Laser Diode drawing less voltage than normal.

[m.carroll]

hey guys, i just installed my second diode from a sony optiarc nec burner, and had great success for like the first 15 minutes. all of the sudden, the diode started turning off on its own, and i've come to realize that its not quite off, just a faint red glow from the diode is visible. its drawing 1.56V instead of the normal 2.6-2.7V that it did previously. what could be wrong? is the driver not supplying enough voltage, or is the diode dead? (please not that, that would be horrible). again, everything seemed to be going according to plan, but now i cant seem to get any lasing out of it. any suggestions?

 

[toked323]

i think........your diode has gone to a better place

 

[toked323]

 

[m.carroll]

no shit...after one day of usage...wow. that sucks. i duty cycled it and everything...anything specific i could've done wrong?

 

[chido]

Whoa hold on there, let's not loose hope yet, if it's drawing less voltage then there's got to be something wrong with the driver. What's you input voltage??

 

[toked323]

was it cooled? heatsinked well?, how much current was going into it?

 

[m.carroll]

alright, built with a ddl driver, 3ohm resistor between adj and vout. there's a 16V 47uF capacitor and a 1n4001 silicon diode to protect against reverse current. the source voltage is 2x cr123's at 7.7V (fully charged). it is heatsinked using a jayrob heatsink for an aixiz module, with 420mA current going through it.

something i noticed recently, is that it USED to put enough voltage through initially to lase (2.6ish V), and then quicky diminished to the 1.5v. now it wont even go up that high.

*frustrated*  :-/

 

[chido]

Damn, looks like you're really unlucky. ;D All I can think off right now is if you doubled checked everything, mainly the batteries voltage.
Did you check the 1.25v reference between the Vout and the Adj of the LM317?

 

[Ace82]

It's really hard to tell from over the net. ;D Maybe it has to do with how you installed the diode into the housing. Maybe you smashed it too hard? It is really fragile and doesn't like loosing its' virginity! I actually bore the aixis housing just a little to where the diode doesn't need to be forced into place. To where is slips in nice and easy, like an experienced woman.... then I use a couple dabs of super glue just to secure it once it's in. As long as you built the driver correctly, the diode will not just die.

 

[rkcstr]

If there's nothing wrong with the driver... it's possible that the diode was:

-damaged by the current... since we're overdriving them, it's possible, though most people have good luck with these diodes, you may have gotten one that doesn't do quite as well as most.

-damaged by you.... either heating it too much with a soldering iron or possibly static discharge from handling without using a anti-static bracelet could have damaged the diode enough to not kill it but severely shorten it's lifespan.

These are all possible theories, but really the point is, it happens;  all of us have been there.... personally I've killed two burner diodes and I think about 3 blu-ray diodes  :-[

 

[Fred_DASP]

At least there is a new company to my 3 dead diodes

Sorry... hehe

"...static discharge from handling..."
Is it easy to happen?

 

[rkcstr]

At least there is a new company to my 3 dead diodes

Sorry... hehe

"...static discharge from handling..."
Is it easy to happen?

For Blu-ray diodes, it's very easy... but for the larger reds, I don't know. I know that any voltage spike is bad for a laser diode, and static is VERY high voltage, though very low current. I'd just say it's better to be safe than sorry with handling raw diodes. Once they're in a circuit with a capacitor on them, you don't have to worry.

Also, along similar lines with voltage spikes... ALWAYS discharge (short out) a capacitor before attaching or removing from a laser diode!

 

[m.carroll]

i was totally electrically isolated, tied into an earth ground with a bracelet, and i press fit the diode gently and slowly into the housing...the driver doesnt get the 1.25 refrence voltage, maybe i'll try desoldering the diode and using a load diode to make sure the driver is working right again...

 

[m.carroll]

not to fear, minor crisis avoided. turns out my p.o.s. battery charger from DX was just that, a p.o.s. it wasnt charging both batteries, only one, so i charged the other one, and it lased. my diode is not dead, was just underfed!! yay!! [smiley=dankk2.gif]

 

[chido]

Nice to hear you figured it out, any time you see the LM317 isn't giving its 1.25v reference check the batteries, it'll most likely be their fault.

 

[m.carroll]

Nice to hear you figured it out, any time you see the LM317 isn't giving its 1.25v reference check the batteries, it'll most likely be their fault.

word. now to modify this crappy charger so it doesnt happen again. i'm so happy with my brand new beast. it burns through the black part of a cd case in 5 seconds. as soon as i stop being amazed i'll post pics and vids. thanks for all your help guys.