Re: HOw to pulse a samll pen laser 650nm < 5mw

I use a transistor driven by ttl or cmos logic. Most pen lasers use 3
batteries at 1.5 volrs each so using 5volts (ttl logic voltage) will
damage laser. I usually put a couple of diodes in series with the
transistor and the laser.

+5 volts---diode---diode---+-laser---collector of npn transistor.
common ground---emitter of npn transistor.
ttl or cmos or 555 timer------1K resistor-------base of npn transistor

Dave

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