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Green 532nm DPSS laser pointer...

Discussion in 'LEDs and Optoelectronics' started by Externet, Jan 16, 2019.

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  1. Externet


    Aug 24, 2009
    Looking to make a 5mW(optical) at 532nm generic cheap laser pointer module that operates on 3V (2xAAA cells) work from 4.2V fully charged to 2.5V full discharged 18650 cell.

    The Vf for 808nm is supposed to be 1.9V. Such pointer is supposed to have a current regulator IC built in. Would it be safe for the module to run on a 18650 cell instead, with no alterations ?
    To operate down to a minimum cell voltage of 2.5V, and the diode being 1.9Vf; the maximum Vdrop by the regulator should be 0.6V; right ?
    What voltage drop imposes a LM317 type of series current regulator ?
  2. BobK


    Jan 5, 2010
    An LM317 has a dropout of about 2V, but why are you asking that if the module has a current regulator built in? What you need to know is what range of voltages the module operates at.

  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Plus you don't operate LEDs or laser diodes from a constant voltage source anyway. You'll need a constant current source instead, see our respective resource on driving LEDs.
  4. Externet


    Aug 24, 2009
    Thanks, fellows.
    Those cheap laser pointers publish no specifications of their built-in drivers, or if they could accept 4.2V from a lithium cell; and I need to use their factory drivers to keep at the mandated allowed 5mW optical output.
    A constant 3V supply as the 2xAAAs they are meant to work by design could instead supply the laser built-in driver module. For using only the laser diode without its driver, then I should go for constant current, but is not the case.
    A DC-DC circuit to provide always 3V to the unmodified pointer could work, but may not cease at 2.5V to prevent the lithium cell to overdischarge.
    Checking deeper, seems those cheap drivers do not use a LM317 type of current regulator but a series transistor and a LM324 IC to set current limit.
    Have to examine them closer...
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