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Did my power controll switch killed my LD?

alessnilsen

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Hi! I finished mounting my powerfull red laser using a GSA-H55N laser diode and a DDL driver set to 415mA, after some play burning plastic, I decided that my laser is too dangerous and need some way to limit the output power.

The circuit I used is this:



For some days it worked like a charm, but someday, when I was burning plastic, suddently my LD died and becomes a LED.

Can my driver killed my diode? It's safe to use?

I think when I switch the driver from low power to high power, the driver sends a power surge, dimming the lifespan of my LD. Maybe a large capacitor helps.

Thanks! :thanks:
 



Cyparagon

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Yes, this will almost certainly kill laser diodes. The contacts are only open for a millisecond or less, but when they are open, there is no voltage on the ADJ pin and the lm317 raises the output voltage to try to increase the voltage on ADJ. You can get a huge spike in 1ms - up to 11V depending on the load. A much larger cap might help, but you would need to switch this while the circuit is off to be safe. You could also switch in a resistor in parallel, so even when the contacts are open there is still a feedback loop.
 
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Down with Umbrella

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I could be mistaken but the drivers I build I put an IN4001 diode in just after the battery and a second capacitor. I get spikes with my velleman DC power supply and lost a diode or two to that :/
Edit: I didn't loose the diode while using the driver but with the dC power supply.
 
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alessnilsen

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That's sad! You said to put a capacitor in parallel with the driver?

I'll try to rewrite my driver circuit including a resistor in parallel with the switch.

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I done this circuit, it's safe?

 
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Cyparagon

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Much better. The larger capacitor is not needed for that resistor configuration. It would be better to use a smaller low ESR cap like ceramic.
 

Leodahsan

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If your switch is double poled (like the common 110-220v switches, called "chave H-H" in portuguese), you can even insert a "medium power" setting (add one more resistor).

For the cap parallel to the LD, I always use a 100nF one, soldered close to the LD pins...

:beer:
 

Cyparagon

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If your switch is double poled... you can even insert a "medium power" setting

How are you going to get three power settings with two switch positions? :undecided:
 
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alessnilsen

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If your switch is double poled... you can even insert a "medium power" setting

I think I can't do that, my switch is a "toggle switch", with only two positions.

For the cap parallel to the LD, I always use a 100nF one, soldered close to the LD pins...

I always put it close to the driver, away from the LD, the pin that I use to hold the LD don't allow me to put it too close. But I know, close to the LD is better.

-------------

My last LD died! I've assembled the new circuit and tested it, worked well. I hung up and went to have a break, when I came back and turned on the laser again, he died without any explication!

I think my power supply is bad, chinese crap! When I plugged it into the outlet, I heard a big "pop" from the sparks.

Since my last LD died, I can't do anything more.
 
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Bionic-Badger

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Well, the LM317 should protect your laser diode from surges. You could also try putting a reverse-polarity protection diode on your circuit as well, in case there's a bad hook-up or something like that.
 

alessnilsen

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Well, the LM317 should protect your laser diode from surges. You could also try putting a reverse-polarity protection diode on your circuit as well, in case there's a bad hook-up or something like that.

I think this driver will not work, why? Look carefully, the correct circuit is this:



But now I'm confused, what circuit did I used? I should check!
 

Cyparagon

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AH! I didn't even notice you had the ADJ/OUT pins backwards :p. I should have caught that.
 

alessnilsen

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Hahah. Yes, I spent some time to percept that.

My driver assembly is correct. I'll replace the LM317 with a new one, maybe it helps.
 

alessnilsen

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I've got some new LD's, I assembled all and it works very well!

Now I'll try to get a better lens for my new laser.

Thanks for the help! :)
 




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