hard use the soldering iron again to smelt the wax only very close to the thread (the Minimag body should stay fixed because of the wood which is still in the hardend wax). But be carefull to not smelt the O-ring. Doing this second smelting helps you to get a very exact wax shape of the thread! *I noticed that the thread of the epoxy adapter made in the wax shape fits better (tighter) than the one of the adapters made directly in the head.*

After the wax is hard again screw the Minimag body very very carefully out of the wax. Now you have an exact negative wax shape to make the epoxy adapter. Put first the copper bolt (for the positive contact) and then the washer (for the negative contact) very carefully in this shape and then pour the epoxy in it. After the epoxy is hard you can easy remove the adapter.

For making more than one adapter you have to make a new wax shape for each adapter - but that's fast and easy done.

I've made a new drawing of the improved epoxy adapter which shows also how to make this wax shape and the epoxy adapter in this way shape.

Jeff1500, it would be great if you would publish this new drawing under the same link http://edusite10.tripod.com/remuen/adapter.html instead of the old drawing. I send you the jpg-file by email. Thank you very much!


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## remuen (Jan 9, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
Remuen: Do you know how they solder such small connections? How about your friend Thomas. Does he know? Do they do it by hand with a big magnifying glass? How do they make the circuit boards?
*<HR></BLOCKQUOTE>

Jeff1500, I've made my first experience with soldering SMD parts. I'll come back on this topic and give you the informations I got in a short 'training course'.

Here just a first impression: The soldering itself is not easy but easier than one thinks. The challange begins already with placing such tiny 08/05 SMD parts or a SOT23 chip on the board and to keep them on its place while you try to solder it. 

IMO there is only one way to learn it: Buy such a laborotry board we already discussed about and a few of these SMD components and give it a try.


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## jeff1500 (Jan 9, 2002)

http://edusite10.tripod.com/remuen/adapter.html 

Here it is. I just refreshed the same address. That's very nice work. I'll study it for a while. 

Is the adapter fixed in the head? When you switch it on and off does the adapter move with the head? It looks like you install the led board / converter / adapter as a unit and then the unit locks into the head. Then the whole thing moves up and down to make contact with the battery top. The copper bolt slides in and out of the hole. Is that the way it works?

I got some parts on the way home from work today for my max757 version. I got a switching potentiometer to make a dimmer and some regular circuit board.


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## remuen (Jan 9, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*http://edusite10.tripod.com/remuen/adapter.html 

Here it is. I just refreshed the same address. That's very nice work. I'll study it for a while. 

Is the adapter fixed in the head? When you switch it on and off does the adapter move with the head? It looks like you install the led board / converter / adapter as a unit and then the unit locks into the head. Then the whole thing moves up and down to make contact with the battery top. The copper bolt slides in and out of the hole. Is that the way it works?

I got some parts on the way home from work today for my max757 version. I got a switching potentiometer to make a dimmer and some regular circuit board.*<HR></BLOCKQUOTE>

Jeff1500, thank you very much for placing th drawing!

You're right, the adapter is fixed in the head and and moves up and down if you screw the head so it makes contact or not. Before you try to make such an adapter you should first read my earlier post on page 6 of this thread and especially also the describtion of the improvements on page 7. BTW, I think I should somehow bring the whole thing together into one post or one document, which will happen latest when I have my own homepage. In the meantime you have to go through the various posts.

The adapter itself has a thread which fits exactly into the thread in the Minimag head. The length of the copper bolt (positive contact) in my adapter is about 7 mm so it touches the positive contact of the battery before the washer (negative contact) touches the Minimag body. If you screw the head more on the body the copper bolt will first press the batteries a bit more into the spring in the tailcap which gives a better contact pressure means a lower contact resistance. The light is switched on as soon as the washer touches the Minimag body.

The more you screw the adapter from top into the Minimag head the more room you will get in the top end of the head to place the leds and the booster. But if you want your Minimag still sealed you have to look that the O-ring (fixed on the Minimag body) is still completly in the Minimag head if you screw it into the off position. After adjusting everthing in this way you should fix the adapter with some epoxy in the Minimag head.

As 'housing' for the booster and to fix the LED board I take a small piece of a plastic tube as described in the post with the improvements. The LED board can be glued either directly into the Minimag head or on this plastic tube to fix it (I would not take epoxy to fix these parts so you can remove it better). But in my version the adapter, the regulator board and the LED board aren't a single unit which I can screw as one complete unit into the head - that could be a next improvement! I put one thing after the other into the head because it seems to me that this is the easier way. 

BTW, the adapter part with the washer is only about 3 - 4 mm high to get as much room in the head as possible. Making this whole thing was a bit a 'try and error construction'. I had to make 6 adapters to come up to this final version which now works perfectly (IMO).


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## remuen (Jan 10, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
You definately need to get a digital voltage meter. However, for current measurements, you should use a resistor. Get a .1 ohm or a .01 ohm resistor. Connect it in series with the LED. Measure the voltage across the resistor. If you use a .1 resistor, multiply the voltage by 10, or if you use the .01 (that's what I use), multiply it by 100. The number will be your current being used. You need a DMV to do this though, because it's hard to tell with the analog. If you search the Zetex thread, you'll find Duggg and MrAl explaining this to me. 
*<HR></BLOCKQUOTE>

I discussed this issue with MrAl in the Zetek thread because it was not really clear to me why using these resistors. I thougt using two digital ammeters which I could let in the circuit would be better and simplier than using these resistors. Here the most essential of what MrAl explained to me and what changed my mind:

_It's better to use a resistor of about 0.1 ohm to measure current because:
1. you know exactly how much resistance you are inserting into the circuit.
2. ammeters might have too high an internal resistance.
3. eliminates extra lead length associated with typical ammeter leads.
4. eliminates any extra ammeter inductance._

The whole explanation can be found in the Zetek thread.

For future measurment I'll take a 0.1 resistor in series with the batteries/power supply and another one in series with the LED's to measure the voltage drop across these resistors and then calculate the current.

The formula to calculate the current is: I = U/R 
In this special case one can calculate:
- Voltage across resistor x 10 = current in amps or
- Voltage across resistor x 1000 = current in milliamps

Because I didn't have such 0.1 ohm resistors and it's not easy to get them I switched ten 1 ohm 0.25 watt resistors (which are very small) parallel together. It is recommanded not to use eg. a wired 10 watt shunt resistor because of the inductivity such a resistor has.

Point 3 and 4 af MrAl's explanation could (but must not) be a reason for wrong values in my former test results, because we're working with a switcher IC that is working with a high frequency above 1 MHz and I used a old analog ammeter which has for sure some unknown inductivity. Any inductor or capacitor can influence the function of the circuit.

I discussed this issue also with Thomas. He agreed on MrAl's explanations. And additionally he told me that *all circuit boards with this kind of switcher ic should always be as compact as possible* because of the same reason - the smaller the better they work.


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## ElektroLumens (Jan 10, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*

And additionally he told me that all circuit boards with this kind of switcher ic should always be as compact as possible because of the same reason - the smaller the better they work.*<HR></BLOCKQUOTE>

Remuen,

I purchased a .1 ohm SMD resistor, and mounted it on a small piece of scrap PCB. I soldered 2 wires to this resistor board, and use this is series with the circuit, for testing the current. I found that I must test the current right on the small resistor board to get accurate readings. This has worked very well for me.

As regards size of the circuit and placement of components, I think it is extremely important. I found that by reducing the size of the circuit board to only 1", with all the components so very close together, the board acutally is able to pump out more current, than when I place this very same circuitry on a 1" X 2" board. I'm talking about a difference of 300mA as opposed to 390mA, at 3.3 volts. I had to really tweak the bigger board to come up to the 390mA of the smaller board. SIZE MATTERS! The smaller the better.

Wayne Johnson


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## jeff1500 (Jan 10, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*

Because I didn't have such 0.1 ohm resistors and it's not easy to get them I switched ten 1 ohm 0.25 watt resistors (which are very small) parallel together. It is recommanded not to use eg. a wired 10 watt shunt resistor because of the inductivity such a resistor has.
*<HR></BLOCKQUOTE>

This is a good comment.


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## remuen (Jan 10, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*... I found that by reducing the size of the circuit board to only 1", with all the components so very close together, the board acutally is able to pump out more current, than when I place this very same circuitry on a 1" X 2" board. I'm talking about a difference of 300mA as opposed to 390mA, at 3.3 volts. I had to really tweak the bigger board to come up to the 390mA of the smaller board. SIZE MATTERS! The smaller the better.
*<HR></BLOCKQUOTE>

Wayne
Your experience proofes that these circuits must be small from the beginning even if it's only for prototyping ...


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## remuen (Jan 11, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*I found that by reducing the size of the circuit board to only 1", with all the components so very close together, the board acutally is able to pump out more current, than when I place this very same circuitry on a 1" X 2" board. I'm talking about a difference of 300mA as opposed to 390mA, at 3.3 volts. I had to really tweak the bigger board to come up to the 390mA of the smaller board. SIZE MATTERS! The smaller the better.
*<HR></BLOCKQUOTE>

Wayne
I think the pictures in papasan's thread the MAX757 one inch disc revealed inside show your MAX757 converter? Really nice - and best of all it works!!

I've two questions on your MAX757 converter:

1. Is there any chance that you can make the board smaller to bring it into a 2AA Minimag? On the first picture it seems that there is still some free space on this board?

2. I'm interested to make some experiments with the MAX757 on my own because I hope it's a bit easier for me as a beginner than with the the SMD chips LT1613/LT1932. So I can make some first practice. Therefore it would be very interesting for me to see your MAX757 circuit design (drawing). Could you give me some more information on it? BTW, I hope I can get the MAX757 chip easier than the LT1932.

Thanks in advance!


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## jeff1500 (Jan 12, 2002)

Here's my max757 dimmer. I got it working today. Fixed R2 keeps it from overloading the leds.

http://edusite10.tripod.com/led3/dimmer.html

I'm using it to replace R1 and R2 in this circuit:

http://edusite10.tripod.com/led3/max757.html

It's very helpful for voltage and current sensitivity studies. I have six white leds. Four of them like to run at 3.5 volts. Two, that I bought at a later date, like to run at 3.7 volts.

The current ramps up very quickly above these voltage values. Maybe that's the advantage of current regulation instead of voltage regulation, but then you have to jump up to a much higher led series voltage. I may use some 10 ohm resistors to even things out if I run them all together.

My desktop prototype is a little bigger than everyone elses. It fits in a small shoe box, but it still seems to work fine. I think one of these days I'll be able to stuff it into a Dorcy 4AA flashlight.


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## ElektroLumens (Jan 12, 2002)

Rene,

Well, I had a heck of a time getting the circuit as small as I did. One thing you have to remember is that the chip does produce a small amount of heat, and does need a small amount of heat sink, which is provided by the copper on the board, which is why I chose the 2oz copper clad board. If the size comes down more, than a small heat sink might be placed on the IC. You look at the board, and see a lot of room but you should look at it without any magnification. Also, I put all the components on one side, except for the MAX757 chip, which is on the flip side, not pictured. In that open space you see is where the MAX757 chip is. Now if I used 2 sided copper PCB, some of the components would fit on the other side, and I suppose the size might come down a bit, but I don't know how much more. A fellow CPFer kept prodding me on to get it smaller and smaller, to the one inch disc. This is suitable for use in many applications, but not for the MINI MAG. I think perhaps for the MINI MAG, a smaller regulator chip might be chosen?

email me at <[email protected]> I don't have your email at home, to answer the question you had emailed me about earlier. When I get your email, I'll give you the answer.

Wayne


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## remuen (Jan 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Here's my max757 dimmer. I got it working today. Fixed R2 keeps it from overloading the leds.

http://edusite10.tripod.com/led3/dimmer.html

I'm using it to replace R1 and R2 in this circuit:

http://edusite10.tripod.com/led3/max757.html
*<HR></BLOCKQUOTE>

Jeff1500, thanks for your Information on your MAX757. I'm a bit short in time for the moment but will tomorrow or on monday look into this circuit and try to understand it. I'm quite sure I'll have some questions about it.


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## remuen (Jan 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*

Well, I had a heck of a time getting the circuit as small as I did. One thing you have to remember is that the chip does produce a small amount of heat, and does need a small amount of heat sink, which is provided by the copper on the board, which is why I chose the 2oz copper clad board. .....

.... A fellow CPFer kept prodding me on to get it smaller and smaller, to the one inch disc. This is suitable for use in many applications, but not for the MINI MAG. I think perhaps for the MINI MAG, a smaller regulator chip might be chosen?
*<HR></BLOCKQUOTE>

Wayne

It's already 12:15 pm here in Central Europe! I read about your time problems in another thread. It seems we have the same problem: I'm working in a fulltime job 45 - 50 hours per week, have a family with two children and also some church activities. And also Thomas is very busy ...

So it's a pitty that your MAX757 does not fit into the Minimag. This would at least help me. It seems that I have to go more into the whole matter to make such a smaller booster for the Minimag on my own. Of course Thomas will furtheron help me but not doing the whole job for me. 

BTW, I didn't want to offend you because of the size of your circuit board. I thought that there must be a reason for the 'unused' room on your board because you wrote several times that it was hard to bring it down on this size. Your argumentaion because of the heat sink seems very important to me and I will keep that in mind in case I can make my own booster! Thanks for this hint!


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## ElektroLumens (Jan 12, 2002)

Hello Rene,

No, I'm not offended at all. My target was a one inch disc. I had no intention to make one smaller. 


I did order some 2 sided PCB board, but the place I ordered it was out of stock, and didn't include it in my order. Perhaps when I get my hands on some, I might pursue an even smaller disc, that might work in a Mini Mag, using boths sides of the board.

I wanted to make a regulator for use in a flashlight head like the Garitty AA, which is around 1 inch in diameter. There are a few others in this size range. I also wanted to make a disc to sandwich into a 'C' or 'D' cell flashlight battery compartment, and also to make something to be used as a 'D' cell or 'C' cell dummy. And I have accomplished this goal.

I also have someone designing me an aluminum flashlight housing for the Luxeon Star, and my regulator. It might be out of my fincancing range to do something like this, but I'll find out soon. To me the 2 'C' cell size flashlight, with the Luxeon, is the perfect size.

Wayne


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## remuen (Jan 12, 2002)

Hi Wayne

I have some other projects too eg. modifying a small headlamp (I now own a Petzl Tikka with only 3 LED's) for running and an old 2D flashlight. But I like the small flashlights much more because I can them easy take with me. That's why I have always an ARC AA (LE) with me. And as I own 3 Minimags and 2 Minimag clones this is my first priority. Because of the size I will concentrate on the LT1613 or LT1932 chip for this project.

I'm quite sure I will make some other mods too. I already think about this old 2D flashlight with a Luxeon star - and maybe also a Minimag with this Luxeon Star. But then I would need another booster for the higher current. And as I start up really from the very beginning I think I should give a try to the MAX1674 for this 'high current booster'. Maybe the Zetek would be another solution but it seems to be a too big challange if I look what these fellows in the Zetek thread are doing with the inductors. That's far above my level of electronics.

Is the aluminium flashlight housing the improved version of your 'copper pipe' flashlight idea?


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## remuen (Jan 13, 2002)

Wayne Johnson, Jeff1500 and everyone looking into this post:

I just took a bit a closer look into the MAX1674 datasheet. I'm not an expert but I think there are some points which make this chip interesting:
- its dimensions are smaller than the ones of the MAX757
- it needs much smaller capacitors 2 x 47uF instead 100 and 150uF
- it has a higher output current up to 0.5 or 1 amp
- it works from a lower input voltage (0.7 to 3.3/5 volts)
- Maxim promisis a higher efficiency up to 94%

IMHO this chip could be a good solution to drive 8 - 10 white Nichia's or one Luxeon Star even if the current limit is set to 0.5 amps (needs less heat sink). And the board could be made smaller so it could fit into a Minimag head.

What is your opinion about this chip? What did I overlook? Why is or isn't it one of the best chips to make a voltage regulated booster for most of our applications?


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## ElektroLumens (Jan 13, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Wayne Johnson, Jeff1500 and everyone looking into this post:

I just took a bit a closer look into the MAX1674 datasheet. 

What is your opinion about this chip? What did I overlook? Why is or isn't it one of the best chips to make a voltage regulated booster for most of our applications?*<HR></BLOCKQUOTE>

Rene,

Yes, the aluminum flashlight I'm making is a version of the 'pipe' flashlight. The pipe was just a prototype to show people what it could or should be. I have this out on loan so I don't have it for photos either. It is with someone who is evaluating it for the aluminum flashlight housing. It will not be in the same category as the ARC LS, nor is it meant to compete with it. It will be bigger, with 2 C batteries, and the tooling will not be as sophisticated or as elegant. Just a knock around tool box flashlight, or something to use for walks, whatever. A longer battery life and cheaper batteries flashlight.

The MAX1674 is a good choice, mainly for the smaller size, and better claimed efficiency, and of course, getting more current. I will take a closer look at the specs on this regulator, as it has been recomended to me by several others. 

I hope to get a few samples, and I'll design a circuit board, to be as small as possible, and perhaps this will work with the MAG Lite?

The claimed efficiencies is like the claimed battery life of certain flashlights. They say 2 or 3 hours for a certain flashlight, but actually you get 1 hour of bright light, and 2 hours of faded light. The efficieny of some regulators falls, the more that is demanded of them, so far as I can tell. The claimed efficiency for the MAX757 is 84%, but that is at lower current output. When I demand 390mA from it, I get only 74%. Of course, there might be ways to improve this?

By the way, I have the MAX757 working even from .5 volts (from 2 AA's, so each battery is down to .25 volts!). The Luxeon was dim, but the regulator is working way below the specs value?

Wayne


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## **DONOTDELETE** (Jan 13, 2002)

Just some clarification as to why 0.1 ohm is the "ideal" value for a current sense resistor.

With a current of 500mA, a 1-ohm resistor dissipates 250mW, which is a huge fraction of the input power, and it would significantly influence the performance of the circuit.

Now, a 0.01-ohm resistor only dissipates 2.5mW at 500mA, but the voltage across it is only 5mV---a challenge for most voltmeters to read with any accuracy.

0.1 ohm is a good compromise. 25mW is negligibly low power, and 50mV is much easier to measure accurately.


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## remuen (Jan 13, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
... The claimed efficiencies is like the claimed battery life of certain flashlights. They say 2 or 3 hours for a certain flashlight, but actually you get 1 hour of bright light, and 2 hours of faded light. The efficieny of some regulators falls, the more that is demanded of them, so far as I can tell. The claimed efficiency for the MAX757 is 84%, but that is at lower current output. When I demand 390mA from it, I get only 74%. Of course, there might be ways to improve this?
*<HR></BLOCKQUOTE>
The claimed efficiency at 200mA is 87% for the MAX757 and 94% for the MAX1674. There are obviously some parameters like input voltagge and output current which influences this figure.

Hey, great that your MAX757 gets down to 0.5V. That's what I expect a good booster to do to squeeze the batteries completly! The one in the ARC AAA does it also (I've made a runtime test with it on a low battery). Can you still restart your MAX757 circuit at this input voltage? The ARC AAA doesn't restart below a certain voltage except you're waiting until the battery has recovered.


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## ElektroLumens (Jan 13, 2002)

Rene,

If the claimed efficiency of the MAX1674 is 94%, and it comes even close, that's a very attractive feature, and makes it something worth pursuing. We should both work at it, and see what we can come up with, and compare our results? Perhaps first get something working, and then work on reducing the size. If the use is for 10 LED's than the 200mA is the figure to work with. I would shoot for 350 - 400mA myself, to power a Luxeon.(For the cost of 10 LED's, I can purchase 2 Luxeons, which each are brighter than 10 LED's.) I have still not looked at the specs, but I have them stored in my computer, and intend to look at them soon. I just need to find the time to design and etch the board, and of course, assemble the board. 

I would like to know about using the electrically conductive epoxy. Seems like it might be a good choice. No soldering! I would like to experiment with this method with these tiny parts. I believe it is 70% silver, mixed with epoxy.

Wayne


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## remuen (Jan 14, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
If the claimed efficiency of the MAX1674 is 94%, and it comes even close, that's a very attractive feature, and makes it something worth pursuing. We should both work at it, and see what we can come up with, and compare our results? Perhaps first get something working, and then work on reducing the size. 
*<HR></BLOCKQUOTE>

I just ordered samples of this chip. So I am willing to get into this work. Let's do it! (For me: Let me learn it!)

I think we should agree on a certain target we want to reach. My (hidden



) target is to have only one small booster circuit (should fit into the Minimag head) for all our common applications means from using a single cell up to 3 cells and for a load like a single LED driven with 40 milliamps and up to 400 - 450 milliamps for a Luxeon Star or 10 LED's. As I'm a beginner I still hope this is possible.

We should settle a few main values because the circuit would obviously not be able deliver an output 500 mA at 4.5 volts on an input voltage of only 0.7 volts and reach an efficiency of 94%. *You have much more experience to say which values would be a realistic target*. IMO at the end we will have a table with some values as targets like this:

Vin | Vout | Iout
0.7 | 3.6 | 100
1.5 | 4.5 | 200
3.0 | 4.5 | 450
4.5 | 4.5 | 500

I would suggest that you are going to make some measurements with your MAX757 circuit with different loads and input voltages - something like I did with the LT1613 circuit board two weeks ago - unfortunatly with a very poor equipment. Then we will have something to compare with. 

BTW, in a short time I will be much better equiped to make such measurements because I've will have three digital multi meters (the cheapest one for $8, a second one for $18 and the third one for $30) and an adjustable power supply 0...30VDC. I have already the $18 DMM, the other devices should arrive in the next few days. I ordered them more than 2 weeks ago. And last but not least: I do have the two 0.1 ohm resistors to measure the in-/output current.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
If the use is for 10 LED's than the 200mA is the figure to work with. I would shoot for 350 - 400mA myself, to power a Luxeon.(For the cost of 10 LED's, I can purchase 2 Luxeons, which each are brighter than 10 LED's.) ...
*<HR></BLOCKQUOTE>

For the moment I concentrate on the Nichias only because I've more than enough to do to get a good booster. And with the LED I don't have problems with heat sink even I will drive them up to 40 milliamps which means 280 mA for 7 and 400mA for 10 LED - so it's about the same target current as yours. 

BTW, the longer the more I think about using the Luxeon Star in the future. But first I want to complete the Minimag mod with 5 - 7 LED's. Using a Luxeon star in this mod would give me some new mechanical problems to solve. So I am going to take one step at the time.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
I would like to know about using the electrically conductive epoxy. Seems like it might be a good choice. No soldering! I would like to experiment with this method with these tiny parts. I believe it is 70% silver, mixed with epoxy.
*<HR></BLOCKQUOTE>

I don't know this electrically conductive epoxy. But I hope you will give me some information about it if it's a good thing! In every case it seems interesting. But I'm not quite sure wether one can use it with the SMD parts. I'm a little experimenting just to place these tiny parts on a board and make some wire connections. A hard job if one is not skilled. Using this special epoxy now as a beginner I suppose I couldn't use the board any more because after placing the parts there would be more short cuts on this board than anything else ...





It almost seems to me that soldering is the easier part and placing the components and making the additional wiring the harder one!

Let's do it!

René


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## remuen (Jan 14, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
With a current of 500mA, a 1-ohm resistor dissipates 250mW, which is a huge fraction of the input power, and it would significantly influence the performance of the circuit.

Now, a 0.01-ohm resistor only dissipates 2.5mW at 500mA, but the voltage across it is only 5mV---a challenge for most voltmeters to read with any accuracy.

0.1 ohm is a good compromise. 25mW is negligibly low power, and 50mV is much easier to measure accurately.*<HR></BLOCKQUOTE>

Duggg, thanks for your hint. I would have this problem with my multimeter when using 0.01 ohm resistors because the lowest range is 2000mV means I could measure 1mV which would be a current of 100mA..... - but in a few days I will get a better DMM with a resolution of 0.1 mV.

BTW, what do you as one of the ZETEK experts think about the MAX1674 chip?


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## remuen (Jan 14, 2002)

Hi Wayne

I just made some calculations I didn't think to make before (Thomas has given me a hint). It will help us to come to some target values. It deals with the power consumption or better the input and output energy.

If we look on the circuit the input and the output energy is in the ideal case the same (100% efficiency). If we have for example a load which consumpts 400mA at 4 volts this is an output energy of 1600 mW. In the theoretical ideal case the input energy is the same. If our input voltage would be only 3 volts then the input current should be 1600 / 3 = 533 mA.

*But now we have to consider two very important points:*
1. As we work with a switcher the input current is not steady - it is pulsed. This means on the input we have during the switching periods a much higher current than these 533mA. We have to multiply it with about 2 = 1066 mA. But the MAX1674 has a current limit of 1 amp = 1000mA. 

2. We have not the ideal case and therefore the efficiency is not 100%. Let's say we could reach a good 90%. So that means we need an input energy of: output energy / 0.9 = 1600mW / 0.9 = 1777mW. Therefore the input current would be 1777 / 3 = 592mA x 2 = 1184mA. This is still above the current limit of 1000mA!

To find the max output current we have to make the calculation otherway round:

*with 3 volt input voltage*
The current limit is given by the MAX1674 and is max 1000mA means about 500mA considered that it is pulsed. Let's take an efficiency of 90%. So with 3 volts input the input energy is 500mA * 3 = 1500mW. The max available output energy is therefore 1500mW * 0.9 = 1350mW. With 4 volts output voltage we could reach 1350mW / 4 = 337.5mA

*with 2 volt input voltage*
The input energy would be 500mA * 2V = 1000mW. Output energy is 1000mW * 0.9 = 900mW. Output current with 4 volts output voltage therefore 1000mW / 4 = 250mA.

*with 1.5 volt input voltage*
The input energy would be 500mA * 1.5V = 750mW. Output energy is 750mW * 0.9 = 675mW. Output current with 4 volts output voltage therefore 675mW / 4 = 169mA.

So my target mentioned in my former post was a bit too optimistic!


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## ElektroLumens (Jan 14, 2002)

Hey Rene,

Wow! Great calculating! You're way ahead of me in this department. 

I need to do a test with the MAX757, with perhaps a 200mA load (10 Nichia's), and see what the efficiency would be. Most probably it will be much better than at 390mA with the Luxeon. As you point out, efficiency drops with heavier load requirements.

Now also consider the AA batteries, how much current can 2 AA batteries supply, at, say, 3 volts? Now, at 2 volts, or 1.5 volts? This is what I've seen. As the batteries get lower in output, their ability to provide the needed current is also quite a bit reduced. The batteries get real warm at lower input voltages, meaning there is a fair amount of internal resistance, and probably power waste. I don't think 2 AA batteries are the best choice for powering the Luxeon, although they do work. That's why I'm going with 2 'C' batteries in my own flashlight design. A 10 hour burn time as opposed to 2 hours.

I still think it would be interesting to do something with the MAX1674.


Wayne


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## **DONOTDELETE** (Jan 14, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Duggg, what do you as one of the ZETEK experts think about the MAX1674 chip?*<HR></BLOCKQUOTE>


Advantages:

1. The Maxim circuit can use a smaller inductor than the Zetex.

2. No external diode or transistor is required.

3. No ultra-low-value Rsense resistor is required.

4. It has a superior shutdown circuit to the Zetex 310.

5. The 1675's 280mA limit is more than acceptable for a string of Nichias.


Drawbacks:

1. You are dealing with an 8-pin device inside a 3x3mm MSOP-8 footprint---very difficult to solder.

2. With 2.4 volts in and 3.3 volts out, efficiency with the 1674 is only 85% at 300mA. And while the 1675 is 94% efficient with 2.4 volts in and 3.3 volts out, max output current is only 280mA---a tad low for a Luxeon Star.

3. The chip sells for $3.36 (directly from Maxim), which is much more expensive than the $0.81 Zetex 310.

4. The 1674 and 1675 are rated at only 330mW continuous power dissipation at 70°C. The implication is that they can handle more power at 40°C, but it's not clear how much more.


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## ElektroLumens (Jan 14, 2002)

Duggg, remuen,

I am looking at the graph chart for the MAX1674, and it seems like it is showing that with 2.4 volts in, and 3.3 volts out, at 300mA, it is getting 95% efficiency, and the line is still going up, as if 350mA would be 95% or a little more. Am I reading the EFFICIENCY Vs. LOAD CURRENT graph incorrectly? With only 1.2 volts in, at 350mA, the efficiency drops to 85% or possibly less. 


As I have said earlier, I have the evaluation board for this chip. I'll do an efficiency test with it driving the Luxeon. I hope also to do this with the LM2621 as well, but I need to modify it for 3.2 or 3.3 volts first.

Before I try to learn how to micro solder, I want to be sure the circuit performs as claimed.

Wayne


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## remuen (Jan 14, 2002)

Duggg, Wayne

Yesterday evening and this morning I was/I still am very short in time. I come back on your posts.


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## remuen (Jan 14, 2002)

Duggg, Wayne

First point: Wayne, I think it would be very good if you would make some tests and measurements with your eval board. We then can look wether my calculation is near the reality or far away. I think the efficiency rate of 90% I calculated with is too high - but it was a good figure to calculate .

I had no time to look into the datasheet. Therefore just a few thoughts as a kind of brainwriting:

- My idea was that the Zetek circuit would cover the high end range, mainly the Luxeon Star applications. The MAX757 or now the MAX1674 could be used for the mid range field means a Luxeon Star (not at its optimum) or 8 - 10 Nichias. The low range ( a few Nichias) would be covered by the LT1613 or LT1932.

- The circuit board should be small

- We should be able to use just a few standard components

So I think the MAX1674 is not exactly but almost that what I looked for - except the maximum current at a lower input voltage (see Duggg's post and my calculation). A higher current rate would be better. Another point: I would still prefer a solution with a current controller. It's much safer.

I just looked shortly into the Zetek thread and saw the efficiency measurements of papasan. I didn't study them but it seems that this Zetek circuit causes really a lot of problems which at least I could not solve - it's far beyond me what you Duggg and MrAl and papasan are doing. I'm also afraid that in the end this Zetek circuit needs components which are very hard to get (special inductor or capacitors with low or high ESR and so on).

So IMHO we should decide wether the MAX1674 can supply enough current for us or not. If not we had to look for another solution. If I get the samples from Maxim I will try to make a circuit board (hope I can do it or somebody will help me).


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## remuen (Jan 15, 2002)

Wayne

I had just a short discussion with Thomas in the coffee bar. He mentioned that it would be no problem to find a linear switcher in a SO-8 housing (like the MAX1674) for a higher current rate. I will look into this together with Thomas in the next days. Then we can decide what we're going to do.


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## ElektroLumens (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Duggg, Wayne

First point: Wayne, I think it would be very good if you would make some tests and measurements with your eval board. *<HR></BLOCKQUOTE>

remuen,

Well, total bummer! The MAX1676 evaluation board is not working. I forgot that a while back, I applied the power reverse polarity, and the input capacitor litteraly exploded. I just replaced this capacitor last night, but, alas, it still doesn't work. If you know someone who knows how to work on such small circuitry, you're welcome to it to try and fix it.

From looking at the small MAX1676 10 pin chip, I do not see how I myself could ever solder something so tiny!?

Do I understand correctly that you know people who work on such circuits? If so, I could mail this board to you. The regulator IC itself, or another component or components might be bad??

Wayne Johnson


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## **DONOTDELETE** (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*Duggg, remuen,

I am looking at the graph chart for the MAX1674, and it seems like it is showing that with 2.4 volts in, and 3.3 volts out, at 300mA, it is getting 95% efficiency, and the line is still going up, as if 350mA would be 95% or a little more. Am I reading the EFFICIENCY Vs. LOAD CURRENT graph incorrectly?*

I believe you are looking at a combined chart of the 1675/76, not the 1674, even though "MAX1674toc03" appears on it.

On the graph you will see the words "Ilimit=500mA", which applies only to those devices; the 1674 graph has a current limit of 1 amp, so its graph says "Ilimit=1A".

The reason the line stops at 300mA is that the 1675 cannot safely handle output current higher than that---actually 280mA, according to another chart.

*From looking at the small MAX1676 10 pin chip, I do not see how I myself could ever solder something so tiny!?*

Although the 1676 has 10 pins, the 1674 and 1675 only have 8, so they should be somewhat easier to solder.<HR></BLOCKQUOTE>


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## **DONOTDELETE** (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*I'm also afraid that in the end this Zetek circuit needs components which are very hard to get (special inductor or capacitors with low or high ESR and so on).*<HR></BLOCKQUOTE>

The "special" inductor saves a lot of money and greatly improves efficiency. It's very easy to make---you take a commonly available bead core, and you wrap a wire around it a couple of times. That's it!

As far as ESR goes, all DC/DC converter circuits are more efficient if you use low-ESR output capacitors.

If space is not an issue, or if cost is, simply use the largest WVDC electrolytic, as generally the higher the WVDC, the lower the ESR. If space IS an issue and cost is not, then you are best off going with a low-ESR tantalum like the Kemet.

Both of these "hard to get" items are available from www.digikey.com.


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## remuen (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
Do I understand correctly that you know people who work on such circuits? If so, I could mail this board to you. The regulator IC itself, or another component or components might be bad??
*<HR></BLOCKQUOTE>

Yes to your first question because we develop and produce the hardware for our security systems/access control systems on our own (btw, we are also programming our software).

I have to ask someone in my company if he would repair your eval board. In every case you had to deliver the switcher ic because we have for sure no MAX167x in stock and you know it's hard and expensive to get these chips here in Switzerland.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
I believe you are looking at a combined chart of the 1675/76, not the 1674, even though "MAX1674toc03" appears on it.
*<HR></BLOCKQUOTE>

Thanks for your explanation! I did not yet have the time to look into the datasheet, because I was all day off in a meeting. So I'll do it tomorrow and hope I will learn a bit more about switchers and how to read their datasheets.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
The "special" inductor saves a lot of money and greatly improves efficiency. It's very easy to make---you take a commonly available bead core, and you wrap a wire around it a couple of times. That's it!
*<HR></BLOCKQUOTE>

Sounds to me almost as easy as soldering SMD parts ......



. A question: Is the gap between papasans and your efficiency results caused by the different core? 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
As far as ESR goes, all DC/DC converter circuits are more efficient if you use low-ESR output capacitors.
*<HR></BLOCKQUOTE>

I know, but I saw a few post where this issue has been discussed. I didn't study them carefully so I didn't really understand what you have talked about the ESR. Sorry for that but because of my language problem I need more time to read and really understand. And often I'm a very short in time and then I read things only 'diagonal' (??? I don't know if this is understandable in English???)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
Both of these "hard to get" items are available from www.digikey.com. 
*<HR></BLOCKQUOTE>

Ok, I take back what I've wrote about getting these parts. 
Only one minor thing: For an order of a small qty of LT1932 chips Linear Technology would charge me with $28.00 only for the shipment. Maybe Digikey will do this too? Or does not deliver to Europe like many other US distributors? Uff - it's really hard and expensive to live here in Europe if one needs something from the USA. Only William from TTS does help us poor European guys and ships for only $5.00.
Conclusion: It's only maybe hard to get these items but it will be almost for sure very expensive.

It's now 12.55 PM here in Central Europe. Duggg and Wayne, have a nice evening! For me it's time to go to bed - in only five hours I have to get up again ...


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## **DONOTDELETE** (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*And often I'm a very short in time and then I read things only 'diagonal' (??? I don't know if this is understandable in English???)*

Perhaps you mean "skim"?

*For an order of a small qty of LT1932 chips Linear Technology would charge me with $28.00 only for the shipment. Maybe Digikey will do this too? Or does not deliver to Europe like many other US distributors?*

Digi-Key does ship internationally. According to their catalog, they charge $6 for international handling, plus the cost of flying a box from the US to Switzerland. You will also be responsible for any duties or taxes.<HR></BLOCKQUOTE>


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## remuen (Jan 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
Perhaps you mean "skim"?
*<HR></BLOCKQUOTE>

Thanks, that is exactly what I wanted to say (I looked into the dictionary)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
Digi-Key does ship internationally. According to their catalog, they charge $6 for international handling, plus the cost of flying a box from the US to Switzerland. You will also be responsible for any duties or taxes.*<HR></BLOCKQUOTE>

Ok, it's easy to get the items but still expensive. Some figures to proof it:

5 bear cores (eg. $0.50 each) $02.50
international handling $06.00
shipment (estimated) $15.00 
custom duties $00.00
taxes $00.25
handling costs of our 
postal services (because of the taxes) $08.00
*Total costs $31.75*

That's not really cheap. I hope you do now feel real compassion for us poor Europeans.


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## remuen (Jan 16, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*
Now also consider the AA batteries, how much current can 2 AA batteries supply, at, say, 3 volts? Now, at 2 volts, or 1.5 volts? This is what I've seen. As the batteries get lower in output, their ability to provide the needed current is also quite a bit reduced. The batteries get real warm at lower input voltages, meaning there is a fair amount of internal resistance, and probably power waste. I don't think 2 AA batteries are the best choice for powering the Luxeon, although they do work. That's why I'm going with 2 'C' batteries in my own flashlight design. A 10 hour burn time as opposed to 2 hours
*<HR></BLOCKQUOTE>

The C batteries are obviously much better for a Luxeon Star. But if one wants to have a smaller flashlight one has to use the AA's as well. I don't know how much current they can supply. In every case it's import to have the input capacitor to supply a higher peak current (with our DMM's we measure only an average current and not the duty cycle peak current. To see the peak current one would need an oszilloscope or whatever this thing is called in English).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jeff1500:
*
It's very helpful for voltage and current sensitivity studies. I have six white leds. Four of them like to run at 3.5 volts. Two, that I bought at a later date, like to run at 3.7 volts.

The current ramps up very quickly above these voltage values. Maybe that's the advantage of current regulation instead of voltage regulation
*
Originally posted by remuen:
*
Another point: I would still prefer a solution with a current controller. It's much safer.
*<HR></BLOCKQUOTE>

To proof this statement I made a row of measurements with some of my white LED's - this time absolutly correct with 2 DMM's and a good power supply. Here the main results:

---| LED1 | LED2 | LED3 
U(V) I(ma) I(ma) I(ma)
3.0 | 02.5 | 01.7 | 02.8
3.5 | 33.6 | 20.2 | 12.1
3.6 | 53.5 | 31.2 | 14.8
3.7 | 87.5 | 47.3 | 17.6

I did not expect such a 'bad' result. For your background information: LED1 and LED2 are Nichia's maybe produced in different production series, LED3 is possibly a Nichia too but I'm not sure (it looks exactly like the other ones). In every case LED1 would not live very long with this current. BTW, Jeff1500 mentioned a similar result with his LED's in one of his last posts.

I don't know whether the Luxeon Stars do also vary and how much. Has someone already make some measurement with them?? If they vary - even not as much as these LED's - a current controller is the only safe solution. And this means the MAX1674 could not be used!


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## remuen (Jan 16, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*Do I understand correctly that you know people who work on such circuits? If so, I could mail this board to you. The regulator IC itself, or another component or components might be bad??
*<HR></BLOCKQUOTE>

Wayne
If you don't find another - means more convenient - solution, then Phillipe who is in charge for our electronic lab would look into your eval board and repair it. 

As I said before we would need the MAX1676 chip (or whatever it is on the board) because we don't have such a switcher - and you know about our shipping and cost problems if we had to order the chip in the USA. So you had to send me the right switcher ic together with the eval board.


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## **DONOTDELETE** (Jan 16, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*$31.75---That's not really cheap. I hope you do now feel real compassion for us poor Europeans.*<HR></BLOCKQUOTE>

You forgot to add $5 handling fee to Digi-Key for your order being under $25






However, shipping could be much less than $15. Global Priority Mail to Switzerland is just $5 if the items can fit in a 15x25cm envelope and it weighs under 3.6kg.

Can't do much about your $8 in duties & taxes, though!





The good news is, bead cores are not all that exotic. Any large electronics store should sell them at much less cost.


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## remuen (Jan 16, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*You forgot to add $5 handling fee to Digi-Key for your order being under $25





However, shipping could be much less than $15. Global Priority Mail to Switzerland is just $5 if the items can fit in a 15x25cm envelope and it weighs under 3.6kg.

Can't do much about your $8 in duties & taxes, though!





The good news is, bead cores are not all that exotic. Any large electronics store should sell them at much less cost.*<HR></BLOCKQUOTE>

Sounds at least $5 cheaper!



So I do have self-pity with us as poor Europeans.


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## remuen (Jan 16, 2002)

I took the first (and only) prototype of the LT1613 circuit board and made some measurements - now with the right equipment (3 DMM and my new adjustable power supply) and also with the resistors to measure current. The results show that the booster is working as supposed - except the efficiency is far below of what it should be.

There are some reasons for this:
1. The resistor used to fix the current consumps some of the power
2. I think the inductor is to high with its 22uH.

I'm going to discuss the result with Thomas and look what he says.

More informations will follow.


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## remuen (Jan 17, 2002)

Here some results with the first prototype of the LT1613 booster circuit. It's still the same circuit from which I get earlier such confusing results. Obviously my equipment and my mesuring method was not as it should be. Now it looks much better:

*1 white Nichia LED*

```

```
*3 white Nichia LED in series*

```

```
*5 white Nichia LED in series*

```

```

As said earlier it works like a current controlled booster should work. Next target: Improving the efficiency! A pity that we loose 1.25 volts output (across R2 which is 39 ohms in series with the LED) which is about 41 milliwatts. But R2 is needed for the current regulation because this switcher doesn't have an integrated current controller.


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## remuen (Jan 18, 2002)

Wayne, Jeff
I said in an eralier post I will try it! And I did it tonight - I really did it!!






What did I do? Oh sorry: I've soldered a small SMD circuit board on my own - without any help! The circuit has no function. I put just a few resistors, capacitors, an inductor and a diode together and made some additional wirings between the components. The soldering joints (hope that is the right expression) seem to be OK.

I got only a short introduction from a guy in our company. I'll tell you more about it tomorrow and will give you the hints I've got.


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## papasan (Jan 18, 2002)

i made up a mag head replacement today using the zetex 310 ic...man, what a pain in the a$$...

it works fairly well but it's not as bright as i'ld have hoped...aparently i've reached the max that the coil i'm using will put out because lowering the Isense resistor (which should raise the output) doesn't make it any brighter...i haven't been able to get any decent readings off of it, probably because there is no smoothing cap so the voltage and current are all over the place (read 2.57V accross the output, but the 3 nichias that were wired in series were bright)...it's probably about twice as bright as my arc-aaa le...kinda flimsy too, the first time i put it on the head and twisted the top on i twisted the main power leads together and shorted it...oops!...the light is turned on and off by pushing down on the LEDs, not ideal...there's a little room around the edges, maybe i can shave the reflector down and use it (would make it a little brighter, too)...

maybe i'll get some pictures later...


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## papasan (Jan 18, 2002)

friday night and i'm home taking pictures of my flashlights...how much of a geek am i?...





left is my bad-boy, right is the arc-le...never noticed how 'green' its tint was until now...need to work on the aligment, prolly has some to do with the plastic lense pushing down on the LEDs to turn it off...sorry about the crappy pic, it's hit or miss with my camera...
















so any good ideas on a way to keep the lense off the LEDs?...looking at the reflector i don't think it's tall enough...maybe a clear or reflective tube that barely fits around the LEDs and sticks up a little higher...where to find one...


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## vcal (Jan 18, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*friday night and i'm home taking pictures of my flashlights...how much of a geek am i?... 
left is my bad-boy, right is the arc-le...never noticed how '
so any good ideas on a way to keep the lense off the LEDs?...looking at the reflector i don't think it's tall enough...maybe a clear or reflective tube that barely fits around the LEDs and sticks up a little higher...where to find one...*<HR></BLOCKQUOTE>

You might try borrowing an O-ring off of an Infinity (if you have one, or a dead Krill lamp).

Also, those _garden-hose_ rubber washers can be used as spacers and can be found at the hardware store.-You can reduce the diameter with a pair of scissors to fit into the inside of the head -and then place it just inside of the lens of that AA Mag light-I used 'em on one of mine



The rough outer edge doesn't show at all when assembled.
If that still doesn't give you enuf clearance-try using double or triple washers. Good luck.


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## remuen (Jan 18, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*i made up a mag head replacement today using the zetex 310 ic...man, what a pain in the a$$...

it works fairly well but it's not as bright as i'ld have hoped...aparently i've reached the max that the coil i'm using will put out because lowering the Isense resistor (which should raise the output) doesn't make it any brighter...i haven't been able to get any decent readings off of it, probably because there is no smoothing cap so the voltage and current are all over the place (read 2.57V accross the output, but the 3 nichias that were wired in series were bright)...it's probably about twice as bright as my arc-aaa le...
*<HR></BLOCKQUOTE>

Hello papasan
Thanks for your pictures! Great idea to do it. The board with the LED and the Zetek booster looks really good! I think I should have a digital camera too.

For three Nichias in series you would need an output voltage of somewhere between 10...11 volts (which will give a current in the range 20...40 milliamps) to get a reasonable brightness. I don't know wether your ZETEK circuit can deliver this voltage - I thought it's in a lower range so you had to switch the Nichias parallel?

I think for the use with 2 AA batteries you need that capacitor on the input to smooth the current - but where to place it?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
...the light is turned on and off by pushing down on the LEDs, not ideal...there's a little room around the edges, maybe i can shave the reflector down and use it (would make it a little brighter, too)...

...the plastic lense pushing down on the LEDs to turn it off...

...so any good ideas on a way to keep the lense off the LEDs?...looking at the reflector i don't think it's tall enough...maybe a clear or reflective tube that barely fits around the LEDs and sticks up a little higher...where to find one...
*<HR></BLOCKQUOTE>

Why don't you use the epoxy switch adapter I've made for this Minimag mod? You'll find the information here page 9 and a drawing of the whole thing here http://edusite10.tripod.com/remuen/adapter.html. It works very fine. Main advandages are:
- more room in the head 
- no wirings to the switch/bulb socket
- no other mechanical adaptations to bring the switch to work

I tried various solutions to bring the whole mechanical thing to work - that's the only good way I have found. And with this solution you won't have any problems with the adjustment of the LED - the stay adjusted.


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## papasan (Jan 19, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*For three Nichias in series you would need an output voltage of somewhere between 10...11 volts (which will give a current in the range 20...40 milliamps) to get a reasonable brightness. I don't know wether your ZETEK circuit can deliver this voltage - I thought it's in a lower range so you had to switch the Nichias parallel?*<HR></BLOCKQUOTE>

if you look at the data sheet, they have 4 LEDs in series in their design...i think that's why they spec a 68 or 100uH coil...and the LEDs all put out the same amount of light when run in series, not so when they're run in parallel...

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*I think for the use with 2 AA batteries you need that capacitor on the input to smooth the current - but where to place it?*<HR></BLOCKQUOTE>

also on their data sheet, the most efficient method is without a capacitor...i'm thinking that the energy is being pulsed and the power graph looks more like A/C current instead of DC now...a cap would smooth it out some, but since the nichia LEDs can take a pulse of 100mA, why bother?...it would just take up more room and leak energy...

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Why don't you use the epoxy switch adapter I've made for this Minimag mod?*<HR></BLOCKQUOTE>

i wanted to keep the mag light as much as original as i could, plus i wanted to make this conversion as easy as i could...the only differences between this and a 'normal' mini-mag are the lack of reflector and a different bulb...looks like i'm gonna get into dremeling the reflector, tho, so there goes that =)...

btw, put some fresh 1600 mAH NiMHs in last night at 9:23PM, it's now 7:04AM or almost 10 hours later...looks like it's still at 100%...i would imagine it could go for a couple days like this, we shall see...


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## remuen (Jan 19, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
... and the LEDs all put out the same amount of light when run in series, not so when they're run in parallel...
*<HR></BLOCKQUOTE>

I didn't know that the ZETEK can deliver such a high output voltage to drive the LED in series. Sorry!

When I look on my recent measurment results on 3 LED's then running them in series is the better way. The current I measured on 3.6 volts:
LED1 53.5mA
LED2 31.2mA
LED3 14.8mA
Running these 3 LED in parallel wouldn't be really good ...

Btw, LED 1 and 2 are Nichias I got in the same delivery, LED 3 is the last one from an earlier delivery. LED3 looks like a Nichia, but I'm not sure about it.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
also on their data sheet, the most efficient method is without a capacitor...i'm thinking that the energy is being pulsed and the power graph looks more like A/C current instead of DC now...a cap would smooth it out some, but since the nichia LEDs can take a pulse of 100mA, why bother?...it would just take up more room and leak energy...
*<HR></BLOCKQUOTE>

Seems I have still a lot to learn - i was in the opinion that the efficiency would be better with a capacitor in the input because it helps to supply the high duty cycle peak current the AA cells can do - but you've have used NiMHs which can supply a higher current than alkalines ... I make my tests with alkalines to simulate the 'worst case'.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
i wanted to keep the mag light as much as original as i could, plus i wanted to make this conversion as easy as i could...the only differences between this and a 'normal' mini-mag are the lack of reflector and a different bulb...looks like i'm gonna get into dremeling the reflector, tho, so there goes that =)...
*<HR></BLOCKQUOTE>

That's how I started - and after many hours of trying different ways and repairing what didn't work or got broken or ... or ... I have 'stolen' Peter Gransee's simple but perfect working solution in the ARC AAA and adapted it to the Minimag where it works perfect too. With this solution I'm no longer afraid of having to repair or adjust something after my two boys have played with the Minimag ... - I think Peter knows why he has choosen this kind of solution. Keep it safe and simple = KISS.

Another point: I was never really happy with the original switch. Even they claim it as self cleaning I had from time to time some contact problems .... KISS again! The epoxy adapter switch is self cleaning too and you can increase the contact pressure just by screwing the Minimag head a bit harder on the body (with the original switch you can influence the contact pressure only with the spring in the tail cap). I'm convinced I will never again have any contact problems with the modifyed Minimag.

Btw, when you have the right tool you can easy remove the original switch/bulb socket and later on make a reverse mod because you still have all original parts. That reminds me that I've forgotten to say: To bring my adapter to work, you need to file away the anodization on the top of the body to get a good contact between body and the negative contact (= washer) of the adapter. The epoxy adapter can always be easily removed when you heat up the Minimag head.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
btw, put some fresh 1600 mAH NiMHs in last night at 9:23PM, it's not 7:04AM or almost 10 hours later...looks like it's still at 100%...i would imagine it could go for a couple days like this, we shall see...*<HR></BLOCKQUOTE>

Hope we have to wait a couple of weeks until you must post that the test is over ...


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## jeff1500 (Jan 19, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> Then solder the other side of the component. If you have a chip with a couple of pins don't try to solder each single pin. Move the iron tip with the solder along the pins like you would paint them with the solder. If you have applied enough flux and only a very little bit of solder this works. <HR></BLOCKQUOTE>

1. Do you mean that if you get just the right amount of flux and solder, the surface tension of the solder will open up the gaps between the pins and you can use the solering iron like a big paint brush?

2. What are you soldering the chip to? Is it a preprinted board from a factory?

3. How many watts is your soldering iron?

4. What diameter solder wire are you using?

Papasan: Looks like you are using just plain circuit board. Is it just solder strings or wire I see connecting the different pins?


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## remuen (Jan 19, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*1. Do you mean that if you get just the right amount of flux and solder, the surface tension of the solder will open up the gaps between the pins and you can use the solering iron like a big paint brush?
*<HR></BLOCKQUOTE>

Exactly this happens! 

Have you ever tried to connect two pins on a bigger board only with solder? It is sometimes not easy because the gap opens again and again. This happens here too but because it is a very small gap you need only a bit of solder to close it. That's why you should take as less solder as possible on the iron tip.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*2. What are you soldering the chip to? Is it a preprinted board from a factory?
*<HR></BLOCKQUOTE>

It is such a laborotry board to make prototypes as we discussed earlier. The soldering points on this board fit exactly to the SOT23 pins.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*3. How many watts is your soldering iron?
*<HR></BLOCKQUOTE>

I don't know - something between 20 and 30 watts. But with the Weller soldering irons this is not the main point because you can buy iron tips with various soldering temperatures somewhere between 300 - 450° C. When you are buying the tip from a good distributor you will find each iron tip type with 4 - 5 different soldering temperatures. But unfortunatly I also don't know what temperature the tips have I bought in a small electronic shop - they where all in a box and the guy did not know which type they are and which temperature they have. So I just bought three different types to try them out. And it worked. 

Remember what Phillipe told me: It does not depend on the soldering iron - using enough flux is important (but he also agreed that with the right equipment one can easier solder). And as I don't want to spend a lot more of money in my equipment at the moment (I already bought an adjustable power supply and 3 digital multimeters - all together a few hundred dollars) I am just using what I have.

Btw, Duggg told in an earlier post in this thread what type of soldering iron and tip he recently bought.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*4. What diameter solder wire are you using?
*<HR></BLOCKQUOTE>

It is a 1mm solder wire - a bit to thick. A thinner one would be better.

I can only recommand that you're going to do what I did: Buy some kind of a board for SMD prototyping and a few cheap SMD parts and try to solder them.


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## remuen (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
Remuen: Do you know how they solder such small connections? How about your friend Thomas. Does he know? Do they do it by hand with a big magnifying glass? How do they make the circuit boards?
*<HR></BLOCKQUOTE>

Hello Jeff1500 and Wayne

I promised to give you the hints I've got from Phillipe who is responsible for our electronic lab and the expert for soldering SMD boards. 

Phillipe gave me only a very short introduction in the SMD soldering technique. It's not really a special technique, only a few hints. If one can already solder it is easier than one thinks.

To show me on what it really depends Phillipe used an old Weller soldering iron with a small electromagnetical standard screwdriver tip (about a 2mm tip) - very similar to the one I use at home since about 25 years! With this he only wanted to demonstrate that no special equipment is needed.

But there is one really important point: *Without enough flux (liquid or better gel) it is almost impossible to solder SMD components* (except you're already an expert)! 

*Philippe's soldering tips are: 
-----------------------------------------------*
<UL TYPE=SQUARE><LI>Make sure the soldering iron tip is clean (clean it with a brush)

<LI>Coat everything you want to solder carefully with enough flux!!!

<LI>Take only very very little solder on the iron tip. The more solder you take the more short cuts you'll make. 

<LI>First try just to fix one side of the component on the board. Don't look on the quality of this soldering joint - it's more a glueing than a soldering. To 'glue' the component hold it down with the tweezers or a small screwdriver or whatever you have while soldering it.

<LI>You don't have to place the component exactly on the board because it will automatically 'swim' into the exact position when the solder is fluid.

<LI>Then solder the other side of the component. If you have a chip with a couple of pins don't try to solder each single pin. Move the iron tip with the solder along the pins like you would paint them with the solder. If you have applied enough flux and only a very little bit of solder this works.

<LI>Then go back on the first side (the one you have only 'glued') of the component and solder it again. If you don't hold the component down it should now 'swim' automatically into the right position because the solder gets fluid.

<LI>Finally check the soldering joints with a magnifying glass. 

<LI>In case of short cuts remove the solder with the iron tip (of course without any additional solder on the tip). This works better when you first apply some more flux.

<LI>If the soldering joints are not good then apply again some more flux and solder them again. Take only more solder if you are really convinced you need more! It's not easy to remove the solder!
[/list]

That's all! 

And her my own practical experience after trying it the first time:

I'm happy that I've bought such a 'helping hand' with a magnifying glass. I do really need it. 

It was more difficult to place the SMD components on the board than to solder them. What I mean is that you have to use tweezers to pick up these tiny little parts, mayby first you have to unpack them (eg. the diodes), turn them on the right side, bring them into the right position on the board - and everthing without loosing them somewhere on the carpet .... Another very difficult thing is to make some wire connections because I had to make it also with the tweezers and the magnifying glass - and the tweezers are huge through the magnifying glass and the wire is still thin and the holes in the board unbelievable narrow ... After all I know how a surgeon feels when he is operating in a human brain! 

I tried a few different soldering tips - some of them I bought especially for this big and very dangerous adventure. But finally for me a small screwdriver type (~1mm) was the best solution. 

The soldering itself was much easier than I thought. The only thing: First I didn't apply enough flux but took to much solder. It worked much better when I started to safe solder and spending more of the flux. - - - Ok, you're right: I had to make some of the soldering joints at least twice and I had also to remove some solder because of short cuts on the board. Ohhh yeah - the parts didnt always 'swim' into the exact position as they should because I pushed them away with the iron tip.

But finally I've to say it's a pitty that I didn't try it before.


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## remuen (Jan 20, 2002)

Hello Waxne, Jeff, papasan, Duggg and CPF fellows

In the last few weeks we have posted a lot in this thread. This afternoon I made a short conclusion of what we have reached. 

I think the main part is still the epoxy adapter which I could bring in to solve the mechanical problem with the switch/bulb socket. *But we do not have a stepup booster we can use in the Minimag.*

OK, Wayne and Jeff have MAX75x circuits which are working. As far as I know from Wayne his booster has a good efficiency and works also on an input voltage below one volt. But unfortunatly for the Minimag mod the board size counts very much - and the MAX75x circuit boards don't fit into a Minimag.

Papasan has recently proved that the ZETEK booster they are designing in the ZETEK thread fits into the Minimag - at least without the input cap and with 3 LED's in series. For me this ZETEK booster could be a (or one of two) solutions. Therefore I have some questions about it:
<UL TYPE=SQUARE><LI>How does the missing input cap influence the circuit?
<LI>Does the size of the circuit board allow to put more than only 3 LED's into the Minimag? Looking at the pics papasan made it seems to be difficult.
<LI>How many LED's can be switched in series - or the otherway round asked: What is the max output voltage to drive LED's with 35 - 40mA?
<LI>Is the ZETEK circuit a current controlled booster?
[/list]

On my side I have a 'on the fly' prototype of a circuit with the LT1613. The first efficiency results are bad. I've to look together with Thomas if and how much it can be improved. 

And for me personally I've to say that I have learned a lot in the past few weeks! I'm still not an expert but am now able to understand the most what the electronic experts are talking about.

*That is what we have reached up to now!* (I hope I didn't forget to list something!)

Hey, I think we now should stand up and prove that we can bring it to a good end! In the last days I looked aroud in the CPF and the net and didn't find a really convincing solution for a Minimag mod. Of course there are some good ideas, some bright mod's and so on. 

I am convinced that if you with all your knowledge, with your experience, with your knowhow and ... and ... help to work on a good solution for a booster then we can do it better.

Just a few thoughts about where to go:
<UL TYPE=SQUARE><LI>I think we should concentrate an a solution with 5 - 7 LEDs. Don't blame me for this - but a LS solution will for sure cause some new serious problems in a Minimag (heat, size, switch the second) and this would end in a never ending project ... . Look at Peter Gransee's ARC LS project and how long professionals worked on it to bring it to work. There are some other flashlights out there in the market which are much more suitable for an LS mod.
<LI>IMHO the only good solution with Nichia's is switching them in series and driving them with a current contolled booster
[/list]

For your info: 
I have some of the LT1932 switchers in order and will give them a try. According my calculation with the energy formula it should be good to drive 5 Nichias with 35 - 40mA. But the lowest input voltage is only 1 volt so this will not be a single cell booster. And it will not have the same efficiency as the 'CPF ZETEK booster' - except Duggg, papasan and MrAl are going to optimize it ....

*Who comes in and helps to bring this project to a good end? Who want's to share what he/she knows about boosters? Who is willing to spend some time into this for us and a lot of other CPF fellows?*

Wayne, Jeff, Duggg, papasan: It would be great if you help me furtheron! And to all others: It would be great to meet you the first or second or third time here in this thread! 

*And it would be great to make a great Minimag mod together with you!*


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## **DONOTDELETE** (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen asks:
*How does the missing input cap influence the circuit?*

It doesn't, at least not if you're using high-quality NiMH cells.

*Does the size of the circuit board allow to put more than only 3 LED's into the Minimag? Looking at the pics papasan made it seems to be difficult.*

A double sided circuit board may allow 5-7 standard LEDs, if the inductor is placed behind the board. 

*How many LED's can be switched in series - or the otherway round asked: What is the max output voltage to drive LED's with 35 - 40mA?*

I know that without any load at all, the capacitor develops over 25 volts.

*Is the ZETEK circuit a current controlled booster?*

No. Output current is proportional to supply voltage.

*The LT1932 circuit will not have the same efficiency as the 'CPF ZETEK booster' - except Duggg, papasan and MrAl are going to optimize it ....*

It _may_ be possible to get better than 80% using a homemade inductor and the Zetex ZHCS2000 rectifier, but if the designers at Linear Tech say "up to 80%", it may be an uphill battle.
<HR></BLOCKQUOTE>


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## ElektroLumens (Jan 20, 2002)

Sorry I haven't posted much, I've been sorta busy these past few days.

You're correct, the MAX757 is too large for the MINI MAG. I'm considering several chips and designs which will be down to the small size, but it'll be awhile in the design stage before I come up with something.

The MINI MAG is going to be a tough one, because of it's small size. 

Regards the soldering iron, I have the Weller model 4624, which is has variable heat settings, and a vacuum. I also have a 'OK INSTRUMENTS BTR 1000' soldering station vacuum, which works totally awesome for sucking the solder out.

Later,
Wayne


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## ElektroLumens (Jan 20, 2002)

papasan,

This mod, the LED's on the Zetex regulator, is awesome. Nice work!

Wayne


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## Daniel Ramsey (Jan 20, 2002)

I know the Minimag is nice and everyone uses it but it has no "room" for developement. I have successfully done Brinkmann Legend Luxeon mods using 3 N cells, my next step is to use the 3AA version with the AA batteries for a longer run time, first with a resistor and then later a dummy spacer w/regulator. Twist turn heads have too many problems plus is a wear point and were originally designed for a bulb and not the beam pattern of a LED or a Luxeon with the optics. For up close work I find the small hot circle of light more of a hindrance compared to the even spread of a good LED so the heads on my mods are loctited down.The next step is to put in a touch pad for the on/off function. Tailcap switches are fine for now but the demands that I have seen so far from most of the CPF members is that whats needed is multi output LEDs, white hi power, low light off color, UV or Infrared. Thats what I plan to mill out is a hand held Mil-Spec 40+ hour on low setting and minimum 1 hour on high. It must have a universal attachment for use on helmets, pocket light or area light.Something similar to the HDS Action Light comes to mind but smaller and with different wavelength LEDs.


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## **DONOTDELETE** (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*I know the Minimag is nice and everyone uses it but it has no "room" for developement.*

That's not true. There is just enough room in the MagLite head for the Zetex board, an LS, and the collimator. The board was designed with the MagLite in mind.

*The next step is to put in a touch pad for the on/off function.*

Now that I do agree with. Tailcap switches are bulky, unreliable, and expensive.
<HR></BLOCKQUOTE>


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## Daniel Ramsey (Jan 20, 2002)

Thats definately a valid point, if the tailcap was extended then yes it opens up more area for a regulated power supply. Whoever can get a lathe up and turn out these with a controller installed should make a good return.


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## **DONOTDELETE** (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*Thats definately a valid point, if the tailcap was extended then yes it opens up more area for a regulated power supply. Whoever can get a lathe up and turn out these with a controller installed should make a good return.*<HR></BLOCKQUOTE>

Since everything fits in the head, there no need for any machining of the flashlight---although the LS needs a little trimming.

But that brings up an even bigger question: what to do with the space in the tailcap that no longer needs to be occupied with a spare bulb?


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## jeff1500 (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*For me this ZETEK booster could be a (or one of two) solutions. Therefore I have some questions about it:
<LI>How does the missing input cap influence the circuit?*<HR></BLOCKQUOTE>

I have a 47 micro F input capacitor on my max757 test circuit. I just plugged it in and out a few times to see what happens. I measure the exact same voltage and current to within 0.01 through the two leds both with and without the capacitor.

It probably does something you could see on an oscilloscope, but for a flashlight, looks like it just wastes space.


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## remuen (Jan 20, 2002)

Hello good morning all together

It's a bit tricky - while I was sleeping you have posted a lot. Thank you very much! 

And now you are already in bed or will soon go to - and I'm ready to go to work. Sorry, this morning I'm a bit short in time because I had to prepare a work for today. So I had no chance to get into the Minimag issue but I will come back on your posts as soon as possible. Hope I will find some time during the day for some first replays or questions ...


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## ElektroLumens (Jan 20, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*I have a 47 micro F input capacitor on my max757 test circuit. I just plugged it in and out a few times to see what happens. I measure the exact same voltage and current to within 0.01 through the two leds both with and without the capacitor.

It probably does something you could see on an oscilloscope, but for a flashlight, looks like it just wastes space.*<HR></BLOCKQUOTE>


Now you have me wondering, why I did finally include the input capacitor in my design of the MAX757. I think that in testing with the different input/output voltage cofigurations, I seemed to get the most current from this circuit, when I included the input capacitor. It will still generate output, even with down to .5 volts and a bit below. I think that the input capacitor also it helps quiet down ESR, having the input capacitor, but on a flashlight, this really doesn't matter too much. 

Now, I have to do some more testing, just to see if I need that 150uF tantalum capacitor, which cost me $3.00. I am using 150uF, both for the input and output caps, and either a 100uH or 68uH inductor. 

For the Mini Mag, it seems that the Zetex 310 will be a good choice, because it is soooo small! Awesome job these flashaholics are doing with this Zetex circuit design! 

Wayne


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## remuen (Jan 21, 2002)

Oh folks, I'm happy that you are making me a lot of work with studying all your posts and asking questions




! That's the way we are moving towards our target ....! Terrific!

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*



.... at least not if you're using high-quality NiMH cells.

Click to expand...

*


> <HR></BLOCKQUOTE>
> 
> IMHO we should consider that most of the people still use AA alkalines. How will/does the ZETEK circuit work on these alkalines without an input cap - especially on *low alkaline AA cells*?
> 
> ...


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## **DONOTDELETE** (Jan 21, 2002)

Alkaline batteries can't provide as much current as NiMH batteries of the same size.

In fact, run time with alkalines is about 1/3 that of NiMH's.

Another problem with alkalines is that they're 1.5 volts per cell, as opposed to 1.2 volts. This means Rsense has to adjusted using alkalines to limit max current to the LS, and then if NiMH's are used with that same Rsense value, they'll be noticeably dimmer.

Of course, alkalines have a couple of advantages: 

<UL TYPE=SQUARE><LI>they're a lot more reliable than NiMH's when left in a drawer for several weeks or months
<LI>it's true that NiMH's don't like to be run into the ground, something that's not a concern with a discardable battery.
[/list]

The Zetex circuit is small and works quite well if you stick to just NiMH's, but a more ideal circuit would be a true current regulator, one that would provide constant 350mA current regardless of input voltage and cell chemistry.


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## **DONOTDELETE** (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*I'm also wondering why this input cap exists in almost all design proposals if we could get the same output without it??*<HR></BLOCKQUOTE>

There are three reasons to use an input capacitor:

<UL TYPE=SQUARE><LI>To compensate for high internal resistance in the battery.
<LI>To compensate for high impedance in the battery at the high frequencies at which DC/DC converters typically operate.
<LI>To protect the chip against the inductor discharge spike when the battery is disconnected. 
[/list]

I can see that under certain conditions, an input capacitor might help. However, I observed no significant improvement with the Zetex circuit using NiMH cells.

As far as inductor discharge goes, some chips, like the ZXSC300, apparently are designed with some internal protection. Others may not fare as well.


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## **DONOTDELETE** (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Wayne Johnson:
*I have to do some more testing, just to see if I need that 150uF tantalum capacitor, which cost me $3.00.*

The output capacitor is much more important than the input capacitor, for two reasons:

<UL TYPE=SQUARE><LI>It provides energy to the LED while the inductor is charging. Without the capacitor, the LED would be dark during this part of the cycle, and thus overall brightness would be less.
<LI>It regulates peak current to the LED. Without it, the LED is forced to absorb the peak inductor discharge current, which may damage the LED.
[/list]

*Awesome job these flashaholics are doing with this Zetex circuit design!*

Thank you




<HR></BLOCKQUOTE>


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## remuen (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
This means Rsense has to adjusted using alkalines to limit max current to the LS, and then if NiMH's are used with that same Rsense value, they'll be noticeably dimmer. ...
*<HR></BLOCKQUOTE>

Hi Duggg
Thank you for your explanation. It seems I didn't understand something: 

You mentioned before that the current follows the voltage. I suppose you mean with voltage the output voltage and not the input voltage. Therefore the ZXS310 is a voltage controller, isn't it? 

If yes IMHO the Zetex circuit wants to provide a constant output voltage as long as poosible. The output current depends (up to the switcher's limit) on the load resistance according the formula I = U/R. So why has Rsense to be adjusted if you have lower input voltage? If the voltage of the source drops because of using it you also do not adjust Rsense because the circuit wants as long as possible try to keep that output voltage by changing its pulses. This means the input current gets higher the lower the input voltage is (input energy x effeciency = output energy).

Where do I make a mistake in my thinking?


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## jeff1500 (Jan 21, 2002)

Rsense = .1? for the zxsc300 chip looks hard to find.

I'm starting to like the LT1932 more and more, but do you have to set the external resistor according to the battery type? I don't like that idea. If that's the case then would you first make a voltage regulator circuit to feed the current regulating circuit? 

If any of this stuff it true then I guess I'm back to the Max757 even though the led current will vary.

I'm starting to think I'll try soldering surface mount components one of these days. I looked at "Surfboard" adapters today.


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## remuen (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Rsense = .1? for the zxsc300 chip looks hard to find.
*<HR></BLOCKQUOTE>

The ZXSC310 circuit needs som part which are not easy to get but for return you will have a high efficiency and a high output current! Duggg, papasan an MrAl have optimized the whole circuit to get this high efficiency. Duggg told me in an earlier post that all the needed parts are available at Digikey.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
I'm starting to like the LT1932 more and more, but do you have to set the external resistor according to the battery type? 
*<HR></BLOCKQUOTE>

No, in the LT1932 circuit you have to adjust the maximum output current with Rset. 

The switcher will then try to supply the output voltage needed to reach this current through the connected load. The input voltage can vary between 1 to 10 volts. 

This current regulation is the advantage of the LT1932 - and also the fact that the input voltage can be higher than the output voltage without additional parts fo a sepic circuit.

The drawbacks of the LT1932 compared to the Zetex are the lower output current (but needs no additional output transistor) and the lower efficiency.

I would like a booster which would combine the advantages of the ZXCS310 and tne LT1932. But where is this to find?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*
I'm starting to think I'll try soldering surface mount components one of these days. I looked at "Surfboard" adapters today.
*<HR></BLOCKQUOTE>

Great. If I could do it you can do it too!


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## **DONOTDELETE** (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Duggg mentioned before that the current follows the voltage. I suppose he means with voltage the output voltage and not the input voltage.*
<HR></BLOCKQUOTE>

No, the output current is proportional to the input voltage. For example, with 2.7 volts in, you get 400mA out. With 2.4 volts in, you get 350mA. At 2.1 volts, 310mA.

The ZXSC300 charges the inductor until it senses 19mV across the current sense resistor, then it lets the inductor discharge for 1.7 microseconds.

As battery voltage declines, it takes longer for the inductor to fully charge, so there are fewer discharge cycles per second---so output power drops, and output current follows.


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## **DONOTDELETE** (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*Rsense = .1? for the zxsc300 chip looks hard to find.*<HR></BLOCKQUOTE>

You're right. Not only are the low ohmic resistors hard to find and expensive, they're often available only in high power versions that are physically larger than desirable.

Fortunately, you don't need to buy such resistors. #32AWG copper wire has a resistance of 0.0055 ohm per centimeter, so a 2cm strand will work just as well, and is not only cheap, but small.

Using this "copper resistor" has an even more important advantage: you need to tweak the Rsense value for a given LS and power source. For example, 0.019 ohm may be the correct value, and finding such a commercial resistor may be difficult. But it's a piece of cake using a copper strand.


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## **DONOTDELETE** (Jan 21, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>*Duggg told Remuen in an earlier post that all the needed parts are available at Digikey.*<HR></BLOCKQUOTE>

Well, I lied, a little.

Although you can get #32AWG wire from Digi-Key, you don't want to, because strands of such wire can often be found in ordinary lamp cord and/or speaker wire. For example, #24AWG speaker wire is often made up of seven strands of #32AWG wire.

Also, the bead core requires a few centimeters of #24AWG magnet wire. This can be found in large reels at local electrical supply shops, but you're better off asking for a short scrap length from a local electric motor repair shop, which you'll often get for free.


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## papasan (Jan 22, 2002)

thoughts about source batteries...

playing with both NiMHs and alkalines the output seems to be very similar with the zetex cicruit...it starts a little higher, but that output doesn't last long and drops in a more flat line (a diagonal line discharge curve, NiMHs have more of a 'plateau' type discharge curve)...i plan on using NiMHs mostly because i would rather recharge my batteries than discard them, but i want to leave my alkaline path open...i even tried lithiums for a little while (although i think they're used a little, backups for my camera) and didn't see a huge output difference after 10 minutes or so...i plan on tweaking the board to 320mA or so off of fresh alkalines and then the other battery types i use will just follow suit off of that...

i've got 2 LS driver boards made, both are pretty much the same (one is physically smaller) except for that one has an input capacitor and one doesn't...the one with the input cap has a little worse efficiencey and stays brighter for a little longer but doesn't have a long, drawn out ending, it just pretty much goes out 30 minutes after it starts to dim...

i found a much better way to suck more of the power out of the batteries was to lower the output a bit...lowering the output from ~380mA initial output to ~310mA initial output added about 1.5 hours onto the run-time - from 2 hours to 3.5 of good light...

i do like the zetex circuit but it does have it's shortcomings...ideally it would regulate and ideally it wouldn't need the very small ohmage resistor...i'm not really satisfied with the strand-of-infinitly-breakable-and-shortable-piece-of-very-small-wire approach yet, but it does function properly...i still have the max1674 board sitting here waiting for digikey parts...

btw, my mod lasted somewhere between 12 and 20 hours at full brightness...when i noticed it at the 20 hour mark (left it face down, oops) it was pretty dim (about like a straight 2cell hook-up)...i measured one of the NiMH batteries at 0.09V...oops...the other say 0.9V...redesigning the board to take a bigger coil, so i can drive the LEDs harder, and a few other changes...


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## remuen (Jan 22, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*No, the output current is proportional to the input voltage. For example, with 2.7 volts in, you get 400mA out. With 2.4 volts in, you get 350mA. At 2.1 volts, 310mA.
*<HR></BLOCKQUOTE>

Duggg, please correct me if I'm wrong with the following statements:
<UL TYPE=SQUARE><LI>a voltage regulator tries to keep a constant output voltage on a varying input voltage independend of the output load 
-> output current is proportional to the output load
<LI>a current regulator tries to keep a constant output current on a varying input voltage independent of the output load 
-> output voltage is proportional to the output load.
<LI>With the ZXCS310 booster the output current is proportional to the input voltage on a given load. The logical conclusion is that also the output voltage must be proportional to the input voltage. And this means neither the output voltage nor the output current are constant if the input voltage or the output load are varying 
-> it is a stepup conversion but no regulation?
[/list]

Either I'm right with these points or something goes wrong in my head.
Sorry that I am as slow in uptake the ZXCS function. Please help me .... I don't want to reinvent this booster but only understand how it works.


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## **DONOTDELETE** (Jan 22, 2002)

Remuen, I think you are correct on all three points.

A regulator and a DC/DC converter are totally different circuits, although many DC/DC converter chips include a voltage regulator.

But don't let the lack of regulation get you down---remember, over 99.9% of all flashlights have no regulation whatsoever, yet they remain completely functional.


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## remuen (Jan 22, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*
But don't let the lack of regulation get you down---remember, over 99.9% of all flashlights have no regulation whatsoever, yet they remain completely functional.
*<HR></BLOCKQUOTE>

Thank you Duggg for helping me! I hope I was not boring to you ...

I think your Zetex circuit is still a very good booster - especially considering the efficiency. But the missing regulation is a disadvantage because in the practical usage one has the effect that the light dims when the battery voltage drops .... 

IMHO it is very hard to find a regulated booster which can be used for the Luxeon Star and is as small enough to fit into a Minimag. And that's a big advantage of your Zetex circuit: *Beside the good efficiency it can supply a high output current and it fits into a Minimag!* 

_*added later:
Another big advantage I've forgottten to mention: The Zetex booster circuit already works very well!!*_

This brings me back to a point I mentioned in a very early post in this thread that we possibly will have more than one booster for a Minimag mod because I om my side would like a current regulated booster.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
playing with both NiMHs and alkalines the output seems to be very similar with the zetex cicruit...
....and didn't see a huge output difference after 10 minutes or so... 
*<HR></BLOCKQUOTE>

Thanks you, papasan. We know now that the Zetex can be used with all types of batteries. I think this is a very important point!


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
i still have the max1674 board sitting here waiting for digikey parts...
*<HR></BLOCKQUOTE>

... and I'm still waiting for the MAX1674 samples I ordered. 

Papasan, what do you mean shouldn't we try to find a switcher with a current regulation as the LT1932 has but with a higher output current ( up to 300mA) and possibly a better efficiency? Especially with LED's the voltage regulation is not really the best solution - but also with a Luxeon Star a current regulation would have some advantages - eg. compensate a thermal runaway ...

I think the voltage regulators are designed for other applications where one need the same voltage on various loads - eg. driving a small motor or something like this ..

Btw it seems that the current regulators are not as efficient as voltage regulators. Maybe the have the same effect as my LT1613 prototype circuit has: For the LT1613 which is initially a voltage regulator one needs a resistor on which one looses some energy

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
btw, my mod lasted somewhere between 12 and 20 hours at full brightness...when i noticed it at the 20 hour mark (left it face down, oops) it was pretty dim 
*<HR></BLOCKQUOTE>
It seems you tried to get a runtime of a week .... but you've got the proof that with only 'face down' the runtime doesn't increase ...


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## remuen (Jan 23, 2002)

Duggg, papasan

Can you tell me what the minimum start up voltage of the Zetex circuit is?


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## MrAl (Jan 23, 2002)

Hello,

Although it's interesting to have 
current regulation so that the LED stays
lit to full brightness over the life of 
the battery, it's also interesting to
have some regulation with some dimming
at the end of the battery's life.
With rechargable cells like NiCd and
NiMH, the discharge curve is very flat so
that near the end of life the available
capacity falls of very sharply. This means
you get pretty decent regulation even
without a regulator circuit. Also, you
get an indication that the batteries have
run down and you need to replace them before
the light actually goes out, which is nice
too. One thing i didnt like about
incandescents is that when the battery runs down
the bulb draws even more power, dimming the
light even faster. I like to have some
indication that the batteries have run 
down and it's time to change or recharge them
while i still am getting some decent light out of
the thing. Also, using perfect regulation
will only get maybe 5 more minutes of full
brighness out of the light while non
regulation will still be lit just at somewhat
decreased brightness.

Using alkalines though, you may see some
dimming when there is as much as 25% capacity
remaining, so i think regulation would
improve alkaline battery powered lights
unless you need an indication that the 
batteries are running low sooner for some
reason. Keep in mind without some dimming,
you wouldnt know the batteries are almost
dead untill the light goes out, after which
you cant see in the dark to find your
other twenty three flashlights 

Take care for now,
Al


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## papasan (Jan 23, 2002)

the start-up voltage of the zetex is rated at a minimum of .7V...

basically, from what i've seen (and i know only what i've found in the past 3 weeks or so, i'm a novice) that there are two type of DC/DC step-up converters...

there are switching type converters (like the max757, max1674, zetex3x0) that charge a coil until it reaches some critical mass and then discharges it...i haven't seen any 1 or 2 cell regulated switching converters (one that would work down to < 1V) in my searches...

then there are ones that charge capacitors instead of coils, these are called charge-pump converters, that i haven't messed around with at all...alot of these do have regulation but all the ones i've seen only have an output of 200mA at best...i'm not sure if these rely on current or voltage sampling to regulate themselves, but i think that caps hold current as coils hold voltage so i would guess that they are regulated by current...

with the LS the zetex does do a fairly good job of keeping up the current until the end...at least using NiMHs, the light stays bright and strong for 75% of the battery life until it's putting out just a dull glow...

since voltage and current and intertwined to keep a certain current through a particular object you need to keep a certain voltage as well...

anyhow, of course, i'm always looking for the 'best' circuit...if you find a good one let us all know...


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## **DONOTDELETE** (Jan 23, 2002)

Of course a regulated output has its advantages. But there are several disadvantages:

<UL TYPE=SQUARE><LI>There's no such thing as a lossless regulator, so there will always be a tradeoff between regulation and efficiency.
<LI>With strict regulation, battery energy will be consumed much faster, resulting in a much shorter run time.
<LI>You can damage NiMH cells by repeatedly overdischarging them below 0.9 volts/cell, something easier to do with a regulator.
[/list]


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## remuen (Jan 23, 2002)

Welcome MrAl

Great that you are joining us in this thread. I do have the big hope that now all you 'Zetex experts' are helping us. 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MrAl:
*Although it's interesting to have current regulation so that the LED stays lit to full brightness over the life of the battery, it's also interesting to have some regulation with some dimming at the end of the battery's life. With rechargable cells like NiCd and NiMH, the discharge curve is very flat so that near the end of life the available capacity falls of very sharply. This means you get pretty decent regulation even
without a regulator circuit. Also, you get an indication that the batteries have run down and you need to replace them before the light actually goes out, which is nice too. 
*<HR></BLOCKQUOTE>

Just to make sure that you don't missunderstand me: I don't think that your Zetex booster has a big lack having no regulation! If you use it on rechargable cells or lithiums you're absolutly right.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MrAl:
*Using alkalines though, you may see some dimming when there is as much as 25% capacity remaining, so i think regulation would improve alkaline battery powered lights unless you need an indication that the batteries are running low sooner for some reason. 
*<HR></BLOCKQUOTE>

It is a fact that most people use alkalines mainly because of their reliability and availability. I'm one of them too because I have so many flashlights and I don't use each one a couple of hours per day. With rechargable cells I had always the well known problem that the cells were down when I took a flashlight out of the drawer ... -> greetings from Mister Murphy



!

I think we are looking from two sides on the same thing: You have more the Luxeon Star in mind and I am more concerned with Nichia's. I like these different views here in this thread because IMO there is not only one (good) way to modify a Minimag! Why not find two of them? O sorry, I wanted to say why not find a second one (the first one is your Zetex circuit!). 

I don't know the characteristics of the Luxeon Star. With Nichias I think one has always at least a few minutes time to change the batteries even one uses a current controller. The reasons are:
<UL TYPE=SQUARE><LI>only a perfect booster would supply the full current until the batteries are dead. The reality is that the output current drops also with a current controlled booster before the batteries are completly down. Of course with NiMH/NiCd/lithium cells this 'dim out' time will be shorter than with alkalines - but I think low batteries will still be indicated early enough
<LI>Nichias give still some light even if the current falls below 1mA. At 0.x mA one has still some kind of night light.
[/list]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MrAl:
*Keep in mind without some dimming, you wouldnt know the batteries are almost dead untill the light goes out, after which you cant see in the dark to find your other twenty three flashlights 
*<HR></BLOCKQUOTE>

It's always the same: The light goes out exactly when if it is needed most! That's why I like the nice feature called moonlight mode in the ARC AAA. I wonder how Peter could realize this on such a tiny little circuit board?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*basically, from what i've seen (and i know only what i've found in the past 3 weeks or so, i'm a novice) that there are two type of DC/DC step-up converters...
*<HR></BLOCKQUOTE>

I'm a beginner too and try to learn and understand DC-DC converters and the whole lot of all the other stuff needed for making my own flashlights. You know already more because I only know linear switchers using inductors.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*since voltage and current and intertwined to keep a certain current through a particular object you need to keep a certain vilatage as well...
*<HR></BLOCKQUOTE>

The differencies between these two kind of controllers are:
<UL TYPE=SQUARE><LI>The *current controller* keeps the output current constant even when the input voltage or the (output) load are changing. 
- If the input voltage drops the average input current will be increased. (following the simplified formula output energy = input energy x efficiency) 
- If the load is lower (= higher resistance) the output voltage must get higher too to keep the current on the some value. (U = I * R)
- If the load is higher ( = lower resistance) the output voltage must drop too to keep the current on the some value.

<LI>The *voltage controller* keeps the output voltage constant even when the input voltage or the load are changing.
- If the input voltage drops the average input current will be increased. (following the simplified formula output energy = input energy x efficiency) 
- If the load is lower (= higher resistance) the output voltage will be kept on the same level but the current will drop. (I = U / R)
- If the load is higher (= lower resistance) the output voltage will be kept on the same level but the current will get higher
[/list]Of course these points are only correct as long as the controller is in a state in which he is able to regulate something. Eg. the input current will not be increased when the batteries are not able to supply a higher current (will happen much more with alkalines than with NiMH)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*anyhow, of course, i'm always looking for the 'best' circuit...if you find a good one let us all know...
*<HR></BLOCKQUOTE>

If it only would be as easy .....

The best one I found up to now is still the LT1932 from Linear Tech. It's a new current controller which will be good for a an output current of 200 to 300mA output (depending on the efficiency) and an output voltage up to 34 volts. Very small (SOT23), high frequency (= smaller components) and input voltage range from 1 to 10 volts - whereas the input voltage can be higher than the output voltage eg. when driving 1 to 2 LED's on a 9 volt battery without any additional sepic circuit.

The LT1932 is more for driving Nichias than a Luxeon Star - but we do have your Zetex booster for this (using 'we' assumes that we all others are allowed to use it too).

If you (or you or you ..) find a better one let us all know...

Btw, I explained it earlier to Duggg: I'm a very very poor European. Our distributors don't have all of the parts or sell them only in huge quantities. Therefore I've to order most of the special parts in the USA. This is 
a) very expensive (shipment costs, taxes) 
b) very boring because one has to wait wait wait wait wait wait ...
a means that sometimes I can't/don't order something because its just much to expensive (worst case: a core for eg. $0.25 will cost me up to $30).
b means that I am sometimes not able to act faster like just now because I'm waiting waiting waiting waiting waiting .... (gives me a bit more time for writing huge posts



)


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## **DONOTDELETE** (Jan 23, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen says,
*That's why I like the nice feature called moonlight mode in the ARC AAA. I wonder how Peter could realize this on such a tiny little circuit board?*<HR></BLOCKQUOTE>

Moon mode occurs when the DC/DC converter cuts out, and the LED gets its power directly from the residual energy in the battery.

The Zetex circuit also has a moon mode, since the LED is always in series with the battery.


----------



## **DONOTDELETE** (Jan 23, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen says,
*It is a fact that most people use alkalines mainly because of their reliability and availability.*<HR></BLOCKQUOTE>

It depends on the application.

The _only_ time I use alkalines is in an unexpected or emergency situation: If the lights suddenly go out, or I'm on an extended outing and all my NiMH's have been exhausted.

But for virtually all other applications, where you _know_ you're going to be using the flashlight (hiking, camping, casual spelunking, etc.), NiMHs not only give longer run time, but are way less expensive over time.

One way to get around the annoying NiMH self-discharge characteristic is to always leave them in a charger, then hook the charger to one of those cheapie lamp timers, and set the timer so that the charger is on only a half hour a day. That keeps the NiMH's topped off without constantly overcharging them.


----------



## remuen (Jan 23, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*Moon mode occurs when the DC/DC converter cuts out, and the LED gets its power directly from the residual energy in the battery.
*<HR></BLOCKQUOTE>

The ARC AAA dims first at about 0.8 volts slowly from full brightness to the moonlight and keeps this moonlight on the same brightness for 3 to 6 hours. 

The ARC AAA *must* have some regulation to switch into this moonlight mode and keeps regulated on a much lower level of only a few milliamps LED current. Otherwise a LED would not work on a battery voltage lower than 1 volt. I squeezed an AAA battery down to 0.4 volts and stopped the test when the light was still bright enough to find something in the dark garage. After a recovery time of about 30 minutes I measured these 0.4 volts without load!! It is almost unbelievable but there are other flashaholics who did a similar test with a similar result! So it did not happen by accident with only one ARC AAA. It is the circuit design!

Peter Gransee doesn't give any hint about how it is done. One had to make a reverse engineering to find it out. But the whole circuit is in epoxy so it would not be easy to do it.

Do they possibly use a very small OP to dedect a low voltage and to switch into the lower but regulated mode?


----------



## **DONOTDELETE** (Jan 23, 2002)

Well, DC/DC converters are supposed to cut out at a specific voltage, but in practice they often continue to operate at lower and lower frequencies until the output voltage approximates the input voltage.

The "regulation" you observe is simply the flattening of the battery discharge curve as current approaches zero. As current drops, the battery is more able to maintain its voltage.

The Zetex circuit behaves similarly. I found an old pair of AA alkaline batteries in the junk drawer and decided to conduct a moon mode test.


```

```

I had to suspend the moon mode test in order to check out some new bead cores which arrived today. The results of that test can be found on the Zetex thread.


----------



## remuen (Jan 23, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*The Zetex circuit behaves similarly. I found an old pair of AA alkaline batteries in the junk drawer and decided to conduct a moon mode test.
*<HR></BLOCKQUOTE>

Thanks Duggg, you have convinced me! It also stays a certain time on a very low output level.

Another thing:
<UL TYPE=SQUARE><LI>Which Luxeon Star do you intend to use for the Minimag mod?
<LI>Where do I get it best?
<LI>How do you mount it together with the Zetex booster into the head? Is the epoxy adapter of any use for this kind of mod?
[/list]


----------



## remuen (Jan 24, 2002)

I just looked a bit around to find another current controlled switcher ic. But all I found have some big drawbacks, mainly a to a high input voltage beginning somewhere at 1.5 to 2 volts as the lowest values. The LT1308 hit all records because it seems to need a 2200uF (in words: two thousend two hundred) cap in the output!

If it only would be easier ....

The LT1932 is still the favorit for becoming the little brother booster of your Zetex booster!


----------



## MrAl (Jan 24, 2002)

Hi there again remuen,

The LT1932 chip looks interesting.
It even has a dimming input pin.
Im not sure if it can be made to
handle 350ma output or not though.
The apps they have shown go up to
10 led's only. The input voltage
requirement increases as the number
of led's rises, but i suspect that's
only because they are connecting all
of their LED's in series. It
may work at higher current for 2 cell
applications, but it would have to
be tried i guess. The output transistor
minimum output current spec is only 400ma,
so it might not work for outputs up to
350ma as the peak inductor current is
typically at least twice this value,
and usually higher then that even.
Perhaps 200ma output?

Good luck with it,
Al


----------



## remuen (Jan 24, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MrAl:
*
The LT1932 chip looks interesting. It even has a dimming input pin. Im not sure if it can be made to handle 350ma output or not though.

.. The output transistor minimum output current spec is only 400ma, so it might not work for outputs up to 350ma as the peak inductor current is typically at least twice this value, and usually higher then that even.
Perhaps 200ma output? 
Al*<HR></BLOCKQUOTE>

Hi again MrAl

I also expect the output current limit will be somewhere between 200 to max 250 mA. Therefore the LT1932 can obviously not be used to drive the Luxeon Star with a good brightness. But my target with this booster is more to switch a couple of LED's in series and then the output current will not be higher than max 40mA - but on a much higher voltage.

Therefore the switch current of max 780mA will be the limiting factor. According to the simplified energy formula (output energy = input energy x efficiency) and considering a duty cycle of about 50% the LT1932 should be able to drive 6 - 7 LED's in series with 40mA - and into the Minimag fit max 7 LED's. 

As soon as I have the LT1932 I will try it out. On 3 volts it should be no problem. But how does it behave on only 1 volt input voltage? Let's see wether my estimation is correct or not.


----------



## **DONOTDELETE** (Jan 24, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Remuen asks,
*Which Luxeon Star do you intend to use for the Minimag mod?*

I plan to use a white Luxeon Star without optics, part number LXHL-MW1C. I have filed its hexagonal board into a circular shape 17.5mm in diameter, which fits snugly in the head of the MiniMag. I'll be using the collimator from an LS/O I inadvertently fried a couple of months ago.

*Where do I get it best?*

You would probably be best off ordering it from Future Electronics, since they have distributors in Europe. Go to http://www.futureelectronics.com/1033/fai/countries.asp?Val=Europe 

*How do you mount it together with the Zetex booster into the head?*

The board fits against the battery compartment. The LS sits on a ridge on the inner diameter of the head, and the collimator fits nicely against the LS.

*Is the epoxy adapter of any use for this kind of mod?*

Possibly, although I was just going to modify the tail cap by drilling a hole and sticking a small switch in the end---see, I found a good use for that space after all




<HR></BLOCKQUOTE>


----------



## MrAl (Jan 24, 2002)

Hi again,

remuen:
I'd like to see how this chip (LT1932) works out too. Let us
know how you make out with it.

Duggg:
Did you encounter any major problems trying to file the LS square
board into a round one? I was thinking of doing something like 
this as well but wasnt sure if it would ruin the board or the
LS diode or something.

Take care for now,
Al


----------



## jeff1500 (Jan 24, 2002)

I found a cell phone on the sidewalk today that got run over by a car. I'm taking it apart to practice with surface mount parts.

How does an LS run at lower current levels? What I'm wondering is: If I run an LS at 200 mA, is that the same as running 10 leds at 20 mA each?


----------



## **DONOTDELETE** (Jan 24, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by MrAl:
*Duggg, did you encounter any major problems trying to file the LS square
board into a round one?*<HR></BLOCKQUOTE>

Nope, the board behaves as if it's solid aluminum. It's tricky getting the curve right. I cut out a circle 17.5mm in diameter from a piece of paper, then traced the circle on the back of the LS.


----------



## **DONOTDELETE** (Jan 24, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jeff1500:
*How does an LS run at lower current levels? What I'm wondering is: If I run an LS at 200 mA, is that the same as running 10 leds at 20 mA each?*<HR></BLOCKQUOTE>

According to the Luxeon Star spec sheet, a white LS puts out 12 lumens at 200mA.

According to Don Klipstein at http://www.misty.com/people/don/led.html white Nichias have a typical efficacy of 17 lumens per watt. At 20mA, the typical forward voltage is 3.6 volts, so that's 72mW, or 1.2 lumens.

So ten Nichias driven at 20mA put out 12 lumens---the same as a Luxeon Star.


----------



## remuen (Jan 25, 2002)

Hello Duggg

Thank you very much for the informations!


_Duggg, MrAl, papasan, Wayne, Jeff and all the other posting here 
----------------------------------------------------------------
I just looked into the last posts and thougt: It is terrific how you all sharing your knowledge









! Asking a question means one gets a detailled answer with additional informations, explanations, links, results of a test especially done to help and explain .....









!_


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## MrAl (Jan 27, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*Nope, the board behaves as if it's solid aluminum. It's tricky getting the curve right. I cut out a circle 17.5mm in diameter from a piece of paper, then traced the circle on the back of the LS.*<HR></BLOCKQUOTE>


Sounds good! I might attemp this at some
point but its going to have to be
after more LS's become available. It
seems they are hard to get right now.
Do you think we will see a whole lot
of them after March?

Also, i was examining mine and i can see
that the LED inside is simply soldered
to the pc board like any other LED except
that the leads come out the side.
I wonder how hard it would be to just
buy the LED itself without any board at
all and mount it to something ourselves?
Is this what they mean by the 'emitter',
just the LED itself, with no board at all?
I could easily fit this and our small pc 
board into a minimag.

Take care,
Al


----------



## **DONOTDELETE** (Jan 27, 2002)

Yes, the Luxeon Emitter is just that, the LED not mounted to any kind of heat sink.

But, considering the BW01 emitter costs $11.55 and the MW1C hexagonal LS costs $12.00 (and both were in stock at the time) it was an easy decision for me.

Hopefully the delay is due to Luxeon gearing up to produce the high-dome whites. If it is, it will be worth it, as my high-dome amber has a much nicer pattern than the low-domes.


----------



## Daniel Ramsey (Jan 27, 2002)

I stopped buying the complete Luxeon several weeks ago when there was a backorder so the bare emitters is what I only work with now. Its not hard at all to solder the terminals, I use a very fine silver bearing solder and a 15 watt iron, do not forgot about the middle metal button on the backside its what must be in contact with a heatsink. I use devcon 2 ton epoxy which is good to 200F to bond the emitter to a short solid brass rod that is in turn inside of a thickwall aluminum tube, these are available at most hobby shops, its 1/4x .049 aluminum tappable tubing and 5/32 brass rod. The brass rod is soldered through a 5/32 hole drilled into a dime on the backside with the alum. tube flush with the back of the emitter and the front of the dime, makes good heat transfer and dissapation. The dime is ground down for mounting on my 2AA Brinkmann flashlight but the principle works so it could be used elsewise for other applications. Make sure your wire connections are also epoxied over so there is no stress on the emitter tabs. try flattening some PC solid junber wires a bit for a better solder surface.


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## remuen (Jan 27, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*How do you figure this? At least in simulation, I can get about 10-20mA ripple current on the LT1308B with a ceramic (very low ESR) 10uF cap on the output. And I've rigged the LT1308 up to work as a constant-current supply!
*<HR></BLOCKQUOTE>

bikeNomad, welcome to this thread!

Concerning the LT1308B: You're absolutly right. It seems that I need glasses to read datasheets and circuit diagramms







. It was 220uF in the typical operating circuit and not 2200uF!! Sorry for this mistake!

I am very interested in your results because the LT1308B was on my list to look a bit closer into the data - until I made this mistake. But now I will take it back again on this list.


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## remuen (Jan 27, 2002)

Duggg, MrAl, papasan

Today I tried to order some parts for the LT1932 booster. Now I understand why you are winding your own inductors because the SMD inductors with 4.7uH/6.8uH/10uH I need have all a resistance of 0.9 ... 2.2 ohms.

It seems that I have to go the same way as you and make handwinded inductors.....!

Which core should I choose for a SMD inductor which is as small as possible? I think with all your experience you know the right one to get a better efficiency. 

Thanks in advance!


----------



## **DONOTDELETE** (Jan 27, 2002)

If you hand-wind your own core, it won't truly be SMD





For the Zetex circuit, the best results have been gotten by winding 3-4 turns around a bead core 11mm in length and 5mm in outer diameter, made of "material 73", or a similar material with a permeability around 2500.


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## bikeNomad (Jan 27, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Duggg, MrAl, papasan

Today I tried to order some parts for the LT1932 booster. Now I understand why you are winding your own inductors because the SMD inductors with 4.7uH/6.8uH/10uH I need have all a resistance of 0.9 ... 2.2 ohms.

It seems that I have to go the same way as you and make handwinded inductors.....!

Which core should I choose for a SMD inductor which is as small as possible? I think with all your experience you know the right one to get a better efficiency. 

Thanks in advance!*<HR></BLOCKQUOTE>

Before you try to wind your own, consider looking at existing parts. If you're looking for a 4.7uH part, Digi-Key has (for instance) the Panasonic ELJ-EA4R7MF inductor, which is a size 1210 (2.5 x 3.2mm) package with 0.18 ohm resistance (see the catalog page). And they have the ELL-6RH and ELL-6SH parts if you want lower resistance (though these are about 6mm square x 3mm high)

And remember that you may be able to get by with a lower inductance than the datasheet might suggest; first, you can stand quite a bit of ripple on your LED current, and also look toward reducing ripple if necessary by using a low ESR ceramic (1 or 2uF will do it!) for the output cap rather than a tantalum.


----------



## bikeNomad (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*I just looked a bit around to find another current controlled switcher ic. But all I found have some big drawbacks, mainly a to a high input voltage beginning somewhere at 1.5 to 2 volts as the lowest values. The LT1308 hit all records because it seems to need a 2200uF (in words: two thousend two hundred) cap in the output!
*<HR></BLOCKQUOTE>

How do you figure this? At least in simulation, I can get about 10-20mA ripple current on the LT1308B with a ceramic (very low ESR) 10uF cap on the output. And I've rigged the LT1308 up to work as a constant-current supply!

If you're using an aluminum electrolytic (or even a tantalum) this could be the problem. The output ripple has more to do with ESR than capacitance (at the 600KHz frequency of the LT1308, the impedance due to the capacitance of even a 1uF cap is very small).

Test results coming soon (after my DigiKey order)...


----------



## remuen (Jan 28, 2002)

Hello bikeNomad

first I come back to our earlier posts:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*
How do you figure this? At least in simulation, I can get about 10-20mA ripple current on the LT1308B with a ceramic (very low ESR) 10uF cap on the output. And I've rigged the LT1308 up to work as a constant-current supply!
*<HR></BLOCKQUOTE>

I just found a circuit diagramm for the LT1308B with current controlling I downloaded from somewhere (unfortunatly I didn't note from which website). The LT1308B is driving 2 Luxeon Stars in series. This guy uses a 1200uF output cap! Maybe this brought me to write 2200uF (220uF + 1200uF = 2200uF



). I think there must be a certain reason that such a cap is used. Besides that: The LT1308B needs more external parts than the ZXCS310 which has no current regulation but a current limiter. Even with SMD parts it will be hard to bring it down to a board size that will fit into a Minimag. I'm looking forward to your results with the LT1308B.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*
Before you try to wind your own, consider looking at existing parts. If you're looking for a 4.7uH part, Digi-Key has (for instance) the Panasonic ELJ-EA4R7MF inductor, which is a size 1210 (2.5 x 3.2mm) package with 0.18 ohm resistance (see the catalog page). And they have the ELL-6RH and ELL-6SH parts if you want lower resistance (though these are about 6mm square x 3mm high)
*<HR></BLOCKQUOTE>

Thanks for this link! It seems that I have to order almost all needed parts in the USA. Our European distributors have either not all these parts or sell them only in huge quantities! I hope Digi-Key will not charge to much for the shipment .... 

The smaller size is very interesting for me because the LT1932 booster should be as small as possible because I will use it also for other mods.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*
And remember that you may be able to get by with a lower inductance than the datasheet might suggest; first, you can stand quite a bit of ripple on your LED current, and also look toward reducing ripple if necessary by using a low ESR ceramic (1 or 2uF will do it!) for the output cap rather than a tantalum. 
*<HR></BLOCKQUOTE>

First I will try the values suggested in the datasheet and then change some parts to look what happens.

As far as I know a to a low inductance could probably cause some problems because of the higher current peak. I don't know how it affects also the efficiency. But I will go as low as possible - also with the output cap because a higher ripple would be no problem for the LED's.


----------



## remuen (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duggg:
*If you hand-wind your own core, it won't truly be SMD





For the Zetex circuit, the best results have been gotten by winding 3-4 turns around a bead core 11mm in length and 5mm in outer diameter, made of "material 73", or a similar material with a permeability around 2500.*<HR></BLOCKQUOTE>

Hello Duggg

It's sometimes difficult to express myself in English! If I would take a dictionary to write all these posts I would never come to an end. Therefore I do always hope that you fellows will understand what I mean - and you did it again - even with a smiley



! (I didn't want to ask for a true hand-winded SMD inductor but for a core as small as possible to use on a SMD board).

Ok, thanks for your hint. But regarding the post of bikeNomad I will first try to use such a Panasonic inductor which has a much better DC resistance than the ones I found. 

I have still the target to make the LT1932 booster as small as possible and the core you mentioned is already half of the size of my first LT1613 prototype board. The LT1932 circuit board should be even smaller than the LT1613 prototype ....

If this standard Panasonic inductor doesn't really satisfy I will come back to the hand-winded inductance issue for this booster.

It seems that I have anyhow to make such a hand-winded inductor because I also intend to make a Zetek booster. But for this I do have the 'shopping list' posted by papasan/MrAl in your Zetex thread.


----------



## remuen (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*How do you figure this? At least in simulation, I can get about 10-20mA ripple current on the LT1308B with a ceramic (very low ESR) 10uF cap on the output. And I've rigged the LT1308 up to work as a constant-current supply!
*<HR></BLOCKQUOTE>

bikeNomad, I come back on this topic again - hopefully the last time. 

I have to correct me: *I do not need glasses to read datasheets and circuit diagrams



!* 

In the design note 179 for the LT1308 you will find a sample circuit diagramm with a 2200uF output cap in parallel to a 100uF cap. Wheter it is necessary or not - at least the designer of this circuit thought it would be necessary



.

When evaluating a ic for me I don't really care for each detail in a first run. If something is very curious to me or is far away of my ideas I 'throw it away' - and this happened with the LT1308 after I've seen this huge output cap.

Please don't blame me if I'm wrong - but without going deeper into the matter I've got the impression that the high efficiency of up to 90% can only be reached with a big output capacitor.........

*Added later:*
------------
Btw, could the Maxim chip MAX1771 be a replacement for the LT1308B?


----------



## bikeNomad (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
* 
Please don't blame me if I'm wrong - but without going deeper into the matter I've got the impression that the high efficiency of up to 90% can only be reached with a big output capacitor.........
*<HR></BLOCKQUOTE>

If you look in the datasheet, you'll see a discussion of using multilayer ceramic output capacitors. They use a 10uF cap. Look at it this way: you're interested in the impedance of the cap, not its capacitance. The LT1308B is no different in its requirements than any other 600KHz step-up circuit. At 600KHz, a perfect 10uF capacitor would have an impedance of 0.026 ohms. Of course, the world is not perfect. Even good tantalums in this size have a much larger than 0.026 ohm ESR (like maybe 0.15 ohms), so their impedance is dominated by their ESR. Aluminum capacitors are much much worse. So your 2200uF aluminum/tantalum capacitor combination would have a much larger impedance than a 10uF X5R ceramic capacitor. And would be much bigger! And wouldn't have the efficiency...


----------



## **DONOTDELETE** (Jan 28, 2002)

It's not only about impedance and ESR.

If you're looking for a maximum brightness solution, the output cap needs to be able to store enough energy to drive the LED while the inductor is charging. I don't think 10uF will quite cut it; most of the circuits specify 220uF for that reason.

And then there's the ripple issue; the smaller the capacitance, the more the ripple. Although Nichias are relatively immune to ripple, Luxeon Stars are less tolerant.


----------



## MrAl (Jan 28, 2002)

Hello again Duggg and others,

I agree 101 percent.

As we have posted in the Zetex thread,
we realized quite a bit about the LS's
tolerance to the ripple output, especially
when it's running close to the manufacturers'
published maximum average current spec.

We found that 100mv peak of ripple is about 
the most that should be allowed without
exceeding the current spec. After that,
you're on your own as far as reliablilty
and length of life is concerned. You 
might get lucky, or you might not.
If you're running at 250ma instead of
350ma average current, your output could
stand 200mv peak of ripple. It works out
to about 100mv at 350ma, and add 100mv per
100ma decrease under 350ma average, or
about one mv/ma for every ma under 350ma
average output current.
This theory already allows for an additional
10 percent safety margin, so no additional
safety precautions should normally be 
needed regarding the average current and
ripple voltage/current.

In reality, it's closer to 100mv
per 120ma, which is closer to 0.83mv/ma,
but even i would use 1 mv/ma as a close
enough estimate and i think im the 
most cautious one here 

Good luck with your LED circuits,
Al


----------



## remuen (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*
Look at it this way: you're interested in the impedance of the cap, not its capacitance. 
*<HR></BLOCKQUOTE>

Hi bikeNomad

If this would be true why sould one use a capacitor? 

The main point an output capacitor is used is to smooth the output voltage. The low ESR helps to get the better efficiency means keeps the losses as low as possible. Without an output cap you should have the best efficiency because you wouldn't have any losses on the cap. 

As Duggg already mentioned with Nichia's you don't really need a capacitor because a high ripple (almost) doesn't influence their function. Linear Tech recommands this for some of their switchers if one wants to get the highest possible efficiency in lightening applications. Btw, in some applications/flashlights Nichia's are pulsed with up to 100mA peak current.

But on the other hand: The higher the load and the lower the allowed ripple (as MrAl explains) the bigger the output cap has to be. And with 'only' 600kHz switching frequency you need a bigger cap to smoothen the ouput voltage as with 1.2MHz.


----------



## **DONOTDELETE** (Jan 28, 2002)

What tpye of Epoxy is being used to form the Epoxy switch for the MiniMag. I'm forming the wax as I write this and will be ready to form tomorrow.

I would like to have the band name for the Epoxy and if available where it might be found!

Thanks,

zyrtecx


----------



## bikeNomad (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*Hi bikeNomad

If this would be true why sould one use a capacitor? 

The main point an output capacitor is used is to smooth the output voltage. The low ESR helps to get the better efficiency means keeps the losses as low as possible. Without an output cap you should have the best efficiency because you wouldn't have any losses on the cap. 

As Duggg already mentioned with Nichia's you don't really need a capacitor because a high ripple (almost) doesn't influence their function. Linear Tech recommands this for some of their switchers if one wants to get the highest possible efficiency in lightening applications. Btw, in some applications/flashlights Nichia's are pulsed with up to 100mA peak current.

But on the other hand: The higher the load and the lower the allowed ripple (as MrAl explains) the bigger the output cap has to be. And with 'only' 600kHz switching frequency you need a bigger cap to smoothen the ouput voltage as with 1.2MHz.*<HR></BLOCKQUOTE>

Not really. The reason you want a cap (and a low ESR one like a 10-20uF ceramic) is so that you can get the maximum brightness out of the Luxeon. You really don't want to run these above 350mA peak. So the higher your ripple voltage, the lower you have to make the average output current to avoid the 350mA peak values. (As noted, 1mV of output voltage ripple causes about 1mA of output current ripple).

The cap is not just a filter, either. It is needed for control loop stability.

Also, with these high frequency circuits, they will run worse (higher ripple, lower efficiency) with (say) a 180uF aluminum electrolytic capacitor than with a 10uF ceramic.

The reason? The 180 uF is not as good a filter even though its capacitance is higher (because it has a very high ESR, maybe 0.3 ohms (Panasonic ECA1AFQ181)).

By going to the very large caps (1200 uF aluminum electrolytics) you start to see < 0.1 ohm ESR. But why bother with a huge cap like this when you can use a small 10uF with 0.002 ohm ESR?

The efficiency will be higher with a lower ESR, because ESR dominates the impedance at these frequencies and capacitor sizes. And the higher the ESR, the higher the wasted power.

The power dissipated in the caps is very small, anyhow, if the ESR is low enough. And if they let you run the LS nearer to 350mA average, isn't it better?

Regardless, these concerns are the same for any high frequency boost DC-DC converter. Changing from 1.2MHz to 600KHz should only result (at worst) in changing the cap by a factor of 2, not by >100.


----------



## remuen (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by zyrtecx:
*What tpye of Epoxy is being used to form the Epoxy switch for the MiniMag. I'm forming the wax as I write this and will be ready to form tomorrow.

I would like to have the band name for the Epoxy and if available where it might be found!
*<HR></BLOCKQUOTE>

I first used some epoxy I still had at home. As it was empty I have thrown the box away... It was an epoxy used to repair cars and I bought it in a 'do it yourself' store.

_Oh man now you're challenging me because I've to explain something in English I can explain only in German:_




Since then I use Araldit Standard which also works very fine. I don't know if you know this brand name. This is a two components glue or cement or whatever you call this. It's delivered in two tubes containing a resin and a hardener and you have to mix both before you use it. After about 12 hours it gets very hard. Btw, there is also a Araldid rapide available which hardens in a much shorter time but this wasn't strong enough.

IMHO most epoxy or two components glue/cement which get hard enough should work. I even thought about using liquid metall (the one you use to repair metall parts) but didn't test it up to now.

I tip not puplished yet: It's easier to solder the 'plus wire' on the copper bolt before you poor the epoxy in the wax form.

Good luck!


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## brightnorm (Jan 28, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Daniel Ramsey:
*...I use devcon 2 ton epoxy which is good to 200F to..... *<HR></BLOCKQUOTE>

Daniel,

I have used the Devcon 2 ton for several years in a very critical, non flashlight-related application

Do you or have you ever used it in a prolonged high stress situation? (flexing and bending forces, occasional exposure to full water immersion for 12 + hrs, etc.)

I am concerned about the possibility of it eventually breaking down under constant wear. 

I don't mean to be mysterious about all this, but I'm using it in a professional capacity in a highly atypical, possibly unique application which is better left unspecified.

Any info will be greatly appreciated.

Your project sounds fascinating. Don't underestimate the appeal of smaller configurations, however. Of course you must first take care of your immediate clients, but if this expands into a larger venture I believe there would be commercial potential in a variety of configurations. The 4AA format is very appealling, despite all the debates about energy efficiency. I used to be sold on a 4C config for flashlights (UK 4C Dive light, etc) but I finally changed my mind when I saw the performance of the UK 4AA on Ray-O-Vac Maximums. Interestingly, when I substituted 4 Energizer AA Lithiums, the brightness increased noticably, but it was the run time that really surprised me: an increase in the duration of "functional" 
brightness from approx. 3 hours to 4.5 hours. That's a 50% increase. 

Anyway, congratulations on being one of our real innovators, someone who gets his creations out into the real world where they are apparently an immediate commercial success. 

Good luck with your business.

Best regards,
Brightnorm


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## remuen (Jan 29, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*Not really. The reason you want a cap (and a low ESR one like a 10-20uF ceramic) is so that you can get the maximum brightness out of the Luxeon. You really don't want to run these above 350mA peak. So the higher your ripple voltage, the lower you have to make the average output current to avoid the 350mA peak values. (As noted, 1mV of output voltage ripple causes about 1mA of output current ripple).
*<HR></BLOCKQUOTE>

bikeNomad, first I have to point out two things:

<UL TYPE=SQUARE><LI>I do not support the use of a big cap. The lower the capacity the smaller the size of the cap and the better for me!
<LI>I'm not an expert in those theoretical things - it's almost 30 years since I've learned all this stuff and in the meantime I've forgotten most of it. But I will try to dig out all this forgetten knowledge I've once learned. 
[/list]

Ok, if you only want to have a low ESR you could take a wire instead a cap



. 

But you want to have a cap because this cap has same more effects. One is to store some energy in it. During the current pulses from the inductor it stores energy and will supply this stored energy to the load during the pulse pauses.

It is obviously: A cap with 1000uF can store much more energy than one with 10uF. The ESR represents the ohmic resistance of a capacitor. A low ESR is necessary to avoid any losses during the loading and unloading of the cap. A different ESR does not influence the capacitance itself but the cap's ability to load the energy into that capacitance.

How does the cap smoothen the output cap? 
<UL TYPE=SQUARE><LI>During the the current pulses from the inductor it is cutting the current peaks because it behaves like of resistance when loading the energy into the capacity. This resistance depends also on the value of the ESR. A high ESR increases the resistance and lowers the smoothening effect on the current peaks and also the cap does load less energy. The higher the current peaks are the lower the ESR should be and the higher the capacitance to cut these peaks.
<LI>During the current pulses from the inductor the cap does unload by supplying the stored energy to the output load. The more energy is stored the higher the current it can supply.
[/list]

Ok, if you need a smoother output current you can not only use a small capacitance with a low ESR. You really do need a certain capacitance to supply the needed energy during the pulse pauses and also to cut the current peaks by loading more energy into the cap.

Therefore the capacitance at least depends on 
<UL TYPE=SQUARE><LI>The frequency or better on the pulse pauses: The longer the pauses the higher the capacitance must be. 
<LI>The needed output current: The higher the current the higher the capacitance must be.
[/list]

For a Luseon Star with its 300 to 350mA I think the capacitance should be something about 100 to 470uF depending on the above mentioned points.

With this explanation all my knowledge about this topic is exhausted. It's really a to a long time since I've learned all this. And it is the first time since more than 25 years I use all this stuff again - just to design such a small booster circuit!


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## remuen (Feb 8, 2002)

It was the initial target of this thread to put together all informations about modifying a 2AA Minimag. I then didn't know that there are such a lot of (more or less important) things to discuss.

This thread would never be complete if I would not place a link to two other threads and a great web site.

Duggg, MrAl, mercator, papasan an some other CPF fellows have designed a small but very efficient stepup regulator with the Zetex ZXSC310 chip. They have done a brilliant job in the 'Zetex-thread' Zetex ZXSC300 single-cell LED driver. 

If you want to learn how to design a DC-DC converter and what you have to consider then I can only recommand that you are going to study this thread! All the immense knowledge and good ideas of these guys are freely given to all of us!







Thank you, Duggg, MrAl, mercator, papasan and all others who have participated. 

Who ever was wondering what these guys were doing all the time in the Zetex-thread and why they put such an effort and a lot of time in this project has got the answer when Duggg opened this thread: Zetex 2AA Luxeon MiniMag Mod. Here they finally presented an excellent Minimag mod with a Luxeon Star driven by the Zetex booster






!

Something would be missing if I would not place a link on mercator's great web site describing the whole Zetex Minimag mod. There you will find not only all informations on how to do it but also the designs of the Zetex boards and the part list for the Zetex booster. Mercator, it is one of the best web pages I know!






Here is the URL to this page: http://www.5thcolumn.org/zetex/project.


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## Gransee (Feb 12, 2002)

I just read through this and the Zetex thread. I have to hand it to you guys, this is a great mod.

It combines the most popular flashlight ever with the brightest LED available. These threads summerize all that the CPF is.

If you sold a drop-in module for the 2AA mag, I think it would be popular. For about 30-40 bucks almost anyone could upgrade their mag to LED in about a minute. The module could also work in other 2AA flashlights that utilize the 2-pin connector. I think I remember a 2-pin type 2AA with a tail switch.

This type of module lends well to pick and place manufacturing. A SM inductor could be used to speed assembly. Since the housing and accessories are already provided, time to manufacture is greatly diminished and inventory simplified.

If I where Mag, I would definately manufacture something like this for their lights. They have been wanting to get into LEDs and this would leverage their current facilities with minimum startup time.

Mag would probally include an LS optomized reflector to keep costs down and maintain the focus function. I would also add clips to the board to help it wick heat to the housing. The pins would be beefier and/or an adapter added to impove the pin connector interface and make it easier to plug in for the casual user. Mag would probally redo the circuit with discrete transistors (a la brinkman) to make it cheaper.

Unlikely though. If they do come out with an LED module or bezel (instead of a complete LED flashlight), they will probally not used the LS because of it's cost. We'll see 5mm whites used instead. Basically the Brinkman flashlight all over again.

Their marketing will probally talk up the "longer run time" and "space age light emitting diode technology", etc.

Anyways, your Mag conversion is a cool mod guys.

Peter Gransee


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## **DONOTDELETE** (Feb 12, 2002)

Thanks Peter for your praise and the insight into the manufacturing process.

And I agree with you that a 5mm MiniMag will come out well before an LS version, for the following reasons:

<UL TYPE=SQUARE><LI>Purchase cost. As you pointed out, the circuit adds $30 to the cost of an otherwise $12 flashlight.
<LI>Operating cost. Only around two hours of run time per pair of alkalines.
<LI>The twist switch. The rotating switch/head assembly can not only twist the electronics out of its socket, it can crush it into oblivion.
<LI>No focusing ability. Since LEDs don't project light spherically, using a reflector to focus won't work well. An adjustable collimator would be needed instead.
<LI>No candle mode. The LS only projects light through a 110-degree viewing angle, unlike the halogen bulb which, like a true candle, has almost 360-degree coverage.
[/list]

That said, the MiniMag mod still is very cool! I attached it to my bike helmet last night and it did a pretty good job of lighting the trail, considering it's only one watt!


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## remuen (Feb 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Gransee:
*
... If you sold a drop-in module for the 2AA mag, I think it would be popular. For about 30-40 bucks almost anyone could upgrade their mag to LED in about a minute. The module could also work in other 2AA flashlights that utilize the 2-pin connector. I think I remember a 2-pin type 2AA with a tail switch.

This type of module lends well to pick and place manufacturing. A SM inductor could be used to speed assembly. Since the housing and accessories are already provided, time to manufacture is greatly diminished and inventory simplified...
*<HR></BLOCKQUOTE>

Thank you Peter for joining this thread and for your compliments!

Astonishing that your are going to support your 'competitors' with some good suggestions



. But I think you know that we don't really want to compete your products. Even the idea of the drop-in module is great it is not our intention to realize this (but ARC could do it). Maybe one of our CPF fellows will make some kind of a kit for such a mod. For me and some others it's just fun to make a own unique flashlight.

It was my initial idea of making a Minimag only with white Nichias. The 'Zetex people' Duggg, MrAl and Mercator have 'stolen me the show'






with their great Zetex + LS mod (to be honest: The Zetex + LS mod is the very best Minimag mod and I didn't and don't want to compete with this). The Nichias are the 'little man's solution'. I will soon come back on this as soon as I get some parts ordered a long time ago ...

_Btw, did the Swiss outdoor equipment dealer I mentioned in a email a few months ago contact you?_


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## remuen (Feb 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*
I will soon come back on this as soon as I get some parts ordered a long time ago ...
*<HR></BLOCKQUOTE>

I have just built my first version of the DC-DC converter with the LT1932 chip from Linear Technology and have also made a first but very short test run (just to look wether it works or not).

Here in Central Europe it's already very late and I'm tired so I don't want to make all the measurments now. But I can say that it looks like it would work better than claimed on the data sheet








I will soon come back on this ...


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## remuen (Feb 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*I have just built my first version of the DC-DC converter with the LT1932 chip from Linear Technology ....

... I will soon come back on this ...*<HR></BLOCKQUOTE>

The LT1932 is since about two months my personal favorite for driving a couple of LED's in the Minimag. Because of some known reasons I had to wait a long time until I've now got these chips. 

I opened a new thread for this DC-DC regulator with which I am going to use to finish my Minimag mod. You will find it here: LED driver with the LT1932 from Linear Technology


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## InTheDark (Mar 4, 2002)

I just finished my first LS mod of the MiniMag.



I used the zetex circuit posted by Duggg and MrAl and the mercator and the others. The good news is that it's a complete drop-in replacement for the minimag switch, which means all I have to do is remove the switch mechanism and put the circuit in it's place, and switch out the reflector for the lens. I'm using the circuit board as a contact to the body of the light, so that acts as my switch. I'll try and take some pictures of it when I can.


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## Bushman (Mar 5, 2002)

got all of the parts, now i must try...thanks douggg


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## remuen (Mar 5, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*The good news is that it's a complete drop-in replacement for the minimag switch, which means all I have to do is remove the switch mechanism and put the circuit in it's place, and switch out the reflector for the lens. I'm using the circuit board as a contact to the body of the light, so that acts as my switch. I'll try and take some pictures of it when I can.
*<HR></BLOCKQUOTE>

InThe Dark, very interesting how you have eliminated the original switch mechanism. 

I've made an epoxy adapter with exactly the same function just to eliminate this switch. Possibly your solution is the better one. I already thought about an improved epoxy adapter in which the pc board is part of the adapter. 

I'm waiting for your pictures to see how you have solved this problem.


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## InTheDark (Mar 5, 2002)

I don't have a digital camera, so I'll try and develop pictures and see how they turn out, so it may take me a while. I basically put the zetex circuit on one side of the circuit board, then drilled a whole in the board to for the negative lead. so the whole bottom side of the circuit board is the negative contact for the switch. I'm trying to find a way to protect it, but I don't think epoxy is thin enough to surround the whole circuit, plus I think it might screw up some of the components. I tried some other sorts of glue, but they didn't work out very well. After I finish this one, i'm gonna try and replace some of the components to fit the circuit into a PR base bulb.


By the way, does anyone know how long the zetex circuit will run on 1 AA? I hooked it up and got it to light, but I haven't done a run time test on it.


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## remuen (Mar 5, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*
I don't have a digital camera, so I'll try and develop pictures and see how they turn out, so it may take me a while. I basically put the zetex circuit on one side of the circuit board, then drilled a whole in the board to for the negative lead. so the whole bottom side of the circuit board is the negative contact for the switch. I'm trying to find a way to protect it, but I don't think epoxy is thin enough to surround the whole circuit, plus I think it might screw up some of the components. I tried some other sorts of glue, but they didn't work out very well. After I finish this one, i'm gonna try and replace some of the components to fit the circuit into a PR base bulb.
*<HR></BLOCKQUOTE>

It seems that you have made a similar construction as I did with my epoxy adapter.
Take a look on the describtion I have posted on page 9 and the drawing of the whole thing here http://edusite10.tripod.com/remuen/adapter.html. This adapter works very fine. Maybe one can improve it with your idea means using the board instead the washer? Even I still call it 'epoxy adapter' I used later on a two component glue (Araldit, I dont't know if it is available in the USA).


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## InTheDark (Mar 5, 2002)

remuen,
I must have missed that link the first time I read this thread. Anyway, it is somewhat similar to the epoxy adapter, except that I put the circuit on upside down so that it is inside the body of the mini-mag. Since I can't draw as well as you, I'll just try and describe it. The circuit board is exactly the same size as a AA battery and about .5 inches long, and it would go in between the positive contact of the battery, and the lip on the top of the mini mag, right about where you have the cupper bolt labeled on your drawing. The LS sits on top of this board where the purple epoxy adapter is shown on your drawing. The collimator on the LS is the same height as the reflector on the Minimag, so when it is screwed down all the way, the collimator pushes against the black plastic ring surrounding the LS, which pushes the whole circuit board torwards the tail of the flashlight. this breaks the contact between the lip and the circuit board, just like the original switch on the mini-mag. I hope this makes sense. Basically, the circuit replaces the black plastic plug that is inside the body of the flashlight, so when you unscrew the head, all you can see is the LS, the rest of the circuit is inside the body.


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## LEDagent (Mar 5, 2002)

...speaking of making drop-in modules. Would anyone be interested in making me an LS mag? I'd pay of course.





..let's see what this gets started!


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## remuen (Mar 6, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*
... Since I can't draw as well as you, I'll just try and describe it.. *<HR></BLOCKQUOTE>

I think I haven't exactly understood how you made your 'booster switch'



.

I understand how the LS works as a switch. But I don't really see how you have mounted the board into the Minimag and how you have made the contacts to the battery/housing and to the LS.

Can you possibly make a hand drawing (eg with the Windows Programm Paint) and send it by email? Are you using a double sided board?

Another question: Did you design your own Zetex circuit or did you use the ZLT+?


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## remuen (Mar 6, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by LEDagent:
*...speaking of making drop-in modules. Would anyone be interested in making me an LS mag? I'd pay of course.
*<HR></BLOCKQUOTE>

You should ask Elektrolumens. As far as I know he makes also mods for customers.


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## InTheDark (Mar 6, 2002)

Yes, I'm using a double sided circuit board, one side has the circuit on it, and the other side is used as the negative contact to the body. I drilled a hole in the board and put a small jumper wire to connect the flat side (the side without the circuit) to the negative lead on the zetex circuit. I'm using the same circuit posted by doug. If you take apart the minimag switch, there's two pieces, the one that you pull out which looks like a flat disk with two legs on it, and the black plastic plug where the two contacts are for the bulb. That is the part my circuit replaces. But instead of the small piece of metal that the minimag uses to make contact to the body, I used teh whole bottom side of the circuit board. I'll try and draw something up, but if you look at your drawing, my cicuit would sit right in between the positive contact of the battery, and the epoxy adapter.


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## **DONOTDELETE** (Mar 6, 2002)

InTheDark, clever idea with the drop-in switch replacement! It allows the head to be screwed on completely, and eliminates the need for a tailcap switch.

How do you handle the positive terminal?

How do you keep the LS from twisting its leads?


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## InTheDark (Mar 6, 2002)

Duggg,
The positive terminal comes through the circuit board through an insulated wire, and just I'm going to solder it on to the LS board. The LS won't twist it's leads because it's connected to the circuit board, only the collimator is attached to the head. The collimator pushes against the ring surrounding the LS, which I'm hoping is strong enough to push against the springs. It's supported underneath, so I don't think it'll be a problem. I've made a few changes to my original design, mostly to deal with the heatsinking issues. I'm still trying to find a way to keep the LS heatsink attached to the body when i turn it on, so I can use the whole body as a heat sink. I think I can do it if I reverse the switch action, so I screw it in all the way to turn it on and unscrew to turn it off, but then I don't have to ability to use it in candle mode.


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## papasan (Mar 7, 2002)

i think he was asking how you handle the positive contact from the battery to the circuit board...

i had trouble picturing all this until i read the posts 3 or 4 times...a picture, even a crude one, would be nice...

so you drill a hole into the circuit board for passing the positive wire through?...i take it that you use very small guage wire...


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## InTheDark (Mar 7, 2002)

Oh, for the positive terminal, I just soldered a wire onto the circuit board, then brought it straight up and bent it 90 degrees and soldered a metal tab on it. The metal tab is a disk about 1/4 inch in diameter and slightly cupped, and acutally looks just like the positive terminal on an AA. Just imagine having two batteries with the positive terminal touching each other, that's kinda what it looks like. I'm trying to draw up a crude sketch, but it will take a while. 

And for the positive terminal coming through the circuit board, i just use regular insulated wire, not really that small, I think it's probably about 18 gauge? I'm not positive. It's about the same diameter as the wires in my car.


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## remuen (Mar 10, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*
...I don't have a digital camera, so I'll try and develop pictures and see how they turn out, so it may take me a while. ...
*<HR></BLOCKQUOTE>

InThe Dark, thanks again for sending me the pictures by email. As already said, this is a great idea. IMO it is the way to make a Minimag mod with any kind of booster.

*Duggg, papasan and all others following this issue:*
InTheDark sent my a couple of photos showing how the ZLT+ Minimag switch replacement looks like and how it is put into the Minimag. The old wisdom comes true: A picture says more than tousend words. Looking at these pics everything is clear. And as I said before: InTheDark had a great idea to make this kind of mod. If InTheDark allows I could forward these pics to you too.

*Mercator, Elektrolumens, Jeff1500 and to all others having a website:*
Neither InTheDark nor I do have a website to publish these pictures. Would one of you be willing to host the pictures of InTheDark's Minimag mod with the ZLT+ on your website? I think they are worth that everyone interested in this mod can see how it is done. 

Who is going to offer some free space on his website to InTheDark?


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## papasan (Mar 10, 2002)

i could host the pictures if you wish...either way i would be interested in seeing them...


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## remuen (Mar 11, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*i could host the pictures if you wish...either way i would be interested in seeing them...*<HR></BLOCKQUOTE>

Papasan, that would be great. Thank you.

Papasan and InTheDark, I think you should discuss on how to do it directly. So InTheDark can add his comments to the pictures and also the latest infos. Then let us know the link.


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## papasan (Mar 11, 2002)

[email protected]


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## Bushman (Mar 11, 2002)

hey dougggg i need to get a hold of you could you please email me at [email protected]
regarding the zetex circut.


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## jeff1500 (Mar 11, 2002)

I'd like to see the photos too. Where do I look?


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## Mercator (Mar 11, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*

Mercator, Elektrolumens, Jeff1500 and to all others having a website:
Neither InTheDark nor I do have a website to publish these pictures. Would one of you be willing to host the pictures of InTheDark's Minimag mod with the ZLT+ on your website? I think they are worth that everyone interested in this mod can see how it is done. 

Who is going to offer some free space on his website to InTheDark?*<HR></BLOCKQUOTE>

Sure.... Send the pictures and any text and I'll include them on the original Zetex page.

*-Mercator-*


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## InTheDark (Mar 11, 2002)

Thanks to everyone for hosting the pictures. I sent them to remuen, so maybe he can send you the picture since it takes me forever to e-mail them. They're not very good, i didn't have a camera so I used a camcorder to capture them. I'd take some more, but I kinda disassembled it to make some changes, I'll try and take some more pictures when I'm finished.


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## remuen (Mar 11, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*i could host the pictures if you wish...either way i would be interested in seeing them...*<HR></BLOCKQUOTE>

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mercator:
*Sure.... Send the pictures and any text and I'll include them on the original Zetex page.
*<HR></BLOCKQUOTE>

Papasan, Mercator, thanks again to both of you. 

I am going to send InTheDark's pictures to you with the original comments of InTheDark so you could include them on your web pages.

Mercator, would you please send me your email adress to [email protected]?


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## remuen (Mar 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*...I sent them to remuen, so maybe he can send you the picture since it takes me forever to e-mail them ... *<HR></BLOCKQUOTE>

InTheDark, I'm ready to send the pics to Mercator and papasan. 

Just for your information: I have cut your original pictures without loosing any information - i have only removed some of the background. The size of all 5 pictures together is now only 96kB instead 811kB.


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## remuen (Mar 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*...I sent them to remuen, so maybe he can send you the picture since it takes me forever to e-mail them ... *<HR></BLOCKQUOTE>

I have sent the pictures to papasan and jeff1500. 

As soon as I have Mercator's email adress I will forward them to him too. I think it is a great idea of Mercator to include your idea on the original ZLT+ web site because it comletes the ZLT+ Minimag mod.

Btw, I think publishing your pc board layout would also be necessary because it seem to be quite different to the ones already shown on the ZLT+ web site.


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## remuen (Mar 12, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
*
As soon as I have Mercator's email adress I will forward them to him too. 
*<HR></BLOCKQUOTE>

Done!


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## papasan (Mar 12, 2002)

here's a quicky to tide people over...
http://home.cox.rr.com/babynoah/itd_mm.html 

looks very nice...how did you get such a lovely round PCB?...


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## jeff1500 (Mar 12, 2002)

I got the pictures. Thanks. Very interesting.


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## remuen (Mar 15, 2002)

If you study the thread ZLT+ fried....  you will see that we could run into a problem with our Minimag mods. 

I must emphazise: *The problems mentioned in this thread are not really ZLT+ problems because every current controlled booster will behave in the same or a similar manner!!*

The problem with the Minimag mod is the wiring (if you have wired the LS to the booster as eg done in InTheDarks solution and if you use the original kind of switching on/off by twisting the head) because the wires could break. 

I remember that I mentioned this problem already two or three months ago in a post but I then did not know that it could cause such problems with damaging the booster and/or the LS. This wiring was one of the main reasons why I made the epoxy adapter shown here http://edusite10.tripod.com/remuen/adapter.html. 

I am still convinced that InTheDark's solution to put the booster into the Minimag in place of the original switch is great. 

*Now I am wondering if someone has a solution to overcome the drawback of the wiring to the LS in this solution without using a tailcap switch? Has someone an idea how to combine the advantages of InTheDark's solution with the ones of the epoxy adapter? Fellows, this is now your chance to prove your own brightness and not only the one of your flashlight







*

_Btw, I must admit that my light is not as bright as it should be to find out a solution



_


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## papasan (Mar 15, 2002)

i actually do have an idea to help this...i'm curious, has anyone tried electrifying the heat sink yet?...ie: using it as the negative lead?...i would imagine it would be okay, it shouldn't short anything out, but i'm reluctant to experiment with a $15 part...

also, one of my concerns is the fact that the copper and aluminum are rubbing together alot...different metals will corrode each other when in contact, electricity usually speeds up this corrosion process...just look at the battery terminals in your car...anyone know of any aluminum PCBs?...


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## InTheDark (Mar 15, 2002)

remuen,
There shouldn't be any problems with the wire breaking, because the LS should be attached directly to the board, not the head of the minimag. So there is no twisting of the LS when you're turning it on and off. But I'm not sure how using the negative contact as the on-off switch is gonna affect the circuit, even with a tailcap switch, the effect is basically the same. But I'm interested in using the Zener diodet that you mentioned in the other thread. Can anyone explain to me how this should be hooked up, and will it prevent future circuit's from getting fried?

Papasan,
I thought of electrifying the heatsink, but I decided against it because this might cause problems in the switching, depending on how the heatsink is designed. Because of the way the mag switch works, if the head is screwed down all the way, it pushes the circuit board further into the body and breaks the negative contact with the board. If the heatsink were electrified, and you turned the head all the way to turn off the light, most likely the heatsink will come in contact with the top of the body. Even though the top of the body is anodized, if there are any scratches on it, the light will turn on again. I think it's better to leave the heatsink unconnected, which is why I left the wires insulated to pass through the heatsink without making contact. And about the corrosion between the copper and aluminum, I thought about it, but it wasn't a big concern in my mind. If I get the circuit working, then I'll probably just solder a washer onto the board to use as the contact, instead of using the copper circuit board. By the way, has anyone tried the heatsinks from Digi-key, are there any good one's to use inside the maglite? I was looking at a T-05 heatsink, but i'm not sure it will fit.


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## papasan (Mar 15, 2002)

terrible with words, i will try to explain it...

jump the negative of the LS to the heatsink...glue, using conductive epoxy glue, or solder a small diameter but a bit wide washer (or perhaps it's better to explain it as a small piece of pipe) to the LS heatsink...put an insulator around the rest of the heatsink (ie: nylon washer or such)...now glue or solder (tho soldering would be hard for this part since it's going between the collar at the top of the mag-lights battery tube) the piece fo pipe to the bottom side of the double sided PCB or washer or whatever you're using as your negative contact to the body of the mag-light...voila...this would also make it so that the whole unit is one piece, so any twisting or turning is all done together...also, you could use the inner diameter of the pipe to run your positive wire, making it even more solid...

it seems like alot of work, tho, for a simple light...

i've picked up a brinkmann legend 2AA for experimenting...so far i'm not too impressed..the rubber grips make it a little bit wider so that it doesn't fit into sheathes and whatnot made for the 2AA mag-lite...the swtich on the back has a plastic button and makes the light considerably longer (for some reason they have a half-inch spacer at the top of the battery under the lamp, they could have made the light only slightly bigger than the mag, especially since it has no spare lamp)...also, the construction is not all aluminum, so i doubt it will last as long as a mag...the switch is fairly nice tho...positive feedback and sounds/feels solid besides the plastic cap...


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## InTheDark (Mar 15, 2002)

Papasan,
I think I understand what you're expaining, and that's pretty much how I planned on hooking it up, except that if the bottom of the heatsink comes in contact with the aluminum, then you end up with a two position switch, i.e, the maglite will be on when the head is unscrewed, it will turn off when you start to tighten it down, and might turn on again when you fully tighten it down. I tried putting an insulator (nylong washer) between the bottom of the heatsink and the circuitboard, but it ends up being too thick and I can't screw the head down all the way. 

I also picked up the brinkmann legend, because I wanted to use a light with a tailcap switch, but I ended up not using it because it felt a lot cheaper than my maglite. The whole construction felt very cheap, especially the threads. The only good part on it is the tailcap switch, but too bad they made it mostly plastic.


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## remuen (Mar 15, 2002)

Hey folks, I must say: Your lights are brighter - you must have a Luxeon Star in your head. I have only a modified candle



. Sorry bushman I didn't remember that you already wrote about this in an earlier post.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
terrible with words, i will try to explain it...
*<HR></BLOCKQUOTE>

And what shall I say? Terrible with English words .... While you are already thinking about how to solve the problem I still try to understand what you have written. So you are always two steps in front of me.








I think this solution you are discussing could really work. IMHO the 'two position switch' wouldn't be a good solution. The Minimag could be switched on by accident.

Papasan: 
I was also thinking about a piece of aluminium pipe but could not find a way how to mount it or better how to make the connection when the pipe is mounted. Making this connection from the pcb to the LS seems to be a bit tricky. 

Recently I played with wire wrap pins. Could they help us? What I mean: First solder these pins to the pcb. Then drill two little holes in the LS board (if necessary), put the LS on the Minimag and solder the pins from top on the LS. But maybe these pins are not strong enough to keep the whole thing together as an single unit.

Bushman:
You mentioned in an earlier post that you are working on the heat sink. I think this is the other main problem in the whole construction. Somehow we should bring the heat away from the LS to the Minimag housing or Minimag head. Did you already find a solution for this?

Concerning the zener diode: I can't really explain in english how this special diode works. There are expressions like 'Sperrrichtung' or 'Durchlassspannung' which I cannot translate. But I will send you a mail with a drawing how you have to hock up in this circuit. Maybe there is someone else which can explain it to you in a less terrible English






how a zener diode works ...


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## bikeNomad (Mar 15, 2002)

The idea of using a Zener diode across the output is this:

the positive output goes to the Zener cathode. The Zener anode goes to the negative output (common).

A Zener diode is a diode whose current rises sharply at a certain predictable voltage when reverse-biased. So below that voltage, no current will flow in the Zener; above it high current will flow.

Since the output of the power supply is current limited by its design, if you add a Zener whose breakdown (rated) voltage is above the highest operating voltage of the LS, you will prevent the output cap from charging any higher than that voltage.

Some things to consider:<UL TYPE=SQUARE><LI> there will still be some current surge through the LS because the cap will be at a higher voltage than it wants to run at. Since the ESR of these caps is much lower than the dynamic resistance of the LS, if you have the cap charged to (say) 200mV higher than the usual 350mA operating voltage of the LS, then when it connects there will be a surge of 200mA above that current, or 550mA. The length of that surge depends on the size of the capacitor. Every 100mV of voltage difference means another 100mA of current through the LS, which really shouldn't see any more than 500mA.
<LI> the Zener diode will have to dissipate the entire output of the circuit, which could be over a watt. So you either have to heatsink it or use a big Zener.
[/list]

I'd personally recommend just making sure that your connections aren't intermittent (that's what solder is for).


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## remuen (Mar 15, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by bikeNomad:
*The idea of using a Zener diode across the output is this:

the positive output goes to the Zener cathode. The Zener anode goes to the negative output (common).

A Zener diode is a diode whose current rises sharply at a certain predictable voltage when reverse-biased. So below that voltage, no current will flow in the Zener; above it high current will flow.

Since the output of the power supply is current limited by its design, if you add a Zener whose breakdown (rated) voltage is above the highest operating voltage of the LS, you will prevent the output cap from charging any higher than that voltage.
*<HR></BLOCKQUOTE>

bikeNomad, thank you for this short and very good explanation. 

I have two points to add:
<UL TYPE=SQUARE><LI>The main purpose of this Zener diode is to protect the output cap as you wrote but also the output transistor. If you choose a diode with a Zener voltage only a bit higher than the operating voltage of the LS (eg a 3.6 volt Zener diode) there is a good chance that the LS will be protected too. But the Zener voltage has to be only 0.2 to 0.4 volts higher than the operating voltage which is a bit critical. To protect only the circuit the Zener voltage can be higher (3.9 or 4.3 volts) which would be even better for the correct and good function of the circuit. This is because the point where a current flows through the diode is not exactly as sharp as with a switch so at 3.3 volts already a current could flow through the Zener diode.
<LI>The Zener diode has to take the whole output current of the circuit which is in our case limitied to about about 350mA by the circuit but not the whole output in watts as the LS has to. So a Zener diode witch can stand this current is needed. And today already a Zener diode in a very small SOT23 housing can do this without a heatsink.
[/list]

I agree with you and Duggg that a good connection between circuit and LS is the best protection. Thats why I started to discuss this issue here too to find a solution for such a good and safe connection. But just to remind: Up to now no soldering champ felt from heaven so a Zener diode will help less skilled people to protect their circuits in case of a bad soldering joint.


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## InTheDark (Mar 16, 2002)

Okay, you guys have lost me with this circuit talk. But from what I've been able to understand, if I were to put a zener diode in parallel with the cap on the zetex circuit, it will protect the circuit and possible the LS from frying if I have a loose connection? I found a couple of diodes on the Digikey website, is a 3.6V/350 mW enough, or would a 3.6V/1W diode be better? they're only $.25 each, so it'd be worth it to add a little protection on the circuit, even if it never gets used.


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## papasan (Mar 16, 2002)

doesn't the circuit short out if the zener diode kicks in?...i've heard of nimhs catching fire or exploding when they were shorted out...even alkalines with their higher resistance don't like this and may get hot, leak, etc...


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## remuen (Mar 16, 2002)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
*I found a couple of diodes on the Digikey website, is a 3.6V/350 mW enough, or would a 3.6V/1W diode be better? *<HR></BLOCKQUOTE>

InTheDark, if you have only this choice you should choose the 1W version. If possible it should be a SMD part which is smaller and fits better on a pc board. 

I would wait with ordering the Zener diodes as Dat2Zip and maybe someone else are just looking into the matter in the other thread. I'm not quite sure how the 3.6 volt Zener diode influences the circuit as I do not have one to test. A 3.9 volt and a 4.3 volt version do work very well but will not be the same good protection to the LS as a 3.6 volt Zener diode.

Btw, I just sent you an email with the drawing showing how to put such a Zener diode into the circuit.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by papasan:
*
doesn't the circuit short out if the zener diode kicks in?...i've heard of nimhs catching fire or exploding when they were shorted out...even alkalines with their higher resistance don't like this and may get hot, leak, etc...*<HR></BLOCKQUOTE>

The Zener diode does not make a short cut to the NiMH's. Look at it as a replacement load for the LS in the case the LS isn't connected to the circuit. The circuit will still work and limit the output current to the adjusted value of about 350mA. So nothing else will happen to the NiMH's - for them it is the same situation as when the LS would be connected.


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