LASER Module loses brightness when in use

Discussion in 'General Electronics Chat' started by CVMichael, Aug 3, 2012.

  1. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
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    I bought this laser module: http://www.robotshop.com/ca/sfe-green-laser-module.html

    What I got IS NOT what is in the product picture. See attachment images of what I actually got (I removed the button and connected wires directly).

    It is using a LM358 op-amp.
    The module loses brightness when the laser gets warm. After about 10 seconds, you can barely see laser! If I leave it off for a while, then I turn it ON, it's bright again for a few seconds.
    When it's warm, and I turn it OFF and then ON, I see a short burst of bright light, then it goes dim after a few milliseconds.

    I need the laser to pulsate at 50% duty cycle, and about 10 to 20 times per second. The frequency depends on the brightness of the laser and also the brightness of the environment.

    Because of the way this laser driver module is built, I have a feeling it is not supposed to pulsate? (I think because it is using caps, it takes a while to initialize)

    Do I have to make my own laser driver that is designed to pulsate? Anyone knows a good schematic for what I need?
     
  2. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
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    The laser is very bright when it's cold. So I don't think it's a problem with the laser diode... I am pretty sure that it automatically adjusts to the temperature, that is why it gets dim after a while. And I can feel it getting warm when I touch it.

    I don't know... what ARE you thinking?
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    U need to limit the lazer diode forward current to a safe value.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Supposedly that's what the included PCB is doing.. Unless he has screwed that up too..
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    do I see a VR there ?
     
  6. BMorse

    Senior Member

    Sep 26, 2009
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    this will not be controllable by PWM or any modulation because this uses a DDL driver, and DDL drivers do NOT like being modulated at high speeds.
     
  7. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
    416
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    I did an experiment today.

    I removed the PCB board from the laser diode, and connected the PCB with the laser diode with 2 wires (about 2 inches distance between them). The laser acted exactly the same!! The PCB got hot which made the laser dim.

    So it's the laser driver that is messed up, not the laser diode.

    I've been looking online for laser drivers. Mostly I found one schematic (see attached).

    Do you think the attached schematic will work for my laser?
     
  8. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
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    What is that supposed to be?

    And why do you keep posting that and then deleting your post???
     
  9. #12

    Expert

    Nov 30, 2010
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    It's an LM317 wired as a constant current source. Lacking the specs of the laser diode, we can't guess what the final settings will be from here.

    That circuit can be added to a 555 timer chip to get the on and off timing.
     
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