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Thread: How to simulate a Laser Diode ?

  1. #1
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    Question How to simulate a Laser Diode ?

    Hi all,
    This is my first thread here, and I ask your indulgence in advance for my bad English.
    Here, I am looking to make a dummy load simulating a laser diode, which can be used in two situations (or more):
    1 - Check correct operation of a power supply for diode laser (DPSS)
    2 - Make a specific power supply with a diode laser which we know all the features (wine, Vrev, Inom, Ithreshold ... etc.)
    I tried dummy loads based on several diodes in series with a resistor to simulate the voltage drop, but the behavior at the current level is not good, it is limited to I = V / R (the R of resitance in series with the diodes)
    I stumble a bit on the thing, so if someone can help me at first to work on the 808nm IR diode between 2 and 5 watts.

    Thank you in advance to all.
    Christophe.

    ( and thanks to google for is partial translation... )

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Use a 1R0 or 2R0 resistor and three large silicon diodes in series. The resistor acts as a load and the diodes simulate the voltage drop of the laser diode.

    -----/\/\/\-----:>]------:>]-----:>]-------

    Steve

  3. #3
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    Does the laser diode voltage vary with current? I always assumed it stayed constant based on how other diodes work.

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    Quote Originally Posted by mixedgas View Post
    Use a 1R0 or 2R0 resistor and three large silicon diodes in series. The resistor acts as a load and the diodes simulate the voltage drop of the laser diode.
    I'd rather say 0R1 for a 5W diode - at 5 or 6A the drop across a 1R resistor will most likely be higher than the supply voltage to the driver.

    Quote Originally Posted by JohnYayas View Post
    Does the laser diode voltage vary with current? I always assumed it stayed constant based on how other diodes work.
    Yes, it changes with current.

    /Thomas

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    Quote Originally Posted by JohnYayas View Post
    Does the laser diode voltage vary with current? I always assumed it stayed constant based on how other diodes work.
    It varies for all diodes - just very little. It varies about the same for laser diodes, a few hundred mV.

    Quote Originally Posted by Badpip View Post
    at 5 or 6A the drop across a 1R resistor will most likely be higher than the supply voltage to the driver.
    Also, most resistors don't like 30W of heat

  6. #6
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    Hi all,

    I have some resistors that support 100w and more...
    ... But a diode behaves as a nonlinear load and its equivalent resistance is very low (approximately 0.25R for a 808nm 2W>5W)

    @ Steve: this is the first thing I tried (as said above) but in this configuration for up to 2A it far exceeds 2.2V max allowable by the diode, otherwise it remains to 20mA.

    I continue research on my side.

    Thanks.

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    -----/\/\/\-----:>]------:>]-----:>]-------
    Pretty accurate model, except for:
    ESD sensitivity
    Reversed voltage sensitivity.
    Emitting coherent light.

  8. #8
    mixedgas's Avatar
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    Try Shottkey diodes with a low Vf.

    Maybe mosfets wired as diode?

    Steve

  9. #9
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    I'm trying the dummy load to adjust a cheap driver, but something is wrong ...
    I tried 3 different testers, but the reading always remains 20\22mv
    the driver works correctly with the connected diode I can adjust the power without problems, but I can't read with the tool ...I'm using some 1n4007 and a 1ohm resistor

    this is the driver
    https://www.ebay.it/itm/650nm-532nm-...72.m2749.l2649

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