Pulse Width Modulation (PWM) Laser Communications Circuit / Video

This is a demonstration of how to construct your own PWM LASER Communications System, it shows a detailed schematic and basic explanation of operation. You will also see a video demonstrating the system in operation. Any questions on circuit specifics please ask.

Special thanks to all those who helped contribute.


C4 within the LASER driver circuit can be omitted if your regulator is close to your power supply, if you have some distance between the two leave it in.

If you want to plug in an un-powered microphone, its fairly easy to set up a power supply on the microphone input.

The voltage divider network resistor values on the inputs of LM311 comparator can be any value, just as long as they are equal. This should be self explanatory.



C1 (4.7uF) = [ + ] Terminal 6 Opamp for Audio Input [ - ] Terminal 2 for LM311

C2 and C3 (3.3nF, 100nF) (Use ceramic capacitors given they are in the nF range - no polarity requirements).

C4 (10uF) = [ + ] Terminal 3 of LM317 [ - ] Earth


C1 (100nF) (Use ceramic capacitor given they are in the nF range - no polarity requirements).

C2 (10uF) = [ + ] Terminal 8 LM386 [ - ] Resistor R3 1.2k

C3 (22uF) = [ + ] Terminal 5 LM386 [ - ] Earth

C4 (220uF) = [ + ] Terminal 5 LM386 [ - ] Speaker Positive
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