Sound Driven Laser Show

This instructable will show you how to build a laser light show that moves and pulses with the music. Instead of making a circle or series of circles, this creates a chaotic pattern. Here’s the really short version:

1. Take apart a CD or DVD drive.
2. Remove laser focuser.
3. Glue small mirror to focuser.
4. Attach speaker wires to the focuser coils.
5. Bounce a laser beam off the mirror.
6. Pump up the volume.

The beating heart of this device is the laser focuser* out of a CD or DVD drive. When it’s doing its mundane job in a CD player, it moves up, down, left, or right to keep the laser focused on the surface of the disc. The lenses are mounted on a set of very thin flexible wires that require very little force to move. The two electromagnets are powered by a DC voltage and are attracted or repelled by two permanent magnets. For this device, we’re going to use the speaker output from a stereo to provide voltage to the drive the electromagnets. A speaker uses a coil and a magnet, so it’s the same sort of concept.

WARNING: If the impedance of the coil is too low, it could cause damage to your stereo amplifier. I’ve had this run for hours at a party with no ill effects to my equipment. I can’t guarantee the same will happen for you. I’ve measured a few of them and they ranged from 2.5 ohms to 6 ohms. Home speakers are usually 8 ohms, car speakers are usually 4 ohms. If you connect to both coils in parallel, the impedance will be cut in half.

This video shows the device in action.  Since it's dark, it's hard to see the scale, but it was projected about 25' across the shop.  The pattern was about 3' across for the first part, and about 10' across for the second part with higher volume.

*I don’t know if that is the correct name for that part, but that’s what I’m calling it. See Mitch Hedberg’s Appliance Naming Institute for more on that.

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Just did this and it worked amazingly. Thanks so much. However I ran into a problem. It only worked for about 30 seconds until two of the little wires that holds the laser focuser in place burnt away to nothing when I turned up the volume. Now it obviously doesn't work at all.
Any suggestions on a fix or how I could improve another one so that that won't happen again?
bloomautomatic (author)  smokyjoewood122 years ago
I'm guessing you just had too much power going through it. Heavier wire or less power would be the only answers. Typically older equipment is heavier than newer equipment, so maybe if you got one out of an old CD drive (1990's) it might handle more power.

Sorry it took so long to respond.

lordvellos2 years ago
cool, planning on making one to enrich all family parties, but 2 questions, is there anyway i could assure that the impedance would remain within the desired? and what happens if i use one independent set for eache direction, i mean um set of wires for each direction and one stereo output for each? it wouldnt drop the impedance right? but what about the effect? is it possible to wire it in series? thanks from brazil!
bloomautomatic (author)  lordvellos2 years ago
Not sure about that. Maybe add some resistors inline.

If you use one channel for each direction it will move more, but I'm not sure you would really notice it.

Wiring in series should make the impedence higher. Not sure what effect it would have.