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Laser driver

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Raj:
Oh, yes I'm trying to drive a diode extracted from separated from the array (the diode is a used one) Right now I'm in the testing phase. If it can cut through materials I want it to, I'll turn it into an engraving machine later.

janoc:

--- Quote from: Raj on November 10, 2017, 11:58:23 am ---Oh, yes I'm trying to drive a diode extracted from separated from the array (the diode is a used one) Right now I'm in the testing phase. If it can cut through materials I want it to, I'll turn it into an engraving machine later.

--- End quote ---

If you have extracted the diode from the block, do not forget to put it in some other heatsinking material or it will cook itself.


--- Quote from: mikerj on November 10, 2017, 10:20:04 am ---This sounds like scaremongering; you can run laser diodes from constant currents perfectly safely with a small amount of care, provided you aren't trying to exact the maximum possible power from them.  Feedback is required if you need to compensate for temperature and ageing effects, but in many applications some variation in output is not a problem.  Thermal protection would make sense for higher power diodes like the one the OP is using however.

--- End quote ---

Well, the datasheet explicitly mentions the requirement for optical feedback on this one. Considering how powerful the laser is, I would say it is a very good idea to include it. The problem is that the optical power goes up the colder the diode is with the same current (the lasers and LEDs are more efficient when cold). So if you are unlucky, on a cold day the diode will destroy itself because the output power got exceeded for a short moment and ruined the mirrors.

Constant current driving with no optical feedback is only really usable for things like cheap laser pointers.

And yes, you are right about the supply transients - the maximum current must not be exceeded even for very short time (milliseconds!) otherwise the diode will be destroyed.


janoc:

--- Quote from: Raj on November 10, 2017, 11:58:23 am ---Oh, yes I'm trying to drive a diode extracted from separated from the array (the diode is a used one) Right now I'm in the testing phase. If it can cut through materials I want it to, I'll turn it into an engraving machine later.

--- End quote ---

If you have extracted the diode from the block, do not forget to put it in some other heatsinking material or it will cook itself.


--- Quote from: mikerj on November 10, 2017, 10:20:04 am ---This sounds like scaremongering; you can run laser diodes from constant currents perfectly safely with a small amount of care, provided you aren't trying to exact the maximum possible power from them.  Feedback is required if you need to compensate for temperature and ageing effects, but in many applications some variation in output is not a problem.  Thermal protection would make sense for higher power diodes like the one the OP is using however.

--- End quote ---

Well, the datasheet explicitly mentions the requirement for optical feedback on this one. Considering how powerful the laser is, I would say it is a very good idea to include it. The problem is that the optical power goes up the colder the diode is with the same current (the lasers and LEDs are more efficient when cold). So if you are unlucky, on a cold day the diode will destroy itself because the output power got exceeded for a short moment and ruined the mirrors.

Constant current driving with no optical feedback is only really usable for things like cheap laser pointers.

And yes, you are right about the supply transients - the maximum current must not be exceeded even for very short time (milliseconds!) otherwise the diode will be destroyed.


jmelson:

--- Quote from: janoc on November 08, 2017, 03:12:39 pm ---
Eeeep! Do not drive a laser diode with a simple resistor! That will work for a short term test but it is a very poor solution. It is the best way how to turn your laser diode into a crappy LED

--- End quote ---
Well, I've been doing exactly that with an old 670 nm laser diode in my photoplotter for the last ** 20 ** years, without damage.  I don't need to push it to the maximum output level (5 mW) so it has some margin.

Jon

Raj:
Oh well.... Underdriving is a different matter.I ain't gonna do that. What use it will be too me after buying such expensive diode

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