Infrared 980nm Laser using LM317

LiveRock · Oct 2, 2008

Hi

With all the parts, it took me one whole day to build my 980nm laser.

Parts:
- 980 nm Laser Diode, 500 mW, bought from heuroscience many months ago
- Azxiz Lens module
- Small project box
- LM317 with heat sink
- Electronics parts 3.9 ohm 1/2 watt resistor, 10 mF cap, 1N4001 diode, 1 uF cap
- 3 x AAA batteries
- Battery holder - bought a $3.9 torch just to get this part

I calculated the value for the resistor for 300 mA and got about 4 ohm.
When I actually measure the current draw, it is only 200 mA, so I don't know why..

brtaman · Oct 7, 2008

Hey,

Nice clean build you got yourself there

For a 500mw diode aren't you driving it a bit low either way?

The reason you are not seeing the current you have set, is due to the fact that you are not supplying enough voltage to the driver. The lm317 driver has a dropout of 2.25v, and works best with around 7.2v imo. I suggest replacing either the batteries and adding 2x3.7v AAA sized li-ion batts or adding a battery holder that can take 4 alkaline batts which should be adequate given its an IR diode, though maybe not for the entire range of the batteries life-span.

Thanks
brtaman

Cyparagon · Oct 7, 2008

4.5V should be enough. If it drops 2.25V, that leaves 2.25V for the diode, which should be sufficient. I believe IR diodes operate at 1.8V or so.

brtaman · Oct 8, 2008

Yeah when they are fully charged it should be enough, however when alkalines are not fresh, a high current draw such as 300ma will push them below operating voltage from what I have seen.

I suggest adding an extra 1.5v batt just to see where that gets you. You will lose nothing even if it doesn't help your predicament.

LiveRock · Oct 8, 2008

You are right! When I use an external power supply and set it to 5 volts, the current shot up to 300 mA and the laser burns more furiously. The axiz module became hot to touch!!

Later, I decided to 'experiment' and increase the voltage to 6 + (no additional heat sink), and went very very hot, burning my fingers, and after like 5 seconds, it went dead.

So much for experimentation :-(

I guess if I had added active cooling or additional heat sink, the diode would still survive..

Now, it just give out a very weak IR light thatbis only visible by my mobile phone camera....

>>>>>>>>>>> lesson learned.

LiveRock · Oct 8, 2008

I found another project box that looks nicer.

I am left with my last 500mW, 980nm Laser diode that I bought from heuroscience and will probably start on the next built sometime later.....

Tw15t3r · Oct 9, 2008

Oh wow.... you just killed it just like that?

I thought most would know that if the module gets hot, it's time to power down and let it rest!

btw how do you aim for IR lasers? attach a low powered pointer to help?

LiveRock · Oct 13, 2008

Ya, it was a grave mistake :'(

Can't aim at all as it is invisible. The range is also very short; about 4 cm away from the lens.
I just want to play with it to burn stuff like rubber, floppy disc, etc.

Short range also means it is not as harmful when I accidentally aim it at someone else..... or am I wrong? It is just as dangerous?

Tw15t3r · Oct 13, 2008

I believe the short range you seem to be having is because of the focusing. You probably either focused it to work at short distances or focused it in such a way that the beam diverges. Either way there is still IR coming out, and although it may not burn stuff, it is still harmful, and thus you should avoid pointing at people unless they are really really far away (40-50 yards?)

I suggest a laser pointer to help you aim your beam so that you know roughly where it's going.

LiveRock · Oct 14, 2008

Thanks for the advise. Definitely will not aim at people intentionally, just worry that I do it unintentionally; especially it is invisible...

Anyway, I am working on another build using a different design and batteries..

Infrared 980nm Laser using LM317

LiveRock

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brtaman

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Cyparagon

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brtaman

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LiveRock

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LiveRock

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Tw15t3r

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LiveRock

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