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.