DIY Audio Controlled Laser Show!

Thanks to Instructables, our hackerspace The Rabbit Hole received 2 Wicked EVO laser pointers. They are fairly powerful green lasers and we thought it'd be cool to use one of them with some sort of audio application.

Naturally this led to us thinking, what would a laser look like if we controlled it with audio? Some instructables have the entire chassis of the laser controlled with the vibration of speakers, and some have the laser beams influenced by audio through mirrors on the speakers. This instructable is looking to directly control the laser beam with your audio source of choice!

What you'll need:

• Scraps of wood for a base
• Wicked EVO laser (or any other laser in their line)
• 2n3904 transistor
• Solder + Soldering Iron
• 2x4 female header
• Random mirror
• Random alligator clip
• Female 1/4" jack
• Audio Source!

For extra flair:

• Color splitting prism from broken projector
• Scrap wood
• Broken screwdriver bit
• Power drill
• 2-part epoxy

We used some old wood scraps and made a stand for the laser.

We put the laser through and removed the back end because we wanted to transform it from being battery powered to wall-wart powered. So to do this, we stripped the ends of the wall wart. The - (GND) side was soldered to the center of the laser, and the + side was soldered to the alligator clip which was clipped to the side of the laser.

In the laser, there is a 2x4 male "slot" that allows for control of the laser. It would be easy enough to have female-to-female wires that go from each of the pins to a female 1/4" jack, but decided that'd be too many separate wires running all over the place.

Instead, we decided to take a 2x4 female header and solder the female 1/4" jack to it. The header would be plugged in so as to avoid all of the wires. [All directions will be assuming the laser beam points upwards and the laser control slot is facing towards you]

The GND pin of the 1/4" jack was soldered to the bottom left pin of the 2x4 header. In the pictures, it looks like it is touching the top left pin, and it is, but that connection is not necessary for audio control. It also will not harm the laser if the GND pin is touching the top left pin.

We're using the 2n3904 transistor - make sure you check the datasheet whenever using transistors so you know which leg is the base, collector, and emitter!

On the 2n3904 with the flat side facing towards you, the legs are (1) Emitter, (2) Base, then (3) Collector.

So solder the emitter to the second pin from the left, top row. The base is soldered to the tip side of the 1/4" jack. And finally the collector is soldered to the shield pin of the 1/4" jack.

So once you've plugged in your audio source, you should see the laser pulse according to the volume/pump of the music. If you aim it at a scrap of a mirror angled at 45 degrees, that light goes up against your ceiling for a cool effect! You'll see a starfield pattern against the ceiling pulsing with the music.

For our flair effect (really quite a bit of silliness), we used a color splitting prism from a broken projector. It came with its own little chassis and had a single screw hole in it. So we made a wooden base for it, affixed it to the chassis with a screw, and then epoxied a broken screwdriver bit in its center.

Once the epoxy had cured, we put the screwdriver bit into a power drill and spun it with the laser shining into it!

This made for some pretty crazy light show action - as you can see in the video :)

And voila! Crazy audio controlled laser light show!