[punkky] has been documenting his adventures building digital clocks. They each use six 7-segment LED displays, but he’s been gradually changing how they are built. The first version used a CMOS BCD-to-7-sement latch on each display, which is tied to a PIC16F627a. For the next run, he added multiplexing, so he could drive all the segments using just thirteen pins. He’s posted a final schematic with code and details of how the clock timing actually works.
Blinkomat, an LED matrix, turned out quite well. 240 LEDs controlled by an Atmega 16 is what we call a decent bookshelf decoration. The dimensions of 12×20 were chosen due to the fact that the microcontroller has 32 I/O lines. The LEDs are switched on and off using multiplexing. The brightness, controlled by pulse width modulation can be varied by 16 levels. The overall effect is quite smooth an fun to look at. He has programmed it to do other things than just cellular automata. Our personal favorite is a simple sine wave. Watch it after the break.
