The earliest televisions used a spinning disk technology called the Nipkow disk, which is exactly what [Science ‘n’ Stuff] recreated with their Arduino-based mechanical color television (video link, also embedded below.) The device reads video and audio from an SD card, and displays the video using a precisely-timed RGB LED visible through a perforated spinning disk. The persistence of vision effect results in a video that is small, relative to the size of the disk, but perfectly watchable. A twist is that the video is in color!
A Nipkow disk is a fairly simple and electromechanical device that relies on timing; something a modern microcontroller and RGB LED is perfectly capable of delivering. In this device, the holes in the disk create 32 vertical scanlines with 96 “pixels” making up each of those lines. Spinning disk technology was always limited to being monochromatic, but in this implementation, each “pixel” is given its own unique color by adjusting the RGB LED accordingly.
The first video shows off the device and demonstrates it working; note that it may look like there are multiple little screens, but the center one can be thought of as the “true” display with the others essentially being artifacts due to light leakage. If you’re interested in the nuts and bolts of exactly how a Nipkow disk works, then the second video is what you’ll be more interested in, because it goes through all the details of exactly how everything functions.
Another neat thing about Nipkow disks is that image acquisition is really not much more complex than image display.
[via Arduino Blog]