# 1st homemade light from scratch- sst90 aspheric H2O proof - 10 AMPS build log



## gt40 (Jun 15, 2010)

Since getting the jet 13x40 lathe and a mini mill, I am finally starting to try to use it to make some stuff. The learning to lathe thing is no joke. This thread is to document my progress on my first light from scratch.

Basics:

Led: sst90 top bin

Battery: (1) Battery Space 26650 battery (4000mah/10 amp)

Switch: mosfet with hall effect sensor and a magnet embedded in a ring on the outside of the body i.e. when you turn the ring so the south pole of the magnet is over the hall effect sensor, it turns on.

Driver: It is direct drive 

Optics: Aspherical 32mm lens from surplus shed

Heatsink: solid copper slug 1 1/2" long.

Additional cooling: The body will be substantially grooved and solid t6 aluminum to act as a giant heat sink in addition.

This light will be completely water proof and divable with o rings throughout. I will probably use it primarily as a super bright fairly compact light for walking my 3 dogs. I wanted something almost as bright as my mag 3c sst90 aspheric build in as compact as possible. 

The light is being built also as an exercise to build skills with the lathe and mill as I am a total newbie with a big lathe 

Here are some pics of the raw build so far:

full light pic 1:






from the top:






I am going to taper the head and groove it + still have to machine the "donut switch" to fit on the outside of the head.

Here is the donut I have to machine:






It will be machined to just slightly larger the tube and be grooved or knurled and it will sit in a groove on the tube with o rings to make it rotate smoothly.

Here is a close up of the aspheric I got from surplus shed. It is supported by an o ring on the bottom which is in a groove I machined in the ledge on the inside of the head:






Here is a shot of the bottom o ring:






There is another o ring on top of the lens so it is supported on both the top and bottom by them to help provide some shock resistance as well as hopefully water and pressure proofing.

The lens is held in place by a threaded sleeve. I cut a couple of notches in the top and made a temp tool to allow it to be tightened. I will machine the top of the light better for the finished light:






Here is a shot of the bottom of the head showing the threading. Everything is 16 tpi. Learning to thread has been the biggest challenge so far, and I am still learning but everything seems to fit well without slop or binding:






Here is a shot of the threads on the tube. I am still learning here:






I will post more after I do some more machining and make the switch and heatsink. 

I have access to anodizing cheap from the shop that works on my race car so the finished light will be anodized after it is finally finished.


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## RedfishBluefish (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Nice job on your Dive light! You may want to move it over to that forum for more comments. Good luck!


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## gcbryan (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Very nice! I like your choice of the manor of switching.

As a dive light a larger diameter head would probably be better if you are going to need to use it to cut through the water (and viz) in any manner other than as a flood light for video or something like that.

Can't wait to see the finished product!


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## gt40 (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*



gcbryan said:


> Very nice! I like your choice of the manor of switching.
> 
> As a dive light a larger diameter head would probably be better if you are going to need to use it to cut through the water (and viz) in any manner other than as a flood light for video or something like that.
> 
> Can't wait to see the finished product!


 
Thanks for the comments. I am still learning as I go along here.
I held the aspheric lens in front of the electrolumens edc I upgraded to an sst90 and imr 18650 (7 amps) and it has a pretty focused beam. It should also be interesting to see how much I lose vs the 3c mag aspheric that was my first light with an aspheric (MG). 

Basically, I am building it as a compact light with a lot of light that will still fit in a pocket for walking the dogs etc. The water proofing is just figuring out stuff for an upcoming dedicated dive light build. I figured if it works, I can also throw it in my bc as a backup light.


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## Mettee (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*

looks good, I cant wait to see it finished.


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## wquiles (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Awesome!

I also have plans for a diving light with a magnetic outer ring and using hall effect sensors, so I am most interested in your project. Please let me know what sensors you end up using.

In my concept I am planning on using more than one sensor to try to have at least two levels, and to perhaps feed this "level" to a regulated driver from TaskLED - at least that is what I have plan so far in my head.

Please keep us posted - I am looking forward to learning from your experiences in this project.


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## gt40 (Jun 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*



wquiles said:


> Awesome!
> 
> I also have plans for a diving light with a magnetic outer ring and using hall effect sensors, so I am most interested in your project. Please let me know what sensors you end up using.
> 
> ...


 
Here is what I am using: IRLz34n and hall effect sensor melexis u51881

There is no reason why you cant have 2 or more all sensors as they are super tiny. I was actually thinking the same thing. Trying to learn the lathe part and just wanted a different switch than a judco.


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## wquiles (Jun 16, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Thanks for the info on the specific switch. Are you going to use the through-hole sensor or the surface mount one?




gt40 said:


> Trying to learn the lathe part and just wanted a different switch than a judco.


And you are doing great with the learning part on the lathe. Nothing like a real project to try out stuff. I learned the little I know about machining from mostly this forum, and of course hands-on.

By the way, here, how did you made the o-ring groove inside the head?


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## gt40 (Jun 16, 2010)

*Re: compact sst90 aspheric waterproof light build log*



wquiles said:


> Thanks for the info on the specific switch. Are you going to use the through-hole sensor or the surface mount one?
> 
> 
> 
> ...


 

I cut the groove with one of those kennametal multi tools you posted about using an a3 insert. I mounted so the insert was pointing in the face and it works quite well.

FYI, here is where I got the hall sensor:

http://www.sparkfun.com/commerce/product_info.php?products_id=9312

Data sheet: http://www.sparkfun.com/datasheets/Components/General/Hall-US1881EUA.pdf

I got the through hole version as it is already super tiny. I only imagine trying to solder the surface mount version.


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## wquiles (Jun 16, 2010)

*Re: compact sst90 aspheric waterproof light build log*



gt40 said:


> I cut the groove with one of those kennametal multi tools you posted about using an a3 insert. I mounted so the insert was pointing in the face and it works quite well.
> 
> FYI, here is where I got the hall sensor:
> 
> ...



Thanks for the link. Not only mounting/soldering the surface mount part would be a little bit more work, but because it does not have the wires, it would also be harder to "aim" or position for optimum relationship to the magnet. Once I finish the development of the PhD-M6 pack I will dedicate more time/effort to working with the hall effect sensors and my MagnetoDrive concept light.

Will


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## gt40 (Jun 22, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Update:

Did some work with the switch. I made a version with a reed switch I had laying around and one with the hall effect sensor. 

The reed version worked perfectly. On the other hand, the hall effect sensor didn't. Apparently, I didn't feed enough voltage with the 3.3v M cell I was using for testing so I will see if it works properly at proper voltage tonight. I reviewed the data sheet on the sensor and it runs on a 3.5v to 28 volt range. I will see if it was just an issue of voltage or it doesn't put out enough to turn on the gate of the mosfet. 

This is my first mosfet switch setup so I am happy it works at least with the reed. I still want to use the hall effect sensor though.


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## wquiles (Jun 22, 2010)

*Re: compact sst90 aspheric waterproof light build log*



gt40 said:


> Update:
> 
> Did some work with the switch. I made a version with a reed switch I had laying around and one with the hall effect sensor.
> 
> ...



That is always an advantage for the reed switch - being a passive element it does not need voltage/current to turn ON/OFF. 

Please keep us posted


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## gt40 (Jul 6, 2010)

*Re: compact sst90 aspheric waterproof light build log*

UPDATE:

Got the body more roughed out with the ring switch and stuff. I am almost done with the heatsink too. Here are a few more pics:

Bodyshot:






Ring with magnet hole. I found some 1/8" diameter really strong magnets. The magnet will be in the hole with some colored epoxy or brass cover:






Backshot:






Inside the head shot showing the aspheric:






Close up of the ring knurling:






Threaded inside sleeve to hold the aspheric lens against the o ring:








Lens o ring:






Lens:






Head threads:






Final shot in my hand for perspective:






I have ordered a bunch of different hall effect sensors to test and hopefully find one that will work with the mosfet I am using. The circuit does work fine though with my reed switches. 

After I am done with the heatsink and switch I will do some grooving and cleanup. Sorry about the crappy phone pics...


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## wquiles (Jul 6, 2010)

*Re: compact sst90 aspheric waterproof light build log*

Very cool - nice progress 

What keeps the ON/OFF ring in place? A lip on the body, side facing the tailcup, and the head on the other? Is it metal on metal, or you have a sleeve/spacer of some kind?


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## gt40 (Jul 6, 2010)

*Re: compact sst90 aspheric waterproof light build log*



wquiles said:


> Very cool - nice progress
> 
> What keeps the ON/OFF ring in place? A lip on the body, side facing the tailcup, and the head on the other? Is it metal on metal, or you have a sleeve/spacer of some kind?


 
The ring is held in place by the fact that it sits on a portion of the tube that is smaller in diameter than the rest of the body and snug because of o rings. I only put one on and it holds nice now. The head of the flashlight stops just short of the ring when it is tightened down and so the ring is "captive between the head and larger body section following the ring, yet rotates without binding. I made a ring with inside grooves to match the o rings on top of that so it isn't going anywhere.

Here is a pic of the tube without the ring:


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## wquiles (Jul 6, 2010)

*Re: compact sst90 aspheric waterproof light build log*



gt40 said:


> The ring is held in place by the fact that it sits on a portion of the tube that is smaller in diameter than the rest of the body and snug because of o rings. I only put one on and it holds nice now. The head of the flashlight stops just short of the ring when it is tightened down and so the ring is "captive between the head and larger body section following the ring, yet rotates without binding. I made a ring with inside grooves to match the o rings on top of that so it isn't going anywhere.
> 
> Here is a pic of the tube without the ring:
> 
> (snip pic)



Gotcha - that makes sense, and thanks much for the additional picture. I like the o-ring idea :thumbsup:


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## gt40 (Jul 10, 2010)

*Re: compact sst90 aspheric waterproof light build log*

I finally got a working hall effect sensor based switch! 

I tried a whole bunch of sensors nothing would work. The tiny amount of current in the 20ma to 50 ma range just wouldn't turn on the mosfet I was using. I tried a darlington transister and hall effect switch combo and presto. This works really well. The transister is rated at 80 watts range and ran completely cool running a p7 led. Here is short video of the circuit. Excuse the bench but I was trying over 2 dozen combos till I got this:

http://vimeo.com/13236791

The components to make this south pole magnetic activated circuit are:



1. darlington transister

2. hall effect sensor

THAT'S IT...

I don't think you can even make simpler circuit. This seems to go on and off more reliably than the reed switch I was going to use as a back up.


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## wquiles (Jul 10, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

That is a little confusing to me. Can you please post a diagram/schematic of the exact circuit that you are using, with all of the parts that you are using? 

The MOSFET's don't need current to turn ON, just enough voltage at the gate (I am assuming you are using an N-channel MOSFET). It could be that since the Darlington transistor has higher gain, that it then provided enough voltage at the gate of the MOSFET to finally turn it ON.


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## gt40 (Jul 11, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



wquiles said:


> That is a little confusing to me. Can you please post a diagram/schematic of the exact circuit that you are using, with all of the parts that you are using?
> 
> The MOSFET's don't need current to turn ON, just enough voltage at the gate (I am assuming you are using an N-channel MOSFET). It could be that since the Darlington transistor has higher gain, that it then provided enough voltage at the gate of the MOSFET to finally turn it ON.


 
I am not an engineer here and know just enough to be dangerous. 

Here is a diagram:






Non of the regular n mosfets i tried would work and I tried latching, bipolar, etc hall sensors and a simple unipolar one seems to work, but only with the darlington transisters. Not sure why but the circuit is turning on and off every time and doesn't seem to get hot so far. I will try it with the sst90 at 8-9 amps and see if that is the case still but it works and is pretty tiny. You could easily get 2 transisters and hall sensors together to create a high and low with this.


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## SirJMD (Jul 11, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

What is your supply voltage?
Which hall effect sensor are you using?
Which MOSFET are you using?

Im studying electrical engineering, so i might be able to locate your problem.


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## wquiles (Jul 11, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

Ahh. Now with the diagram things make sense to me 

According to the data sheet of the Hall switch (page 4 of 12, lower right picture for the UA package), its output pin goes LOW (to GND) when it feels the South pole within the active range, so if your MOSFET was an N-channel, which was waiting for a HIGH (Battrery +) at the GATE to turn ON, it would never turn ON. If you can let me know the exact part number of the MOSFET(s) you were trying it would be very helpful to verify this.

From your diagram it looks like you have a PNP Darlington, which makes sense it works, since it needs a LOW signal to turn ON. This Wiki page has a good explanation and pictures of the various types of bipolar and FET transistors:
http://en.wikipedia.org/wiki/Transistor

Note that although you have this setup working and it is not getting warm, the right MOSFET will have an even lower ON resistance, therefore working even better as a true switch than the Darlington (or any other bipolar) ever could.

Then again it is hard to argue with a working solution. If you test it with the highest possible current you will ever see, for extended periods of time, and it does not get too warm/hot, then consider it a good circuit and move on with the rest of the project


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## gt40 (Jul 11, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



SirJMD said:


> What is your supply voltage?
> Which hall effect sensor are you using?
> Which MOSFET are you using?
> 
> Im studying electrical engineering, so i might be able to locate your problem.


 
For this light, (1) 26650 3.7v battery space 

Hall effect sensor: http://www.simplemotor.com/hallswitch.htm

I have a bunch also from digikey with different specs.

Mosfet: IRLZ34

I would really appreciate any help you can offer. I am pretty frustrated after having the darlington, simple motor hall sensor combo work and then killing 2 sets putting it in the light with my newbie soldering... (different issue) Basically, the darlington combo started turning on the led barely visable even when the magnet wasnt there. Prefer n based mosfet that will turn on with a hall effect sensor and handle 10 + amps and work every time.


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## wquiles (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> Prefer n based mosfet that will turn on with a hall effect sensor and handle 10 + amps and work every time.


If I am reading the data sheet of the Hal sensor correctly, the output goes LOW when the magnet is in range. Can you please verify this behavior?

If that is the case, that the Hall sensor outputs a low (close to GND or Bat "-"), then you can't use an N-channel MOSFET since the N channel needs a high voltage from Gate to Source to turn ON, and since the Hal sensor you are using gives you the opposite. This is why the PNP Darlington works, since it needs the low voltage to turn ON.


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## gt40 (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



wquiles said:


> If I am reading the data sheet of the Hal sensor correctly, the output goes LOW when the magnet is in range. Can you please verify this behavior?
> 
> If that is the case, that the Hall sensor outputs a low (close to GND or Bat "-"), then you can't use an N-channel MOSFET since the N channel needs a high voltage from Gate to Source to turn ON, and since the Hal sensor you are using gives you the opposite. This is why the PNP Darlington works, since it needs the low voltage to turn ON.


 
I haven't been able to verify it because I killed the simple motors hall effect sensor re soldering it. I also wasn't able to find any data sheet there, only the description link which I already posted.

I did however try the infineon unipolar TLE4905L with the IRLZ34
and it didn' turn it on. Here is the link to the data sheet for that one:

http://media.digikey.com/pdf/Data Sheets/Infineon PDFs/TLE4905L, 06L, 45L, 45-2L.pdf

Any suggestions would be appreciated.


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## b-bassett (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

hi all
this may be completely wrong but i think i read somewhere that some hall effect sensors will output low when a south pole is used will output high when a north pole is used.

might be worth a shot?


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## gt40 (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



b-bassett said:


> hi all
> this may be completely wrong but i think i read somewhere that some hall effect sensors will output low when a south pole is used will output high when a north pole is used.
> 
> might be worth a shot?


 
I tried both poles 

I guess I need a hall sensor that outputs positive voltage when it gets close to the magnet and sufficient to turn on the gate. I am reading greek though looking at all these data sheets...


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## wquiles (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

I have not done an exhaustive search, but for the little I have found searching on Digikey, it seems that most Hall sensors are designed to output LOW/GND when the magnet is in the active area.


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## gt40 (Jul 12, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

Here are some diagrams for the 3 version of circuits I am trying to make work:

Reed switch version:












Finally, the darlington pnp version would look just like the chart above except for the following:

substitute irz34 mosfet for darlington pnp- 

Gate= base
collector= source
emitter= drain

I would like to find a hall sensor that outputs "high" and will work with the mosfet. Not sure what to do at this point..

On another note, I also found this circuit in instructables but still trying to understand the other components. It seems to use a "latching" sensor: http://www.instructables.com/id/Door-Activated-LED-Lighting-using-Hall-Effect-Sens/

Final question: I have found a number of hall effect sensor circuits referencing "pull up" resisters in the circuit. could this be the missing piece?

In any case I am having a bunch of darlington transisters and hall effect switchs I got to work in the original working circuit overnighted and will do some real testing of them after more carefully soldering a new circuit. I found it is easy to burn them if you keep the soldering tip on for too long.


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## MikeAusC (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> I would like to find a hall sensor that outputs "high" and will work with the mosfet. Not sure what to do at this point..
> 
> 
> Final question: I have found a number of hall effect sensor circuits referencing "pull up" resisters in the circuit. could this be the missing piece?
> ...


 

All the Hall Effect switches I've seen are NPN Open-Collector output - when activated by a magnet the Output gets pulled to ground.

If you're driving a FET from an NPN Open Collector output, you must have a pullup resistor (Output to +) because there's nothing to pull the output above ground when not switched on.

You must never have the Gate of a FET open-circuit - the voltage could drift anywhere.

You can only connect a P-channel FET directly to an NPN Open-Collector output. The FET Drain connects to Batt +.

To use an N-channel FET (most are N channel) you need to use a PNP transistor as an Inverter - Emitter to Batt+, Collector to a 10k Resistor to ground and the FET Gate.


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## IMSabbel (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

I do not want to be annoying, but:

Do you plan on adding a plane window in front of the aspheric? Because you realize that if not, it will not work l underwater because of the index of refraction mismatch between the curved side of the aspheric and the water?


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## SirJMD (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> For this light, (1) 26650 3.7v battery space
> 
> Hall effect sensor: http://www.simplemotor.com/hallswitch.htm
> 
> ...



Kinda need a model name on the HE sensor - the link just explains how the HE sensor works. But if it is like some says, you probably have to use a P-channel MOSFET instead (tho i dont like those - their RON is often much worse than N-channel).

Regarding the MOSFET - you might want to find one with a lower RON, else youre gonna loose quite some power there. Since you dont need to swich more than around 4V, a 60V MOSFET is overkill - the lower the voltage rating, the lower the RON is (in general).


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## gt40 (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

MikeAusC wrote: 


> All the Hall Effect switches I've seen are NPN Open-Collector output - when activated by a magnet the Output gets pulled to ground.
> 
> If you're driving a FET from an NPN Open Collector output, you must have a pullup resistor (Output to +) because there's nothing to pull the output above ground when not switched on.
> 
> ...


 



SirJMD said:


> Kinda need a model name on the HE sensor - the link just explains how the HE sensor works. But if it is like some says, you probably have to use a P-channel MOSFET instead (tho i dont like those - their RON is often much worse than N-channel).
> 
> Regarding the MOSFET - you might want to find one with a lower RON, else youre gonna loose quite some power there. Since you dont need to swich more than around 4V, a 60V MOSFET is overkill - the lower the voltage rating, the lower the RON is (in general).


 
Thanks for the input. I am kinda over my head here and would really appreciate any guidance anyone can offer. I just want to make a switch design for multiple lights that will work on sst90 level power and turn on with an hall effect sensor.

Would something like this work:

http://www.onsemi.com/pub_link/Collateral/MTP50P03HDL-D.PDF

Or this: http://www.toshiba.com/taec/components2/Datasheet_Sync//78/2948.pdf

Or finally this one: http://www.vishay.com/docs/70766/70766.pdf

Also, I am still trying to get my head around what the circuit would look like.

As far as hall effect sensors, I have some of these: http://media.digikey.com/pdf/Data%20Sheets/Infineon%20PDFs/TLE4905L,%2006L,%2045L,%2045-2L.pdf

The 4905L's. Would this work?

Thanks again for the info in advance...


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## SirJMD (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

As far as the HE sensor goes, its active low. This means that the output is inverted of what you would normally experience (normally its: on = high. But not here).

Solution is either a P-channel MOSFET, or a N-channel and an inverting gate driver - such as the TC4426.

As for the MOSFET.. just use whatever you got at this moment, to get it to work. After there, you can optimize. But my guess is, that the MOSFET youre using now, will dissipate around 5W.

Are you using any constant-current curcuit? If so, you need to protect it somehow. Cause if the temperature of the MOSFET rises, the CC-circuit will step it up a notch, and the temperature of the MOSFET will rise even more (higher temp. = higher resistance) - and you will have a thermal runaway (and smoke).

EDIT: Found something that could help you: http://books.google.com/books?id=R8...v=onepage&q=hall effect mosfet switch&f=false

Here they use a 12V-zener diode. Give it a look. Tho it doesnt change that its reversed..


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## gt40 (Jul 13, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



SirJMD said:


> As far as the HE sensor goes, its active low. This means that the output is inverted of what you would normally experience (normally its: on = high. But not here).
> 
> Solution is either a P-channel MOSFET, or a N-channel and an inverting gate driver - such as the TC4426.
> 
> ...


 
I am still unclear here. If I understand right, I need the following:

1. P channel mosfet that can handle 12 amp range and has really low ron.
2. Hall sensor that is active low
3. not sure on on anything else and suggested parts would be awesome.

In the meanwhile, I am proceeding ahead and made a second heatsink using the irz34 and reed switch with an embedded copper core running all the way through. Here are a few pics so far:

IRZ34 ready to be embedded in the heatsink:





Installed and ready to be soldered:






Another shot of the rear. I am going to face and bore this out and install a black delrin sleeve and copper contact plate in the center: 





Hope to cut the channel for the reed switch and wire it up tomorrow per the diagram I posted in the thread. 

This heat sink will eventually have an *LDO10C Driver* put in like my mag 3c so I can add a longer tube and run (2) 26650 imr batteries at a full 9+ amps


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## MikeAusC (Jul 14, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> As far as hall effect sensors, I have some of these: http://media.digikey.com/pdf/Data%20Sheets/Infineon%20PDFs/TLE4905L,%2006L,%2045L,%2045-2L.pdf
> 
> The 4905L's. Would this work?


 
Think of these as a switch which connects the Output to the -ve terminal when it detects a magnetic field. Because it's a semiconductor, you can't rewire it to switch to +ve to drive the gate of an N-channel FET.

So connect the Output to a 10k resistor, connect the other end to the Base of a PNP transistor. Connect the transistors Emitter to +ve. Connect another 10k resistor between the Base and Emitter of this transistor.

Connect the Collector to a 100k Resistor and to the Gate of your N-channel FET. Connect the other and of the Resistor to -ve to ensure the FET is switched off when the PNP Transistor is off.


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## gt40 (Jul 14, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



MikeAusC said:


> Think of these as a switch which connects the Output to the -ve terminal when it detects a magnetic field. Because it's a semiconductor, you can't rewire it to switch to +ve to drive the gate of an N-channel FET.
> 
> So connect the Output to a 10k resistor, connect the other end to the Base of a PNP transistor. Connect the transistors Emitter to +ve. Connect another 10k resistor between the Base and Emitter of this transistor.
> 
> Connect the Collector to a 100k Resistor and to the Gate of your N-channel FET. Connect the other and of the Resistor to -ve to ensure the FET is switched off when the PNP Transistor is off.


 
Thank you for clarifying things a bit. FYI, i found the hall sensor data sheet on the one that actually worked with the tip107 darlington transister: http://www.allegromicro.com/en/Products/Part_Numbers/1321/1321.pdf


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## MikeAusC (Jul 14, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> FYI, i found the hall sensor data sheet on the one that actually worked with the tip107 darlington transister: http://www.allegromicro.com/en/Products/Part_Numbers/1321/1321.pdf


 
This is a Linear Hall Sensor, not a switch.

The output will vary between -ve and +ve depending on the stregth and direction of the Magnetic field. It could drive an N-channel FET directly, BUT . . . . 

The danger when using this to drive a FET or Bipolar transistor is that it may partially turn on the transistor, causing very high dissipation. OK, if the system is designed to work that way, but can overheat the transistor otherwise. Worst case is that the transistor will dissipate the same amount of power as the LED - a simple dimmer, but a very ineffcient one.

EDIT - With no magnet nearby, the output will be halfway between +ve and -ve, which makes it hard to drive a switch. If you place a small Magnet near the sensor it can bias the sensor to go to +ve or -ve. Then the switch contains a stronger magnet of the opposite polarity that drives the output to the other extreme.


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## gt40 (Jul 15, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



MikeAusC said:


> This is a Linear Hall Sensor, not a switch.
> 
> The output will vary between -ve and +ve depending on the stregth and direction of the Magnetic field. It could drive an N-channel FET directly, BUT . . . .
> 
> ...


 
I was wrong on the hall sensor spec sheet. I looked it up based upon the markings on the pic. The place I bought it finally gave up the correct sheet:

http://www.melexis.com/prodfiles/0004824_US5881_rev007.pdf

This is the one that worked with the darlington transister. Could I use it with a p channel in the same way?

Also, I found an example on this hall applications guide that seems to do exactly what I want. The example makes a 50v/50 amp switch with a hall effect sensor and power fet. It is on page 33: http://www.melexis.com/Assets/Hall_Applications_Guide__3715.aspx

Not sure which type of hall sensor or fet they are using though. I e-mailed Melexis and will see if they respond.

One more question, could i use the 5881 hall effect sensor to switch on a p channel like this one: 

http://www.irf.com/product-info/datasheets/data/irf4905.pdf

Thanks btw for responding to my newbie questions:thumbsup:


----------



## MikeAusC (Jul 15, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> This is the one that worked with the darlington transister. Could I use it with a p channel in the same way?


 
This one switches output to ground when it detects a magnet - so it can drive a P-channel FET directly or N-channel via a PNP transistor.

If it's possible to have the LED on when the magnet is AWAY from the sensor (or use the bias magnet mentioned above), then you can drive an N-channel directly.

But are you aware the Hall Switch will draw 2.5mAmp from the battery continuously ?



gt40 said:


> Also, I found an example on this hall applications guide that seems to do exactly what I want. The example makes a 50v/50 amp switch with a hall effect sensor and power fet. It is on page 33: http://www.melexis.com/Assets/Hall_Applications_Guide__3715.aspx
> 
> Not sure which type of hall sensor or fet they are using though. I e-mailed Melexis and will see if they respond.


 
This is a conceptual diagram if it shows no part numbers - the FET will be OFF when the magnet is near the sensor (or use the bias magnet mentioned above).


----------



## MikeAusC (Jul 15, 2010)

*Re: compact sst90 aspheric waterproof light build log*

I really think you need to use a Reed Switch instead of a Hall Switch to avoid the continuous 2.5mAmp drain on the battery when the LED is off.

Connect the Reed Switch between +ve and the Gate and connect a 10k resistor from Gate to -ve.


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## wquiles (Jul 15, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



MikeAusC said:


> But are you aware the Hall Switch will draw 2.5mAmp from the battery continuously ?


Good point. That is certainly one of the disadvantages of the Hall switch being an active device. I think in this case, since the light has a tailcap, one could simply unscrew the tailcap enough to break the electrical connection, much like in the SF lights. Of course that usually works because the threads are anodized, but it is one option to stop the parasitic current draw.


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## gt40 (Jul 16, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



MikeAusC said:


> This one switches output to ground when it detects a magnet - so it can drive a P-channel FET directly or N-channel via a PNP transistor.
> 
> If it's possible to have the LED on when the magnet is AWAY from the sensor (or use the bias magnet mentioned above), then you can drive an N-channel directly.
> 
> ...


 
On a 4000mah 26650, how much parasitic drain is that likely to be in a month?

In any case, I made another heatsink and got the components. I am going to see if I get any significant difference in how much amps I can get off a single 26650 imr running the sst90 between the n mosfet circuit with a reed vs the darlington/hall combo. If the parasitic draw isn't too bad, I like the hall effect sensor idea but I do recognize the elegant simplicity of the reed. The new sink design is a significant improvement each time I re-make it. I have made 4 designs so far and the last one took about 25 minutes with a copper core, delrin sleeving and channels cut for wiring. 1st one took half a day


----------



## wquiles (Jul 16, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



gt40 said:


> On a 4000mah 26650, how much parasitic drain is that likely to be in a month?



Rough numbers ...

runtime = 4000mAh / 2.5mA = 1600 hours to drain

one month = 30 days = 30 * 24 hours = 720 hours in a month

Given this the cell would be drain in approximately = 1600 / 720 = 2.222 months, or approx 2 months and 6 days

In one month, it would drain = 1600 - 720 = 880 hours left after one month, so a little bit under half of the capacity of the cell would be lost to parasitic loss in the curse of the first month.


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## SirJMD (Jul 16, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*

I gotta say.. i would also prefer the reed switch. Its easy to use, its reliable - and no "hidden" drain.


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## MikeAusC (Jul 16, 2010)

*Re: compact sst90 aspheric waterproof light build(Updated video of Hall switch workin*



wquiles said:


> so a little bit under half of the capacity of the cell would be lost to parasitic loss in the curse of the first month.


 
:eeksign: - that's worse than the self-discharge of old-style NiCd's !!!!

You can get quite small Reeds and if you mount them and the bar magnet at 45 degrees to the direction of movement, they can switch with very small travel.


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## wquiles (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

If you want to still use a Hall Effect switch, you can still look for a low-power device, one designed from the get-go to be used in battery powered devices, such as this one:
AH182-PL-ADICT-ND

Of course Digikey is out of stock on this particular device, but my point is that it is possible to have extremely low drains. This particular Hall Sensor consumes 10uA (that is micro-amps), so instead of a little bit over two months, it would take approximately 555 months to drain that cell. Of course, the cell will drain sooner by itself due to its own internal self-drain mechanism :naughty:


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## gt40 (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



wquiles said:


> If you want to still use a Hall Effect switch, you can still look for a low-power device, one designed from the get-go to be used in battery powered devices, such as this one:
> AH182-PL-ADICT-ND
> 
> Of course Digikey is out of stock on this particular device, but my point is that it is possible to have extremely low drains. This particular Hall Sensor consumes 10uA (that is micro-amps), so instead of a little bit over two months, it would take approximately 555 months to drain that cell. Of course, the cell will drain sooner by itself due to its own internal self-drain mechanism :naughty:


 
What "characteristic" on the spec sheet shows the parasitic loss? Is it the supply current or output saturation voltage? 

Here is the melexis electrical characteristics:
*parameter Symbol Test Conditions Min Typ Max Units*​Supply Voltage V​​​​DD Operating 3.5 24 V
Supply Current IDD B < BRP 1.5 2.5 5 mA
Output Saturation Voltage VDSon IOUT = 20mA, B > BOP 0.4 0.5 V
Output Leakage Current IOFF B < BRP, VOUT = 24V 0.01 10 μA
Output Rise Time tr RL = 1kW, CL = 20pF 0.25 μs
Output Fall Time tf RL = 1kW, CL = 20pF 0.25 μs
Maximum Switching Frequency FSW 10 KHz
SE Package Thermal Resistance RTH Single layer (1S) Jedec board 301 °C/W​
UA Package Thermal Resistance RTH 200 °C/W

Here is the one you posted:

*Symbol Characteristic Conditions Min Typ. Max Unit​*V​​​​OUT Output On Voltage IOUT = 1mA - 0.1 0.3 V
Ioff Output Leakage Current VOUT = 5.5V, B < Brp - <0.1 1 μA
Idd(en)
Supply Current
Chip enable - - 2.0 mA
Idd(dis) Chip disable - - 8.0 uA
Idd(avg) AH182: average supply current - 5 10 uA
Idd(avg) AH183: average supply current - 280 500 uA
Tawake Awake Time - 50 100 μs
Tperiod Period AH182 - 50 100 ms
AH183 - 200 400 us
D.C. Duty Cycle AH182 - 0.1 - %​
AH183 - 25 - %

What is the significance of output leakage current vs supply current?

Just trying to understand these things...


----------



## wquiles (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> What "characteristic" on the spec sheet shows the parasitic loss? Is it the supply current or output saturation voltage?



The leakage current is not significant in your application, and even if it somehow were, it is in the micro-amps. Don't worry about it.

The key value that affects your circuit is that *supply current*. It is basically consuming that much current ALL of the time, while you have power applied to it. The supply current is by itself not "parasitic", but in the context of your overall/complete circuit, the hall effect is "sucking" power away even in idle mode, and since "sucking" is often associated with a parasite sucking the life out of something else, you could make the connection that in this case, if the supply current is big enough, the hall effect sensor is "sucking" power away while doing nothing with that power in the idle mode.


----------



## gt40 (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Thank you very much for clarifying that. I will try to find some of the sensors you posted and in the meantime, build the light with the mosfet and reed switch. Any better suggestions on the n channel mosfet than the irz34 i have? I am down to my last one and going to order some more... 



wquiles said:


> The leakage current is not significant in your application, and even if it somehow were, it is in the micro-amps. Don't worry about it.
> 
> The key value that affects your circuit is that *supply current*. It is basically consuming that much current ALL of the time, while you have power applied to it. The supply current is by itself not "parasitic", but in the context of your overall/complete circuit, the hall effect is "sucking" power away even in idle mode, and since "sucking" is often associated with a parasite sucking the life out of something else, you could make the connection that in this case, if the supply current is big enough, the hall effect sensor is "sucking" power away while doing nothing with that power in the idle mode.


----------



## MikeAusC (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> What "characteristic" on the spec sheet shows the parasitic loss? Is it the supply current or output saturation voltage?
> 
> Here is the melexis electrical characteristics:
> ​​​​​​​Supply Current IDD B < BRP 1.5 2.5 5 mA
> ...





The supply Current specification tells you that, over many devices, the supply current will always be within the range of 1.5 to 5 mAmp.

The output saturation voltage tells how much voltage will be between output and -ve when the switch is on and sinking 20mA (it's not a perfect switch with zero resistance).

Leakage Current again means it's not a perfect switch - even when off it sinks some current - that's why you need a resistor from Base to Emitter or Gate to Drain - so the transistor won't switch on from leakage in the driver transistor or FET, or from stray fields.

I donlt know what type of switch the second device is ? ​


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## gt40 (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



MikeAusC said:


> The supply Current specification tells you that, over many devices, the supply current will always be within the range of 1.5 to 5 mAmp.
> 
> The output saturation voltage tells how much voltage will be between output and -ve when the switch is on and sinking 20mA (it's not a perfect switch with zero resistance).
> 
> ...


 
Here it is:
http://www.diodes.com/datasheets/AH182_AH183.pdf

Using a reed switch with an n channel mosfet, any suggestions for the mosfet that will switch fully on with just one li ion battery(3.7v)?

Thanks again for handling my newbie questions...


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## wquiles (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

These should work:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=568-4899-5-ND


http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRLU8743PBF-ND


http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IPS031N03LGIN-ND


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## gt40 (Jul 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



wquiles said:


> These should work:
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=568-4899-5-ND
> 
> 
> ...


 
Thanks a bunch! Have a good weekend.


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## gt40 (Aug 4, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

UPDATE: 

Got the light almost finished. 

I had to remake the head to have the aspheric properly aligned but it is working finally.

Here is a video of the magnetic reed switch in operation. I am very happy with how it turned out. The light turns on every time and is completely sealed. The action of the ring is very secure, smooth and positive with the o rings in the knurled part. Thanks also to everyone who helped with my questions on building this:

http://vimeo.com/13886655

A few pics from the cell phone:

LED through the aspheric:






back of head:





Lens with O rings on top and bottom for sealing and shock absorption:





I am shortening the inside ring piece so it will be flush with the head:





Body shot:





LED:





Beam pattern in mid day lighted room:





top light shot:





My next steps are to make the threaded ring fit on the top of the light so it is flush, grooving and final shaping of the body and applying the finish. I am leaning towards Brownells gun kote gloss metal blue or just have it anodized.

I am also going to make a second tail cap with a gland and remote battery pack so I can have the light work as a proper dive light. The magnetic ring switch will still work if I make a delrin copper insert to take the place of the battery. 

I will take some current readings but it seems almost as bright as the sst90 mag c build i made already. Short wires 18 gauge teflon covered silver coated wire through out, copper battery connector and copper braid tail spring mod with a mosfet to switch the power via the reed switch.


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## wquiles (Aug 4, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Awesome :twothumbs

You need to try take some beamshots at night


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## gt40 (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



wquiles said:


> Awesome :twothumbs
> 
> You need to try take some beamshots at night


 
Here you go:

Beamshot video: http://vimeo.com/13928375


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## Packhorse (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

great build, congrats!!

2 questions

How wide is the beam at what distance? EG beam angle.


What MOSFET did you use to switch on fully at 3.7v?


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## wquiles (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



Packhorse said:


> great build, congrats!!


+1




Packhorse said:


> What MOSFET did you use to switch on fully at 3.7v?


I not trying to answer this one as I don't know what he finally used, but finding a MOSFET that fully fires on 3.7V is not a "rare" or hard to find, at least for an N channel. The MOSFET that I am using on my PhD-M6 driver fully fires at a max voltage of 2.35 volts, and has a max of 5.7mOhm Rds at 25A:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRLR8256TRPBFCT-ND


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## CKOD (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Nice work, l love the finished result. As far as finishing goes, you could use any of the more common gun coatings on the market now (obviously) If youre actually going to be using it in harsher conditions (in water thats not fresh and mostly clean) I'd say norrell's moly resin would be the most resistant (to wear, elements and heat) choice. If its going to be used on land most the time, I'd say Gun Kote would be a perfectly fine choice.

If you anodize it, are you going to polish it first for a shiny finish? or scotch-brite it, or sand/bead blast it for a more matte finish?


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## MikeAusC (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



wquiles said:


> The MOSFET that I am using on my PhD-M6 driver fully fires at a max voltage of 2.35 volts, and has a max of 5.7mOhm Rds at 25A:


 
. . . and you have to pay over ONE dollar to get that


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## gt40 (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



Packhorse said:


> great build, congrats!!
> 
> 2 questions
> 
> ...


 
I will have to measure the beam. The square appears about 15 percent larger than the one projected by my mag c sst90 build with the 52mm mg lens. The lens in this light is the 32mm aspheric I got from SS. I got 10 because I really like the way it projects- decent throw but wide enough for lighting a decent area.

For comparison:
new light: http://vimeo.com/13928375
mag c sst90 with mg 52mm: http://vimeo.com/9088275

Both videos were shot with the same camera at same settings and lens focal length.

Regarding the mosfet, I used one recommended by wquiles:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRLU8743PBF-ND

Here are some new pics now that I made a new insert piece for the top of the head to hold the lens sanwiched between o rings:


























I am going to fill the hole on the knurled ring with colored epoxy so it will look like a button and make a corresponding epoxy filled line machined on the head where the read switch is.


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## somename (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

I'm not up to date on the machining techniques out there, but on a design such as yours, is there a way to make the ring have a positive click feel when you have the magnet over reed switch?

Machining on the opposite side of the ring with groves the a screw on the ring would catch? How could a ring be made to have a positive selection feel so even if your not looking at the light (and you don't see the light come on) you know you have the magnetic in the right position over the reed?

This is a really neat build. I was thinking of helping with electrical schematics/parts back on page one, but now I see you have it all figured out.

Awesome light :bow: and you really set it up nice to have such a great beam with the aspheric head. I like the beam on your custom better than the aspheric Mag.

Ever consider making some of these for others to purchase? Or even just the mechanical parts <---- I have no lathe or mill equipment so all the electrical circuits I could build are useless without something nice to put them in.

:goodjob:


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## gt40 (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



somename said:


> I'm not up to date on the machining techniques out there, but on a design such as yours, is there a way to make the ring have a positive click feel when you have the magnet over reed switch?
> 
> Machining on the opposite side of the ring with groves the a screw on the ring would catch? How could a ring be made to have a positive selection feel so even if your not looking at the light (and you don't see the light come on) you know you have the magnetic in the right position over the reed?
> 
> ...


 

Thanks for the feedback. 

To get perfect focus on the aspheric, I got it close and then machined a few thousands off, put the light back together and checked and repeated until it was perfect. You can de-focus it but I wanted a perfect beam when it was all screwed tight and waterproof. I also made a led centering ring jig to get the led perfectly center for mounting.

In answer to your question about the switch, I am trying to figure this one out. maybe putting a spring loaded ball in a hole in the body under the ring and try to machine a channel with indents. That way ring rotation would be within a fixed narrow range. I think if I put a slightly deeper depression at the end of the channel ends, it may provide for positive engagement. I also am looking at adding some grooving on the body and head but not sure yet what I want.

Note: anyone with any ideas on how to machine a partial hole on the inside of the ring, please share your technique...

Regarding building some more lights for possible sale, I bought 10 aspheric lens, 10 mosfets and extra reed switches so I could make more than one once the final design is figured.


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## somename (Aug 6, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> UPDATE:
> 
> LED:
> 
> ...


 
In the top picture above I noticed only 1 O-ring before the threads. Any idea what kind of water depth this will work for? 
I noticed my UK dive light at home has 2 o-rings in the head.
I am guessing that tight beam should penetrate the water fairly well. But then again, I've never tried an aspheric under water.



gt40; said:


> I am trying to figure this one out. maybe putting a spring loaded ball in a hole in the body under the ring and try to machine a channel with indents.


 
I like the idea of the ball like a bearing rolling along the ring with indentions for the positive engagement.



gt40 said:


> I also am looking at adding some grooving on the body and head but not sure yet what I want.


 
I like the smooth lines on the body, easy to clean off if exposed to salt water diving. But I understand it would be very slippery, especially with gloves on in cold water.

Have you thought about an attachment point for a lanyard? It sure would be sad to drop it while in the ocean and watch it go to the bottom.



gt40 said:


> Regarding building some more lights for possible sale, I bought 10 aspheric lens, 10 mosfets and extra reed switches so I could make more than one once the final design is figured.


 
Awesome! I would actually be interested in trying something like you built, but I want to add an Atmel or a PIC microcontroller and use the reed switches to signal the micro to change levels. The micro would be driving a MOSFET driver (I'd like to experiment with PWM at ~30kHz or so) to change levels on the LED.

How much room is there under the head for electronics?


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## gt40 (Aug 9, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



somename said:


> In the top picture above I noticed only 1 O-ring before the threads. Any idea what kind of water depth this will work for?
> I noticed my UK dive light at home has 2 o-rings in the head.
> I am guessing that tight beam should penetrate the water fairly well. But then again, I've never tried an aspheric under water.
> 
> ...


 
I can modify the heat sink to handle more stuff. I may make a version that is hollow in the inside to allow for the electronics to be on the inside of it. Otherwise, I can machine a flat recessed section for mounting.


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## gt40 (Aug 9, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

I did some more work on the body in prep for finishing it.

Basically grooved the body and machined a lanyard ring.

Here are some more pics:


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## eightballrj (Aug 9, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Look like a great project! I'm amazed at the beam pattern of these aspherics. Anyway, regarding the detents and machining the inside of the ring, I would do your grooving on the inside of the ring with a small milling bit(milling along the principle axis of the ring) and drill the body of the light for the spring and ball. Drilling the ring would be a nightmare.


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## archer6817j (Aug 10, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Hi, awesome build! I'm working on a dive light of my own. I've been trying to follow the thread but unfortunately, not much electrical knowledge. Can you post the final specs of the components and a diagram of the switch wiring? Did you use a resistor with the reed switch? Also, are you using a driver or just direct? Thanks in advance and great machining work as well


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## gt40 (Aug 10, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



archer6817j said:


> Hi, awesome build! I'm working on a dive light of my own. I've been trying to follow the thread but unfortunately, not much electrical knowledge. Can you post the final specs of the components and a diagram of the switch wiring? Did you use a resistor with the reed switch? Also, are you using a driver or just direct? Thanks in advance and great machining work as well


 
Good luck with your build. I have found this to be a great learning experience- thanks to all the info on the site and helpful members. Here is the diagram of my circuit:






I ended up using a mosfet that wquiles recommended and it is working great: 

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=568-4899-5-ND

Almost any cheap reed switch should work. I got some from simple motors and a new batch from mouser that is flat wire coming out of each end. These things are fragile so buy a few extra. The light is currently direct drive with reed switch and mosfet but I may make one with a taskled driver if I can find a good waterproof momentary switch. 

This project has been a great learning experience as I have mastered threading, cutting parts to spec and some basic design things. I wish I had cad but I needed the experience learning to lathe and so I am happy so far because this is my very first light I have made. FYI, i have actually made 4 heat sink designs, 3 heads, two bodies 2 magnetic ring designs and 3 tail caps to get to this design. It is a work in progress but it is getting close to a final design. 

I think I will make a few extra to master making multiple parts to spec once the design is finished. I will make a larger version with a 4up or 7up xpg head and driver after that.

Anyway, good luck with your build and post some pics..


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## lucca brassi (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*








> Originally Posted by *gt40;*
> _I am trying to figure this one out. maybe putting a spring loaded ball in a hole in the body under the ring and try to machine a channel with indents._


 
I think a little growe is enough.


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## MikeAusC (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

I strongly suggest adding a Resistor of around 100kohms between Gate and Ground to ensure the FET is fully turned off when the switch is open.

Otherwise leakage currents could cause a slow drain of the battery when you think the torch is off.


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## gt40 (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



MikeAusC said:


> I strongly suggest adding a Resistor of around 100kohms between Gate and Ground to ensure the FET is fully turned off when the switch is open.
> 
> Otherwise leakage currents could cause a slow drain of the battery when you think the torch is off.


 
I actually have a 15k resister on the fet between the ground and the gate. Is that enough or do I need 100k? The light seems to work fine with the 15k and I don't see any light from the emitter when it is off. I haven't checked it with the meter though.


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## CKOD (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> I actually have a 15k resister on the fet between the ground and the gate. Is that enough or do I need 100k? The light seems to work fine with the 15k and I don't see any light from the emitter when it is off. I haven't checked it with the meter though.


15k is less resistance so it should be fine. 100k was just so it would use less current when the light was turned on. As long as leakage current though the gate doesnt allow charge to build up it's fine. An ideal mosfet wouldn't shut off with the magnetic reed switch, because the gate would be a capacitor and maintain the voltage. Real mosfets aren't ideal, so it leaks down to some undefined level, could be partially on, could be off, could be somewhere where the mosfet is operating in the linear region and overheats. But a simple pulldown takes care of all of that, even 100k or higher.


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## gt40 (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



CKOD said:


> 15k is less resistance so it should be fine. 100k was just so it would use less current when the light was turned on. As long as leakage current though the gate doesnt allow charge to build up it's fine. An ideal mosfet wouldn't shut off with the magnetic reed switch, because the gate would be a capacitor and maintain the voltage. Real mosfets aren't ideal, so it leaks down to some undefined level, could be partially on, could be off, could be somewhere where the mosfet is operating in the linear region and overheats. But a simple pulldown takes care of all of that, even 100k or higher.


 

Before I put the resister in between the gate and ground, the light would stay on. I saw a few threads with mosfets using 10k or 15k resisters so I just went with the 15k and it seemed to work fine. You mention it would use less current when the light is on with the higher resister. Does that mean that I would see higher current to the led by swapping the 15k with a 100k one?


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## wyager (Aug 11, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



somename said:


> Awesome! I would actually be interested in trying something like you built, but I want to add an Atmel or a PIC microcontroller and use the reed switches to signal the micro to change levels. The micro would be driving a MOSFET driver (I'd like to experiment with PWM at ~30kHz or so) to change levels on the LED.


fOCnxPWM = fclk_I/O/(N ⋅ 256)
Attiny45 at 8mhz gives you 31.25khz PWM. Plus, it only has 8 pins total so it's the smallest you can get with PWM. If you want to use an atmel, I'll give you the code :twothumbs of course, for this kind of setup you would want a parasitic drain but even at full speed in awake mode it's only 6mA. In sleep mode it's like 3µA.


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## CKOD (Aug 12, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> Before I put the resister in between the gate and ground, the light would stay on. I saw a few threads with mosfets using 10k or 15k resisters so I just went with the 15k and it seemed to work fine. You mention it would use less current when the light is on with the higher resister. Does that mean that I would see higher current to the led by swapping the 15k with a 100k one?


Sorry, I meant the current though the resistor being wasted. 280 microamps vs 42 microamps with a hot battery. I wouldnt sweat it at all, its all insignificant vs the LED's current. 

But if you want to increase LED current, you could drive the mosfet gate with more then the battery voltage, you could reduce the resistance of the mosefet a bit more. What sort of voltage is dropped over the mosfet at the moment? if its insignificant, I wouldnt worry about it, but it wasnt, then something as small as a CR2032 (or any other button cell of choice) could do it if you put it in series with the main battery, so that the mosfet gate and pull down resistor are the only thing being powered by the 2032, the little battery would only see the 40-200uA load while the light is on, so I'm sure with a higher resistor (100k+) the runtime of the little battery would be quite long compared to the main one.


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## archer6817j (Aug 12, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

So is there any last word on what size resistor you need? I've seen several threads about mosfet switches and they all seem to use different resistors. Obviously this has something to do with the spec of the particular mosfet, but is anyone willing to weigh in on a best option? 

http://www.frys.com/product/1000503#detailed

I picked up one of the NTE-2389 at Frys which seems similar in spec to the one gt40 used...at least in terms of N channel and low opening voltage. 

Alternatively, can anyone give us a (simple) way to determine the specification if there is no easy "answer?"


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## MikeAusC (Aug 13, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



archer6817j said:


> So is there any last word on what size capacitor you need? I've seen several threads about mosfet switches and they all seem to use different resistors.


 
???? What is your question


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## archer6817j (Aug 13, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

My question is, if there is no "easy answer" to what size resistor to use, how do you calculate it for a specific mosfet switching application? 

I've seen people use (or suggest) 5K, 10K, 15K, 100K; and this is quite a range. So what do we need to know in order to calculate the right resistor? 

What I would love as the end result, is to spec out a mosfet switch (part numbers and diagram) so everyone on the forum who wants a mosfet switch can just order the parts and put it together...instead of having new threads and lots of questions each time  I don't mean to hijack but I thouht this thread was the best mosfet switch discussion so far, or at least the most useful for someone who is not an EE. 

Also, gt40, how did you mount the reed switch and mosfet inside of the can?


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## wquiles (Aug 13, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

The reason you need a resistor from the base of the N channel MOSFET to Ground is to provide a path for the "internal" capacitor to discharge. If you don't put a resistor to Ground, since there is no path for the capacitor to discharge, the MOSFET will remain ON for a long time. Assuming that you don't have an external capacitor from the base to Ground (most designs shouldn't), then any value from 10K to 100K will work.

Why that range? It needs to be at least 10K so it is not loading the output stage of most active devices, and it needs to be no more than 100K so that it does not take forever for the MOSFET to turn off. 

This is why you see such a wide range from 10K, 15K, 100K, etc. - they all do the job


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## wyager (Aug 13, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Wquiles-excellent explanation. If you wanted, you could calculate a resistor value that would allow the capacitor to discharge at exactly the rate you wanted, but I think in this case an arbitrary value would be appropriate.


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## DM51 (Aug 14, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

gt40... please resize your pics in post #61 to comply with Rule 3.


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## gt40 (Aug 15, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



DM51 said:


> gt40... please resize your pics in post #61 to comply with Rule 3.


 
fixed...


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## gt40 (Aug 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

I got the light basically done but am starting to re-think the driver part. I am over my head here though and would appreciate some feedback. I got 5.7amps using the clamp meter with a short wire between the battery neg and the body. I want to add the LDO10c driver I used in the mag c aspheric build I did and use it as a boost driver to bump up the voltage a bit so I can get it to 9 amp range off a single battery. 

Not sure if this is possible. The idea would be to make it a boost driver(per data sheet) by feeding voltage to the trim and control with resister and compensate with thermister as I did using it as a buck driver. I think I have sketched out a basic diagram but not sure of the values. I will plug in a pot in place of the resister to determine trim resister values. 

Here is the diagram(sorry poor quality- NOT an EE here!)







Here is the applications guide for the ldo10c driver: 
http://www.powerconversion.com/assets/an_ldo03c_ldo06c_ldo10c_1244754553_appnote.pdf

Assuming adding voltage to the trim will even work, then I have the issue of the mosfet reed switch. can that be used on the high side where it says switch on the diagram?

Anyway, any comments, suggestions etc would be appreciated.


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## CKOD (Aug 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



gt40 said:


> Assuming adding voltage to the trim will even work, then I have the issue of the mosfet reed switch. can that be used on the high side where it says switch on the diagram?
> 
> Anyway, any comments, suggestions etc would be appreciated.


Subtle nuance I picked up poking at the appnotes
http://www.powerconversion.com/assets/an_ldo03c_ldo06c_ldo10c_1244754553_appnote.pdf states that the the ldo10c is a buck topology driver, which would make it operating as a boost driver impossible

http://www.powerconversion.com/assets/an_ldo03c_06c_10c_1199502565_appnote.pdf says its a buck/boost topology which makes sense, and you might not even need to feed voltage into the trim input if you use a PTC themistor, they show it as an option of connecting it to an external source... but dont even show what external source you'd be using.. Vin? Vout? The formulas they list obviously dont match up with the diagrams they say either. They have "Rpot" in the figure 11 equation, but there is no pot in figure 11 

only difference I can spot in partnumbers

LDO10C-005W05-VXJ buck
LDO10C-005W05-VJ buck/boost 

unfortunately their datasheet is almost useless http://www.powerconversion.com/assets/ldo10c_1191530952.pdf and all the X means is "custom option" 


Not the sort of datasheets I like. 12 pages total (including appnote ) about an adjustable smps, and seoul has a 15 page datasheet a LED :duh2:


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## gt40 (Aug 16, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

I have the vj "buck/boost variant. I guess I will just try it. Fyi, mine has worked great for the past 3 months or so with the mag c sst90. That data sheet is confusing. They also say it can work with sinking current...


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## gt40 (Aug 17, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*

Any other suggestions to slightly boost the voltage at 9 amp range of a single IMR 26650?


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## gt40 (Aug 17, 2010)

*1st homemade light from scratch- sst90 aspheric H2O proof reed switch- 10 AMPS*

UPDATE:

I went back and measured amps after fixing a loose wire. It turns out direct drive with a single IMR 26650, short 18 gauge silver teflon wires and low resistance mosfet switch can get you there without boost driver.

I measured via clamp meter and short wire between the battery tail and body.

When I fired up the light it measured this!






after 20 seconds:






after a minute:





*After 1:30 it settled in at 10.65- 10.7 amps off of 1 IMR 26650:*






Shot of the light being measured:





I have not seen anyone get over 5-6 amps off of a single 26650 battery so I am very pleased. 

The light is stupid bright. It is amazing something this compact can put out this much lumens.

Thanks again to everyone who has patiently helped me with my questions while building this. I am almost ready to apply the finish and complete it.


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## DeeperDeeper (Aug 18, 2010)

*Re: 1st homemade light from scratch- sst90 aspheric H2O proof magnetic switch build l*



somename said:


> In the top picture above I noticed only 1 O-ring before the threads. Any idea what kind of water depth this will work for?



As IMSabbel mentioned earlier in this thread, the aspheric lense does NOT work under water when used like this. There must be air on the curved surface of the lense, or not at least water! Put a straight glass on top of the lens, then it's good also under water.

But beautiful work ! :twothumbs


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## archer6817j (Aug 20, 2010)

Hi, two questions.

The first is general. With respect to using aspherics under water, is there anyone who has actually tried it in practice? I'm curious to hear about some experience based observations because it doesn't seem like a couple of degrees of beam angle matters that much...assuming you don't need to maintain the razor sharp die image. 

Second, gt40 (great car by the way) how is your light with head build up? I have a 540 lumen (700ma) rebel star hooked up and my aluminum head heats up to an uncomfortable-to-hold level after about 5 minutes. Just curious about that bad boy sucking down 10 amps and the heat it generates.


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## Barbarin (Aug 20, 2010)

Congratulations, Mr. Quiles. 

Definetively would like to test this beast underwater.

BTW, you are on te way!

Suerte, amigo.

Javier


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## gt40 (Aug 20, 2010)

archer6817j said:


> Hi, two questions.
> 
> The first is general. With respect to using aspherics under water, is there anyone who has actually tried it in practice? I'm curious to hear about some experience based observations because it doesn't seem like a couple of degrees of beam angle matters that much...assuming you don't need to maintain the razor sharp die image.
> 
> Second, gt40 (great car by the way) how is your light with head build up? I have a 540 lumen (700ma) rebel star hooked up and my aluminum head heats up to an uncomfortable-to-hold level after about 5 minutes. Just curious about that bad boy sucking down 10 amps and the heat it generates.


 
I haven't tested it underwater other than leakage test so I don't know about the beam. I was planning to make a top insert with a flat lens in it to provide an air gap for diving and keep it as is for walking the dogs.

Regarding heat: It takes a while to warm up because of the substantial mass of the heatsink and body. There is a solid copper core in the heatsink which is 1.7" long by 1.05" thick + the body is 1/8" thick t6 and solid head. It basically is warm at 5 minutes and then suddenly gets pretty hot after that. 10 amps is substantial amount of heat. The light is small but weighs more than my mag c sst90 build.

Under water this shouldn't be an issue though.

I am putting in a "low" mode of 1 amps by adding a ldo10c driver and second reed switch so you can turn the ring to turn it on and turn it to a second position to get low mode.

I am also going to made a bigger head using the extra 52mm mg lens I have for even more throw and to provide more mass.


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