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Old 04-25-2009, 02:55 PM #1
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Default how to mod a 50mw laser without a pot

Hi all,

First off, i know what's been said in other posts.... dont mod it... it will burn it out / reduce life etc. Well, I'm getting a new one soon, so it doens't matter if I destroy this one. But if it works out, I wont bother getting a new one.

That over, I have a 50mw green that I want to mod up to something more powefull... I read some other posts, and it seemed as simple as turning a pot, and it may or may not make it brighter. Well, I took it apart (invloved cutting it... eh) and there's no pot.

Has anyone got any tips on how to mod this? Pics included below:

Thanks
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Old 04-25-2009, 03:37 PM #2
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Default Re: how to mod a 50mw laser without a pot

Try more volts, if it uses 2 X AAA =3v replace with 1 X 10440 and a spacer =3.7v

Regards rog8811
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Old 04-25-2009, 07:14 PM #3
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Default Re: how to mod a 50mw laser without a pot

Try to keep the current under 600-700mA and it might just work out okay.
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Old 04-25-2009, 07:15 PM #4
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Default Re: how to mod a 50mw laser without a pot

Quote:
Originally Posted by rog8811
Try more volts, if it uses 2 X AAA =3v replace with 1 X 10440 and a spacer =3.7v

Regards rog8811
rog8811 is right. *I had some cheap green ebay lasers that were dim at 2.9 volts, and much brighter at 3.0 volts.

If you have access to a variable voltage power supply, you might want to raise the voltage slowly and see what happens. *That lets you find the minimum voltage that it needs to be brighter. *To keep the temperature rise down, its best to drive it at this minimum voltage.

Since you already cut the case apart, you might want to consider using 3 NIMH batteries which would also give you 3.6 volts. *Here is a handy way to do that: Low cost host for utility laser - DIY project

If increasing the voltage doesn't work, there are a few other options...

1) If the circuit board uses APC (optical feedback), you can connect a resistor across the optical feedback photodiode. *This will fool the circuit into thinking that the IR diode isn't bright enough and it will increase the drive current to it. *I can't tell from your pictures if it uses APC. *If all 3 diode wires actually go to electronics on the circuit board (not just a solder pad), then it probably does.

2) You can unsolder the diode from the circuit board and drive it at any current you want using the driver of your choice.

3) These green lasers are usually temperature sensitive, so you can try finding out what temperature it likes best and holding it there with a TEC.
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Old 04-26-2009, 06:00 AM #5
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Default Re: how to mod a 50mw laser without a pot

Thanks for all your suggestions.

Warske, for point 1) what ohm resister would you suggest, or would a pot be better
2) what would you (or anyone) suggest be a good driver circuit for my laser? I'm rather handy with a soldering iron
3) sorry, what a TEC?

Thanks again all.
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Old 04-26-2009, 02:44 PM #6
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Default Re: how to mod a 50mw laser without a pot

1) If the circuit board uses APC (optical feedback), you can connect a resistor across the optical feedback photodiode...

Quote:
what ohm resister would you suggest, or would a pot be better
Two methods for selecting a resistor:

a) Start high, at 100 meg, say, and work your way down to lower ohms until you get the effect you want.

b) Remove the driver board from the laser diode assembly, drive the laser diode directly with a current source and work out how many uA the photodiode generates when you get to the power level it normally works at. *Then calculate the shunt resistance you would need so that the driver will give it the power level you want.

A pot should work OK if you are careful. * *

2) You can unsolder the diode from the circuit board and drive it at any current you want using the driver of your choice.

Quote:
what would you (or anyone) suggest be a good driver circuit for my laser?
Most people like to use an LM317 or LM317T configured as a current source. *Search for those on this forum and you will find.

3) These green lasers are usually temperature sensitive, so you can try finding out what temperature it likes best and holding it there with a TEC.

Quote:
sorry, what a TEC?
Thermoelectric Cooler

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