Friday, November 09, 2007

History Appliances: Laser Spirograph

A sure sign of a 1970s childhood is a fond memory of doodling with the Kenner Spirograph toy. In the back of my mind I've been thinking it would be fun to build something like it into a history appliance. You can already find software versions online, but I wanted something that could be used at the periphery, rather than the focus, of attention. On a recent trip to Active Surplus in Toronto I realized I could build a version quite cheaply. So here it is: a little too thrown together even to call a hack, this is really a kludge.

I started by cutting a $1 laser pointer out of its casing and soldering some wires to it so I could switch it on and off electronically. Here it is on a breadboard with a 5v voltage regulator.

The laser shines on a mirror that is crazy-glued to a cylindrical piece of dense foam and mounted on the shaft of a motor. I used Lego motors because I had a pair of them. The reflection bounces off another mirror, similarly mounted, and is projected on to a screen made from a 3x5 card. The motors tend to slip around when they are running so I put a rubber mat under each.

The motors are controlled by pulse width modulation, using a Phidgets MotorControl LV board. I used a wall wart to supply 9v for the motors.

To be able to fiddle with the speed of each motor, I used the Phidgets Interface Kit, the mini joystick and a Max/MSP patch.

The whole setup looked like this.

With the motors both running, the dot of the laser pointer is perturbed by first one rotation, then the next, tracing out a familiar spirograph-style image.

As you vary the speed and direction of rotation for the two mirrors, you get a range of different patterns.

To demonstrate, I used the joystick to vary the parameters of the system. In an application, it would be hooked up to streaming data instead. Groovy!

Tags: | | |