The Bulbdial Clock is a project from Evil Mad Scientist that replicates the idea behind a sundial using colored LEDs to cast shadows instead of the sun. As a result of there being multiple "suns" at different heights in this version, we can easily read hours, minutes and seconds from its face.
On three layered rings of laser-cut plywood, 36 LEDs (12 on each ring) take turns firing up to cast shadows. The LEDs on the highest-up ring cast the shortest shadow to resembles the short hour hand on a traditional clock face, the middle ring LEDs cast a longer shadow for minutes, and the lowest ring casts a long second-ticker shadow.
It's also pretty cool to see how the red, green and blue LEDs cast cyan, yellow, magenta or white shadows based on mixing colors of light.
[ Via Geekologie ]