# Hotwire LDO driver! 13mv drop with 1185



## andrewwynn (Sep 25, 2005)

Update: found the chip to make this driver.. read on!

==

Hey folks.. working on turning the 'nano' driver into a voltage regulating FET controlling constant voltage driver for use in hotwire lights.

After Modamag did his testing on the Maglite switch and i did follow-up testing on a couple switches here.. and measured 0.15ohm to 0.16ohm...that equates to about a 1/2Volt loss on the switch in a Mag85.. and that equates to about a 200 lumen drop in output! craziness.

So... enough of that i'm goin' FET found a most excellent FET with RDSon of 0.006 ohm with Vgate=10 and 0.009 ohm with Vgate=4.5. (They are $7-8).. so i looked some more and found a much more common FET that is 0.026ohm at vGate of 5V... $2.30

So.. going to build an FET-based driver for my hotwires.. was going to just use it as a pure switch but with like $1 more in parts i can have it regulate the voltage at least just a little bit (i.e. hold the voltage to 11V or less with the mag85 or the 1331 bulb to keep it from popping when the Vbat is 12.7). 

In any event, my idea was to take a 100kohm pot and trim the Vbulb and put the wiper into the input of the 35mV LDO driver MrAl designed that i use in the nano... using the 100k pot i use to trim the amplifier bias i should be able to find an input wiper voltage that is a little higher than the 4/100ths of volt i typically put into that circuit.. the amp bias can decrease the gain and i can put in some higher input voltage.. maybe 1/10th to 1/5th of volt.. that would be a 1.2:100 ratio on the trimpot.. maybe i'll use a 200k pot, or better use like a 2K resistor in series with 100k pot or something to set the feedback voltage.

In any event using this method i should be able to have a ludicrously low drop out voltage.. even at 3.3A of an 1185... 0.026ohm means 9/100ths of a volt drop... for the 1185 i'm considering using the $7 FET which would be a 2/100th of a volt drop on the FET... 

I will be rewiring the switch of course and having some thick wire like 18 or even 14ga wire hooking things up.. and hope to wire it up such that the switch on the body actually just supplies the power to run the amp and w/o power applied the FET i'll put a resistor to pull down the gate and shut off the FET which will actually also be used as the power control. 

The FET i found is N channel i think.. needs positive gate to turn on... goes on the 'neg' side of the bulb.. i don't have a problem for my designs with that.. i think i'd be interested in a P channel solution for 'the public' so they can't short out the battery if the switch is off and some how short the bulb pin that is always live. 

I think i have a basic ckt design at home i'll try to post that to get thoughts.

Oh.. i have another design idea using the National voltage reg. part, but the dropout voltage is way to high for most designs, but ONE.. i want to drop 14.4V to 12.6 to run an 1166 bulb, and a 'stock' part will do wonders for that design... 

I was trying to find a switcher or anything that will just take a feedback from a pair of resistors to set voltage but can run an EXTERNAL FET.. found a couple from National with 'low and high' FETs i didn't understand how those work.. 

I would love a single chip with 2 resistors to set voltage and external FET solution... or build one based on the nano ckt.. it's absolutely wonderful and should do the trick for what i want to do. 

Thanks in advance.

-awr


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## MrAl (Sep 25, 2005)

*Re: Hotwire LDO driver needed*

Hi there Andrew,

So you're looking to build a higher current LDO then?

Take care,
Al


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## evan9162 (Sep 25, 2005)

*Re: Hotwire LDO driver needed*

Andrew,

Here's a part I've been eyeballing for quite a while:

http://www.st.com/stonline/products/literature/ds/7335/tsm108.htm

It's for powering automotive accessories. Traditional step-down switchmode topography. It uses an external P-channel MOSFET. I can't imagine there being any power/current limitations, since that is ultimately decided by the inductor, switch, and diode.

I've also been eyeing it for LED applications, since it has the ability to limit current based on a sense resistor, and the current sense voltage is only 0.2V. So it might not be too ideal for a single luxeon, but for multiple in series, or a luxeon V, the 0.2V drop isn't too bad of an efficiency hit.

It also has programmable under and over-voltage lockout, so you can protect your rechargables.

And the price isn't too bad, mouser has them for $0.72, and digikey for $1.35


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## andrewwynn (Sep 26, 2005)

*Re: Hotwire LDO driver needed*



MrAl said:


> Hi there Andrew,
> 
> So you're looking to build a higher current LDO then?
> 
> ...



Higher current.. you could say.. if 6 or 7 amps counts. not current regulated this time.. voltage regulated.. no series resistance that way.. i want to take your design and convert it to voltage regulation and have it adjustable at least 'set and forget'.. i.e. with small changes would like to make a 6.6V version a 7.2V version.. a 10.8V version a 12.6V version and a 14.4V version.. the same exact ckt should work with any of them just by changing the bias to the amplifier and the feedback voltage bridge. 

Evan.. waaay too complicated and inefficient... 

here's what i have in mind: 








Here's the description: 

with SW1 open.. C1 will drain through R3 pulling gate to ground = FET off.. this will put E2 (amp ground) high that'll make the amp 'off' ready for switch to be turned on.

Close SW1: 
with FET off.. amp will 'see' high voltage at E2 so also high voltage at B2.. the amp will be 'high impedance' and current will flow into C1 through the 'low R' side of R1.. at some point Q3 will 'turn on' and allow current to pass through the bulb and the Drain V of Q3 will drop pulling down E2 (amp ground)... R2 will generate a feedback voltage... current will flow out of E1 through R2 to the 'amp ground' (Drain of Q3)... and since E2 dropped to turn on the amp.. feedback will develop based on the input at E1 and when current gets high enough the voltage at E1 will become high enough that B2 will rise turning on Q1 which will pull down C2 voltage (of course the gate of the FET). 

With any luck R3 and C1 can be picked to get the 'turn on' to take 1/4 sec or so, and not cause any ugly oscillations.

Once 'cooking'.. as Vbat drops.. the R2 fraction will decrease, pulling down E1.. which will pull down B2 (amplified), which will decrease current in Q1 pushing up the voltage at C2... this will increase the current at Q3.. eventually Q3 should see virtually full Vbat as long as Q1/Q2 can develop that much voltage and the bias can be set just right.. at that point the device will be 'direct drive'.. the FETs i've picked have as low as 0.006 ohm RDSon.. and even the cheap one is 0.026. 

the 'weird part' i think other than having positive on the bulb all the time... is that the 'ground' of the amplifier doesn't go to ground.. but through the FET.. it would seem the amplifier ground and input have to share the same reference for 0V... and i think that should work ok.. 

I'm not lookin' for perfection if there was a 10% swing in output over the life of the batteries i'm not going to cry... 

The KEY is that i want these two things:

1) over voltage protection.. i.e. i want to clamp the Vbulb to 10.8V for example even when freshly charged batteries are 12.7.

2) absolutely the lowest resistance possible... battery-> bulb ->FET -> battery.. and i'll be using some hefty wires.. i would like the total circuit resistance from battery to battery to be on the order of 0.05 to 0.07 ohms max... right now the typically mag switch is like 0.15 ohms... it usually sucks between 100 and 200 lumen off most hotwire solutions. 

So.. does the FET source have to be the same as the amplifier ground for this to work... maybe i have to flip the design over to being positive fed vs negative pull.. 

Like i said... a single IC 'voltage regulator' that is designed to just 'sense' a feedback voltage but control an external FET would be ideal.. just hook up a potentiometer from Vbulb to ground.. the wiper to the input and an FET (P channel i'm guessing) above the lamp.. the regulator monitors the voltage and turns up the gate if it's too low, simple as that... badda bing. 

The result i'm looking for is basically an FET 'soft start' switch... but with the add'l bonus of holding back any peak battery voltage... 

with the right deign a simple switch could be added to change the voltage setting.. i.e. using the same light host with 10.8V or 7.2V and just flipping a switch when you change the bulb to set the output. 

-awr


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## MrAl (Sep 26, 2005)

*Re: Hotwire LDO driver needed*

Hi Andrew,

Since you have plenty of voltage to work with, perhaps you would like
to use an op amp for this design? Makes things very easy, very predictable,
and very temperature stable.


Take care,
Al


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## NewBie (Sep 26, 2005)

*Re: Hotwire LDO driver needed*



andrewwynn said:


> Higher current.. you could say.. if 6 or 7 amps counts. not current regulated this time.. voltage regulated.. no series resistance that way.. i want to take your design and convert it to voltage regulation and have it adjustable at least 'set and forget'.. i.e. with small changes would like to make a 6.6V version a 7.2V version.. a 10.8V version a 12.6V version and a 14.4V version.. the same exact ckt should work with any of them just by changing the bias to the amplifier and the feedback voltage bridge.
> 
> Evan.. waaay too complicated and inefficient...
> 
> ...





If you are trying to "hold back" the battery, in your words, the element that would be doing the holding back is the FET. It will be burning up the "power" you are trying to hold back, until the cells get down to a voltage close to your output voltage.

Thats probably why Evan9162 was recommending a switcher.

What is your battery input voltage on fresh charged cells, and what is your bulb voltage? What is the current to the bulb at this time?

BTW, there are plenty of MOSFETs out there with 0.007-0.001 ohms on resistance...


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## andrewwynn (Sep 27, 2005)

*Re: Hotwire LDO driver needed*

One of the projects is a 7.2V nominal running a 6.6V bulb at 3.75A.

The battery will start at 8.4V and drop to 7.0V.. meaning.. I need a voltage Drop on the FET of 1.8V to start and 0.4V at the end.. at 3.75A that means 6.75W of power dissipated on the FET to start (but quickly dropping to 2.25W for most of the battery life)... at the end of life, it will be 1.50W.. 

The system will put 25W to the bulb.. so.. 25/(25+6.75) = 78% efficiency but really that will last for seconds.. 25/(25+2.25) is the average.. 90% efficiency. 

That doesn't factor in some inevitable wiring losses.. the FET will probably go to 100% saturation before the batteries die which is what i want to happen.

Most of the circuits would be more like this:

10.8V nominal battery -> 10.65V nominal bulb.. 

Basically i only want a ckt to hold back the 12.7V battery voltage of a fresh charge to protect the bulb from those ludicrous startup currents and initial 'overdrive'.. 

Typically a 'mag85' solution would have as much as 0.15ohm resistance.. 10.8V nominal Vbat menas about 10.3V Vbulb... putting an FET in that can bring the switch resistance down to more like 0.05 means.. 10.64 Vbulb and the lumen output goes from 1047 up to 1169. The problem is.. with 0.05ohm ckt resistance and a starting Vbat of 12.7.. means a peak of 12.54Vbulb and that's 37% overdrive on the bulb vs 16%.. and though that 'maths out' to over 2000 lumen.. bulb life drops to 2.0 hrs.. which 'in reality' means most likely 2 seconds.. i don't trust bulb life rating lower than about 8 hrs.. that's when they start getting very finicky. (instaflash). 

I'm looking for something 'dirt simple'.. like the nano driver.. 4 components! I'm working on converting the nano driver to hotwire driver.. using the same basic concept. I don't care if there is some variation, just want to hold back those ludicrisp startup voltages with fresh batteries so i can pare up bulbs that would normally not be possible in hosts thta will eat them for lunch w/o the ckt..

Example.. 

Typical 7.2V nominal soluition: 1111
Typical results: well.. people plug 7.2V into the WA calculator and say 'i have a 880 lumen light'... well.. here's what the 'realistic' calculator says... 

A brief flash of about 1000-1100lumen when 8.4V is unleashed and about 7.66V gets to the bulb... that quickly drops to about 7.2Vbat = 6.66Vbulb and about 672 lumen (using stock PR bulb base).. with a bipin base using stock switch.. probably more like 737 lumen.. but with FET switch.. more like 806 lumen (average). 

however.. if you just put a FET switch in and no LDO soft-start ckt... as much as 8.12V will get to the bulb initially.. and though the 1342 lumen does sound nice... 'til you see the 2.6hr estimated life.. because anything lower than about 7 really is a high-risk for instant flash. 

LDO/FET combo with 7.2V and 1111 means.. dead-flat 806 lumen output for about 80% of the runtime.. dropping to about 730lumen over the last 20% of runtime... coincidentally just about what the non-FET solution has with bi-pin after about 5 minutes of use when the Vbat is about 7.2V. 

(with stock switch, the 1111 should be good for about 600 lumen when the batteries are 90% depleted.. 82% the output).

Yup i've found some nice FETs.. TO-220 is the size i'm looking for and prices around $2.50 i'd like to find... the really low resistance FETs were more like $7. I'm hoping to make something that 'costs' less than $5 maybe can sell for $15-20 (depending on how much labor it takes) if i make them for people to drop in their own mag hotwires... but it will be totally 'open source' so people can make it themselves if they'd like.

-awr


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## JohnMuchow (Sep 27, 2005)

*Re: Hotwire LDO driver needed*



andrewwynn said:


> Like i said... a single IC 'voltage regulator' that is designed to just 'sense' a feedback voltage but control an external FET would be ideal.. just hook up a potentiometer from Vbulb to ground.. the wiper to the input and an FET (P channel i'm guessing) above the lamp.. the regulator monitors the voltage and turns up the gate if it's too low, simple as that... badda bing.


I haven't dived deeply into your requirements but check out Micrel's MIC5156/5157/5158 series of Super LDO Regulator Controllers (http://www.micrel.com). They may be close to what you're looking for.


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## andrewwynn (Sep 27, 2005)

*Re: Hotwire LDO driver needed*

wow cool.. i found a similar part made by TI... but it has a gate output max of 9V... will be great for my lower voltage solutions but need something to run the 14V solutions.... looking closer at this model i think it's closer to a universal solution.. wow on closer examination looks like you saved the day so to speak (so i don't have to engineer two solutions).. the chip is bigger (14pin) than the other solution (8), but it's also cheaper and having ONE chip that will work at 6.6V, 7.2, 10.7 and 14.0V... is awesome.. because i have a light i would like to be able to change bulbs and just by flipping a switch i could convert from 6.6V to 7.2V.. too awesome.

I will be posting results of course.. the neat thing with this solution is that the FET past transistor is used as the on/off switch.. the 'mag' switch ends up just flipping the enable pin... the ckt draws like a micro amp when disabled.. stunning...

the Enable pin is 'high=on' which really makes wiring simple! just a resistor to pull it low when V not applied is all it takes and wire the mag switch to the EN pin.. the battery + terminal from the other side of the magswitch goes to both the Vcc on the chip and the Drain of the FET... than the lamp and back to ground. 

Eureka! this is exactly what i was looking for.. i still would be interested in a 'simple' solution like a P-channel FET and a potentiometer to set the feedback.. no idea how much regulation that would have but if it can at least limit the maximum.. the other possibility i thought of is this:

using a zener to keep the voltage constant.. putting a zener in parallel with the bulb.. and somehow use that to control the gate of an FET... when the zener opens up at the set voltage it closes the FET gate .. just a thought.. really want a simple cheap solution like the likes of that.... maybe a zener for Vref.. a simple chip (no external devices).. that runs the gate of the FET.. 

anyhow thanks TONs that is just what i was looking for for my 'high end' solution. I hope to make some 'turnkey' switches like somebody can send me their magswitch and i'll upgrade it to fet-switch requlated to x, y voltage with a switch to select.

-awr


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## andrewwynn (Sep 28, 2005)

*Re: Hotwire LDO driver needed*

ps.. CPF ROCKS.. that took like 2 days.


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## JohnMuchow (Sep 28, 2005)

*Re: Hotwire LDO driver needed*

Be sure to keep us up to date on what you come up with.


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## andrewwynn (Sep 29, 2005)

*Hotwire LDO driver*

oh how's this for up-to-date.

1) ordered the chips they are perfect and exactly what i was looking for..

2).. 






that is the standard solution.. it would cost about $7 to build and give you absolutely dead-solid voltage output (1% or something).. using a pot to adjust the voltage means you could use different bulbs or 'back off' on the drive level if you want to make them last longer.. 

where to start? 

C1, C2 are for the internal voltage boost ckt to push up the gate drive voltage higher than Vbat (the main problem with this kind of ckt is that to drive an FET the gate voltage has to be higher than the Source... but when the FET starts opening up suddenly Vsource is basically the same as Vbat.. this magic chip has a voltage tripler inside and will boost Vgate up to as much as 14V over Vbat.. the FET i picked wants at least 10V, i think it can handle 20, have to double check.

C3... it's where that gate voltage (output) is stored.. it takes a moment to charge that capacitor when you first turn on the ckt so it is the 'soft start' regulator.. if you want a slower start use a higher value (i'm going to put in a 10µF cap)... ps notice i can type µ now whoo hoo.

the EA is the feedback loop.. it has an internal Vref of 1.235V.. the voltage bridge of R2/R1 is set to make 1.235V when Vout is what you desire, the formula is on the schematic... the chip prefers an R2 of 10k, but i wanted to be able to set full range of 6.5V to 14.4 with just one pot, so 9.0 is substituted.

C4 is the output cap... probably completely unnecessary with this ckt.. the bulb will get 'pulses' but it won't care, the average will keep the voltage at whatever you set it to... i will probably try it with and w/o the cap. 

'Flag' is very cool.. it monitors the output and if it drops below 92% of set voltage it will go TTL low... you can pipe that right back to the 'EN' enable pin which will shut the ckt down.. for this to work of course you need to have a resistor between Vbat and EN, that is R3.. R3 is not necessary without the switch.. EN is a very high impedance pin... the whole ckt pulls like 1 µA when disabled.

now.. 92% of full voltage that works like this.. I would maybe set my 1185 to be 10.7V (so that even with any connection losses at 'nominal' voltage of 10.8 on the battery i get full regulation.. now.. 10.7x92% = 9.844 which sounds awfully high but with NiMH they are 95+% exhausted at 1.1V/cell.. that is what i use for cutoff.. that's 9.9v.. so that's perfect... Lithium Ion.. they are 'stone cold dead' as far as useful output at 3.5V/cell.. and that is 10.5V.. 

It will be a bit weird to have the light 'just shut off' but i'm used to it most of my lights basically do that.. some voltage recovery will happen if you shut if off and you'll be able to turn it back on in a bit.

If you opt to not have that cut off ckt (which will prevent destruction of bat packs from over draining).. you just don't put in the wire from 'flag' or R3.. 

Here's where it gets interesting... 

The chip ALSO includes over current protection.. you can for example.. pre-set a maximum current.. say for an 1185=3.35A.. it will automatically curb voltage if it's ever higher (i think it actually will work for a dead short.. duty cycle will just be like 0.01%).. in any event.. R4 is the optional 'sense resistor'.. and this is how it works.. 

The chip is constantly monitoring the 'drain' input to the FET and also the Vbat... if it 'sees' a difference greater than 35mV it will turn down the output 'til the output = 35mV. the formula is on the schematic for calculating the Rsense value. 

I have the example for the mag85.... it wants 10.5miliohm resistance for that to work out.. I put some AWG mohm/ft values in-case it's possible to just use the lead wire.. or to make your own resistor since it's kind of hard to find a 10.5miliohm resistor... just take 4.884 inches of 24ga wire and bingo.. don't worry that it's pushing 3.35A.. it's supposed to drop voltage... that particular solution will generate 117mW on the bit of wire.. i would probably pot it so i can heat-sink it to the wall.. 1/5th of a watt is not a lot but it'll get warm and there is no air inside the light to cool it off. 

A more interesting solution is that by total random coincidence.. the SWITCH inside a maglite is just about exactly 10.5 miliohm.. I've measured 11mohm w/o progold and 10mohm with it.... you can actually use the switch as your Rsense.. you loose about 20 lumen (1.5%) but it's really sneaky and clever.. oh.. you'll lose that same 1.5% using the 'bit of wire' trick... resistance is resistance.

3) here is the magswitch Rsense trick schematic:






The only difference is that the Vcc is no longer connected to the 'Drain' and goes directly to Vbat (the chip is always powered.. this goes before the switch)... the mag switch now actually hard-disconnects the FET power, just coincidentally since it's not necessary.. just using it that way to limit the current to the lamp..

Note that it still has the 'flag' ckt wired.. R3 and the wire between pin 3 and 14 is still optional (but recommended). 

==============

Well there ya go.. one kick-butt linear voltage regulator for Hotwire.. designed to go around or through the mag-switch your choice (mine i will go around the switch.. I have some solutions that need more current than 3.35A.. and also want to take advantage of the 4miliohm FET i found!).. but for the mag85 solution.. this is the bomb with 'version b'.. because when the bulb is dead-cold i'm betting that the current spikes higher than 3.35A which would not be the case with this 'hack' and it would make the bulb last longer when pushed to the limit.

For me.. many of my bulb choices work ok with Direct Drive... but they are 'super hot' when i first turn them on.. and when the Vbat gets into 'nominal' there is a 15-18% drop in output... I want to keep the voltage of fresh batteries 'at bay' to make the bulbs last longer and have an average brightness that is absolutely constant from full to dead batteries but have that level be maybe 5-10% dimmer than the 'holy cow i'm melting my filament' brightness you get from fresh batteries and an 1185!

Thanks for the tip.. i already ordered the chips i should have a working version within a week.

I have some really awesome combinations lined up.. 800+lumen from 1111 in a 7.2V host.. 900+lumen from a 1160 in a 7.2V host.. and 900+lumen from an 1166 in a 14.4V host.. (the last two are just plain impossible without a voltage regulator because the voltage difference is too great).. the neat part is that DEAD battery voltage is higher than the Vbulb in BOTH of those cases... the light will stay in full regulation the ENTIRE life of the batteries.. a 900 lumen hotwire light that doesn't dim in the least and has soft-start and constant voltage and current protection so the bulb is never hammered by startup surges! I can not wait!

-awr

ps.. I still am trying to solve the problem with a more simplified design... an FET and a dual NPN or PNP transistor for an amp.. or using a 'feedback' amp which has a Vref built in.. or zener diode.. I want the 'po' man' Vreg.. it could be built from $3 in parts i know it.. and a lot easier to wire than a 14 pin IC as well!

if this test goes well i think i'll start offering turnkey switches for about $20-25 if i can find the time to make them.. you'd just need to tell me the voltage you want and which bulbs you wanted to run. 

-awr2


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## JohnMuchow (Sep 29, 2005)

*Re: Hotwire LDO driver*

Excellent! I'm glad the chip looks good for your design.
IMHO, the solution you have is pretty darn simple already. You could spend a lot of time trying to reduce costs a little bit and lose some of the great features of the MIC5156/5157/5158 chip too.

Unless you're like me and the searching/designing is actually the fun part.


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## Kevin Tan (Sep 29, 2005)

*Re: Hotwire LDO driver*

Cant wait awr2!!


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## cy (Sep 29, 2005)

if you end actually making a run..

I'd like one please


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## evan9162 (Sep 29, 2005)

You'll have to make sure you heatsink the hell out of that FET. You'll be dissipating several watts (5-6) initially, and even more during the startup pulse - with a current limit of 3.35A, initial power dissipation in the FET could be 30-40W until the bulb filament warms up

I'd say imposing a current limit on a bulb doesn't make too much sense.


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## wquiles (Sep 29, 2005)

Andrew,

Good job dude!. Thanks for all of your hard work 

Like cy sad, if you end up building these for sale, please do let us know 

Will


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## andrewwynn (Sep 29, 2005)

I do intend to make a 'drop in' for magD switch just swap the whole switch, probably for PR and for bi-pin.. probably with a 'core exchange' deal.. hope to be able to price it about $20 to $25 (similar to LED drivers). I think this will be the cat's meow for hotwire mag mods.. 1% regulation and auto-shutdown and having the possbility of current limiting to boot (a bit trickier.. might just set them to 4A or something.. i don't know what an 1185 takes at startup but those lower voltage high watt bulbs pull more than 3.7A running! 

The capabilities are really just dependent on the FET and i found some winners.. the one i have in the queue can handle instant power dissipation of like 150+W and constant 70 or something (of course only by being heat-sinked to death).. but plan to heat-sink it directly to the side of the body of the light with arctic alumina.. it will be interesting to see if you can feel a 'hot spot' there. The p-channel FETs with single-digit RDson i've only found itty bitty ones that can handle like 2.5W, fortunately i don't need P-ch for this design... i found a 4miliohm FET that actually is an SMT device but heat-sinked can handle the loads mentioned above. 

I ordered both DIP and SOP for the chip so i can build up the ckt nice and easy on my bread board, and build some 'deadbug' drivers from the SOP that will be easier to fit inside the light.

We have something very sneaky in the works, but sworn to secrecy, just stay tuned.

-awr


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## andrewwynn (Sep 29, 2005)

evan9162 said:
 

> You'll have to make sure you heatsink the hell out of that FET. You'll be dissipating several watts (5-6) initially, and even more during the startup pulse - with a current limit of 3.35A, initial power dissipation in the FET could be 30-40W until the bulb filament warms up
> 
> I'd say imposing a current limit on a bulb doesn't make too much sense.



not just 'warming up'.. some of the designs.. like running 1160 from 7.2V.. means like 3.75Ax (8.4-6.5) = 7.15W starting ... and 2.6W continuouis once the bats are warmed up.. the FET i picked are like good for 75+W. It will be very interesting to measure the startup voltage on the FET when set to current limit. How much current normally spikes through the likes of the 1185 or 1160 when first turned on and stone cold? 

Yeah this is a pretty simple design, i think it'll fit in about a penny size ckt... but uses a pretty pricy IC... the raw parts cost is about $7-8... it could be done for $2-3 with some simple solution and 'do the basics'. 

The current limit just happens to be 'built in' to the chip... it's a 33mV drop on a mag85 that is otherwise unnecessary so i will probably leave it out, unless in testing i find there is like a 5A spike at startup and in that case i'll leave it in... for reasons mentioned before.. bulb life and battery surge (not kicking in protection ckts)... the FET can handle a lot more power so 'why not' i figure.

-awr


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## evan9162 (Sep 29, 2005)

Initially, the bulb will probably have 0.25 ohms or less of resistance - so you could see startup surges over 20-30A for the first few ms. You'll have to check the safe operating region of the FET to see if it can handle 150-200W pulses for a few ms.

The FET can only handle 75W when attached to a huge heat sink. You need to look up the specs for the thermal resistance junction-ambient (no heat sink), and the maximum power dissipation with no heat sinking. For surface mount packages it's something like 0.5W with no additional copper besides the minimum mounting surface, and for TO-220 it's usually like 1W with no heat sink attached to the tab.

Are you willing to reveal what FET you're planning on using? (unless I missed it in the above posts)


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## andrewwynn (Sep 30, 2005)

been wondering about the startup resistance of bulbs.. 12V/.25ohm = 48A.. i think i really like the idea of max current.. might not be necessary since i'm going to have a ramped startup anyhow.. maybe like 40-50 mSec startup.. possibly as much as 100-200 msec.. i picked an FET that can handle full power for short term specifically so i can hold back any amount of current or voltage in a 'soft start' incan solution.. as well as constant loads of up to 7-9W in the case of battery/lamp voltage mismatches of up to several volts (i.e. running a bulb at 12.5V from 4xLIon.. where startup Vbat is as high as 16.8V!).. 

The FET i picked is the IRL3716.. 4 mohm resistance! 110 to 200W max power dissipation.. and i plan to heatsink directly to the body of the light so not too worried about the likes of 3.35A x 12.7V (absolute dead short on the load.. full power dissipation on the FET)... unless i made some major oversight the FET looks dead on perfect for this job.. 13mV dropout at 3.35A (1185).. meaning i could see as much as 10.787V get to the bulb! (if i blow off current regulation).

I have the parts all ordered so i can breadboard the driver next week.. should have an operational light or two by next weekend. I will do some 1msec peak readings of voltage and current to see exactly what happens with the 1185 and other bulbs. My goal of course it to get constant output of the max i can push the 1160 in a 7.2V host.. i believe i can push the bulb to at least 800+lumen (unless i got some bum data from my hotwire guru). 

The other 'gems' that can be pushed if current and voltage are limited at startup... the 1166.. i actually got that bulb to operate at over 14V, but only by pre-heating it at 10.8... it blew the first time i tried to light it up cold with 14+V (which i expected.. it was a 'tester sample'.. no pain no gain.. RnD).. 

I believe that bulb can be run at over 12.5V.. that is only 12% overdrive.. and that is over 900 lumen! (bulb lumen)... i have a host lined up to run it... can't wait to see if i have to dial it back.. even if i have to run the lamp at 800 lumen.. it will be 800.0 lumen from 100% to 0% of battery.. no dimming whatsoever... my least favorite thing about hotwire bulbs.. dimming. 

-awr


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## evan9162 (Sep 30, 2005)

That's a very nice FET. 

One thing to note: Look at page 4 of the datasheet at the Maximum Safe Operating Area graph. That's what you'll want to watch in terms of startup (and if you want to use current limiting). It'd probably be a good thing to graph the startup current of your bulb if possible, to see how much current it pulls and how long it takes to settle down to steady state levels, just to make sure you won't be damaging the FET in any way.


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## andrewwynn (Sep 30, 2005)

thanks.. yeah i agree i think i found a kick butt FET.. i will double check the page you say 'cause i do want to keep within the limits.. i don't think the startup will be more than about 50-100ms even with the 4.7µF cap i plan to use vs 1µF for the startup.. i should have all the parts by monday to breadboard one of these drivers.. i will post all the exact details for people that want to copycat, but hope to offer a complete drop-in sometime very soon.

-awr


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## NikolaTesla (Oct 2, 2005)

The head of the KIU kit will be a good heatsink. The ULTIMATE Mag85 will materialize soon. 12 Cell Modamag to 3D coming on line soon. Plenty of spare voltage to regulate down. Add 1 FM 3D bored tube, Install KIU/AWR regulated Mag switch. Add 1 Super reflector. 1 dozen CPB 1650's to fuel it. 1 new WA1185. 1 coated glass lens. As soon as Andrew whips up the regulator, between both of us, (I have the rest of the parts) we should have a prototype for show & tell. I can't wait :naughty:


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## NewBie (Oct 2, 2005)

If you need a source for the IRL3716, Arrow has 507 in stock at 1.74 ea at the higher online pricing.

Newark has them for 1.55 ea, 756 in stock.


MIC5158BM is 3.03 ea, 190 in stock at Arrow.
MIC5158BM is 2.6105 ea at Future

Looks as though when you choose the right combo there, you are looking at 4.17 total, and the rest of the parts are insignificant in price, easily 5 dollars. Adding the 1 dollar for the board, and 1 dollar for assembly, would put you nicely within your 7 dollar target.


When setting everything up such that the dead battery voltage is higher or equal to the bulb voltage, this means the regulator will be burning up power (Vbatt-Vbulb)*Current= Lost Watts turned into heat, the whole time, with the amount of heat it is making being alot higher when the cells are fresh.

All the LDO is doing is buring up the difference between the Vbatt and Vbulb.

Any idea on the losses in the beginning, middle, end?

How do you figure you'll pull the heat out, pot it to the flashlight body?

The soft start is a really big deal, most especially when overdriving, as I found a year ago, on the Thor's Hammer regulator that I've been fiddling with when I get a chance. Saves a ton of bulbs. You won't need the current limit portion of the regulator if you get the soft start capacitor selected such that the soft start time is longer than the filament warm-up time. By implementing the soft-start I mentioned on Thor's Hammer, I've gone from flashing 2/3rds of the bulbs at an extreme 14% overdrive, to zero, even after using the same bulb for a long time. Even to the point of passing the Tc hours point on several bulbs, and well past the B3 point.

It would be interesting to see just how far a person can push a bulb, when using soft start and with regulation.

I know there are a few folks that have waned on eloquently about the soft start making no difference at all. Sorry, but bench tests say otherwise. If a fella was running a bulb within spec, and in the specific bulb design, the filament wasn't pushed very hard at all (kinda like underdriven- cooler filament temps like you find in auto bulbs or signal flashers), as is with certain bulbs, in order to get a very long life out of them, then there is a good chance a person might not see a difference. But in high performance bulbs, where the filament is driven considerably harder, ran at a higher Kelvin temp for increased efficiency, I see a considerably improved lifetime with soft-start, even when ran in spec.

Insta-flashing is a real pain on alot of these high performance lights, some folks even do a partial discharge to help limit the surge current. And some of these bulbs are just a tad bit more expensive than the 10 cent bulbs in cheap lights...

The availability of various regulators with soft-start circuits is a real nice thing and it will be great to see them in more and more lights, quickly saving folks considerable money that can be used to purchase more lights. Increasing the reliability of the hotwire is a wonderful thing, but choosing the right parts for the job is important for relability in the electronics, and it appears you did a great job there.

The drawback, for the bulb sellers, significantly reduced revenue from decreased insta-flashed bulbs.


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## andrewwynn (Oct 2, 2005)

oh i love logging in and seeing detailed replies!

I ordered the FETs from digikey.. i get things 'next day' from them for like $3 shipping.. i live like a 6 hr drive from them so UPS and USPS are 'next day'. 

I think i ordered the driver chips from arrow, they are enroute! 

The only other part with any price at all is if i put in a nice big output cap it could cost 30-50¢.. and a nice reliable potentiometer i usually pay 40¢. (anybody wondering how to type a ¢ on a mac you type option-4). 

I have a spreadsheet that shows me the power dissipation on the FET with totally fresh batteries.. on some configurations it gets as high as 7+W but just for a minute or two and quickly down to 3-4W. (as much as 10% or so). 

pot to flashlight body=yes.. actually i'm hoping to get away with this concept.. arctic alumina from the FET to the body and using a spring of some sort (possibly just some foam rubber).. to push the FET from the PR post against the body of the light. 

I need regulation for some of the bulbs ... i want to put an 1160 (5V bulb) into a 7.2V solution.. which of course is 8.4V no-load fresh batteries! I also want to put the 11.6V 1166 into a 14.4V solution.. i got it to work once with bats that aren't fully charged.. I agree that soft start will be enough for any of the combos we use that work already (like 1331 in 10.8v solution).. which is likely to blow with fresh cells but if it took 1/3sec to turn on would probably be fine. 

I will be finding out 'just how far' i can push a bulb.. those two bulb options have the possibility of being over 900 lumen if i can push them as hard as i hope to. 

empirical evidence in the 'real world' shows absolutely that soft start will help from blowing bulbs.. how often in your life have you had a bulb blow just while on vs when you first turn it on.. stress breaks things, period... less stress less breaking, does not take rocket science. 

when i bought my hotwire light (KIU socket mag3d).. it came with two 1331 bulbs.. one never worked the other i blew within 1 week... the add'l 'afterburner' from the fact that LiON or NiMH batteries have 16% extra voltage from 'rated' when fresh off the charger makes matching bulbs pretty tricky. 

It took me like three allnight sessions to find the match of parts, but major kudos to JohnMuchow for finding a different make of the controller (the one i had found and already had in my order did not output enough voltage to run the higher voltage ckts.. was virtually identical in operation for the lower voltage solutions but had a voltage 'doubler' vs. 'tripler' and wouldn't boost the voltage high enough to run the 14V solutions... 

I had found a number of 'decent' FETs that were like 20mohm and 17mohm but when i found the one with the combo of FOUR and with 100-200W instantaneous power capability... 

I found a different solution that i also bought the parts for.. and would be easier for the avg. joe to wire up.. only has the FET and a single 8-pin chip that i think is available in 'DIP' format.. so easy to solder it's crazy.. I will make a schematic for that design and post it as well because it would be easier to 'copy cat' me.. i think it would be humorous if somebody copy-catted me before i even get the chips and build one i think that'd be funny.

I have a PR 1166 and plan to build a ckt to run it at like 12.5V in a 14.4V solution.. but not one that would be recommended.. it's an envelope-pusher... (4) 14500s in a FiveMega 1D light... and the other model i'm workin on is the 1160 in a 7.2V (6x17500 2D)... both of those should be about 900 regulated lumen. I should have the parts by tuesday, so hope to have those built and running before wed when my life becomes 'nanoworld'. 

Some of my motivation is to have more reliability, but to be able to push bulbs harder to make them more efficient and brighter.. but i can't stand 'dimming' so probably that's the initial motivation.. to make a hotwire light that outputs say 700, 800 or 900 lumen and every time you turn it on.. that's what comes out.. just like what i'm used to with LED lights.. constant output start to finish!

-awr


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## evan9162 (Oct 2, 2005)

Andrew,

I'll bet you're going to need something better for thermal transfer from the FET to the light body (especially for 7W). You're trying to mate a flat surface (tab of a TO-220 package) to a round surface (inner wall of Mag body tube) - You won't get much thermal transfer, even potting with AA or something similar. I'd suggest a rounded chunk of aluminium or copper if possible. 

Another thing to try would be to use some 1/2" copper pipe, cut off a 1/2" long piece, drill a hole, and use a screw/nut to compress the pipe between the transistor and body tube of the mag - the pipe will flatten out and should conform to the shape of both the transistor tab, and mag body tube.


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## andrewwynn (Oct 2, 2005)

i should only need to transfer about 4-5W, but i agree on the issue of mating the surfaces.. i might cut a piece of copper flat on one side and curved on the other side to mate the FET nice to the curve on the inside of the body. the transistor i have picked out is not the T0-220 with the screw hole i need to use AA glue to hold the FET to my heat conductor.. which might just be a strip of copper (like 12 ga wire pounded flat). I won't know what i come up with 'til i make the prototype... i'll just have a small heatsink attached on the breadboard and get a sense of how much heat i have to deal with. Thanks for the idea though... i'll def. post what i end up using, it'd be very cool if it ends up being 'collaborative'. 

-awr


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## StoneDog (Oct 3, 2005)

Is there a safe "upper limit" with respect to the battery voltage? Or perhaps it might be better asked, will this ckt allow one to increase Vbat for longer runtimes (sort of like a DownBoy buck regulator with a Lux3)?

Jon


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## NewBie (Oct 3, 2005)

andrewwynn said:


> i should only need to transfer about 4-5W, but i agree on the issue of mating the surfaces.. i might cut a piece of copper flat on one side and curved on the other side to mate the FET nice to the curve on the inside of the body. the transistor i have picked out is not the T0-220 with the screw hole i need to use AA glue to hold the FET to my heat conductor.. which might just be a strip of copper (like 12 ga wire pounded flat). I won't know what i come up with 'til i make the prototype... i'll just have a small heatsink attached on the breadboard and get a sense of how much heat i have to deal with. Thanks for the idea though... i'll def. post what i end up using, it'd be very cool if it ends up being 'collaborative'.
> 
> -awr




For 3 dollars, or 1 dollar at production levels (too high for you), you could do a spiral heatpipe. Not that you need it, but nice way to spread all that heat out over a flashlight body, and it would do it quickly. 4-5W is alot in a contained space. Copper/Al works also, just another way of snazzing it up.

One place:
http://www.acktechnology.com/Heat Pipe.htm


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## andrewwynn (Oct 3, 2005)

stone: the biggest differential i have in the spreadsheet so far is running an 1185 at 11.0V from a 14.4V nominal battery pack.. that puts 3.35A (probably a little more).. through with a 3.33 to 5.73 voltage drop on the FET. This puts between 11W nominal and 20W peak power loss on the FET, but with enough heat sinking it should work it's well within the rated specs.. the efficiency electrically speaking drops like a rock.. that works out to 76% nominal efficiency and 66% to start with... however that is an estimated output of 1300 lumen... an 1154 bulb running at 14.0V will output about exactly the same amount of light, but in that same circuit will be 97.2% efficient nom. and 83% starting... 'electrically speaking'.. here's where it gets werid.. 

at those drive levels it's about 47W to run the 1154 and about 38W to run the 1185.. but with the efficienty loss on the converter it actually takes 49W out of the battery to run the 1185 in that solution and actually 1W less to run the 1154 in that solution.

The bulb efficacy is much higher in the 1185 (35 lum/w) compared to the 1154 (28 lum/w).. but it's bizarre how similar that averages out to a very simliar output in lumen/battery-watt.

To summarize your question to a point-blank answer.. 

The primary motivation for designing the circuit was to allow the use of higher voltage batteries matched to lower voltage bulbs.. this gives two specific results i was aiming for: 

1) brighter output (naturally). 
2) longer regulated runtime. 

The bulb-battery combinations best suited to this so far: 

5V 1160 bulb run from 7.2V nom. battery.. about 90% efficiency and 100% regulation for full battery life.

11.6V 1166 bulb run from 14.4 nom battery... about 86-90% efficiency and also 100% regulation for full battery life.. 

It would be possible in certain circumstances to increase the runtime by adding a cell.. for example we are planning to use the regulator to run the 100W osram bulb in regulation from 12 cells vs the 11 max it can handle with direct-drive... but we don't really expect much increase in runtime, just that the output will be constant... however, especially with lower current bulbs, it would be quite possible, for example to run the likes of a 10W bulb that is 12V from a 14V source for quite a bit longer if not over-driven to the max, so there is not much current so not much power loss on the FET even though there is a high voltage differential. 

This circuit is a linear circuit, no switching.. so the efficiency is directly disproportional to the voltage difference of the bulb and the battery.. doesn't mean there aren't swell trade-off options to get longer runtimes though. 

I did not optimize my search for best runtime but for most output, so i'm sure there are some neat lower wattage bulbs that would work great along the lines you describe.. the 1316 comes to mind for 7.2V operation.. 10W bulb, 236 rateed but 6V bulb.. running at 7.0V you will have regulation for nearly 100% of battery life and get about 80 minutes runtime from a six-pack of NiMH high mAH models.. that's double the runtime of 1111 in the same host. 

it is not practical to 'double' the cells to double the runtime since it's a linear device, but adding a cell or two in a NiMH solution is possible.. but it won't greatly extend the runtime it will mostly just flatten the output (make it more constant). 

========

newbie.. that heat pipe is neat stuff, thanks for pointing it out.. 4-5W is a lot in a contained space, but not too much to have a 'relatively sloppy' heat junction to the case of the light.. the FET can handle heat temperatures waaay too hot to touch, so if there was a thermal gradient from say 70C to 45C across the thermal junction to the case that might actually be nice.. won't have as hot of a spot on the body, just runs the FET hotter. The important things are that 1) FET not hotter than max and 2) SOME thermal junction to the real world. The IC will be seprate from the heat of the FET since it is affected up to 2% by temperature.. it doesn't matter than the FET is affected by temperature becuase the controller will modify drive level to counteract that. 

I should have the parts tonight or tomorrow.. getting excited to build up one of these drivers! I'll most likely start with the 1160 in a 7.2V host i will try to 'hold back' and keep the voltage set to a bulb saving level at first just to make sure everything is working nice. 

Oh yeah.. i'll probably also make one for the 14.4V host to run the 1166.. that one should be on the order of 'nutso'. 

-awr


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## StoneDog (Oct 3, 2005)

andrewwynn said:


> stone: the biggest differential i have in the spreadsheet so far is running an 1185 at 11.0V from a 14.4V nominal battery pack.. that puts 3.35A (probably a little more).. through with a 3.33 to 5.73 voltage drop on the FET. ....
> 
> ...The primary motivation for designing the circuit was to allow the use of higher voltage batteries matched to lower voltage bulbs.. this gives two specific results i was aiming for:
> 
> ...


 
Thank you for taking the time to give such a complete response. I can't say I understand everything completely, but that is because I know very little about hotwire mods right now. I will study this thread a lot more and try to get a better handle. 

I'd really like a nice, bright regualted incan. Something with the SF A2's amazing regulation that everyone raves about but with more light and longer runtime if that's possible. I'm not too proud to go with a lower current bulb if it still beats out something like a Streamlight TL-3 AND will last at least an hour on decent batteries. If that means a Mag 2D bored to accept 8 NiMH, or maybe just a Mag 2C with 2x18650 then so be it. 

Thank you again for your response and your research into this ckt. I will definitely be watching this thread and consider me in line for the final product.

Jon


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## andrewwynn (Oct 3, 2005)

I have a huge spreadsheet i've been working on for about a month.. it includes over a dozen bulbs and about 8-9 different hosts and battery solutions.. since some hosts can handle multple battery solutions.. probably like 20 different combinations of hosts. 

based on the master spreadsheet i made a smaller one that is just for the batteries.. i posted over here a very pretty chart showing all kinds of battery solutions, and their watt-hour ratings. 

I have lights in-the works that will blow away the A2 (well anything in the size-class of the ones i'm working on basically).. I have one light in-the-works that is 1600 lumen from a 2 1/2D (can do it in a 2D but it's pushing the batteries a bit past their recommendation) 

The 'favored' hosts will likely be 2D 800-900 lumen regulated output.. 40 min runtime.. same light in 2 1/2D host is 75min runtime.. 

I Really love the 2D-3 host.. there are a lot of possibilities.. 6AA.. 8AA..R123x9 17500x6... with losing some output capacity you can put 4x17600s in series for 14.4V.. amazing possibilities.

-awr


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## StoneDog (Oct 3, 2005)

Hmmm... the 1160 is rated at 618 lumens at 6.0v. That may not be much in the world of hotwire modding, but it's definitely up there and I would bet it beats an SF M4 HOLA and comes close to an M6 HOLA.

Given that specific application, the 1160 in a Mag 2C driven by 2x18650 would make for a bright little light. Runtime wouldn't be spectacular but might be close to the A2. And if the ckt does indeed cut out when Vbat drops below the desired voltage, then it would be safe to use unprotected cells.

I would be surprised if you and the other hotwire modders would be satisfied with this configuration, but to a newbie it sounds like a great DIY starting point. 

Jon


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## andrewwynn (Oct 3, 2005)

the 1160 is an awesome bulb to put in a magcharger.. you'll get more like 500 to 550 lumen once you factor in switch resistances.. but it's a real winner and a total 'gimme' 

2C 2x 18650 would need regulation to get the voltage down or you'll melt the bulb.. but it's a total winner.. 1.6C and like 37 minutes runtime.. the bulb can be turned up to 'ludicrous speed' or even up to 'plaid'.. i would bet 750-850+ lumens is not out of reach with that 2C 2x18650 solution..

the normal modders haven't done that combo because it requires the regulator.. in-general DD is the only thing people do in hotwire.. very rare to find a regulated ckt, what i'm trying to change. 

-awr


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## NewBie (Oct 4, 2005)

Andrew:

Take note of that MOSFET's datasheet, where the on resistance is specified at an internal die junction temperature of 25 degrees C.

It doesn't take much to raise the on resistance by a factor of 50%, resulting in adddional losses, especially if you have a high thermal resistance from junction to ambient. See page 4.


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## JohnMuchow (Oct 4, 2005)

Andrew,
I'm glad the Micrel chip looks like it's going to work!

I haven't given this a lot of thought but do you even need to worry about the inrush current? Since the regulator will see the big voltage jump across the sense resistor, won't it instantly bring down the FET's gate voltage level to keep the sense resistor voltage drop at 35mV or less? Just size the sense resistor to ensure a max current level that is OK...especially for prolonging bulb life by minimizing turn-on shock.

You've picked a darn good FET there (my favorites are the IRL1404 and IRF1405). Since the FETs are being used as voltage-dropping pass elements, they probably won't ever get even close to being turned on fully. I think that the Rds-on value won't matter too much since they'll be operated in their linear region and the Rds-on will be much higher. You might be able to save some $$ by going to a higher Rds-on FET with equal power-handling specs. Try www.arrow.com, they have some great prices on quantities over 50pcs.

More stuff I haven't thought about too much... 
I'd try to find the FET with the lowest junction-case thermal resistance to minimize the need for a heat sink. The IRF1405 has a j-c resistance of 0.45 so it is a lot more efficient at moving the heat away from the junction and lowering its temperature for a give heat sink size. I'm not sure if it's worth too much of your time at the lower power levels we're talking about here, but it sure made a big difference for an application of mine where each FET was dissipating 45W continuous!  

Good luck with your project!


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## andrewwynn (Oct 4, 2005)

actually it does take 'much'... to rase the resistance 50%.. up to a whole 0.006ohm! is 140C.. or 286F! that's close to melting solder (tangent: i did actually heat up a soldered joint hot enough to melt itslef in an early test of one of my hotdriver circuits!).. i couldn't figure out how the heck this wire kept falling off my transistor but apparently it was heating up hot enough to desolder itself!)

I have the FETs now... i also have the p-ch versions... they are 'rice-size' no wonder they can only handle 2.5W.. but the N-ch 1302 has a case-size that is the size of an T0-220 but w/o the tab and the feet are pre-bent to fit as if surface mounting.... the 'bottom side' is metal.. i will likely be using arctic silver to attach the bottom to some copper that can be made the right shape to fit the inside of a mag body, so i can use very thin layer of AA to conduct heat to the body. 

-awr


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## StoneDog (Oct 4, 2005)

andrewwynn said:


> the 1160 is an awesome bulb to put in a magcharger.. you'll get more like 500 to 550 lumen once you factor in switch resistances.. but it's a real winner and a total 'gimme'
> 
> 2C 2x 18650 would need regulation to get the voltage down or you'll melt the bulb.. but it's a total winner.. 1.6C and like 37 minutes runtime.. the bulb can be turned up to 'ludicrous speed' or even up to 'plaid'.. i would bet 750-850+ lumens is not out of reach with that 2C 2x18650 solution..
> 
> ...


 
Well, if/when this ckt is available I'm definitely going to give it a shot. 'Might even spring for a Mag 2C in HA. 

Jon


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## evan9162 (Oct 4, 2005)

Looks like you got the '1302 in a TO-263 (D2PAK) surface mount package, though the 1302 datasheet shows a TO-220 package. Were you intending to use this package, or would you rather have the TO-220?


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## NewBie (Oct 4, 2005)

Another method for doing this that has proven itself with the cavers is to go PWM.

The well known and infamous LVR regulators for bulbs are designed by Willie Hunt, and you can contact him at [email protected]. It has multiple selectable brightness levels, and has been around for many years, well known, established, and reliable. The multiple levels are extremely handy, especially when you don't need peak lumens and would like additional runtime.
http://www.cs.indiana.edu/~willie/lvr.html

His regulators can handle up to 25 Amps and are 99% efficient.

It varies the PWM duty cycle as the battery voltage drops to hold the bulb brightness constant.

Bulbs are much more suitable than LEDs for PWM, as they respond much slower, responding more due to the heating cooling time constant of the filament, and an average state is reached. LEDs respond extremely rapidly, and an average state isn't reached, even pulsing at 1,000,000 times a second.
(don't get me wrong, there is nothing wrong with PWMing LEDs, when the maximum current is limited).

Though, I didn't see where he mentioned inrush current limiting, there are several ways of doing it, you could run linear up to the point where the bulb filament heats up, then switch to PWM, or run the PWM very fast in the beginning, then switch to a lower frequency once the filament was heated up.

Or you could go all the way and add the cap and inductor, ending up with a switching supply, which you can fully soft-start and all, and if you choose the right switcher chip, you can go to 100% on.


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## andrewwynn (Oct 4, 2005)

i think i typed my reply before JMs post but didn't hit 'send' 'til after.. 

I will probably not need or use the current limiting ckt.... i am putting in a startup cap that is 4.7x the size of the design, it will probably take about 2-4msec to turn on, the 'turn on' is linear in volts.. i will do some measuring of peak current and peak voltage when i'm testing.. my fluke will measure down to 1msec peaks. 

in the ckt with the optional R4 (or the magswitch hack USING the switch of the maglite AS the R4).. it will limit the current to the max of 3.33 to 3.5A. I really would like to have that built in to the circuit.. i do have some high-quality 0.1 ohm sense resistors in-fact that i could use in the R4 case.

In the circuits where the Vbat is close to Vbulb (1185 solution).. the FET will get to the point of being turned on completely, and the 14.4V solution with the 1154.. likewise.. however in the 1160 / 7.2V and the 1166/ 14.4V solution the FET will never be fully turned on.. the FET i picked costs about $1.50 which i don't know that i need to find a cheaper one and this way i only need one for any voltage.. the same exact ckt will work from like 1.5V to 20V. (well the low end might not go quite that low). 

I am going to use the FET with high current through it and high voltage across it.. it won't matter what FET it needs a major heat sink.

In the current design it will be built into the KIU switch which has a solid chunk of aluminum about 26mm diameter and 9-10mm thick... it will be in direct contact with the body and will have AA thermal compound keeping it connected.. probably good for 100W continuous (of course you'd not be happy to hold the 150C flashlight), but the FET would be happy as a clam. 

The FET in a couple of my design possibilities was 9W continuous with fresh batteries and one was about 20W... i do want to have serious power dissipation capability, but 10W is a plenty and i think that what i came up with will only heat up about 15-20C with 10W continuous. 

evan:.. yeah i got the D2pack on purpose.. the 1302s is the D2PAK datasheet.. I wanted something smaller and don't mind having to use arctic alumina epoxy to attach the thing to the heatsink... once i get in under the hood i might want to re-do that so i can use the TO-220 and just screw or clip the thing on but time will tell.

newbie.:

I actually found that exact website when doing my google for LVR. I emailed the email you suggested (and listed) and it bounced. 

The beauty of a switching regulator is of course that there is virtually no power loss on the pass transistor! I was hoping that i would find an IC like the gem that john found that was a PWM switcher but in my case i'm trying to drop so little voltage in most cases that though the efficiency might be as low as 95% early on, they get to 98-99% in most cases where the Vbulb is close to the nominal Vbat. 

I didn't notice if or what he did about the startup current in his regulators.. he uses µC so it can be anything... my bet would be a linear rise in Vgate 'til voltage is achieved.. he does have a really neat feedback circuit that shuts the thing off automatically in the case of no bulb.. quite a nice regulator.. but you can look at the schematics.. quite a bit more complicated than what i'm working on.. i want 'dirt simple'. 

Bummer.. no ICs in the mail today! i have this IC and another neat little IC that is a simple op amp, comparator, and Vref in a single 8-pin chip.. i can build a very simple LDO from that, it's like 6 parts vs 10, not to mention 8 vs 14 pins.. i think for the 'copycatter' that might be a lot nicer and i'll have the circuit online in this thread soon. 

that design is 'ludicrously simple'.. but still uses a 'fancy' part so i have another design i'm working on to make a ludicrously simple ldo just with an FET, a zener diode and a couple pots. 

you can see the thread in batteries included (typically right next to this one)

-awr


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## NewBie (Oct 4, 2005)

Maxim makes a part similar to what you were talking about, but only good to 7V:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1221
High-speed for 5.5V:
http://pdfserv.maxim-ic.com/en/ds/MAX9000-MAX9005.pdf

Microchip also makes one that works to 5.5V:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010431

Linear Tech makes one thats good for 12.6V:
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1004,D4396

Another very interesting part for 32V with ref, current source, and two op-amps:
http://www.st.com/stonline/books/pdf/docs/4950.pdf:


Of course, if you don't need the internal reference, since there are many low cost small external references, you can also always use the very low cost LM392 op-amp/comparator combo.


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## andrewwynn (Oct 5, 2005)

hey i really like some of those.. they are just like the one i found but some have higher voltage maxes.. the one i found has a max too low to work with my 14.4V solution... i need to put a Vdropping diode in series to make it work.. 

I finally took a closer look at how the KIU socket works.. and it looks like i can fit the circuit inside between the KIU base and the plastic magswitch case... the heatsinking to the case will be fantastic. I should be able to put the pot in in such a way i can access it from the top to be able to adjust the output. 

STill didn't get the controller ICs yet.. 

Anybody know of a PWM version of the ICs in this thread? It would allow a wider range of control.. the problem is the circuits get far more complicated when you have to add in the inductor that most switchers use.. it should be possible to have strictly FET/PWM to operate incandescent lights just like the ones mentioned above that willie makes. 

-awr


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## NewBie (Oct 5, 2005)

Could you make it work with one of these, skipping the inductor and integrating or averaging the output waveform before feeding back in?


http://www.st.com/stonline/books/pdf/docs/7335.pdf

I've seen a number of circuits that are used to control peltiers/heaters to a temperature, via PWM on the web, which is essentially very similar to what you want to do, but do it vs. average voltage on the output.


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## andrewwynn (Oct 5, 2005)

i think i saw that exact device .. you would think that putting a cap on the bottom leg of the feedback bridge you could get an average voltage.. the concern i had was w/o the inductor the load will get full voltage pulsed.. maybe just a big enough output cap to absorbe the pulses? I want a device that will go to 100% duty cycle when the battery is low enough and has almost zero dropout, so there can't be any series resistance (inductor, sense resistor).

This is the kind of device i was thinking about.. and with PWM i could use the tiny pch hexfet i found that is 8mohm resistance reading on it says that it has a max duty cycle of 95%, so there would need to be some voltage overhead for this to work, but for several of my designs that would be fine.. i like it, i think i'll have to try one out. 

-awr


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## NewBie (Oct 5, 2005)

andrewwynn said:


> i think i saw that exact device .. you would think that putting a cap on the bottom leg of the feedback bridge you could get an average voltage.. the concern i had was w/o the inductor the load will get full voltage pulsed.. maybe just a big enough output cap to absorbe the pulses? I want a device that will go to 100% duty cycle when the battery is low enough and has almost zero dropout, so there can't be any series resistance (inductor, sense resistor).
> 
> This is the kind of device i was thinking about.. and with PWM i could use the tiny pch hexfet i found that is 8mohm resistance reading on it says that it has a max duty cycle of 95%, so there would need to be some voltage overhead for this to work, but for several of my designs that would be fine.. i like it, i think i'll have to try one out.
> 
> -awr




Right, thats one of the drawbacks of PWM, be it LED or Incandescent/Halogen source.

Of course, as you know, a switcher which can hit 95-98% efficiency, with a little skill, and choosing a controller that can do 100% duty cycle for the switcher, and you get the low loss of the switcher, without the heat produced by a linear, the slow gentile ramp up of soft start, plus the power that had to be burnt up in a linear, can now go to runtime, and a tiny part of it to run the switcher.

Also, since the switcher acts as a method of transforming the power to what the bulb needs, when the batteries are fresh, the load on the batteries (especially current) is reduced, resulting in less loss in the batteries.

Food for thought.

(yeah, I know, you are trying to keep it braindead simple)


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## JohnMuchow (Oct 6, 2005)

Andrew, this was posted by Bob Monsen over on the sci.electronics.basics Usenet group. Just tossing it into the mix.... :naughty: 

Another way to control brightness is to use what is called a PWM circuit. Basically, you give your pass device a pulse every once in a while, and control the percentage of time it is on. Since you aren't just burning up energy with a resistor, it is often cooler and more efficient. A simple circuit for this consists of a cmos 555, an N-channel JFET, a cap, and a pot:

-----------------------o--------------o--Vcc
| |
| ||--'
.--------. | || J1=BF245B
.------+Vss Vcc+----' .->||--.
| | CN555 | | | 
| | | | |
| | tr & th----------o------o
| | | R=470 |
| .---+OUT DISC+---o-\/\/\/\--------o
| | | | | ^ |
| | '--------' '----' |
| | |
| | |
| '-Gate of logic level NMOS ----- C=1uF
| -----
| |
-o------------------------------------o--Gnd

Call the current through J1 'I'.
The period is going to be the sum of the charging time
Tc = (1/3 * Vcc) * C / I

and the discharge time is
Td = R*C*ln((2Vcc - 3RI)/(Vcc - 3RI))

The duty cycle, which is what you are interested in, will obviously be Tc/(Tc+Td) since OUT is high during Tc.

The odd thing is that if you simplify this, the duty cycle doesn't depend on the size of the capacitor; it only depends on vcc, Id(J1), and R. Thus, you can pick a cap that is small enough so you don't see a flash, but not too so the pass transistor requires too much dynamic current. The duty cycle defined by this monster:
Vcc
D = ---------------------------------------------
Vcc + 3 R I ln((2 Vcc - 3 R I)/(Vcc - 3 R I))

So, when R is 0, D is 1, and when R is Vcc/3I, D is 0

That means that when R=Vcc/3I, the thing will simply stop, with output low. The reason is that the discharge pin won't be able to pull the trigger pin lower than Vcc/3. When R=0, it won't take any time to discharge the timing node (well, almost no time) so D <- 1.

The N-JFET will vary as to how much current it will source in this configuration. If it is sourcing too much, put a small resistor between the drain and the point where the gate attaches; this will lower the current. However, you need to make sure that your new resistor times the current isn't bigger than Vcc/3. If it is, the output will get stuck trying to pull the timing cap up to 2/3 Vcc, which means output will be high and your pass transistor will be on all the time. If you can't find a JFET, you can use a couple of PNP transistors as a reasonable current source, like this:

--------o---------o-------vcc
| |
| [Rxx]
| |
e |
b--------o
c |
| e
o--------b
| c
| |
[Ryy] '----- current out
|
GND

Rxx sets the current to near I = 0.615/Rxx. Ryy should provide 1/10 of the
current through Rxx, so
Ryy = 10*(Vcc - 1.3)/I
---
Regards,
Bob Monsen


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## andrewwynn (Oct 6, 2005)

i think you meant to use the ubb

```
tag to format those... 

it will monospace and keep the whitesapces.

the last posts we were talking about using PWM.. i can't tell from that circuit but it 'sounds' like it's just a PWM like the lioncub.. no regulation just a duty cycle percent of output.. can you 'modify' and put that into a 'code' tag so it's readable? 

-awr
```


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## JohnMuchow (Oct 6, 2005)

Awwww, crap. I thought I had monospaced it. I'll get on it.
It's nothing special, just more stuff to add to the mix as possible options and inspiration to better designs.


[Edit] Arrgghh....CPF stripped out all of the spaces. I'll have to manually put them back in later or go get the post again. <deep sigh>


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## andrewwynn (Oct 6, 2005)

i would copy/paste from the source again.. somehow the whole post is in a funny font though, only the 'code' should be. 

there is art to ascii art for sure. 

-awr


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## JohnMuchow (Oct 7, 2005)

OK, I tried everything I could think of and it won't format properly.

...yes, I tried that.

...yup, tried that too.

If anyone is interested in the circuit, send me your e-mail address and I'll send a Notepad file with the post in it (where it's properly formatted). If you want to, check out Usenet's sci.electronics.basics group, 10/2/05, 2:10pm post. Look for Bob Monsen's response to the original post.

I give up.


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## andrewwynn (Oct 7, 2005)

```
-----------------------o--------------o--Vcc 
                       |              | 
                       |          ||--' 
        .--------.     |          ||    J1=BF245B 
 .------+Vss   Vcc+----'       .->||--. 
 |      |  CN555 |             |      | 
 |      |        |             |      | 
 |      |     tr & th----------o------o 
 |      |        |     R=470          | 
 |  .---+OUT DISC+---o-\/\/\/\--------o 
 |  |   |        |   |    ^           | 
 |  |   '--------'   '----'           | 
 |  |                                 | 
 |  |                                 | 
 |  '-Gate of logic level NMOS      ----- C=1uF 
 |                                  ----- 
 |                                    | 
-o------------------------------------o--Gnd
```


you have to put

```
before and after ONLY the 'code'.. the second needs / before the c in code.

This circuit is a simple blinker... you set the frequency or pulse width with the potentimeter.. not sure which, not too familar with the most famous IC ever made ;) in any event.. it would be neat to explore PWM solution but i need something with regulation not just dimming.. the chips talked about earlier show a lot of promise. Also in the 'ludicously simple' thread we have pretty much nailed down a 'dirt simple' design with like 2 transistors and a couple pots.,. could be possible to make a $2 high-tolerance Vreg for hotwire that is made from big enough components to hand-wire on a proto board so people can DIY vs buy pre-fab, i love it when that happens. 

-awr
```


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## JohnMuchow (Oct 7, 2005)

andrewwynn said:


> you have to put
> 
> ```
> before and after ONLY the 'code'.. the second needs / before the c in code.[/QUOTE]Thanks Andrew, I'm sure I tried that, but I guess being sure doesn't mean too much sometimes. :)
> ```


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## andrewwynn (Oct 9, 2005)

got all the parts, what i need is more time.

-awr


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## andrewwynn (Oct 14, 2005)

awesome.. finally wedged in about 90 minutes between nano production and a movie to assemble a breadboard with the hotdriver.

IT KICKS ***. 

I should end the review there, i suppose how do i improve on that? 

Well it's a bit too big to fit in a light just yet but it's just plain awesome and incredible.. i haven't figured out the correct value to use for the pull up resistor for the enable pin to get the shutdown ckt working yet but so far it's been incredible.. The Vout change with Vin change is negligible.. and i've operated it with over 3V of overhead w/o a hitch (FET does get a warm).. but i have a heat-sink on it so it's not a problem at all. I need to get some measurements yet to show the Vdrop etc but it's just plain incredible just as expected and can't wait to make the SOIC version to put inside a KIU socket (there is room between the magswitch and aluminum cup on the socket!).. aiming to put the adj. pot lined up with a hole so i can change the output voltage. 

pictures and numbers to follow. 

Ok.. we ran a few bulbs on it... a 20W12V bulb was the first tester... but here are a couple interesting models:

1166 @ 12.6V and 2.07A = 26.3W.. 965 lumen. 36.7 lum/W! 
1160 @ 6.64V and 3.95A = 25.8W.. 834 lumen. 32.3 lum/W!

note: i may have fixed the flag at some point in the future but didn't update this post.. the next paragraph might be outdated if that happens:

I haven't figured out the flag loop correctly yet. connected like the ckt it just stays off.. i think i need to use an FET to get it to work.. doesn't have enough drain to turn on a PNP it seems... but the N-ch FET i haven't figured out exactly how to make it take the EN low when it goes low.. though here's my latest thought:

right now the schematic shows a pull up resistor above the EN.. the idea is that the flag goes low and should pull the EN down.. the problem is apparently the EN input resistance is so high that it's always down. 

So.. new plan.. voltage bridge from hot to ground.. two 10k resistors.. the center is attached to both the flag and the EN. when flag is high (normal operation.. it measures like 3Mohm), and i didn't measure the EN resistance but it's probably also very high.. this would put just about 1/2 Vdd on the EN which will definitely be enabled.. when the Flag goes low (when Vout < 92% setting).. it pulls the center of the bridge down to zero? putting all the vdrop on the top half of the vbridge and shutting down the IC. 

Well i'm sure there'll be an update soon.

-awr


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## andrewwynn (Oct 14, 2005)

oh.. btw.. running the 1166 i had like 30-40mV drop because the voltage is so high that the Vgs was not high enough to get the 4mohm resistance.. but when i ran lower voltasges like the 1160 at 5.5V.. i measured 13mV drop.. pretty cool. I found a trick i can probably use in the high-voltage designs to reduce the Vdrop, i will be trying them out.

-awr


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## andrewwynn (Oct 15, 2005)

OK.. some neat updates:

first.. the updated schematic:







I finally figured out how to use the shutdown flag.. i had R3 in there but apparently the chip assumes 'off' so the flag pin being grounded on 'energize' pulled down the EN pin... i went through like 6 hoops with crazy voltage bridges even designed a PNP transistor option before i realized what i needed was a simple 0.1µF cap across R3 so that on 'power on'.. when flag wants to be low... C5 holds the voltage drop on R3 low just long enough to turn on the chip.. at that point as long as the voltage is high enough to keep things running 'flag' goes high and R3 lets nearly full Vbat through to the EN pin. 

Oh.. i just realized i never put C4 into my prototype  I also used only R1 and no R2, but i'm changing that.. i don't like the performance changes at various voltages.. R2 is supposed to be close to 10k. 

The latest test: running a 1160 bulb at 6.6V.. holy COW that's bright! 

see for yourself... click here.

3551K color.. 863.3 lumen.. 19.7 estimated hours.. (well i've heard they have the life span goofed on the 1160 on the site so we'll see how long that it'll really last.. the beauty is.. i can just turn down the voltage if it's too high!). 

some numbers from the latest test:
7.2Vbat
6.6Vbulb
.48V FET

6.66Vbat
6.56Vbulb
15mV on the FET.. that actually calculated to exactly 4.0mohm! how friggin cool is that! The reason that is a bit of a surprise... to get 0.004ohm out of that FET.. you need to push the gate with 10V! well that means if you have a bulb with 6.6V on it you need to supply 16.6V to the gate from your 7.2V battery.. the magic IC has a voltage tripler in it... it has a zener to protect against putting too much voltage, clamping it to 16V over the source.. and the FET i picked out can handle 20V gs. 

The thing shut off at 5.2V.. but that works better now.. right about exactly 6V it'll shut down.. but the reality is... since LiON batts are pretty much depleted at 7V.. you'll only see less than 1minute of dimming when the thing dies... other wise absolutely max brightness start to finish!

at nominal Vbat.. it is putting 3.87A through the FET with .48V.. so that's 1.86W.. with 25.54W on the bulb.. that means.. 93% efficiency almost immediately... it only goes up from there. 

I can't wait to get the prototype for the 'ludicrously simple' driver going but that'll probably be in a month or so when i'm done making nanos... they are sooo cute.. you have to go check out the circuits: http://nano.rouse.com 

I can't wait to run some tests with the 1185 and the 1254 bulb! 

I've run the 1166 at about 12.5V.. and it pretty much looks exactly like the 1160 at 6.6.. 

All in all.. thanks to anybody that's helped on this little project.. i will be miniaturizing it to fit into the aluminum cup of the KIU socket soon, probably be like next weekend after i'm done with a couple nano batches. 

-aw


----------



## andrewwynn (Oct 15, 2005)

Here's a pic of the breadboard:





notes: 

the skinny resistor where the right red clip is... i'm just using as a test lead.. same for the one sticking up on the right side.. the black is attached there. 

The tiny white wire over on the right.. that is soldered directly to the gate of the FET.. there is a red and blue one on the drain and source as well.. i was getting errors of 20+mV when i tried to measure from a nearby hole.

the 4.7k resistors are both gone.. they have been replaced with a jumper from pin 3 (near side left is pin1).. to pin 14.

the skiny red wires on the top over the bulb go up to a 3mm SMD 200k pot i was using before i realized i could get by without it completely... now there is just a 50k resistor from Vcc to the EN pin in parallel with the left top blue capacitor. 

notice that i melted the CRAP out of the poor breadboard... I missed it because when i'm running the thing i have a welder's plate in front of the bulb.. oh.. that zener right by the bulb.. that's the welder's plate holder so it doesn't lean against the bulb. Its' really neat to check out the filament when it's lit! (but whoa that plate gets hot too). I think i might wire this ckt up on a perfboard from RS to show people an easy DIY vs the notsomuch DIY that i'll be building with the SOP14 chip.. i will be able to use the SMT caps i bought.. just directly between the pins!

It just keeps getting better and better. I'm going to get this into my 3bore 2D light that runs from 7.2V LiON pack.. and push the crap out of the 1160 and see how long it can take 6.6V and 863 lumen! 560 out the front (using the usual 65% formula). 

863 lumen.. i'll maybe choke that back to 800 just to conserve the bulb life.. in any event.. a helova light from a 2D mag!

The spookier model will be the 1166 running about 900 lumen from a 1D light.. it will be 'overdrive' on the batteries so i won't recommend people copy me but it will be a force to be reckoned with to be sure. 

The 'next level' is we are working on putting the osram bulb they use in the USL into a 12 cell pack in a 3D mag host that is bored inside to fit it.. but regulate the voltage so we get a flatter runtime and with an add'l cell probably even more runtime... i'll only have like 30-40mV drop on the FET running 100W.. i would put that into the 'acceptable' column. 

-awr


----------



## NewBie (Oct 15, 2005)

andrewwynn said:


> Here's a pic of the breadboard:
> 
> The 'next level' is we are working on putting the osram bulb they use in the USL into a 12 cell pack in a 3D mag host that is bored inside to fit it.. but regulate the voltage so we get a flatter runtime and with an add'l cell probably even more runtime... i'll only have like 30-40mV drop on the FET running 100W.. i would put that into the 'acceptable' column.
> 
> -awr



Well, with an extra NiMH, you'd be looking at actually having to drop that additional 1.1V or so, at 8A load current (I assume thats what the bulb draws). Power = Amps * Current. 1.1V * 8A = 8.8 Watts dissipated (the MOSFET has to burn the power it is dropping). Guess what? The power the linear regulator is burning, is what the additional cell contributes. The advantage, is that you get to stay in regulation longer, before the bulb starts dimming. There is some additional power burned due the internal resistance of the MOSFET, but it is minimal, at about 1/4 Watt. Without the extra cell, you'll still dim like the standard light. The advantage? Less insta-flash with the circuit.


----------



## andrewwynn (Oct 16, 2005)

yup about 9W is what i estimated.. i didn't do all the math but my estimate was that it would run about the same time just w/o dimming... actually the switch that the mosfet would be replacing has more resistance so that's a wash. And yes.. no more insta-flash but also.. could set the output voltager higher than the nominal voltage if the bulb can handle it.. i.e. 11 cells = 13.2V... with 12 cells i could use 13.5 or something.. that is still way less than the 15.2 that 11 cells are going to have fresh off the charger.. the voltage 'ramps up' to full with this regulator.. probably in just like 20-40 miliseconds but still not instantaneous as well. I haven't done peak measurements with the current yet but the voltage measurements my meter only goes down to 1msec and there is no peak whatsoever.. does not overshoot the set voltage.

back to the non-dimming.. i've noticed that with heavy drain that NiMH are really exhausted at 1.1V... so.. 12 cells x 1.1V = 13.2.. coincidentally the exact same as 11 x 1.2... in other words i 'just now' did the math.. and it works out to no dimming 'til exhaustion.. when we've pulled 7-8A out of the CBPs we have been measuring 1.2V/cell still.. that's pretty exciting.. i'm sure the body will get warm around the switch from the mosfet heat sinking but as the bats. drain the FET losses drop, so it might not be that terrible, and like you said.. no worries about the bulb blowing. 

-awr


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## StoneDog (Oct 17, 2005)

hmmm... So does this Kiu socket work in a "C" sized mag? A 2C w/ 2x18650 and an 1160 would make a _nice_ little light. 

Jon


----------



## andrewwynn (Oct 17, 2005)

There is a socket like KIU for C.. not sure if it's actually KIU.. and yes... 1160 and 2 18650s would be able to get you at least 800 lumen, the testing is going to start soon to see what realistic battery life you can get but i've been running the one on the bench hot enough to melt my breadboard.. about 860 lumen.. I got some advice that it's good to keep the bulb below 6.3V but when the regulator keeps the voltage below your set voltage i'm thinking it'll be higher possibilities. 

-awr


----------



## andrewwynn (Nov 12, 2005)

Ok.. finally had a bit of time between nano building to 'take a break' yeah right.. and fix the bug in the driver that was driving me MENTAL! 

(the bug: the shut down ckt defaulted to 'off'... if it was connected at 'startup' it would say.. 'oh.. there is zero volts on the shutdown pin i must have already shut off' and the hysteresis program held it off no matter what the voltage.. aaarrrgh.. 

So.. squashed the bug.. glad i was doing the testing at low voltage (1160 bulb).. because as it turns out.. much harder to fix at lower voltages.. when i moved up to the 1166 bulb the problem was much less of a problem. 

Oh.. i managed to bump off the voltage setting resistor with the 1160 bulb in there... and it puts Vbat to the bulb in such a case.. i couldn't figure out why it didn't seem to be regulating but the only way to be sure it so turn up the voltage 'til the output voltage stops climbing... well.. the voltage stopped climing at about EIGHT VOLTS... it went right to ZERO! oops! well fortunately i had a different bulb to finish the work... i think i need some more 1160s though i'm clean out. 

Oh i just have to know so here i go look. 

8.0V on the FIVE volt 1160 stats look like this: (yes i'm completely aware the calculations aren't that accurate when going more than 20%, but it's still interesting!)

4.47A... 35.7W.. 1700 lumen.. 47.4 lumen/watt.. 3761 CCT.. 107% overdrive.. and 66 degrees Kelvin above the melting point.. it did last approximately 1.0 seconds... but i was 'ramping' the voltage.. and in the mid seven volts.. wow did that look pretty! 

Now onto the more serious... 

First i tested out the circuit with a $4 westinghouse 12V 20W bulb.. and preset the voltage to about 12.5.. so it would be close so i could run the 1166.. the voltage was within 1/10th of a volt when i switched to the 1166.. 

Setting the voltage input to 14.47 V to simulate running from 4x LiON.. the bulb was getting 12.5V.. at 2.04A.. changing the input voltage from 16.8V to 14.0V (dead cells).. there was no appreciable change in bulb voltage.. 12.50V the whole time.. 

That works out to: 
914 bulb lumens
594 torch lumens.. of course in my case there is not torch.. just the bulb sticking up out of the melting breadboard).
25.7 watts.
2.05 amps
35.6 lumen/watt.. 
8.2 hr expected life span
3533 CCT
12% overdrive
162K from melting point
86.8% driver efficiency. (just about 4W lost on the circuit)

I plan to run this bulb in a 2D host with a modamag 8AA->2D hacked into series-parallel... that will get me a 1.4AH 14.4V source.. running at 2.04A means about 40 minute runtime.. 900 lumen 2D flashlight.. (600 torch lumen).. it will also not dim in the least 'til the last minute where it'll plummet like a rock down to about 700 lumen before shutting off. 

For fun i took a LionHead i had handy and held it over the bulb while i lit it up.. and holy cow what a nice bright light! 

here's a picture of the thing operational on the bench:






the rest of the slide show is HERE

Darn, just noticed i unhooked the second meter which was typically either showing the bulb voltage or the LDO (which btw was 0.006V once the Vin is 12.506V or lower.. however the 15V is the current Voltage IN, not bulb voltage! 

Oh some fun trivia on that picture!

Lot's of fun things to see. 

the heat-sink for Fivemega's BAM is in the bottom left.. some progold sitting on top of a panel of nano PCBs just above that.. 

TWO fluke 87s.. a III and a V.. 

A bunch of nanos almost completed... i love the look of the chargers chips when still attached.. like solders in rows.. the light heads are on the board to the left of the chargers.. 

Looks like there is a bit of a spool of 10µF caps. .

The heatsink on the FET on the hotdriver got up to at least 182F!.. I was pushing it to the limit to see how much power it dissipated with fresh cells (16.8V!).. answer: 8.77W!

Just above the breadboard is my welders plate held onto a machinist square by a rubberband.. that is normally between me and the bulb for protection both from light and possible explosion of the bulb. It is really wonderful to see the likes of an 1166 running at 12.5V from less than a foot away but through a welder's plate!

In the magnifying lens.. you can see one of my favorite tricks, i hope somebody copies.. you can see the jaws of the vice i use to hold circuit boards while soldering.. and there is a spool of no-clean Kestrel (sp) solder... but see the round circles? those are stacks of magnets.. you can only see the 'top' magnet, but this is the arrangement.. i have 1/4 inch tall stack of 1/8th inch diameter magents.. two of those stacked near each other.. and on top.. a 1/4 inch diameter 1/8th inch thick disc magnet.. arranged like a 'stone henge' arch.. there are two of these and of course they are on the vice 'sideways' so 'top' is actually toward you.. 

This allows me to pull the solder around in a circle almost effortlessly.. but the magnets 'grab' the solder so it doesn't move much when i'm wetting the tip of the iron

Oh last mention on this picture... the bench power supply.. i honestly have no idea how i survived before getting it.. most useful tool in the shop. 

It was less than $200.. it can do up to 60V at 3A or up to 6A at 30V.. has 4 digital displays showing the two independent supplies and their voltage and current.. 

So.. now that the circuit is completely operational and working exactly as planned.. I suspect in a week or so when i get around to maybe batch 4 of the nanos i'll take another break and finally get the driver assembled into my KIU socket into my 2 1/2D FiveMega.. so i can stop melting my darn 1185 bulbs!

Check back in a week or so. 

-awr


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## NewBie (Nov 12, 2005)

andrewwynn said:


> Setting the voltage input to 14.47 V to simulate running from 4x LiON.. the bulb was getting 12.5V.. at 2.04A.. changing the input voltage from 16.8V to 14.0V (dead cells).. there was no appreciable change in bulb voltage.. 12.50V the whole time..
> 
> That works out to:
> 914 bulb lumens
> ...



To use your 35.6 lumen/watt, thats at the bulb. 

IMHO, it is always proper to calculate for losses in the circuit/"ballast"/regulator.

This drops to 30.96 lumens/watt, once you include your circuit losses.

Why did you choose to use 14.47V battery voltage for all the calculations? Did you figure that as an average voltage?

Lets say the 4.2V 18650 cells drop to 4V under load. 4x Li-Ion gives you 16V.
Losses for the regulator are 16V-12.5 = 3.5V, so you take 3.5V * 2.04A= 7.2 Watts loss. (1-(7.2Watts/25.7Watts))*100 = 72.1 % Efficiency. At this point, the total efficiency drops to 25.7 lumens per watt.

I see the small MoliCell ICR-18650J drops to 4V at 2A load, in the beginning, so thats why I used 16V. Figure you did everything at what you figured was the average?


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## andrewwynn (Nov 12, 2005)

don't read too much into a 'freeze frame' of a non-static event.. 14.47 was just the Vin at that particular moment in time... that wasn't a battery.. it was my bench power supply and it was me aiming for 14.4 and over shooting. 

LiON will drop to 3.6-3.7 within a minute of heavy use... i use AVERAGE voltage for my AVERAGE efficiency.. i always use 3.6V for nominal LiON voltage for such calculations. 

yes.. the 35.6 lumen/w is the bulb.. i was just talking about the bulb in those numbers.. wasn't interested in the lumen/W of the whole circuit though it is a valid and interesting number. 

The far more accurate calculations for that circuit are here: 

Nominal Vin: 14.4V
Nominal Vout: 12.5V
Nominal Current: 2.05A. 

Power in: 2.05 x 14.4 = 29.52
Power out: 2.05 x 12.5 = 25.625

That makes for 86.80 % nominal efficiency.. which is actually outstanding considering the amount of voltage i'm shedding at the current drive levels.

getting 914 bulb lumen from 29.52 W = 31 lumen/watt. 

Yes.. at first.. when the batteries are actually 16.8V and about 9W is dropped on the regulator it's 'quite ugly' but that lasts less than a minute.. what you are not taking into consideration very well is the overall average.. since when Vbat gets close to Vbulb... say.. right at the LDO cutout.. 12.507 Vin and 12.500 Vbulb.. now it works out to:.. 

2.05 x 12.507 = 25.639W in
2.05 x 12.500 = 25.625W out.. 

that is 99.94% efficient.. dropping a mere 14mW on the FET! (there is only negligible other resistance in the circuit.. i will be using 18ga wire.. a total of maybe 2-3mohm resistance.. which will be about another 12mW loss. 

When calculating for runtimes etc where it's important.. i always calculate the total circuit.. this was just to show the BULB values.. 

In the end.. the important thing is the average power figures and the average efficiency so i use average values for the calculations... the result.. very useful important real-world details like running 900/600 lumen from a 2D size light for 40 minutes.. that's pretty awesome!

-awr


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## NewBie (Nov 12, 2005)

Ah good, so you do understand the 30-31 lm/W concept for the average lumens. This is important, as most incandescent setups don't have a converter, so it is essential to include it in the lm/W calculations.

Now taking this a little further. As you get into higher powers, than are used with LEDs, you get into an area where it is much easier to get into the 95-98% efficiency range with a switcher.

Remember that loss that is in your linear regulator? I think we said it was 7W or so at the beginning, slowly dropping to 4W, and finally petering off to nothing. Well, if you utilize a switcher, you can reduce that loss to under 1.25W, and with a little work, 0.5W.

Carefully selecting a switcher chip that can run to 100% duty cycle (and there are a number of them out there), you'd be able to recover an average of 3.5W or so during the drain, and lowering the load on the batteries, which increases the runtime.

You could even use a set of jumpers to select different regulation voltages, to accomodate a variety of bulbs, and even cell packs, making five or six cells, with low losses, quite possible.

Anyhow, something to think about.


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## wquiles (Nov 12, 2005)

Andrew,

Is the circuit shown in post #12 above ready to go? Fully tested? I want to know since I want to start ordering some parts to build one 

Will it work well in the 4.5-4.8V range for a WA1319 in a 1D running from 4 CBP1600 high current cells?

Thanks in advance,
Will


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## andrewwynn (Nov 12, 2005)

there is one small modification to the circuit... in the 'optional' shutdown ckt i stole the 47uF cap from C4 (which is not used) and I'm using 50kohm for R3. In addition because i was having issues with load affecting output voltage i changed R2 to 4.7k.. but when i make the actual-size ckt w/o all the xtra wires i'll be trying to go back to 8-9 kohm. 

One last change from the schematic currently listed is that the switch is reloacted to between C5 and pin 14... basically.. pin 3 is wired to hot via R3 and parallel to C5 (now 47uF).. and a switched jumper goes from pin3 to pin14... that's the enable or 'on' switch... the circut is powered continuously. It was only drawing like 17uA when disabled last time i tested but i'll be doing further testing wheni have the unit operational in a light of course. 

The circuit is designed for use as low as like 1.5V but i've only tested it down to about 6.5V. 

I would do like me and buy the DIP14 chip from like arrow or future electronics.. the other parts from anywhere.. RS makes a perfect little perfboard that you could use to solder onto and have a dip-socket you could use rather than using a breadboard. 

I bought all SMD devices and plan to build my first prototype by soldering the SMT chips directly actross the legs of the device. 

The picture above is the exact circut as shown in the schematic with a tiny modifcation to the shutdown ckt and the R2 as described above... it works absolutely brilliantly.. even when running the 1166.. the voltage at cutoff is 2.9V/cell on the batteries.. 

The shtudown/startup issue is more of a problem at lower voltages.. example.. if the batteries get low enough to 'shutdown'.. it would take about 6-8 seconds for C5 to charge enough where it would allow me to restart if voltage is applied... so it's conceivable you could put the batteries in and press the button fast enough that i won't startup... but waiting 10 seconds absolutely always worked... when running the 1166 bulb at 12.5V.. that reset 'wait' time is less than 2-3 seconds.. so there is a chance it will be a longer wait to first use after first installing batteries (this is only an issue after the low-voltage cutoff triggers and only the first time using the light after replacing power). That was the problem i had to fix.. before finding the right combination of where to cut power and what R and C to use.. it would only fire up like 20-60% of the time after reapplying power after a low volt cutout sequence (basically they hysteresis that keeps it off after the event kept working even after replacing the power!). 

So.. now it works and it's awesome and perfect.. i've run my 1166 for well over an hour now at 12.6V.. and the 1160 before i melted it by accidentally applying 8V.. ran for more like two hours at 6.5-6.6V.. both of those are about 900 bulb lumens at that point... it was quite a sight to see.. you can get some idea from the pictures.. most of which the flash did not fire because of the bulb. 

-awr


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## andrewwynn (Nov 12, 2005)

every time i try to 'quote' somebody exploder crashes me dang it.. just lost a 30 min. post. 

ok.. yes i looked into switcher chips.. but the LDO is so much more convienent.. for a bunch of reasons:

1) simpler to construct
2) fewer parts
3) far less in-line resistance.. important because many of my 'uses' are really for just holding back fresh bat voltage.. i.e. regulating 3LiONs to 10.8V like they are supposed to be.
4) no inductor or diode. 
5) no RF noise

The primary benefit would be able to switch bulbs w/o switching battery packs.. that would be a very cool thing.. i've definitely and i'm sure i will continue to look into switcher solutions they are marvy. 

I just 'fell in love' with the little LDO controller used here.. has everytihng a boy could want.. current regulation, voltage regulation, soft start.. low voltage cutout... i don't think it has thermal cutout or regulation.. 

The low volt cutout is an ABSOLUTE MUST since i use RAW cells or NiMH.. either of which over discharge is a no-no. 

I have some really creative solutions of batteries and bulbs.. like a mag85 in a 2D host using 8 primary Lithium AAs... 900 lumens (bulb).. 54 min runtime... the best parts.. one-two punch.. 1) zero maintenance on the batteries.. so it can sit around for months w/o use.. and 2) like 36 hr estimated bulb life when only driven to the 9.87V required to get 900 bulb lumen! The other one in a simlar class is the 1160 run from 9 123s.. 863 lumen for 58 minutes.. in a 2D host.. primary cells.

I want to make some really nice hotwire lights for people that don't use their light daily or even necessarily weekly.. the light you leave on your night stand for instant access if you really need it but don't use it for daily chores, that sorta thing. 

In any event.. 800-900 lumen (500-600 torch lumen) from primaries in a 2D host is doable.. just need the regulator to make sure that that resting 9V on the batteries doesn't get to the 5V 1160 bulb! under load the CR123A sags a LOT! 2.5V at an amp is the number i use for my calculations.. so.. 9 batteries is 3x3 or 9V resting.. but 7.5V under load.. looks like the 1111 would even be better.. could run that at about 900 lumen for about an hour from 3x3 Lithium 123 primaries! 

-awr


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## NewBie (Nov 13, 2005)

andrewwynn said:


> every time i try to 'quote' somebody exploder crashes me dang it.. just lost a 30 min. post.
> 
> ok.. yes i looked into switcher chips.. but the LDO is so much more convienent.. for a bunch of reasons:
> 
> ...



Definitely, essentially basic electronics.




andrewwynn said:


> 2) fewer parts
> -awr



Yes, and in trade, you burn up 4x or more power with your circuit




andrewwynn said:


> 3) far less in-line resistance.. important because many of my 'uses' are really for just holding back fresh bat voltage.. i.e. regulating 3LiONs to 10.8V like they are supposed to be.
> -awr



Somewhat less in-line resistance. There is one MOSFET and one inductor in line, during both phases of the switcher operation. So you use a nice N-Ch MOSFET at 0.003 ohms and a 0.0025 ohm inductor. Still the total is what, 0.0055 ohms? Again, your trade-off burns up the power, but yes, it is simple.





andrewwynn said:


> 4) no inductor or diode.
> -awr



Most modern switchers don't use diodes anymore anyhow. And you can get inductors with less resistance than MOSFETs. You are limited to how high you can go over the bulb voltage with your circuit, or you start burning some really serious power with your linear regulator. A buck switcher would convert the power, and draw less current from the batteries, which would reduce the losses in the batteries themselves.

In fact, if someone wants to run 9 cells with the 1185, it isn't much of a problem for the switcher, and you will utilize more of the cell energy, since you'd only be pulling 0.712 Amps out of them. At higher currents, the losses in the cells are greater.




andrewwynn said:


> 5) no RF noise
> -awr



Properly constructed, this isn't much of a problem anyhow. When folks were trying to constrain the circuit to fit in a 2AA Mag, trade-offs are made, which cause that problem.


Anyhow, consider it some day.


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## andrewwynn (Nov 13, 2005)

already under consideration from the get-go.. i looked at several really neat switcher chips when developing this very circuit because i like all the benifits of switcher chips also, but i'll be able to make this one a lot sooner and with less grief. 

In even the 1166 in 14.4V solution where there is quite a lot of power burned up on the FET.. efficiencies in the high 80s.. i'd be surprised to find one that can best that.. 

However efficiencies aside.. i like the idea of a buck/boost ckt that can run the likes of 1111 through 1166 from a 10.8V host etc. 

that's a very interesting idea of using higher cell voltage to reduce internal resistance losses... but I wouldn't expect efficiencies higher than 90-92% in any switcher ckit like the type you are describing.

There is no way the case is closed on this subject.. just this round goes to LDO. 

-awr


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## NewBie (Nov 13, 2005)

andrewwynn said:


> that's a very interesting idea of using higher cell voltage to reduce internal resistance losses... but I wouldn't expect efficiencies higher than 90-92% in any switcher ckit like the type you are describing.
> 
> -awr




I'm currently holding in my hand, a stock eval board, which with no alterations and 25V input, I tested at 96% efficiency at 12V and 2A output, goes up to about 96.5% at 3.5A output, and 95.5% at 5A output. It matched the datasheet efficiency curves, within 0.5%. 

With some tinkering, to optimize it for a particular output current, and spending an extra dollar on the inductor, I'm certain the efficiency could be pushed higher.

Not bad for a stock eval board.

True, linear regulators are always the simplest, and quickest to get working the way you want, with a very low level of complexity. 

Good Job and Congrats!


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## andrewwynn (Nov 13, 2005)

that's really awesome... i think the reason for the higher efficiencies ironcically.. higher current  (the circuits i'm working with are always 1A because they are running LEDs).. when i get to 'round two' of the regulator for hotwire i will definitely explore the switcher version.. it would be so nice to have just one single battery and be able to run any bulb... can you try 14.4V input with 4A 6.5V output as well as 12.5V and 2A output?.. and what is the required overhead.. i.e. can i run 12.5V down to at most 14V input? 

ps.. you type really well with one hand. (just teasin' cause you typed 'you are holding in your hand'). 

-awr


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## NewBie (Nov 13, 2005)

andrewwynn said:


> that's really awesome... i think the reason for the higher efficiencies ironcically.. higher current  (the circuits i'm working with are always 1A because they are running LEDs).. when i get to 'round two' of the regulator for hotwire i will definitely explore the switcher version.. it would be so nice to have just one single battery and be able to run any bulb... can you try 14.4V input with 4A 6.5V output as well as 12.5V and 2A output?.. and what is the required overhead.. i.e. can i run 12.5V down to at most 14V input?
> 
> ps.. you type really well with one hand. (just teasin' cause you typed 'you are holding in your hand').
> 
> -awr




You don't know the half of it... One hand has a 3/8" dia hole in it that was drilled about half an inch deep, ouch!

This particular one is not a 100% duty cycle version with the built in charge pump to keep the top MOSFET on for 100% of the time in an ultra low drop configuration. There are some controllers made for topside P-ch, which would not neet the pump, but it is harder to get the high efficiencies. I've got several controller/drivers that will do 100%, not sure where they are hiding, amongst thousands of parts right now. 94.1% at 15Vin with and output of 6.5V at 4A. At 15Vin, 12.5V at 2.5A out, 96%.

Even this could be customized and improved. 

You could also do your own charge pump with a standard floating gate driver, and achieve the 100% duty cycle capability.


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## andrewwynn (Nov 13, 2005)

as long as i can have full regulation i'm not concerned about a few % of efficiency.. The ability to pull the current from the batteries at higher voltage means the lower loss in the batteries will almost certainly counter the difference in efficiency.. 

lemme see how this would compare.. at 7.2V i'm pulling 1.2A out of the 17500 cells.. that's about 1.2C.. but if i can use a 14.4V solution in the same host.. means i need 8 15400 cells.. 27.6W (including converter loss).. means.. 0.96A.. or 1.27C... oh well.. I forgot need to use smaller batteries to get the higher voltage.. so i guess.. no improvement but not a big deal either... it would be of exceptional convenience to have one battery solution for all bulbs. I do favor bigger cells though.. so what about a buck/boost driver where i can use 7.2V to power a range of bulbs from 6V to 14V? 

-awr


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## NewBie (Nov 14, 2005)

andrewwynn said:


> as long as i can have full regulation i'm not concerned about a few % of efficiency.. The ability to pull the current from the batteries at higher voltage means the lower loss in the batteries will almost certainly counter the difference in efficiency..
> 
> lemme see how this would compare.. at 7.2V i'm pulling 1.2A out of the 17500 cells.. that's about 1.2C.. but if i can use a 14.4V solution in the same host.. means i need 8 15400 cells.. 27.6W (including converter loss).. means.. 0.96A.. or 1.27C... oh well.. I forgot need to use smaller batteries to get the higher voltage.. so i guess.. no improvement but not a big deal either... it would be of exceptional convenience to have one battery solution for all bulbs. I do favor bigger cells though.. so what about a buck/boost driver where i can use 7.2V to power a range of bulbs from 6V to 14V?
> 
> -awr




But a fella can grow the host, and take advantage of the lower cell loss and the higher efficiency of the switcher.

There are a few buck-boost parts that will maintain 90% efficiency over the range you mentioned, and one of them will do 95% on either side, pushing 98% at the crossover voltage.

Unfortunately, a boost increases the losses in the cells, as it draws more current from them to make the higher voltage. A buck is the opposite, the current goes down in the cells, increasing their efficiency.


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## andrewwynn (Nov 14, 2005)

true but i'm stuck in a host.. so far i'm just making mods for mags.. so.. boosting voltage means using smalla batteries.. 

However i could see some neat possibilities including 3x 18650 in a 3C and bucking that down to run the 1111 for example.. you can hold it in overdrive to the likes of 900 lumen pretty easy that way.. whereas running from 7.2V it'll start there but quickly drop to 800 or so. 

-awr


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## NewBie (Nov 14, 2005)

andrewwynn said:


> true but i'm stuck in a host.. so far i'm just making mods for mags.. so.. boosting voltage means using smalla batteries..
> 
> However i could see some neat possibilities including 3x 18650 in a 3C and bucking that down to run the 1111 for example.. you can hold it in overdrive to the likes of 900 lumen pretty easy that way.. whereas running from 7.2V it'll start there but quickly drop to 800 or so.
> 
> -awr




But, can you fit 6x 14500 or 6x 18650 into a 3D? That could get you into the 2 hour runtime range, especially with the reduced losses in each cell, due to the lower current.


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## andrewwynn (Nov 14, 2005)

can fit 9x 17500 in a 3D... you can fit 12 14500 in a 3D.. now that's a very interesting solution.. See.. with my LDO.. putting 1185 into a 14.4V solution is horribly inefficient.. oddly enough even so it's just as efficient overall as the 1154 which runs at 14V but is far less efficient in lumen/watt.. 

That would be a most excellent use of the switching driver. 

What you can fit into that host is 12xR123 for 14.4V... you could also put in 12X NiMH... also for 14.4V.. at 35W and say 95% efficiency.. means you need.. only 2.55A from the cells vs 3.35.. that is not insignificant a difference.. very interesting though there. 

In addition.. it would be nice for the primary based solutions like running the mag 85 from 12x 123 primaries.. which would be 12V no-load but 10V under load. 

I will definitely be exploring 'version two' of the hotdriver in the form of a switcher.

-awr


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## NewBie (Nov 15, 2005)

andrewwynn said:


> can fit 9x 17500 in a 3D... you can fit 12 14500 in a 3D.. now that's a very interesting solution.. See.. with my LDO.. putting 1185 into a 14.4V solution is horribly inefficient.. oddly enough even so it's just as efficient overall as the 1154 which runs at 14V but is far less efficient in lumen/watt..
> 
> That would be a most excellent use of the switching driver.
> 
> ...




Speaking of the 12 R123 cell configuration, and your 12.5V bulb at 2.05A, do you realize you'd only need to pull less than 0.6A out of the cells? There would be a tremendous efficiency increase in the batteries alone, with a switcher vs. a linear.

Hopefully I can get you interested into researching it more for your products. There are some really nice improvements you can make with a switcher in those configurations...


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## andrewwynn (Nov 15, 2005)

yes i did realize.. actually i already knew all this.. just wasn't going to happen for 'round one' because of the simplicity of the LDO solution and that i already within 2 days had a schamtic and within 2 weeks had an operational breadboard model. 

Most of the designs the LDO is intended for are basically only for over-voltage on fresh cells protection.. my brother just blew the second 1185 bulb within 1 week from freshly charge CBP 1650s.. i'm thinking it could have something to do with the colder weather? (nothing else changed).. I would put the LDO ckt set for 10.8'v into the 10.8V hosts for exasmple.. then for the majority of the use.. the efficiency is like 98% or more.. that's what this circuit was designed for.. being able to use a bulb that will handle nominal voltage just fine but not the overvoltage: 

prime example: [email protected] which likes to blow at 12.6.. .1331.. same scenario, but even more flashable. 

the 14.4 host to run the 1185 with a switcher is a very interesting option.. because the bulb can be pushed to a constant 1300 lumen vs the 1200 and dimming you get from 10.8V.. but with 3.39A at 1316 lumen with the 1185.. (11.0V).. that means.. 39W on the input side of the switcher.. divide that by 14.4V and get only 0.9A from each stack.. 

What's it all meab Basil? (austin powers quote)

Means that running an 1185 from a 14.4V host can get you 96% vs 76% efficiency which would convert to a runtime improvement of 47 minutes vs 37 minutes with the same exact bulb and batteries, only using the switcher you propose vs the LDO of my current design.. 

As you can see i'm aware of the times when the switcher kicks the snot out of the LDO, and haven't turned my back on it.. who wouldn't like a mag 85 that stays bright like that first juicy minute or two.. but also won't blow your bulbs trying to run it at 12.6V! 

Oh....i think i mentioned it above.. but i was able to witness an 1160 bulb operating at 8V! (i think that calculated to like 1300 lumen!).. of course only for a fraction of a second but it was one BRIGHT fraction of a second! 

-awr


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## legtu (Nov 15, 2005)

How about using a microcontroller? 

A couple of caps, a microcontroller, FET, regulator and resistor(s)/voltage ref should do it. The regulator takes care of the vin to the microcontroller. Microcontroller takes care of the voltage regulation via PWM, undervoltage shutdown/lockout, soft-start, etc. It can even be made to 'auto-sense' the vin and adjust accordingly to a pre-programmed bulb parameters. The circuit itself should be fairly simple but the 'complexity' goes into programming though...

Efficiency should be fairly high regardless of vin right?


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## andrewwynn (Nov 15, 2005)

There are people working on µC hotwire drivers.. it's a really neat idea to be sure... i like the idea of the auto-sense for the Vin. 

-awr


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## Bimmerboy (Nov 15, 2005)

Hope nobody minds me jumping into this highly technical thread for a moment, but I just discovered this thread and skimmed through it some. I gotta' keep an eye on this.

Just so I don't have to try to understand everything going on here, could I ask for a quick and dirty explanation on what possibilities this holds for the 1185?

One thing I'm wondering is if an eventual driver would fit in with my 1185's present battery scheme of using a 9AA to 3D holder with NiMH.


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## cue003 (Nov 15, 2005)

is this mod ready to go into lights... namely my lights...  

I would love to get the full potential out of the hotwire mods I already have.

Curtis


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## andrewwynn (Nov 15, 2005)

the main deal is that you can push bulbs harder w/o worrying about instant flashing them.. for example.. 9x17500 cells is nominal 10.8V which is great.. 1234 lumen.. but at 12.6V.. (what fresh LiONS x3 will be).. it's a barnstorming 2052 lumen.. but the CCT is 0.9% from the melting point (though i understand that that is not 'exactly' the melting point)... it compares to 5.3% away at 10.8V.... 

I've blown 2 1185 bulbs in the past week.. one from 1/2 hr aged and one from 3hr aged CBP 1650s.. charged as always with the batteryspace smart charger which tops them off to 12.4 or 12.5 just as expected. 

the 9AA->3D is exactly the host i blew my two 1185s using.. Oh i blew another one in my 2 1/2D host 

I wouldn't expect 'quantities' of this driver before the first of the year.. but dec. is a possibility. 

-awr


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## NewBie (Nov 15, 2005)

legtu said:


> How about using a microcontroller?
> 
> A couple of caps, a microcontroller, FET, regulator and resistor(s)/voltage ref should do it. The regulator takes care of the vin to the microcontroller. Microcontroller takes care of the voltage regulation via PWM, undervoltage shutdown/lockout, soft-start, etc. It can even be made to 'auto-sense' the vin and adjust accordingly to a pre-programmed bulb parameters. The circuit itself should be fairly simple but the 'complexity' goes into programming though...
> 
> Efficiency should be fairly high regardless of vin right?




The major problem with the uC with MOSFET switch is that you are still whacking the bulb with the full voltage, even if you go fast. A uC with MOSFET switch doesn't regulate the output voltage at all. It may achieve an average current, but that is done by turning the MOSFET off and on. Thats what PWM is, Pulse Width Modulation. You adjust the on time to off time ratio to achieve a different average current.

Additionally, you are still drawing the power out of the batteries at full current, during the time you are whacking your poor filament with the PWM pulse. So you don't pick up as big of gains for efficiency inside the cell.

The other problem with PWM, is that you can't go too high with the battery voltage.

Yes, it may be better than nothing, but highly doubtful you could push the bulb as far as you could with a linear or a switcher.

You can get the uC and MOSFET PWM to not stress the filament as much by running the PWM at a higher frequency, but in doing so, you burn more power switching the MOSFET off and on, and also burn power in the MOSFET during the transistion time.

But it is possible to implement a switcher with a uC, by adding an inductor and capacitor. Henry of HDS did this a few years back with the ARC4.


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## innerlight (Nov 17, 2005)

I'm in for one of these drivers when they become available

Rick


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## glire (Nov 18, 2005)

This thread wants to make me learn stuff I don't know at all... yet (hopefully) 

Newbie,
Can you point me to a 'modern' boost switch regulator example (shema, parts, actual experiences, etc).
Thank you.


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## andrewwynn (Nov 22, 2005)

Very exciting news! 

the 'shrinking hotdriver'. 






the prototype! a few bugs went away going from the breadboard to the prototype board! now it works exactly as designed.. not a tiny bit of voltage swing depdending on load anymore.. you can set it with no load.. and the voltage will be the same with 4A. 





Here's the first operational 'in the light' hotdriver.. I put it in a 1D host from fivemega, using (4) 14500 cells for 14.4V.. and running an 1166 bulb at 12.48V.. 909 bulb lumens.. output is absolutely constant 'til the last 30-40 seconds where you can just start to detect it's dimming before it shuts off.

the rest of the slideshow is here:
shrinking hotdriver


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## StoneDog (Nov 22, 2005)

Standing by w/ PP!


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## wquiles (Nov 22, 2005)

Andrew,

Like StoneDog, I got Paypal ready - I was going to order parts and try to build one, but I rather pay a little more and get the module from you 

Let us know when these will be ready 

Will


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## savumaki (Nov 23, 2005)

I've been following this for sometime and I get the same feeling I got when I was waiting for my firstborn to come along. 

I'm not sure I can afford him but here he comes :goodjob:

Karl


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## andrewwynn (Nov 23, 2005)

I have parts lined up.. the plan is as soon as nano production is done to crank out about 20-25 of these complete kits.. just drop in a maglight with a 5/64th hex put in your bulb and your battery pack and turn it on. 

Not exactly sure what the total price will be but it will be reasonable for what it is... considering the ludicrous cost of high-power lights 'in the real world'.. like the M6 battery holder for $90.. holy cow!.. get a much nicer one for $35 from Fivemega! 

-awr


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## greg_in_canada (Nov 23, 2005)

I hope you wore a faceguard when you powered up the breadboard prototype to protect you from the naked bulb (possibly exploding).

Greg


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## andrewwynn (Nov 25, 2005)

I use a piece of welder's glass.. you can see it in some pictures.. sadly i broke it so i need a new one.. so today and lately when testing my 'faceguard' was my forearm... does a decent job of knocking down the directed lumens too. 

We got what we are now calling the "Mag100R" fully operational last night.. 3000 estimated torch lumen.. basically the same as the USL but doesn't dim... it is a sight to see it here (beamshots comparing to a mag85).


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## vacuum3d (Nov 25, 2005)

Andrew, Great stuff. I've been following the thread as well. Where does the line start? 
Can this driver be easily adjusted to handle different bulbs and battery voltage input?

Thx,
ernest


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## andrewwynn (Nov 25, 2005)

voltage is adjusted by an accessable trimpot.. anywhere from like 1.5V to 30V is possible.. Vbulb has to be reasonably close to Vbat... but the FET can easily handle 10W or more.. it is possible to run an 1185 at 11V from a 14.4V host.. just not very efficient. 

-awr


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## cue003 (Nov 27, 2005)

deleted....sent PM instead


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## NextLight (Nov 27, 2005)

Hi Andrew,

I'm in for a couple of finished drivers and several kits, if you choose to sell them. My Metcal soldering stations need the excercise.


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## vacuum3d (Nov 27, 2005)

andrewwynn said:


> voltage is adjusted by an accessable trimpot.. anywhere from like 1.5V to 30V is possible.. Vbulb has to be reasonably close to Vbat... but the FET can easily handle 10W or more.. it is possible to run an 1185 at 11V from a 14.4V host.. just not very efficient.
> 
> -awr


That's great! :thumbsup: PP Ready!
This could mean the end of unregulated hotwire! I can't wait.


ernest


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## js (Dec 5, 2005)

Andrew,

I just got finished reading this entire thread, and if I didn't have such a headache I would be laughing.

Are you insane? You want to heat sink 4 to 8 watts to the body of the flashlight? Good luck my friend. Good luck. That part of the flashlight body right above the FET or Transistor will burn anyone who touches it.

And I've got to say that this is not really a "regulator" is it? As much as it is a "soft start + peak holdback" circuit. Why bother to "regulate" when you are just throwing away the excess energy? Just go to direct drive and a soft-start circuit as Newbie suggested from the get go, and like Snoopy posted about in the Homemade and modified lights forum some time ago.

I thought, when I first heard about this and saw the pictures, that it was a switcher. That it HAD TO BE a switcher. Now I see the full horror of the situation.

My God man. You really have no fear do you?

The "FET can easily handle 10W or more . . ." ???!!!???

Well, yes, but only if it is properly heatsinked. This means either a fan blowing hard on a reasonably sized heatsink, or one mother huge heatsink with large fins, completely open to the air with plenty of natural convection.

Tell me, have you actually TRIED to dump 10 watts into a flashlight body, with the FET somehow mounted to the flashlight itself, or are you just going by some spec sheet and short tests done outside the light, on the bench?

And are you sure that you haven't simply fried your FET in the first second or two? Because in many cases, FET's will fail on, and thus you will get light and measure low on resistance, but you won't be holding back any voltage.

This is an unworkable solution for high current and overvoltage situaitons. *YOU CAN NOT DISSIPATE 4-8 WATTS TO THE FLASHLIGHT BODY* You just can't, Andrew.

I know I sound like an *** here, but I just had to say this. Sorry to be so negative, but . . .

I'm nonplused. Nevermind. I've said my piece.

Well, there is one more thing. The MB20 SF M6 battery holder is much better made than a FM holder, even though those are nice and pretty well made. Just not as nice as an MB20.

Oh, and for high draw rates, you acutally want a LOWER ending cell voltage than for low draw rates. So instead of 1.0 v/cell, it might turn out to be .8 v/cell for a 3 or 5 C draw in order to actually reach end of cycle and get the full capacity out of the cells.


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## mpf (Dec 5, 2005)

I think you are being a bit hard, js. (but not completely wrong)
I am working on a linear buck regulator and the heat calcs go like this.
40C ambient,
25C rise,
total 65C

Fet J to Case 4.3C/W
Case to heat sink mounitng 1.6C/W
heat sink (not the barrel just a small finned sink inside the barrel) 12C/W

Max Junction temp 175C - 65C (air temp around the heat sink) => 110C
110C / 17.9C/W (sum of the above)
= 6.145W dissipation.

Now this is at 40C ambient. If you allow 25C ambient then the air in the barrel (and the barrel itself) is 50C 
I grant you this is hot but my Tesla runs at 53C (25C ambient) at the moment so I know what it feels like. HOT but not so hot if you hold it all the time it is running as your had drains away some of the heat.

So on the basis of this 6 Watts looks OK to me for say 15min and 8W is OK to for a short time using the thermal mass of the torch as a heat sink.

In my design I expect the battery voltage to drop over the first 10min to close to the Led running voltage so the wattage dissipation will be small after the that. 

It takes longer the 15mins for the torch to heat up to 50C so I don't think there is a problem.

Having said all that, the best effeciency and lowest heat dissipation is gained if you keep your battery voltage very close to the lamp voltage. 
matthew
p.s. Assuming my circuit does not oscillate I am expecting <100mV drop at 3A
p.p.s. Of course my 20W 6 Led torch has lump of metal in the head that the leds are mounted on and this adds to its thermal mass.


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## evan9162 (Dec 5, 2005)

You can easily dissipate 4-8W into a mag light body - people do it all the time, especially with Space Needle/MR-X type lights. 1.5A into a Luxeon V is roughly 10W, and these lights aren't impossible to hold. In fact, walking around with those lights results in a light that is just warm to the touch - it doesn't take much airflow to cool a mag light significantly, even with 5-10W of heat going into it.


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## cue003 (Dec 5, 2005)

Curtis


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## Luna (Dec 5, 2005)

evan9162 said:


> You can easily dissipate 4-8W into a mag light body - people do it all the time, especially with Space Needle/MR-X type lights. 1.5A into a Luxeon V is roughly 10W, and these lights aren't impossible to hold. In fact, walking around with those lights results in a light that is just warm to the touch - it doesn't take much airflow to cool a mag light significantly, even with 5-10W of heat going into it.





Don't confuse driving at 10W with dissipating 10W though

I think you can dissipate 8w in a mag body for a period of time assuming airflow and a persons hand as a part of the thermal mass. It is just horribly inefficient.


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## evan9162 (Dec 5, 2005)

I'm not confusing the two. Over 85% of the power going into an LED is given up as heat, and with a Luxeon, it's directly into the slug and into the heat sink. For all intents and purposes, they are the same thing. 

I've actually measured the thermal resistance of a mag body. In still air, it's about 5C/W. However, move it around even a little bit, and that drops to around 1-2C/W. 

Besides, the peak power loads that the regulator will have to deal with will only be for the first few minutes of battery life. Andrew is trying to match batteries closely with bulb voltage requirements, so that only a couple of watts is going up in the regulator for the majority of the battery life. The peak power loads of the regulator aren't unreasonable for a mag body, especially since they will be a short term thing.


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## Luna (Dec 5, 2005)

evan9162 said:


> I'm not confusing the two. Over 85% of the power going into an LED is given up as heat, and with a Luxeon, it's directly into the slug and into the heat sink. For all intents and purposes, they are the same thing.




Now you have a Mag having to sink the heat being generated by the ~30w 1185 and the 8-10w of the FET. That is the difference.


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## StoneDog (Dec 5, 2005)

Well, I'm not at all qualified to comment on this one way or the other. Instead, I'd like to say that there is a market (unless I _am_ the market) for a low-cost solution that will let us run high-end bulbs mods at the very limit w/o blowing. I don't care so much about efficiency because nobody seems to have (as a standard offering) a hotwire regulator. If this is as close as I can get to some sort of soft-start/switcher/PWM/thingamajigger w/o contracting someone to do a high-dollar low-volume run then I'll take it.

Jon


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## litho123 (Dec 5, 2005)

I've been testing one of these Kiu/awr regulated sockets for the past several nights and have done two separate full 45-47 minute runtimes on it. Now that I have 24 batts fully charged, I plan tonight to do the 2 runs back-to-back. Then I'll open the socket up and see what effects, if any, the heat is doing to the parts.

That's using the 1166 bulb (specs) 11.6v, 1.97a (22.85w)
overdriving it with 12 AA nimh batts and the voltage set at 12.5v
using the Ray-O-Vac I-C3 2000 nimh batts

It has been warm to hold, but not intolerable, even when switching hands ... maybe a tad warmer above the switch than on the head.
It is a little eerie to have the light auto cutoff at the runtime's end because, to my eye, it hasn't really started dramatically dimming. I wonder if I deplete the batts on my other lights too much before stopping to recharge them. :thinking: 

I like the fact I can install freshly charged batteries in the light, throw the switch and not have to worry about blowing the bulb.


I'll be testing other bulbs ...
I'll change the voltage and try it with the 1185 bulb on 10 AA nimh.
Then change the voltage and try it with the 1274 bulb on 8 AA nimh.
Then change the voltage and try it with the 1111 bulb on 7 AA nimh.


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## evan9162 (Dec 5, 2005)

Luna said:


> Now you have a Mag having to sink the heat being generated by the ~30w 1185 and the 8-10w of the FET. That is the difference.



The 8-10W is only for a few minutes, and most of that 30W is shot out the front in the form of IR.


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## bwaites (Dec 5, 2005)

I'm fairly certain that js is addressing the issues with the Osram lamps more than the WA lamps, and I will also.

The USL already gets VERY hot during a full run, and trying to dissipate any MORE heat would be foolhardy, if not impossible. Remember, one of the reasons to keep the runtime down on the USL was that heat dissipation. 

BUT...I think the other thing that needs to be addressed is that this really is a regulator in name only. It does NOT function like the regulators we are all familiar with in Luxeon based lights, the regulator in the Surefire A2 or the regulated pack that js makes for the Surefire M6.

In reading this thread, and I will admit my EE skills are nowhere near those of Andrew, js, or many others here, it appears that this is, at its most basic, a waste of a cell. Essentially, the energy from one cell is used to maintain a level output, and that energy is dissipated into heat. It is not used in any other manner. Soft start is a nice feature, but using that extra cell means that you have to go up a whole D cell size in the Mag body, just to get that same output. NiMH cells have very flat discharge curves anyway, and, in fact, few people can tell me when the USL has been on for 5 minutes vs 30 seconds, so I'm not sure that the "regulation" here is as great a deal as it would seem to be for a light that runs longer. You can MEASURE the difference, I'm just not sure you can tell the difference in real life.

After all of the complaining Andrew did about the MB20 and the use of the energy from the 123's, this seems a little counter productive!

That said, I'm glad someone is investigating hotwire drivers. Having a ready source of them seems like a good idea, since the LVR can only be had in quantity. 

I just wish there wasn't so much inherent loss in this solution!

Bill


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## NikolaTesla (Dec 5, 2005)

No problem on this end with full charge run of 12 cpb 1650 on Osram 100 running at 114 watts. Just light and heat. No smoke or failure. Perfect brightness till end of run. I will waste one cell for that anytime,:naughty: :rock: :lolsign:
13.18 volts. surge limited by regulator, works just fine.
It did not get to 100 degrees C.


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## andrewwynn (Dec 5, 2005)

JS.. 

hey.. apparently you are not up-to-speed on high-power FET tech.

The FET I'm using is rated for CONTINUOUS dissipation of 210W at room temperature.. and 100W continuous at 100C.. 212F.. the hottest we've gotten any light is about 140F... the lifespan of the batteries is a limiting factor.. the juice runs out long before it can overheat. 

The average power drop including the battery pack and FET with the 100R is approximately 6W.. the Lioncub disspates like 5! Tables have turned on the do the research before posting concept i guess. 

6W loss on a 115w bulb is 5.2%.. that's twice the efficiency of my fatman driver boost ckt in many configurations.. and in the high-power LED lights i make.. they dissipate 16+W into the handle of a 1 1/2D maglight and even those don't get all that hot. 

It takes a LOT more power than single digit watts to be a problem with good FETs.. the FET i have can handle 180A continuous at room temp and 130A at 100C... of course that is 'full on'.. and i use it linear.. so that's where the power limit comes into play.. and even at over 200F, it can handle over 100W dissipation.. i could run a 13V bulb from a 24V battery and still have a bit of room to spare. (of course the light body would be 200+F).. 

The reality is it's an absolutely excellent mate for any solution where the battery voltage is remotely close to the lamp voltage. When i run a 7V 35W bulb from a 9.6V source.. that was the only time i've noticed the FET heat, and even that was not any big deal.. 2.6V x 7a = 18W.. that was where you can really tell there is heat coming out 

The FET has a very good heat sink.. called the holder's blood stream! good for at least 10-20W. 

We tried this in the Mag100R of course.. and it works absolutely fantastically well! I've measured 4mohm resistance on the FET. 

The light holds regulated voltage within 0.01V .. once the battery voltage has dropped to bulb voltage.. there is a 35mv Drop between Vin on the regulator and Vbulb.. so when the Vbat drops to Vbulb there is extremely low resistance in the circuit.. about the same as 12 inches of 18ga wire. 

MB20 holder has a LOT more internal resistance than a FM holder.. it has 12 contacts in it.. compared with 9 contacts with the FM.. in addition.. the contact area is a point on the MB20.. and.. they require the spring tension you can't turn it tight to get a firmer grip.. i had to fix the springs on the brand new MB20 i got.. two of the batteries fell out just from shaking the holder.

the MB20 is a work of art, and well designed.. worth $90 not a chance.

In the testing i've done.. the difference on a 60WH battery between 1.1V/cell and 0.9V per cell was 30 seconds in runtime.. 

6 hrs 20 minutes.. or 6 hours, 20 minutes and 30 seconds.. not worth it.

-awr


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## Luna (Dec 5, 2005)

evan9162 said:


> The 8-10W is only for a few minutes, and most of that 30W is shot out the front in the form of IR.


 

Obviously a good portion of the output is being radiated but one just has to grab then head of the Mag85 to realize that quite a bit is being sunk into the body(from the lens and reflector absorption and residual from the 650deg envelope). 


Considering the runtime is only a 'few minutes' (ok 20ish) you are still wasting a good deal of power. If a simple powerdrop is needed, there are many easier and more efficient designs. This circuit is obviously not meant to be all purpose regulator but more of a mild buck(or did miss something??). No harm no foul, you just don't want to load it up where you are dropping 10watt of your power to drive a 30watt souce.


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## andrewwynn (Dec 5, 2005)

I figured i'd have that reply separate.. Sorry to be blunt and point out when somebody is wrong.. but we built it it works fantastically well.. point made.

MPF.. the 'heat sink' in the case of my design is the body of the light.. there is about 3" of surface area contacting the entire perimeter of the light from the aluminum that is directly AAd to the FET. 

The smaller lights cause no problem becuase the power on the FET is typically less than a fraction of a watt.. on the big light.. it might start at 9 but quickly is less than 6 and the light is out of power in 7 or 8 minutes. 

We will have accurate under load measurements very soon in the Mag100R. 

Luna.. there is very little difference between driving an LED at 10W and dissipating 10W.. for all practical purposes they are exactly the same.. ever notice how much heat does NOT come out of an LED light? it all comes out the back. 

In the case of the FET.. only the DIFFERENCE between Pin (battery) and Pout (bulb) is on the FET.. typically this is less than 1/2 to 1%.. in extreme cases.. as much as 30%.. and in the case of the Mag100R.. between the battery pack AND FET there is about 9W total.. the battery probably is responsible for taking up 1/2 of that so maybe 4 1/2W on the FET nominal. 

Startup is different.. probably about a 30W surge of power on the FET.. good thing it's designed for 200!







That is a graph of the lumen output calculated from bulb voltage with the Mag100R compared to the USL... any wonder why i think 12cells and a regulator is a better solution than direct drive from 11? it is a completely non-issue that some of the power is spent as heat.. 7-8%.. whoo hoo.. let's compare to the 40% lost as heat in the M6. At least I'm talking about 1/2 of 1 cent to recharge, not $6-7 to replace. 

StoneDog.. this regulator will do what you describe.. the only 'iffiness' would be could it be pushed too hard with 100-200+W light solutions.. in the 'normal human' lights like mag85 it is absolutely perfect home-run solution. 

Litho123 has one of the very few copies of this gem in a pre-production model of the 'hotdriver'.. he's using it as mentioned to run the 1166 from 12AAs.. it's a fantastic combination! 

You will barely see the dimming at the end.. because it shuts off at 75% of brightness.. you will barely notice that if you try.. because your eyes adjust to the dimming. 

Yes you most likely do deplete the batteries too much.. w/o the shut off.. the light will drop off like a brick dropped into water.

the non-flashing bulbs really is my favorite part. 

the 1185 from 10AA is awesome.. set to 13.1V for 1360/880L that's what i have my mag 85 set to.. see the pic: http://mag100.rouse.com

1274 from 8AA is absolutely fan-tas-tic!

1111 bulb from 7AA would be also fantastic.. i use LiON 2x3 for that solution don't need the regulator but it'll save bulbs i'm sure... 8.4V startup is bad. 

Oh.. the high-power drop.. we are talking about with the 100W bulb, not 1185.. in a typical use with the 1185.. there is like 1-2W drop on the FET just for a few minutes. 

... 

IN a full run with the Mag85.. it'll get about as warm as the USL.. remember. this is a 3D host.. more metal to dissipate heat.. 

refer to the graph above regarding is it worth using the extra cell.. the point is to maintain brightness.. it is very nice of a coincidence that the cells just don't have enough energy to keep heating up the light... but clearly with constant power output there is more heat generated with the Mag100 vs the USL, so something to consider of course.

You are exactly correct about what is going on.. but it's not called 'wasting' a cell.. it's called. 'deciding to consume a cell'.. 

The difference would be hard to visibly see.. i think that having the light not blow bulbs with topped off fresh of the charger cells is worth it for that alone.. in addition... having it shut down at low voltage.. very useful. 

40% wasted energy on cells that cost $25/hr.. vs 5-8% energy decided to be spent maintaining constant voltage.. at the monetary cost of fractions of pennies per hour... really not the same argument at all. 

The losses really are not dramatic.. take for example.. based on the TITLE OF THIS THREAD... using it with the 1185.. 

in the 1185 host i have right now.. a 2 1/2D Fivemega with 6x17500 cells from AW.. 

99.4% average efficiency... 

5W initial drop on the batteries for maybe 1/2 a minute with 12.6Vbat and 11.1Vbulb.. meaning.. 81% efficiency for that time.. after about 1-2 minutes.. the Vbat is maybe 11.4.. and it's down to .2Vx 3.41A = 0.7W on the FET.. now it's already up to 97.3% efficiency.. 

So.. that's the way it really is designed to work.. even in the 'extreme' cases like using it for the USL bulb at 120W... it really only has about 5-8% loss on the driver, which in reality is nothing to write home about.. even an AC transformer loses 10%. 

The reality is that in most cases where this driver would be used, the over all efficiency is typically over 97% efficiency.. if it wasn't efficient I'd not have bothered with the design in the first place.

So.. take the 'extreme' example of the 100W solution again.. 

the average power on the FET is about 6W.. so 6Wx8 minutes = 48WMin
the average power on the bulb is about 120W so 120x8 = 960Wmin.

So.. of 1008WM spent in the system.. 960 gets to the bulb and 95.2% of the energy leaving the battery goes to the bulb.. that is not inefficient by any standard... it doesn't matter there is a 30W peak on the FET to start with.. that is what i would call the 'bulbsaver™'

What i say is.. got a better idea that will work better.. build it and get back to me.. this works very well, find out the facts before knocking it (not pointing any fingers or even trying to be stern, just trying to correct apparently a lot of lack of understanding about the relative efficiencies of LDO drivers.. evan taught me that when i was first getting started in this business.. because i couldn't stand the idea of just wasting energy by heating an FET.. but he showed me how the averages work out.. 

consider.. that when the Vbat gets close to Vbulb.. the numbers look like this:

Vbulb: 13.1V.. Vbat: 13.1525 (yes, really)

That means.. Pin = 115.08 and Pout = 114.625

That is an efficiency of 99.6%.. and that was exactly what this particular circuit is designed to do.. when Vbat drops to Vbulb.. 'become a wire'.. the regulator is as efficient as 12inches of 18ga copper wire.. or putting it another way.. it is MORE EFFICIENT than a switch with .007ohms of resistance (most have between 0.008 and 0.010).. 

So.. the proof in the pudding so to speak... does it output more light? does it run at even output? Does it shut off before batteries are over discharged? Does it work? Is the runtime longer? 

The answer is yes to all those.. it's a very good thing. 

Without the regulator no way to make the http://m66.rouse.com for example.. and.. yes with a switching regulator.. it would have higher efficiency.. but I get 86% efficiency even with putting 12.5V into a bulb from 14.4V host, and that is good enough when the recharge cost is not even 1/2 of a penny. 

There ya have it.. any more confusion about efficiencies of LDO, or how much power an FET can handle or how much power the mag body can handle? This ckt is extremely efficient in most circumstances.. and quite reasonably efficient even when pushed hard.

Example.. using 1185 in a 12 cell solution.. it'd be only 77% efficient.. but still have the SAME lumen output and SAME runtime as an 1154 bulb from the same host.. thanks to litho123 above to point out the big 'duh' about using only 10 cells vs 12... that bumps the efficiency up to 93% nominal.. and with 10 cells.. 11.1V will be maintained 'til the last minute of runtime so the light will output maximum light start to finish.

I love it when you design something and somebody else figures out a better way to use it! that's awesome Greg! 

So.. as always post questions and comments... if you think i made an error 'bring it on' (kidding.. i made a big oops forgetting to divide by two in a recent thread and made a pretty tangential statement based on my math error).. I will correct my mistakes if shown to be goofs no problemo. 

I think it's ludicrous that this device is not already in-use in virtually all high-powered flashlights.. I would never design or build an incan light w/o a regulation ckt because the no-load voltage is way too different from under-load and that just melts bulbs.. most of the rest is just 'gravy on top'. 

-awr


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## andrewwynn (Dec 5, 2005)

Luna.. read the post i just showed.. the 10W is not from a mag85 solution.. more like 1/4 to 1/2W typically for the mag85.. 

Most of the solutions that'd use this driver would be in the high 90s for efficiency.. 95 to 99%.. not sure where you got the 10W from a mag85 number.. 10W is an initial number for running the regulator in a 115W solution 'til the batteries drop down to operational levels, where it will be more like 6W continuous.. which is no big deal at all.. my MINIMIGHTY will be 7W!.. 3cubic inches.. i think a 3D maglight body can handle 7W (actually i'm quite sure it can).. my 1.5D BAM soaks up in excess of 16W and just 'gets warm' not even hot.

I did a full run with a mag85 the other day just tail-standing (probably the worst way).. and managed after 50 minutes or so to get the light up to 140F+ on the head.. but after about 10-15 minutes.. 99% of that heat is only from the batteries and bulb.. the circuit is only about 1/20th of a watt at that point. So.. as you see.. extremely efficient once it's not holding back that 'fresh charge' battery voltage which really amounts to 1-3 minutes in the initial startup phase only.

-awr


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## bwaites (Dec 5, 2005)

Ok, from what I can understand, it works, so I'll leave it at that.

2 questions--

1) How much run time on the 100 watt version are you getting?

2) How hot does the head get on a full run?

Bill


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## andrewwynn (Dec 5, 2005)

1) as the chart above shows.. 10 minutes but we are 'cheating'.. we have the 3D host so are using 3/4A size cells  when using CBP 1650s.. the runtime is virtually identical to the USL.. 7-9 minutes.. the mag100 will shut off at 75% brightness.. so when it gets to about 2250L it's 'blink' off.. that probably happens around 8 minutes.. i'm not sure if NT timed it the last time he did the full run. 

2) Quite hot.. not as hot as an M6 in 11 minutes though. I will take temp measurements the next time.. the last time we ran it a lot it was outside and 14F so we could tell it was warm but never got really hot of course with the ambient so cold. .. also the Model he's using is using 12AAs so the runtime is basically identical to the usl.. take that graph above and move the 3000L line from 10m to the left to about 7 1/2 minutes before it 'breaks' from regulation. Won't last but a minute out of regulation. The 3/4As will bring the runtime up to 10 minutes of regulation as shown in the graph. 2000mAH with 1800 of that above 1.1V.. the 1650s on the other hand.. 1.1V is more like 1200mAH.. fatter is stronger that's for sure. 

I will get some temp measurements of head, switch, tail the next time i'm with NT, typically on the weekends he comes up for causing trouble in the flashlight world. 

-awr


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## Kevin Tan (Dec 6, 2005)

Still waiting AWN!!!


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## VWTim (Dec 6, 2005)

It seems most people are ignoring the inital goal of the FET driver, to eliminate the wasted energy in the stock switch. I still want to get on this and build a Mag100R clone, as well as trying one either my 74 or 85


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## NewBie (Dec 6, 2005)

andrewwynn said:


> JS..
> 
> hey.. apparently you are not up-to-speed on high-power FET tech.
> 
> ...




Whoa, hold on there...
On your 180A comment...
Note 6 Page 11, Calculated continuous current based on maximum allowable junction temperature. Package limitation current is 75A. (and thats if you hold the case of the MOSFET at 25C)

If you don't hold the case of the MOSFET down at 25C, things changed as you noticed.

The flashlight temperature is not the MOSFET case temperature, when you referred to the 100C comment. As you noted, at 100C, the part is rated for 100W, but I will refer you to the little 3 in the circle, go to Note 3 on page 11- Pulse width ≤ 400µs; duty cycle ≤ 2%. That means you have to hold the dissipation down to 2% of the time, or on for less than 400 one millionths of a second.

Keep in mind, the Linear Derating Factor of 1.4.

Also, note on page 11, Note 5 This is applied to D2Pak, when mounted on 1" square PCB ( FR-4 or G-10 Material ). It refers to the first page, on thermal resistance of 40 C/W junction to ambient, when mounted on 1" square of a copper PCB. I assume you took my advice that I mentioned here earlier, and worked on heatsinking the part to the flashlight body. Otherwise, it would only take 2.5W to push the die on this part above 100C, in open air on 1" sq. in. of FR-4 Copper clad. The thermal resistance rises to 62 C/W when using the to TO-220AB package by itself.

On another note, you have been fond of referencing the 4 milli-ohms of resistance. Well, when your MOSFET heats up, you'll be looking at more like 6-8 milliohms of resistance (if you keep from getting too hot). Refer to Figure 4, page 3.
http://www.irf.com/product-info/datasheets/data/irl3716.pdf

Anyhow, hopefully this points out a few things you might not have immediately noticed, and hopefully helps you to understand why I was stressing the importance of heatsinking the MOSFET.

For those that don't follow all the technojumblerigamarollthingymajigger talk, basically this circuit is a linear regulator with a soft start. The excess battery voltage is basically burned up as heat, until around 10 minutes in the graph above, when the battery voltage falls to the output voltage, then things fade from there.

As a linear circuit, it is essential that the battery voltage is very close to the desired bulb voltage, or you start burning up alot of power, especially in high current situations.

Essentially it is an electronic controlled resistor, that varies it's resistance to hold the voltage constant, burning up the excess power as heat.


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## Luna (Dec 6, 2005)

andrewwynn said:


> Luna.. read the post i just showed.. the 10W is not from a mag85 solution.. more like 1/4 to 1/2W typically for the mag85..
> ---
> Most of the solutions that'd use this driver would be in the high 90s for efficiency.. 95 to 99%..-awr




I wasn't so clear in my initial statement to evan and I clarified it in my second reply. Simply, if the LED is sinking 8-10w and the FET is sinking 10w into the body, then you have about 18-19w of heat that needs to be dissipated.


AWR, Have you investigated using this and an Avr or PIC as a PWM source? If you don't have any experience with them, you can always prototype with a basic Stamp (I think ratshack carries them now).


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## andrewwynn (Dec 6, 2005)

VWTim said:


> It seems most people are ignoring the inital goal of the FET driver, to eliminate the wasted energy in the stock switch. I still want to get on this and build a Mag100R clone, as well as trying one either my 74 or 85



actually just a KIU socket solves that.. the most important issue with the LDO driver is to hold back the 17% overvoltage of fresh batteries. When we are already over-driving the likes of a 9.6V bulb to 10.8... 12.6 is quite a LOT more.. and i've blown at least 6-8 bulbs just since August.. so.. no more unregulated hotwires for me anymore. 

If you like hotwire and you don't like blowing bulbs you should have one of these drivers (since i'm not aware of any alternative). 

... 

Newbie.. once again on a tangent that doesn't really apply to the situation... 

yes.. i'm aware that to keep 180A continuous you'd probably need liquid nitrogen cooling, but it's in the rated specs i read it right off the chart.

The reality is.. the FET is so over-rated for the particular task at hand there is about a 10:1 ratio of overhead even for the 100W solution and more like a 30-40:1 ratio of overhead for the 35W solution like the mag85. 

I didn't need to take any particular advice to know that to dump 9W+ from an FET it needs to be well sinked to the body of the light.. and it of course it.. directly sunk to the KIU alum. which has 3" square touching the body.. it's sub-optimal because there is anodizing between the aluminum but that's why the surface area.. you can in-fact feel the direct heating from the FET so it is getting the job done. 

I am fond of mentioning the 4mohm because in MOST cases for MOST of the runtime the circuit is in direct-drive mode.. the circuit is designed to be used mostly in the case of the likes of a 10.8V solution running the mag85.. it will be in regulation for a few minutes and than drop down to 4mohm resistance for the rest of the run... the FET will not be hot, and it's an absolutely moot point to bring up that it raises by 2mohm.. there is that much in the wires and in-fact there are 3.5mohm resistance on each pin of the lamp as well. 

You are correct that the voltages have to be 'close'.. but not necessarily that close.. 14.4V to run 12.5 works exceptionally well as does 9.6V to run 8.3V bulb.

Oh.. yes i'm quite aware about the importance of how well heatsinked... the heatsink has fallen off the prototype and breadboard FET once in a while and it takees NOTHING for that think to be close to 200F.. not even a minute! 

Luna.. 

There is no LED in this equation.. this driver is exclusively for hotwire lighting.. maybe you meant lightbulb? that in the case of the 100W bulb.. it might have 10W of heat into the body at the same time the FET is putting in 9W than you have 19W between bulb and FET going into the body.. this is true and is the case with the 100W light initially.. very quickly that FET power drops to maybe 4-6W though. I will have exact measurements soon. 

I have investigated PWM and like it a lot but it's far more complicated! 






That is my entire driver minus the FET.. absolutely IMPOSSIBLE to even come close to that level of simplicity with a PWM driver.

My goal is to have operational mass-quantities of this driver by mid-jan.. that is less than 120 days from concept to sales.. also not likely to happen with a PWM solution.. i will definitely be looking into that for 2006 though.. the hotdriver-2... now with PWM.. quite a likely occurrence.. with that solution than voltage matching is not so critical. 

Maybe somebody else will invent it so i can get back to work on my minimighty! 

Oh.. thanks bwaites for giving me the idea to include thermal protection.. i have the parts on order to add in an automatic shut off if the board reaches 85C.. and not turn on 'til it cools to say 75C or something... it'll be a nice thing for when trying to show off to protect it from self-destructing especially with the 100W bulb and smaller hosts. 

-awr


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## mpf (Dec 6, 2005)

andrewwynn said:


> ... not likely to happen with a PWM solution.. i will definitely be looking into that for 2006 though.. the hotdriver-2... now with PWM.. quite a likely occurrence.. with that solution than voltage matching is not so critical.
> -awr


Not being a hotwire person can I ask, in your future PWM solution are you using PWM to control a constant current (via an inductor) That is using PWM instead of linear to get your constant current control.
OR
are you using it to vary the brightness by pulsing a constant current? That is keep your linear constant current control and pulse the bulb to vary the brightness.
matthew


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## andrewwynn (Dec 7, 2005)

PWM to get constant voltage and current to the bulb vs a linear regulator.. the difference is primarily that in a PWM ckt the voltage can be much different between the bulb and battery without efficiency problems. Basically the FET only is 100% on or 100% off.. so there is virtually no power loss on the FET. 

Can't vary brightness on incan in any practical way.. it's possible to dim, but it primarily dims only by reducing the efficiency.. 

Example.. in a measured experiment I measured 500W from one of those floor-standing.. ceiling bouncing halogen lamps.. and when i dimmed the light to an estimated 10% initial brightness.. maybe even less (dim as i could have it stay on).. it still was pulling 300W from the wall.. 

The PWM design i'd be working on would allow you to for example.. have a 14.4V host (12AA 3D for example) and run just about any bulb from 6.6V 1060 to the 13.1V 100W. 

-awr


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## mpf (Dec 7, 2005)

OK thanks


andrewwynn said:


> Basically the FET only is 100% on or 100% off.. so there is virtually no power loss on the FET.
> -awr



I will be interested to see what effeciency you get. At the sort of freqencies usually used to keep the inductors small there are noticable losses involved it switching the fets.
matthew


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## andrewwynn (Dec 7, 2005)

yup that's why i use an LDO.. no fancy problems.. just Pin and Pout :-D ask george how many prototypes ended up in the bits bucket because of incompatible designs with inductors and switcher chips.. LDOs are a no-brainer, and in most of the cases that this ckt is designed for.. 98+% efficiency average.. which IMHO quite good. 

-awr


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## mpf (Dec 7, 2005)

I agree with you, as I mentioned in a previous post I am designing one also, but in my case I am designing it to be driven by a slow PWM (800Hz) for dimming, so the current regulation has to be 'fast'. 
The fet will arrive tomorrow, hope it does not oscillate.
matthew


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## js (Dec 7, 2005)

Andrew,

Look, the issue here is about heat dissipation, and not about numbers pulled from a FET spec sheet. There is a resistance to the flow of heat from the internals of the FET to the case. So in the ideal situation, where the case is being held at, say, 20C, no matter what the heat load, there is still a maximum power which the FET can hanlde. This is the power which you keep talking about.

It really has no bearing on your situation. Because the case temperature will NOT stay at 20 C. There is a resistance to the flow of heat between the sink and the case, and between the case and the sink, and between the case and the junction. This is basic heat dissipation and flow theory.

Which I'm guessing that you know nothing about. Or you would have been spewing out some C/W figures, just like you spew out all sorts of other figures. (And by the way, where did you get that USL discharge graph? It doesn't seem right to me. It doesn't seem right at all. I have data on a number of USL packs discharging against the 62138, and over most of the run, the voltage is constant at about 12.8 volts, so that should mean a constant lumens number. And yet, your graph doesn't show this. Something is wrong. Where did you get this info?)

That said, I wasn't saying that your driver won't work in a great many applications. I was only saying that, in a hotwire light, you can not sink 6 or 8 or 10 watts to the light. There's already a great deal of heat being generated in the head.

And I stand by that.

If you ever make a bunch of Mag100 L's, then we'll see what happens.

And don't tell me that I didn't do my research, because I did. This circuit is simple and straightforward. I know what your regulator does.

What I don't understand is why you didn't build a switcher from the beginning. There are some nice IC's out there that make it easy to build such a regulator circuit. And yet you tell Evan that it was "way too complicated???"

Anyway, I'm sorry about this whole thing. I should have just kept my mouth shut. I was out of line. Continue on, and best of luck. Time will tell whether or not my concerns were justified.

As for the MB20 vs. FM 9AA to 3D, I stand by my previous statement. I have seen and used them both. We can agree to disagree.


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## js (Dec 7, 2005)

Oops.

I didn't see page 4 when I posted the above. So I didn't see Newbie's comments. If I had, I probably would have more or less just said "what Newbie said".

As for space considerations, Willie's LVR3K is .780" in diameter, and .3" thick. So there's no reason that a switching solution can't be made small, even though it is a more complicated circuit.

AND, if you consider the kind of heat sinking that you need with your driver, then even the LVR3I is a much smaller solution.

But, of course, more expensive, and more or less impossible to get. I hear you on that. Just responding to the implication that a switching solution would have to be larger. Not so. Especially not if you add the heatsinking into the equation.


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## Luna (Dec 7, 2005)

andrewwynn said:


> Luna..
> 
> There is no LED in this equation.. this driver is exclusively for hotwire lighting.. maybe you meant lightbulb? that in the case of the 100W bulb.. it might have 10W of heat into the body at the same time the FET is putting in 9W than you have 19W between bulb and FET going into the body.. this is true and is the case with the 100W light initially.. very quickly that FET power drops to maybe 4-6W though. I will have exact measurements soon.
> 
> I have investigated PWM and like it a lot but it's far more complicated!




The LED was something that evan brought up, it has no bearing on the discussion outside of that.

PWM is very easy to implement these days with the multitude glue-in solutions out. Due to the inertial nature of the glowing element, in many cases you can even ignore the ripple. 

Pics and AVRs are easy to program (the Atmel just need a prototype board, DSUB, and a few 330s to build a prgammer for so you don't even have to buy a programmer) and they already have A/D for voltage sampling so that you have a closed loop solution. The BASIC stamp is a nice start for those that do not have the background. It just isn't a production solution $$$ and size is too big anyhow. Once you have the circuit working then you can port the stamps code over to the microcontroller of choice (about $4 a piece last I checked) The stamp is a pic with a propriatary BASIC interperter, FYI


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## legtu (Dec 7, 2005)

Luna said:


> Pics and AVRs are easy to program (the Atmel just need a prototype board, DSUB, and a few 330s to build a prgammer for so you don't even have to buy a programmer) and they already have A/D for voltage sampling so that you have a closed loop solution.



I already suggested to andrewwynn about using a microcontroller. He's reply is at post #84. 

Newbie has also mentioned some issues related to it...


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## js (Dec 7, 2005)

You know what, I was just plain rude and offensive.

Andrew, I'm sorry. If you want me to edit my posts just tell me.

You are working for the greater hotwire good, and so I should have first and foremost recognized that. So, better late than never:

Thanks, Andrew. And best of luck. If you have found that heat sinking the FET is not an issue, then that's great, and totally unexpected to my mind.

I suppose it's mostly surprising to me because all of my heat flow and dissipation calculations have been for steady-state solutions, and my experience with my linear MAX712 fast-charger was also more or less steady state given the 2+ hour charge time. I was only needing to dissipate 2 or 3 watts there, and I initially thought "NO PROBLEM! That's nothing!"

But I learned the hard way that the real world situation and the spec sheet are two very different things. Even though the heat sink I used was good for 8 watts for 40C rise, that was in a completely open air situation. Even with a perforated box (and mounted to the circuit board), it could not keep the transistor at a low enough temperature to keep its performance parameters within chip spec. It didn't melt down. Instead it would cause the IC to think that end of cycle had occured, and the charging would terminate prematurely.

So, when I saw that you were not using a switcher, and were planning on dropping the extra cell's voltage in a 100 watt light, I was like "*WHAT! THAT'S CRAZY!*" But maybe the thermal mass is enough to keep the junction temperature down below critical. I still get horrified at the thought, though.

And I'm pretty sure that you really want to use some type of transistor here, and not a FET, but whatever. I understand why you want to use the FET: you want the circuit to be invisible once Vbatt=Vbulb. Still, as long as you are dissipating all that power are the start of cycle, you might find that there is a transistor out there that will be more suited to dropping this much power than a FET is. I don't think FET's are normally used this way, are they? Perhaps Newbie could weigh in on this.

And I still very much question that graph of the USL output that you posted. No way that is right, Andrew. Maybe one of the protos with the pack with the bad cell in it, but not any of the production lights.

Here are the specs from the latest discharge curve against the 62138:

0 min, 13.8 volts
1, 13.08
2, 12.95
3, 12.96
4, 12.97
5, 12.95
6, 12.91
7, 12.84
8, 12.76
9, 12.64
10, 12.48
11, 12.27
12, 11.92
13, 11.28

and I turned off at 11.00 instead of at 9.9 because it was the first cycle on the pack. Presumably cycles 2, 3, and 4 would have been even better than this.

Anyhow, again. I'm sorry. I was out of line. I will edit my posts if you want me to, although I generally like to leave my obnoxiousness out in the open so that I am more likely to learn from them and not repeat them. So I won't edit unless you want me to.

Good luck, Andrew. Thanks for your efforts.


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## bwaites (Dec 7, 2005)

Andrew,

I just saw your USL graph. Like Jim, I'm confused.

Where did those numbers come from?

Bill


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## andrewwynn (Dec 7, 2005)

Sorry... the numbers came from a USL thread, i just grabbed the first batch i found.. i'll re-do the graph with the new values just posted.. have to work right now so i'll reply to the rest of the posts next time... i re-did the graph with the 'fix' on it, thanks for getting me some updated information, sorry about including out-of-date data but i believe it was originally posted by either js or bwaites so i figured it was good data... i'm sure it was accuarte at the time just out-of-date. Glad to have the updated data.. and 'good show' on the improved performance.. it really shows the work of JS in that battery pack.. my pack will have at least 2 to 3x the voltage drop of JS's end-to-end soldered pack. 

I feel much better with the latest graph showing a much closer face-off.. there is no way a person could see the difference between the two lights. 

JS.. no hard feelings, i know where you are and were coming from.. it does seem from the surface it's ludicrous to allow upwards of 10+W of power dissipation on an FET but the math and reality all work out, you might have to just 'trust me' 'til you can get one to play with. 

Glad to have the updated figures for the USL, wonder why the original numbers were that low.. i couldn't find things without the search function working with older threads. 

a copy of the updated graph: 






-awr


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## Lurveleven (Dec 7, 2005)

Andrew, how did you arrive at those lumen numbers? From another thread I understand that they are supposed to be Torch Lumens, but rerating the 62138 bulb I only arrive at 2500TL, i.e. (13.1/12)^3.5*2800BL*0.65=2474TL. But you claim 3000TL. I thought you maybe had rerated with the numbers for the 64625 bulb instead, but with that bulb I arrive at 3181TL.

Sigbjoern


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## bwaites (Dec 7, 2005)

Andrew,

I don't remember posting run times for the USL, but it's possible I did, (I've written a few in the last year! )

Lurv, I'm pretty those are Bulb Lumen ratings, that's too high for Torch Lumens.

Thanks for the fix, Andrew!

Bill


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## andrewwynn (Dec 7, 2005)

the L numbers are calculated.. i might have the wrong base Lumen number which of course would make the scale off.. i'm just calculating based on the Vbulb so the comparison would be the same.. 

I think the initial testing was with the 64625 bulb, but now we have the 63138, so probably some re-calculation is in order. 

The numbers are torch lumen, but there is an apparent goof that would make my 3000L become 2500L (at 13.14V). 

I had 3400 as the rated bulb lumen, you have 3600. (for the 64625), the 62138 is apparently 2800? 

I'll re-do the chart soon as i have the correct base numbers... sounds like with the 62138 bulb i'll be around 2500 v 3000 Torch Lumen.. or on the order of 3200 if using the 64625 (if it's 3600). guess i need to find out the base lumen for both those bulbs. 

The only 'point' of the graph is that with the 100R.. Vbulb is maintained at a constant level vs letting the batteries dropping voltage control the Vbulb. 

It is very telling as i mentioned, thanks to the new numbers just how little difference there is between the 100R and the USL.. but with 2000 vs 1650 cells.. there will clearly be a difference in both constant output and runtime.. but i'm glad to see it's not as big of a difference as those initial numbers.. the USL really does kick some serious butt.. and i'd rather see the 100R as an evolutionary step vs a revolutionary step. 

The main improvment IMHO is the ability to run off of fresh charge.. let the FET take the heat (literally).. and of course swappable battery packs. 

As JS recommended i will definitely consider upgrading to a back-to-back soldering solution to drop resistance, but for now it's actually beneficial to spread out the power dissipation amongst the battery pack and not all on the FET.. the bat pack w/o the soldering will drop 1/3 to 1/2V. 

We will be making 2 or 3 more prototypes to put through the paces.. before we'd be going for a quantity 'run' of lights.. over temp protection is planned to be added in.. and so far we have not had any problem with over heating and it is quite nice to be able to use the thing full power without concern of blowing the bulb. 

thanks for the input, and for the inspiration. 

-awr

ps.. the 'initial run' numbers just had the voltage at each minute exactly like just posted.. it was the only one i found digging through the USL thread.. might have been before the pack was soldered so well or something, good to have the updated #s .

-awr


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## andrewwynn (Dec 8, 2005)

OK.. i did goof on the numbers.. i had 3400 vs 3600 for the base lumen on the 64625 lamp.. which should work out to 3181 torch lumen.. and with the 62138 lamp, we'd be at 2474L. 

The graph would not be any different other than the left scale, since i had the same error on both calculations.. but i'll either have to use the 64625 or re-rate the specs of the 100R of course. Not into false claims. 

So.. i was given a bit of bum info to throw my numbers off.. it would be fair to say that the current incarnation of the Mag100R is 2500L not 3000L.. the chart is now updated to represent the fix, thanks for pointing out the goof.

btw.. here is the post where i got those 'troublesome' values.. wonder what the differences are between march and today that make the marked improvement in output.. was that first pack end-to-end and beefy connectors like the final solution? In any event.. quite a nice improvement in the battery pack, as represented in the graphs above.. i updated the initial picture so all are fixed now. 

Kinda glad i made the goof so it was caught. 

Looks like i'll have to use the 64625 to get the output up to 3000L.. i can run it at a mere 12.9V which I should be able to hold in regulation for.. about 1900mAH.. or 1.9/8.75=13.02minutes.. of course.. that's with 2000mAH 4/5As.. the 3D host can hold 2500mAH full As.. which would bump that figure up to about 16-17 minutes.. 

Naturally.. there is a very good chance that it will overheat and shut off if a full-run is attempted w/o more than hand-holding for cooling.. all these thing are still in the 'learning curve' phase, just like any teething pains with the USL.. the Mag100R is only like 2 weeks old maybe 3.. and we've only done 1 or 2 full-length runs.. usually in spurts of 2 or 3 minutes at a time max.. been through maybe 8 cycles on the battery pack and things are looking very good still. 

I measured about 20 mohm per stack or 90 mohm on the whole battery pack.. which is definitely where most of the resistive loses are in this light.. but, that is ok.. there is more overhead than i need with the extra 1.2V cell.. and 90mohm equates to about 0.8V.. and for each contact.. about 1/3W.. definitely enough to make them warm.. we'll be working on and testing the battery pack to see if we need to end-to-end solder the rows.. and i'm already planning to use silver plate for the contacts between the rows.. i would like to see contact resistances in the 2 to 3mohm at the most and i believe that's achievable... the pins on the bulb measured 3 1/2 each the last test... there is more surface area between flat-top batteries than the pins for sure.. hopefully those are more like 2 to 3 already vs the 5 i use for my calculations... we should know in about 15 hours when we do the acid testing.

-awr


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## andrewwynn (Dec 8, 2005)

ps.. oh and thanks again for the sage words of advice and wisdom that keep me course-correcting that will make the best lights. 

-awr


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## js (Dec 8, 2005)

andrewwynn said:


> btw.. here is the post where i got those 'troublesome' values.. wonder what the differences are between march and today that make the marked improvement in output.. was that first pack end-to-end and beefy connectors like the final solution? In any event.. quite a nice improvement in the battery pack, as represented in the graphs above.. i updated the initial picture so all are fixed now.
> 
> -awr



Andrew,

AH! Now that I see where you got the numbers from I can tell you. At first I thought it might have been data from the proto-type pack, which ended up having a cell that was flaky, and then went bad. But not so. This is one of the four field test packs, but still made from the green wrapped CPB1650's. The red/blue wrapped cells are from another production run and hold better voltage under load. The improvement is all in the 1650 cells. Both the Field test pack #1 and the production packs are end-to-end soldered and have *no connectors* in the USL. There is simply a wire soldered to the + contact and then to one lead of the rocker switch. Then one wire from the socket is soldered to the other lead of the rocker switch, and the other wire from the socket is soldered directly to the - contact. You want low contact resistance? How about none? Only resistance in the USL is the solder joints, the IR of the cells, the rocker switch resistance, and the contact resistance bewteen both lamp pins and the socket contacts.


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## NewBie (Dec 8, 2005)

andrewwynn said:


> OK.. i did goof on the numbers.. i had 3400 vs 3600 for the base lumen on the 64625 lamp.. which should work out to 3181 torch lumen.. and with the 62138 lamp, we'd be at 2474L.
> 
> The graph would not be any different other than the left scale, since i had the same error on both calculations.. but i'll either have to use the 64625 or re-rate the specs of the 100R of course. Not into false claims.
> 
> ...




Andrew, were you overdriving the bulbs a little? Did you account for that above?

So the Mag100L is 2474 Lumens is the gist of what you said?

Curious, could you tell me what the internal resistance of each cell is, and how many cells are in one of these?

You are derating the output of the bulb by what, 12% to figure out what is going out the front? So that would be reflector and lens losses?

Thanks.


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## js (Dec 8, 2005)

Newbie,

I'm pretty sure that AWR and company are on-board with the 35 percent loss rate to convert bulb lumens to torch lumens. And yes, he is overdriving the 62138. It is rated at 2800 lumens at 12.0 volts, and IIRC he is driving it at 12.9 = 3600 bLu, which converts to 2344 tLu. For whatever that's worth.


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## Lurveleven (Dec 8, 2005)

NewBie said:


> You are derating the output of the bulb by what, 12% to figure out what is going out the front? So that would be reflector and lens losses?



The output is derated 35% to account for losses.

Sigbjoern


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## Lurveleven (Dec 8, 2005)

JS, he is driving it at 13.1V (at least that is what he wrote in another thread).

Sigbjoern


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## WhiteHot (Dec 8, 2005)

I have been sort of following this thread and the development of the driver. I have a few observations, comments, and questions. I do some electronics design for a living but not much of it is in the area of power supply design so I may know just enough to get myself in trouble.

If I remember correctly, in the very beginning, AWR was looking to reduce the resistance of the Mag switch (the reason for getting excited about the 13mv drop). While going down this path, it was realized that with a circuit extremely similar to this FET based digital switch, soft starting and regulation could be implemented. This led to a design that inherently traded off efficiency and possibly reliability for simplicity and cost. That is not necessarily a bad thing as long as those trades are noted. Personally, I would have approached the problem in a different manner because efficiency and reliability are important to me, especially when something is going to be sold as a finished product. (BTW, I say “possibly” reliability because I believe that the FET junction temp may be getting a bit warmer than it should be based on the power dissipation and my perception of the method of heatsinking.) I think that a few people around here feel fairly passionate about efficiency and reliability and that is where the disagreements are coming from.

That said, I think that a lot of the controversy would end if it is generally accepted that efficiency and reliability were not really factors in the design of this regulator. It should also be recognized that this is not, by any means, the most complete solution to the problem. It is however a solution that works according to AWR’s requirements.

Now for the questions: Is there a target price for this setup? Did I miss any info or pics on the heatsinking and attachment method? Any idea of how long the FET will hold up under the loads of the Mag100? Have you seen any failures yet?


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## andrewwynn (Dec 8, 2005)

Q&A.

JS: So.. good to hear that the production packs for whatever reason hold up better under load.. i still like that the 'field test' model is in the chart.. shows the improvement between them and i have to say the output calculations are just stunning with the USL. 

the switch has resistance.. measure the mV drop on your switch under 8.7A load.. it's likely as much as my FET.. and of course the 7mV on the bulb socket.. the USL really is the epitome of low resistance.. i'm never going to get close the uber-low resistance in that model, just stellar stuff.

I would bet you have about 15-18mohm resistance between the parts you mention. It is a very good plan and execution to have no 'contacts' other than the bulb, no doubt why it performs the way it does. 

Newbie: 

in the first runs the Vbulb has been 13.18 +/- so yes.. to achive slightly more than 2500 torch lumen.. try 13.18 if you want to double-check my math. 

de-rating by the 'standard' of 35%... if i were to use the 62138 bulb i will run it at 13.18.. if i use the 64625, i would run it at 12.9V to hit the magical number of 3000L out the front. 

Whitehot:.. ONLY and i mean ONLY in the case of the 100W lamps does junction temperatur and power loss even remotely enter an issue... in the cases of the likes of the 1185 or 1111 or 1331 et. al. solutions... the power loss on the FET is in a fraction of a watt average.. Tj will basically be the temerature of the housing of the lamp, or maybe 35 to 40C.. an absolute non-issue. Not even sure how the 'extreme heat' debate got into this thread compared with the Mag100 thread where is the only place it could really apply. 

There is considerable power generation on the FET in the 35W 6V lamp solutions using 7 or 8 bulbs to drive them, but i just came up with a really nice almost 900L solution using the osram 35W bulb at 7.0V.. a mere 1.3W disipation on the FET while putting out 38W into the lamp. 

Efficiency and reliability are both factors in the design of this regulator.. it is both efficient and reliable.. there is nothing to point toward anything else. 

Even in the case of the 100+W solutions i do not see any problem whatsoever with reliability.. the design limits of the Tj of the FET aren't going to be hit ever.. it will even shut down in the case of attempted overheating.. there really will be a complete 'non issue' in that regard. 

Have had a couple oddities.. like fine-tuning the startup sequence where with certain lamp/battery combinations the intial voltage sag gets below the 92% shutdown and it immediately shuts off.. another time where i miswired something and managed to deactivate the low voltage cutout.. in any case it never caused permanent damage and was able to be tweaked into submission.. all 4 drivers that were initially built are still fully operational. 

I have been trying to avoid putting out a target price 'cause i don't want to disapoint if it can't be met.. but.. let's consider that a very advanced driver will be incorporated into a KIU socket and mag switch so no user assembly required.. it will not be 3-digits and it won't be $30... (probably closer to 'cost').. but it will be reasonable, fair and worth the $ absolutely. 

Have you ever seen a KIU socket? the entire top of a magswitch is covered by an aluminum disk that is over 3-4mm thick with about 10-12mm side (it is hollow inside).. maybe 7mm depth.. the FET is heat-paste secured directly to that solid aluminum part which has about 3" surface area in contact with the bore of the flashlight body.. it is an excellent heat path to your hand.. where you become the final heatsink.. we will get some temp. measurements soon to get a very good idea of just how much heat differential there is from the FET to ambient.. it's not nearly as much as some speculations have put it.. i would be very surprised if there is more than 40C differential from the FET to ambient.

-awr


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## Lurveleven (Dec 9, 2005)

andrewwynn said:


> the 3D host can hold 2500mAH full As..



Are you sure about this? From what I can see a stack of 4 A cells will go into the threading of the 3D Mag, meaning you will not be able to screw on the tailcap.

Sigbjoern


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## andrewwynn (Dec 9, 2005)

you need to remove the stock switch to fit full As in.. with the switch.. 4/5As will fit.

Oh.. another improvement in the design.. looks like i figured out a way to incorporate the max-current startup.. and it's really neat to watch.. basically.. on startup it will for example start at 1.5V and slowly climb to 5V as the bulb warms up (i was using a 2.5A, 5V lamp for testing).. 

The only problem to solve is delaying the low-voltage cutout to wait for a second or so before kicking in, else it 'sees' that low voltage and shuts off.. funny bit of irony. 

Oh.. the other problem is figuring out what to use for sense resistors that are in the 3 to 6 miliohm range (0.003 to 0.006 ohm).. the typical sense resistor i use is 100mohm! I will probably be using lengths of 24 ga wire.. in testing i've been using 30ga, but not sure how long they can put up with the 9+A spikes that go through.. 

just for fun today i shorted out a 12AA battery pack with some 30ga wire to show my brother what happens (turned about 14mm section incandescent before melting out the center 1/3 or so). 

-awr


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## andrewwynn (Dec 12, 2005)

Very big update!

I was able to figure out the most beautiful soft-start into the circuit.. i also have the design worked out for the over-heat protection (it will shut down if the temperature reaches 85C inside, which is the maximum the chips are designed to handle.. i might make that a little cooler, especially if the 'big gun' (100R) can handle a full run w/o overheating. 

I have to test the new design on the bench, and make a prototype yet, but it looks very good. 

-awr


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## cue003 (Dec 12, 2005)

Excellent news Andrew. Can't wait to get the finished product. 

Curtis


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## daBear (Dec 16, 2005)

How is it going with this project?? How about an update? Thanks.


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## AtomicX (Dec 17, 2005)

Hello Andrew... I have enjoyed this post, having now took the time to read through it more completely, and although I am a newie here and not as "electronically minded" as yourself, I do some tech work in my profession and have seen some strange things happen when heat is involved. I am very interested in this and will be in line for one when they become available. I do however have a question: what are the expected ill effects to the batteries from having this much heat inside the barrel of the light? Just wondering, and didnt notice attention in that direction in the thread. This is going to be great.. and an innovation worthy of applause! I am just concerned about the battery pack. Oh..one more thing, for us people that have multiple lights ( if your here you do, right ?!?! :naughty: ) and we can choose according to need/conditions, would it be a good idea to vent (holes or slots) like Inova has done on some of their lights? I know it's a dry - conditions solution, but would indeed be a simple way to let the air pass through. Maybe I am the only one that would want it..don't know..but I'd do one unit up like this just for giggles. Well, as I said, I'm in line, Andrew ! :rock:


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## flex76italy (Dec 17, 2005)

andrewwynn said:


> Very big update!
> 
> I was able to figure out the most beautiful soft-start into the circuit.. i also have the design worked out for the over-heat protection (it will shut down if the temperature reaches 85C inside, which is the maximum the chips are designed to handle.. i might make that a little cooler, especially if the 'big gun' (100R) can handle a full run w/o overheating.
> 
> ...




:bow: :bow: Andrew many thanks for your :goodjob: 

You have given a contribution for the development of the world


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## andrewwynn (Dec 17, 2005)

that is just hilarious, made my day. 

to ans. the question about the heat.. hopefully the case of the 4/5As will be such as the AA CBP batteries.. they actually PREFER to be hot.. a pack of CBP 1650s will hold considerably more voltage if they are at 110F or more. 

We are considering many options of active cooling should the need arise. At least 4 are actively in consideration. 

There is at least one light on the table that will require a fan.. we definitely are planning on pushing some limits. 

-awr


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## andrewwynn (Dec 17, 2005)

i should mention.. there is no driver-related heat issues in the normal use of this regulator.. i.e. 1111 hosts.. 1185/1331 host.. even the 1166 (which has a pretty high voltage drop).. or the 1274. It's only an issue with the 100W light at this point. There needs to be a high voltage drop AND a high current combined for any important quantity of heat to be generated by the LDO. 

On the other hand.. if the light *already* gets hot just from heat coming from the lamp.. well it's not going to get 'cooler' from having the driver (well, not likely anyhow). 

We have a couple aces up our sleves to help work on this issue on the higher power lights.. for example.. with the LDO it opens up doors not exactly available.. like 60+minute runtime mag85s.. well that will generate a lot of heat.. on about an 80% run the other day i got the bezel up to about 145F. 

-awr


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## mpf (Dec 17, 2005)

andrewwynn said:


> Oh.. the other problem is figuring out what to use for sense resistors that are in the 3 to 6 miliohm range (0.003 to 0.006 ohm)..
> -awr



http://www.micrel.com has an application note no 25 "Minimum size copper sense resistors" which gives design parameters and an example of a 4mOhm resistor.
matthew


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## AtomicX (Dec 18, 2005)

Well...forgive me, I am thinking out loud here and your free to laugh...I have seen on recent threads a couple people machining the heads with grooves. Hmmm...looks like a heat sink to me. :sweat: I wonder if/how effective the air passing through such grooves is. Cheers guys ! I'm in line for one of these when their ready. _Gary


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## andrewwynn (Dec 18, 2005)

well.. that was supposed to be a secret.. we are sending a bunch of heads to said guy for that treatment.

Yes.. surface area is by far the most important thing for steady-state heat control.. mass being the most importnat for startup heat control. (mass and the specific heat of that mass). 

micrel does show how to use even the likes of pcb traces to become that sense resistor.. i didn't say it was a 'hard' problem just a problem that hast to be solved.

I used a loop of about 1 1/2 inch of 30ga wire on my prototype when doing the current limiting testing... now i don't have that part enabled anymore because with the soft starting it's not needed.

-awr


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## NewBie (Dec 19, 2005)

andrewwynn said:


> well.. that was supposed to be a secret.. we are sending a bunch of heads to said guy for that treatment.
> 
> Yes.. surface area is by far the most important thing for steady-state heat control.. mass being the most importnat for startup heat control. (mass and the specific heat of that mass).
> 
> ...




I'm not sure if the Micrel app. note mentions it, but don't put the sense resistor on an outer layer that they plate up, if you can help it. Often, even top notch board houses do not have a precise thickness plating copper process. This causes the resistor formed on the top layer to vary in value. It is best to put it on an internal layer, as they don't get plated up. An alternative, is to have the vias only, selective plated. Talk to the particular board house on this.


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## andrewwynn (Dec 19, 2005)

not to worry newbie.. i don't like that kind of 'hack' anyhow.. i actually am not using the sense resistor in my solutions anyhow.. i chose to use soft start to controlt the current inrush rather than use the built-in current limiting... it seems to have a 'delayed' effect.. i.e. it will turn on 'too hard' than realize it and clamp down the input.. so it would go 6V.. oops too high.. 5V.. ok better.. now 5.2, 5.3 5.4 5.5 ok that's good. 

On one design where a sense resistor is in the works.. i would either form one from wire (i can calculate to 0.001 ohm pretty easy) or use an smt resistor set (a couple parallel resistors also works very well). 

-awr


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## andrewwynn (Jan 4, 2006)

js said:


> Andrew,
> 
> You want to heat sink 4 to 8 watts to the body of the flashlight? Good luck my friend. Good luck. That part of the flashlight body right above the FET or Transistor will burn anyone who touches it.
> 
> ...



We've already 'gotten past' this situation not re-opening the original ticket which is covered.. but it occured to me the other day... 

Since the MB20 pack is only outputting about 60% of the energy into the lamp.. it means that 40% of the energy is going into HEAT in the battery pack .. in other words.. if 60% = 32W than the internal output of the MB20 pack is 53W of which TWENTY ONE watts turns into heat.. in a muuuch smaller body than a 3D maglight.. which explains why when i did the shoot-off with the M6.. the internal temp. rose to 180F+ and the outer shell was over 165F. 

Running the M6 on the six pack of 17500s.. the cells are running over 90% efficient and barely get warm to the touch... runtime of nearly 40 minutes, and stays cool... the batteries maybe got up to 110F and the outside case was about 100F.. (115 at the very top.. and 130 at the bezel). 

In any event when i realized the M6 is dumping over 20W into the body from the battery pack, made me much less worried about putting an average of 5 to 7 into the much bigger Mag100. 

-awr


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## wquiles (Jan 4, 2006)

That 6x17500 regulated battery pack for the M6 looks better and better the more I read into it 

Will


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## andrewwynn (Jan 7, 2006)

update:.. latest driver proto finally operational in a light (well two lights).. no messing around best push it hard to start with.. both me and Tom (NikolaTesla) decided to use our first Mk5 regulator in the Mag100 of course. 

For any of you really daring types... here's my official (to myself) guide for reproducing them:







That tall part on the right is the 11-turn pot.. it was way too twitchy setting the higher voltages with the 3/4 turn pot.. but it costs more than the micrel driver and all the small chips combined.. so the production models will instead have a pair of pots.. one for gross adjustment and one for fine-tuning (which actually is faster and easier to change the voltage with anyhow). 

One nice note.. see that resistor that says '938' on it.. that's the 9.09k ohm resistor from the schematic... and it's addition eliminated load bias from the ckt.. i just set my Mag100 with 0 load (technically.. still going through about 100kohm.. so 132µA).. and once loaded with the full harassment of the osram 100W lamp.. was reading to the 100th of a volt exactly the same reading! (just as it SHOULD) be. 

oh.. holy cow almost forgot.. oscope came in yesterday.. first tests.. 

hotdriver without the soft-start trick:






with the soft-start trick:






explanation: 

The top trace is voltage.. 1v/div.. the bottom trace is current.. 1.33A/div (1.85A, 7.1V steady-state). 

oh.. horizontal is 10 msec/div. 

in the first picture you can see that within 5 msec. the output voltage is full voltage.. actually overshot a bit.. but initially there is a voltage sag that is likely because of voltage drop on the bench supply power leads, or coupled by the bench supply going into current-limit and clamping voltage. 

when doing peak measurements with the fluke 87 to try to get an accurate read of the voltage spike of 9.33A... most likely limited by the power supply.. compared with 5.09 with the soft-start. 

Without the ability to use µC programming to determine the ramp-up i'm sort of limited by how capacitors charge in how the circuit loads but i'm very happy with the outcome even though i'd prefer if there wasn't as much of an overshoot of amperage even though the voltage ramps beautifully. 

I will be very interested to see the scope traces of the other regulators... and my simple-soft-start solution that wquiles. put together. 

I'm hoping that the POWER expended on the bulb is more important than just the current.. because if you look at what will be the product of those two curves.. power going into heating the filament will not be bad. 

Ok.. i made the chart.. definitely it makes a difference!.. power has got to be the important role:






This is the 1316 lamp running at 7.1V and 1.85A nominal in my prototype with the charts regenerated in excel so i could calculate POWER.

HOLY COW.. 

13.14W nominal.. and the soft-start ckt starts at 10W, is held to about 12W as the current is dropping and the voltage is rising.. taking about 250msec before reaching steady-state.

The same exact driver w/o the soft-start ckt included.. 85W spike! that is OVER SIX TIMES nominial or a 550% peak over nominal!

I guess i definitely answered my own question there! no wonder bulbs burn out when you first turn them on. SIX TIMES the power heating that element! 

I could always tell there was a big difference because the bench power supply always goes into current limit (6A) every time i would turn on the ckt w/o the soft-start.. and with the soft-start.. no problemos never kicks in. i used to have occasional problems in the flashlight with the low-voltage ckt kicking in with the extra current causing a voltage sag, and that is completely eliminated because of the way my soft-start ckt works.. regardless of the current spike which is still often double standing current.. the circuit is actually tricked into thinking it's supposed to be outputting the voltage of the ramped curve, so it's happy as a clam as it goes along the curve.. only complaining to turn off the light if the battery voltage can't keep climbing. (basically if you turn the light on and the batteries are dead.. it'll turn on and ramp up the light and 'blink off'.. with voltage regeneration of resting cells you can actually get many cycles of burst light out of a dead battery pack.. say you're M66 dies in the middle of a woods.. you could say.. turn the light on for 1 second every 10 seconds all the way home to light the path in an emergency... full brightness too.. it's kinda nice. 

Here is a graph of just the soft-start ckt and how it works at startup:






There is some adjustability of the time it takes to start up so the x axis is in 'time constants' not in a particular time value. I think it's particularly interesting how the rise in voltage almost perfectly balances the drop in current and makes for almost flat output in power during the startup.

-awr


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## wquiles (Jan 7, 2006)

Andrew,

That is outstanding!. I do agree with you on the overall power thing - the truth is that the soft start trully works. Glad to see the new scope being put to good use 

I am ready if you want/need me to test this prototype on my setup. I have a WA1319 (4.8V), a WA1160 (6.0V), a WA1306 (9.6V), WA1318 (9.6V), and WA1185 (9.6V) to test on my bench setup 

Will


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## andrewwynn (Feb 4, 2006)

Computer model of the circuit board, top view. 





Computer model of the circuit board, bottom view.

Don't ask what all those parts are i made it and i don't even know :-D

-awr


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## BVH (Feb 4, 2006)

Andrew, target release date?


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## andrewwynn (Feb 4, 2006)

I will be building the boards starting next week.. Litho 123 has claim to the first batch, so i'll be another week or two before i can make ones available outside of his buy. Maybe the 25th i'll post on BST or something close to that. 

-awr


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## wquiles (Feb 4, 2006)

These are looking pretty good dude 

Will


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## NextLight (Feb 4, 2006)

IMMEDIATE need for 5, or 3 finished plus 2 kits if that speeds up my first availability.


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## andrewwynn (Feb 4, 2006)

I have enough blanks ordered to make 350 drivers.. not worried about running out. I just finally after like 7 weeks of nearly non-functioning have been able to get back to work and that means i have to spend as much time as i can getting the nanos made, so we'll have to see how fast i can make the hotdrivers, though i have a couple people lined up to fabricate them so i can keep nanoworking. 

oh... ps.. that was the first time i've seen the bottom of the driver 'right reading'... anybody that designs pcbs will tell you that the bottom side of the board reads backwards in the design program.. i also love how it came out with the 'meteor' effect with all the traces on the bottom being circle segments. 

-awr


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## JohnMuchow (Feb 5, 2006)

Nice board Andrew! It's pretty cool seeing this come together. 
What software did you use to model the PCB with?


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## OddBall (Feb 5, 2006)

Oh - so good!!  

Hey Andrew - these can drive a 100W yes?

I'd love to solder my own together if you can supply a kit of parts in a bag? Would it make it easier or can't you supply the component list for privacy type reasons?

I am mentally jumping up and down with excitement! 

Tim.


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## MrAl (Feb 5, 2006)

Hi there Andrew,

Very nice illustrations! It's nice to be able to see the board that clearly
to get a very good idea what these things look like in real life.

Take care,
Al


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## andrewwynn (Feb 5, 2006)

I always model my boards now so i have a 'perfect' example, it is stunning how much they end up looking like the real thing.. example:








notice the details like the raised bump in the solder mask where the ground wire comes off the dual NPN transistor (6-legged creature).

I will definitely sell you a DIY kit-bag to solder up yourself, Oddball. You are correct about the semi-private reasons for being a big vague about what parts are where.. there are only a couple secret components that aren't in the schematic listed earlier, but once they are out there, somebody could reverse-engineer it, but they might as well design their own ala winny.. 

The computer model goes through a few steps.. the PCB is designed with Pad2Pad.. I take a screen shot of each layer and throw those files i save in 'png' format down on my Mac in the basement. I load the layers into photoshop and make the 'solder mask' like 70% transparent wherever there are traces below it. The colors are actually 'picked' directly from a dig. picture of the nano circuit boards and if you look closely you will see there is 'texture' on the solder pads that makes it look a LOT more realistic. 

Once the top and bottom are done (and the bottom is 'mirrored' so it is right-reading).. i save those as a jpg file and load into sketchup which i prepare a computer model of the shape.. in this case 30mm disc 1.6mm thick.. I load the pictures as a 'texture' top and bottom and than poke holes wherever there are vias or holes.. In this case.. holy cow.. lootta holes. 

This is the circuit i use for my 100W light.. the board will be sold as a normal performer or a hot performer for an extra $10... it will include overheat protection.. where it will power cycle if it reaches 185F (85C) internally (btw.. cute relationship between F and C.. like -40F = -40C).. 85C = 185F exactly. This model shown is complete with the temp-sensing circuit.. technically it's R4-R7, the OPA (opamp) and C7 that comprise the temp. sensing ckt.. the plain jane model just doesn't include those.. if you look above the OPA you will see a lable 'td'.. stands for thermal defeat.. and it's a jumper that is solder-bridged if the OPA and other parts aren't there. 

It's a bit of a no-brainer for the thermal cutout.. it is made from 3 resistors and a thermistor that has a specific resistance at a specific temperature. One set of resistors biases the non-inverting input on the OP-amp and the thermistor is matcheded with a like resistor on the other op-amp (inverting) input.. it's set up so as the thermistor rises in resistance .. once it hits the magic temperature.. it flips the op-amp from high to low output.. which feeds the enable pin on the driver chip... since there is no hysteresis built into the high-temp ckt.. it will stay off only 'til the temp gets below the cut-off and it will come back on.. in testing this has caused it to blink on/off at about 1/2 Hz, but more testing is required to see if it will cycle that fast at full temp.. the tester runs at a lower temperature like 50C. 

It only takes swapping that one thermal resistor to achive any cutout temperature i'd like.. and i will aim to fine-tune it for personal comfort once i get some more details about the relationship of internal vs external temperature.. right now it's designed as a protection for the IC.. which can handle 85C (but has testing values up to 120C.. which is why i don't have it cut out sooner). 

Another interesting part is if you look above 'Battery Pos' you will see a set of 3 pads labeled 'cl' and with a '1' by one of the pads.. That is for the current-limit circuitry. if the common (center) pad is soldered to the bottom pad, the circuitry will measure the voltage drop on the main power lead coming from the battery.. by using just the right gauge of wire and the right length, a proper sense resistor is created and a maximum current will be monitored and controlled as well as voltage. One reason this could be utilized is with the right match of lamps, you could for example use an 1111 lamp or the osram 35W lamp and w/o adjusting the output level, jsut swap lamps. This works any time the higher output lamp runs at lower voltage but higher current.. 

In the scenario described above.. the osram lamp takes 6.35A but 7V.. and the 1111 i would set to 7.25V (for 900 bulb lumens).. and since it's only 3.72A it won't come near the current limit of 6.35A of the osram. 

Another key feature of the hotdriver compared to other devices is the ease of assembly... if you are using a solution that is less than 4A, you can skip the wiring to the switch part of the installation.. you only gain about 0.030-0.050V a difference that will add a mere 14 lumen (from for example.. 801 to 815L on a mag 85).. less than a 2% gain.. where in 'light' it takes about 20% difference before you can even see it, and 50% to really notice it... in other words, absolutely negligible. If you look at the bottom of the pad you will see there is a 'ring' in the center and a square pad on the bottom (5:00).. those are designed to contact the spring base from the mag switch (just the outer edge.. since the pos and neg connections for the lamp are right in the center).. and the neg terminal is the slider that goes up the post normally it gets cut off and bent flat and sandwiched between the hotdriver and the magswitch. It'll probably add about 15-20mohms of resistance total to skip hard-wiring but it'll drop a lot of complexity of wiring it up for a DIYer, and a lot of time of assembly.. i will probably offer like a $5 discount to not have the hard-wiring option on complete units i sell.

So.. it's definitely 'coming together' I love when i finally have the computer model, and they will be a 'cake walk' to solder up.. i'm used to the nano boards which are NOT a cakewalk they are so small and tight together is' hard to solder w/o bridging things. 

-awr


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## andrewwynn (Feb 5, 2006)

oh.. btw.. http://sketchup.com for the modeling program, and it should be semi-obvious that the parts are modeled by me, they don't have a PCB library of FETs and Micrel 5158s.. but the software is so easy to use it took maybe 20 minutes to model the driver chip, and 5-10 to make the potentiomer.


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## andrewwynn (Feb 15, 2006)

Hot dawg! the PCBs have shipped! crossing all fingers and toes there are no errors either my fault or their fault in the production.. fortunately.. i have a very good track record.. the other two orders i've done they work exactly as designed.. so not too much anxiety about that... the boards from Pad2Pad are absolutely gorgeous.. exactly to the 1/10th mm as designed. 

Fortunately for me and others.. this board is soooo much bigger than the nano that i will be able to hand-off production including board assembly. 

Pretty excited to see it so close to being a reality. 

-awr


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## andrewwynn (Feb 15, 2006)

Ok.. update. the sales thread is open.. the page is here: http://hotdriver.rouse.com


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