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Why did my laser die?

gigi2

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I recently hooked up a cheap laser module to a mircrocontroller (via a MOSFET), mounted on top of a couple servos.


This worked fine until I invited my coworkers to access the controls for my laser turret. One wrote a script that moved the servos from 0° to 180° and back repeatedly as quickly as possible.

Now my laser is dead. It is very dim and gets hot when power is applied, and both my cat and I are very sad.

Unfortunately, I don't have much information about the laser module itself other than what you see on the linked page. The inside looks like this:

So what killed the laser? My suspicion is reverse voltage from a servo motor. If that's likely the culprit, what can I do to guard against it?

A photo of the whole rig – although I'm not too sure it's very useful given the rat's nest of wires.
 

BobMc

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Wish I could help, hopefully some more knowledgeable than me will answer. I would say keep your co-workers away from it! But that news after the fact. Sorry your cat feels so bad, oh and you too! :thinking:
 

Alaskan

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I would suspect voltage spikes may have done it in, a motor like that, stepping, may produce inductive kick back like a transformer can when de-energized, or a coil, same thing. Perhaps your circuitry has protection built into it for that, but maybe not enough for a sensitive device such as a diode.
 
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You need to make a circuit for the servo, and make a separate circuit for the laser module. No need for a microcontroller to control the module if you have PWM already. That would solve some problems.
 

Alaskan

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Very simple looking regulator on the back of the laser diode too, I doubt very much there is any kind of soft start either. Well, looking at it, I don't see how it could have that. Edut: I should also add, the driver doesn't even look much like a normal constant current driver either, looks like a simple on-off voltage driver for a very cheap inexpensive low power laser diode. I don't see a current limiting resistor, but that is probably all it has on it, if it has that.

Show us a photo of the other side of the little circuit board the laser diode is soldered to.
 
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Chrisbee

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Agreed. I wouldn't share a circuit with anything else for the laser module. And make sure whatever laser module you get, that the driver can handle a 5v input. Some of the boost drivers go to 4.5v max. And if it was a red diode, even 4.5 volts is pushing it. Also, if during rapid movement the servos were hitting full stop, it's possible the laser suffered from some sort of shock. Dropping a laser can kill it, so I can see one being killed from a hard smack from a mechanical stop.
 




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