30mw green laser is burning (pulses question)

Yes, it burns (don't know for how long).

I know the pot mod (this thread is NOT about that). I just bought a class III 30mw green laser for playing, and after trying focusing the beam I noticed it burned black tape (very little). Out of curiosity tear it apart and found the potentiometer, tried to turn it but didn't work (it's fixed).

My curiosity wasn't satisfied so I removed the green laser diode because I was hoping to play with my LM317 driver. After looking carefully at the diode, the 3 legs were connected to circuits, so didn't seem like one leg was "not used".

Plugged the diode to my driver and didn't work. I thought ok I fried it. Tried a pair of AAA batteries to find out (for a fraction of a sec) and the diode did emit powerful green beam. After testing, the diode is not dead, it just flashes. Whenever I plug the current it only flashes once. But when connected to the driver LM317 it gives a very weak green light.

Raised the voltage to the driver at 9V and the beam became brighter but not as brighter as using the driver of the pen or the AAA batteries. No the diode is not harmed, is still a live and kicking.

Seems to me an unusual behavior. BTW the LM317 is still working fine powering my red burning laser (dvd). Any comments or advice? don't tell me is dead, is not dead, if this confuses you I will be happy to expand.

Ok to avoid confusion, I have built a driver that works amazingly well with red diodes, but when I use the green laser it gives a very weak light at 5v, better at 7v and quite decent at 9v, but not comparable to the light using the original driver of the pen.

Connecting 2 AAA batteries gives a very bright light but just for a millisecond, it's a flash. No it's not dead, it just gives one pulse and shuts down (yes it has a heatsink) and as posted above, the 3 legs were connected to the original driver (doesn't seem like there is one unused)

Do you have a picture of the stock driver? What voltage are you inputting to the stock driver? What resistance are you using to set the LM317's current? What is the voltage across OUT and ADJ pins on the LM317 on the different input voltages?

Do not connect 2AAAs directly to the diode. This will either kill it, or drastically overdrive it.

Here is the original driver, back and front



and the laser removed from the pen

Cyparagon said:

Do you have a picture of the stock driver?

Click to expand...

I hope the above images serve for something, the pen used 2AAA batteries

Cyparagon said:

What voltage are you inputting to the stock driver?

Click to expand...

originally 3V from 2AAA, but it has 3 pins, each for each wire on the diode, tried connecting back the laser using only two cables (hoping for the usual + and -) but it didn't work, seems to need the 3.

Cyparagon said:

What resistance are you using to set the LM317's current? What is the voltage across OUT and ADJ pins on the LM317 on the different input voltages?

Do not connect 2AAAs directly to the diode. This will either kill it, or drastically overdrive it.

Click to expand...

My LM317 driver is using one 5W 10ohm for my red lasers (from dvd)
*** connected one 100ohm variable resistor to the 10oh to try adjustements
tried using the same driver for the green one
tried using 1.5V, 3V, 4.5V, 6V, 7.2V and 9V
no luck but the diode is still alive
the output voltage measured was 1.8v

Cyparagon said:

Do not connect 2AAAs directly to the diode. This will either kill it, or drastically overdrive it.

Click to expand...

thanks, just did it thinking the laser was dead, turns out it's alive

this seems odd

Run an led on the original driver and test the mA output. Do the same on the lm317.

Trendkilla254 said:

Run an led on the original driver and test the mA output. Do the same on the lm317.

Click to expand...

Or don't, unless you're going to use a higher powered LED than your standard small LED. Those only need 20mA or so, your LM317 driver using a 5 ohm resistor is set to 250mA.

Everything looks pretty normal so far. One question remains unanswered: What is the voltage across OUT and ADJ pins? This mean one probe goes on OUT, and the other probe goes on ADJ.

A few additional questions. With the stock driver powered up and activated, what is the voltage across the component marked "1R0"? (one probe on either side of it). What is the measured voltage of the power source (either the 2xAAAs or your variable wall plug thing) under load? You may think this value wouldn't change, but it can if you've hooked up something wrong, or if something in the circuit is faulty.

Trendkilla254 said:

Run an led on the original driver and test the mA output. Do the same on the lm317.

Click to expand...

already did it, results below thanks

diachi said:

Or don't, unless you're going to use a higher powered LED than your standard small LED. Those only need 20mA or so, your LM317 driver using a 5 ohm resistor is set to 250mA.

Click to expand...

thanks

Cyparagon said:

Everything looks pretty normal so far. One question remains unanswered: What is the voltage across OUT and ADJ pins? This mean one probe goes on OUT, and the other probe goes on ADJ.

A few additional questions. With the stock driver powered up and activated, what is the voltage across the component marked "1R0"? (one probe on either side of it). What is the measured voltage of the power source (either the 2xAAAs or your variable wall plug thing) under load? You may think this value wouldn't change, but it can if you've hooked up something wrong, or if something in the circuit is faulty.

Click to expand...

thanks

Ok, using the stock driver and the green laser connected and beaming: I get 1.83V out, and... out of range ma!!! I have two cheap multimeters but enough to measure my LM317 driver, it seems the driver outputs a lot of current with love voltage, I'm about to give up on this and continue trying to improve my red lasers :undecided:, I find difficult for now to measure the 1R0 on the stock driver as I have lots of wires and a button to press. The green laser is still alive, I'm about to put it again on it's enclosure and use it as it was, it's almost midnight after too many attempts :crackup: perhaps tomorrow

You're misunderstanding something. Set your meter to volts. with the circuit active, poke the LM317's ADJUST pin with the red probe, and poke the LM317's OUT pin with the black probe. What voltage is on the readout?

Set your meter to volts. with the circuit active, poke the wall adapter's V+ output (same as the LM317's IN pin, if you've hooked it up correctly) with the red probe. With the black probe, poke the wall adapter's V- output. What is the voltage on the readout when the adapter is set to 7.2V?

So, looking back and comparing my findings, the LM317 gives X voltage at constant current (ma) that makes sense, but the original green laser driver gives ok voltage AND very high ma, I have two cheap multimeters and it's out of range, I can't measure it.

Decided to try a simple 555 timer circuit giving pulses to the green laser, I managed to make it blink and also give the illusion of staying on, it worked, but not as bright as the original stock driver, and not even half as bright as the mili instant AAA batteries (no I'm not doing it anymore).

Thanks Cyparagon, I did exactly what you indicate here, below are my findings.

Cyparagon said:

You're misunderstanding something. Set your meter to volts. with the circuit active, poke the LM317's ADJUST pin with the red probe, and poke the LM317's OUT pin with the black probe. What voltage is on the readout?

Click to expand...

1.25V

Cyparagon said:

Set your meter to volts. with the circuit active, poke the wall adapter's V+ output (same as the LM317's IN pin, if you've hooked it up correctly) with the red probe. With the black probe, poke the wall adapter's V- output. What is the voltage on the readout when the adapter is set to 7.2V?

Click to expand...

13.96V

Honestly I was too insisting on trying the 30mw laser, finding a little smoke on black foam made me try more stuff but it's not working (I'm not too handy at this level), I guess it could be possible to push the little diode, it's quite big. I will reconnect it to the original driver and put it on a self made stick to give some use to this thing.

**Please let me know if you see something wrong on my LM317 driver (is the one I use along with my RED DVD laser). This one burns and coat dark foam, some thin cloth and engraves mid-dark foam. Managed to engrave wood trying diff lenses and voltages but lost track on what worked, right now is not engraving wood (it was very thin). And let me know if you have any ideas with the green laser, turns out I managed to turn the adjustment (something more known as pot mod) and no difference.

Thanks!