Everyone and their grandmamas are building cool clocks these days, and Viacheslav Slavinsky‘s “Strobeshnik” is another example. Viacheslav etched stenciled numerals into a HDD platter and strobed LEDs behind the platter to show the time.
Strobeshnik uses stroboscopic effect to create the illusion of persistent numeric display. The hard drive platter has 10 digits, colon and dash marks, cut all the way through it. Behind the platter, in the HDD chassis, there is a PCB with groups of diffused LED’s. Groups of LED’s in each character position can be strobed independently at any given time. By careful timing of the light strobes, an illusion of still-standing numbers can be created.
See the project description for schematics, Eagle files and source code.