Transmitting audio over laser or LED

Posted on Feb 6, 2014

Want to send your audio information via a light wave across the room I built this simple circuit with some modifications that transmits an audio signal via light. The signal simply amplitude modulates the light intensity (aka AM) of a LED and a receiving cadmium sulfide photocell changes its resistance as the intensity varies. Both sides have 8 t

Transmitting audio over laser or LED
Click here to download the full size of the above Circuit.

o 1000 ohm audio transformers, although on my circuit I ended up using the transformer on the receiving side as a voltage booster. I also added a battery and resistor to the photocell receiving side. Be careful-I used an LED because I destroyed a cheap laser pointer when trying the first circuit. The problem with it is the sound card audio is approximately 1 Volt AC at max, and this gets converted to ~12. 5V on the other side (although I found output was usually around. 5 V on the sound card and ~4 to 5V on the other side of the transformer). At least that`s what I measured-I`ve seen people read 4V on sound cards, but I don`t know which is correct.

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