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BUNNIE’S WORKBENCH

www.makezine.com/01/bunnie

GLOWSTICK A GO-GO

Bunnie Huang prototypes two kinetic glowsticks.

G lowsticking emerged out of the tech-no club scene, which features bone-rattling riffs and vicious grooves. Dancers whirled a pair of glowsticks to trace out beautiful, curvaceous patterns and Lissajous figures in the dark of the dance floors.

When high-efficiency LEDs became available, so-called “photon lights” (high-intensity keychain fob LEDs) were used in place of the glowsticks. Eventually, these photon lights became available at carnivals, fairs, clubs, and raves. Moving forever forward, the photon lights evolved to include multicolor LEDs that would sequence through a series of colors, thus tracing a multi-colored path through the dark as the light was swung around.

I’ve always been a big fan of electronic music of all kinds, starting with Information Society and Kraftwerk back in the ’80s. While I was at a party watching glowsticking dancers, I got to thinking. What if, instead of creating a single arc of light, the _{dancers could create whole, two-dimensional pat-} The Back-of-the-Hand terns of light as they danced? So inspired, I began to Prototype hack my own “kinetic glowstick.”

Since I wanted a ribbon of light with a visible pattern in it, I could not use just a single LED like the photon lights. The device had to contain a row of LEDs that would flash with a preprogrammed and pre-timed pattern. This pattern would then smear out in the viewer’s eyes and create the illusion of a solid, 2D pattern in the air.

The requirements for a Kinetic Glowstick:
* ^{A row of LEDs} * A sequencer to control the rate and pattern _{of flashing of the LEDs}
A memory store to contain all the _{LED patterns}
A power source

The sequencer will pull “sprites” from the memory store and relay them to the LEDs. A sprite is jargon from computer graphics for a 2D array of pixels that define an image for use in animations. Many of our old favorite video games, such as Galaga and Pac-Man, use sprites for animation. The number and resolution of the sprites stored in memory will define the richness and variety of images seen by the viewers.

When I start a project, I usually look around for a few spare parts. This prototype began with a circuit board I had built a long time ago for a class that I taught at MIT. The board had a single Xilinx “Spartan” FPGA connected to a row of 16 LEDs — a perfect starting point. The board also had an onboard serial ROM socket for configuring the FPGA

34 Make: Volume 01