HOW TO: Send Audio/Your Voice Over a Beam of Light





Introduction: HOW TO: Send Audio/Your Voice Over a Beam of Light

Have you ever seen those music-synchronized lights before? They're pretty neat. This intructable will show you how to make a device that sends your voice or any other form of audio over a beam of light. The picture below is the finished product. I found the information on this project here. Please note that I used a lot of salvaged parts for this project; you could ultimately make a much better version with the right parts. I have tried to use this setup with a laser, but they seem to be too sensitive, and burn out easily. If there is a very simple solution to using a laser with this, please let me know. There are videos of it in action below.

Step 1: The Parts

You will need:

-A CdS Photocell
-Some battery holders with battery clips if needed (one for the audio-to-light modulator [transmitter], one for the receiver, and one for a microphone (optional))
-One microphone
-An Audio Output Transformer (RadioShack Catalog No. 273-1380)
-Some form of amplifier (I used a battery-powered one from RadioShack (Cat. No. 277-1008))
-Some MONO (NOT stereo) audio jacks (Three will do)
-Some form of LED, Preferably a bright one
-A container to hold all the doo-dads in (for the transmitter). I just used what I had: a pill container. You want to keep all the circuitry concealed in some form of container, because if you touch the circuitry, I found out it gives you a small unpleasant shock (because of the transformer?), and it disrupts the signal to the LED, therefore giving you a bad signal.
-Some hook-up wire

The Pictures below are what I had to buy (except for the mics). I salvaged the rest.

Step 2: The Schematics

These schematics were taken straight from the website I cited.

Step 3: Assembling the Transmitter

The assembled circuit should look something like this. Be sure not to bother with the black lead from the transformer; it is not used in this circuit. The cap of the pill bottle (to the right) has two holes drilled in it for the LED, which I just got from a solar patio light. Make all the connections with alligator clips FIRST to test it, then solder it all together when you know it works properly.

Step 4: The Receiver

The receiver is so simple, a monkey could do it. All you have to do is solder the CdS photocell in series with the battery pack (3 volts), and then solder the two resulting leads to another mono jack. Use the biggest photocell you can find. Also note that it does not matter which way you connect the photocell; it has not plus (anode) or minus (cathode) sides.

Step 5: The Microphone

The Microphone is also extremely easy to hook up. Connect it the same as you did with the receiver. You can find these microphones in cordless phones, answering machines, etc. The one I used came from a broken cordless phone. Once again, the batteries are just to give the microphone some power so that there will be some signal to the amplifier.

Step 6: Using It

To use it, just plug the transmitter into any audio source (CD player, radio, etc.), and turn it on! It will modulate the sound signals into light, and the receiver (plugged into an amp) will turn it back into sound! If you want to modulate your voice, plug the microphone into the input on an amp, and the transmitter to the output (to external speaker) jack. The final product may look a little like the below picture.



    • Epilog Challenge 9

      Epilog Challenge 9
    • Paper Contest 2018

      Paper Contest 2018
    • Pocket-Sized Contest

      Pocket-Sized Contest

    We have a be nice policy.
    Please be positive and constructive.



    Hi RPisces,

    I am doing a science fair project and am having a bit of a problem. I'd love some help! My problem is below.

    As you may know, Radio-shack is going out of business and the transformer is no longer in stock. I did however, manage to get a TL-013 Transformer but i'm not sure how to wire it. Could you help?


    I don't think that LDR is well-suited on such speeds, its response time is too slow to have quality sound. I would recommend a photodiode, or for simplicity, a small solar panel found in most calculators, it will work even better.

    Does the diode receive thing actually work? I'm going for he receiver here, cuz I'm doing he lazer window audio receiving thing, and I want a simple receiver, THAT WORKS!!!!

    Where are the videos? :) please :) thank you

    This is SOOOOOOOO cool. I can't believe it's this simple and actually works!
    I didn't understand what it was at first, though; I thought this was an LED display that was in sync. with an audio input (like a visualizer, kind of). When I realized what it actually was however, it blew my mind. Very cool. Good job.

    Could you tell me the purpose of the transformer here? I mean, couldn't we just use the audio signal to go in the LED so that it blinks as signal amplitude goes up and down? Sorry, i'm a noob. My idea is to put a small microphone instead of a jack, that's why i'm asking.

    Transformers are very important here. Audio signals tend to be really low voltage (the audio output from my MP3 player doesn't even turn on a low voltage transistor). You really do need to step-up the signal in order to get it to work, also because the LED won't get a "clean" output without it.

    The reason there is a transformer is because the voltage of the audio signal is not enough to really do anything at all, so the transformer is there to more or less boost the voltage of the audio.

    can we use an amplifier instead?

    Can't find an audio transformer here

    This seems pretty cool, but I have a hard time imagining what it might look like. If you ever get around to making a video of this I'd love to see it in action.

    Ok. I have posted two videos. One is just of some Pink Floyd being modulated into light. The other is with the microphone, and some Pink Floyd playing on my stereo, being picked up by the mic and turned into light. Enjoy!