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Thread: Connect a Laser module with a microcontroller through Mosfet

  1. #1
    Join Date
    Jan 2018
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    1

    Default Connect a Laser module with a microcontroller through Mosfet

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

    simulate this circuit – Schematic created using CircuitLab
    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?

    Edit: As requested, a photo of the whole rig – although I'm not too sure it's very useful given the rat's nest of wires.

  2. #2
    Join Date
    May 2007
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    1 hr from everything in SoCal
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    2,753

    Default

    I hate to say it but your diode is dead. If I had to guess, the module board might have burned out and sent unregulated current to the diode and toasted it. These diode modules are laser pointer cores and meant to be run off a pair of AA or AAA batteries so, 5V *might* be too much voltage. That's also assuming that the PSU is actually putting out 5V and not >5V

  3. #3
    Join Date
    Oct 2012
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    Germany
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    1,478

    Default

    ... a laser diode has better to be driven by regulating the current, not the voltage! -- and best, not exceeding 90% of the max stated curent by the manufacturer!!

    Another point is, that most cheap lasers are "overdriven" by some ten to 50% ... so it's common, that the life-time is more like some then hours, than the promised ">20000 hours".

    You can DIY your own "safe" driver with a constant-current circuit -- maybe something around a LM317 (this is, what many "proffessional" cheap chinese high power modules actually have) - look into the datasheet of an LM317 on the section "use as current regulator".

    I've developed a pretty simple "cascadable" constant current driver with 5x LM338 for high power diodes or UV-LED's with up to 15 Amps (or more, when parallelized more too) ... but you can use a single LM317 and bigger shunt resistor for something as low as 50mA -- the formula for the resistor is simple: R=1,25V / I => so use a resisitor with 25 Ohms to define a current of 50 Miilamperes through the chip and the laserdiode ...

    Viktor

  4. #4
    Join Date
    Dec 2008
    Location
    Canada
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    972

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    Time to buy another Cheap Laser...IMO
    Here are 10 of them for ~$0.18 USD each....

    https://www.ebay.ca/itm/Mini-6mm-3V-...TfQSVeef4C1kug

    Jerry
    See the LaserBee II and all other LaserBee LPM products here....
    All LaserBee Laser Power Meter Products

    New 3.2Watt RS232/USB LaserBee II LPM REVIEW


    Always in stock and ready to ship....
    Subsidary:-Pharma Electronic Solutions

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