Jim Phillips and Rich Ottosen came up with the idea for the whirlygig and each built one. It is a sign which uses a column of LEDs spun around the perimeter of a circle, such that the LED form a "floating" cylinder to display dot matrix messages through retinal persistence.

Inspired by an exhibit at the Exploratorium in San Francisco, Rich wanted to put together a sign with a column of LEDs that would display messages if you swept your eyes past it. Since in this case the sign is stationary and the viewer (or at least the viewer's eyes) move, it obviously had to be called a Whirlessgig.

This project used all surface mount components, including a PIC16C54 in an SO package, eight LEDs and a resistor pack, all assembled on a small square PC board. The back of the PC board has a metal clip for a coin cell.

In practice, it is difficult to see the message by sweeping one's eyes past the LEDs. It is easier to shake the sign back and forth. We've toyed with adding a mercury switch so the unit can automatically switch the display direction. I think a solid state accelerometer would work better, but it would increase the cost of the unit by a factor of ten.

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Last updated June 4, 1995

Copyright 1995 Eric Smith