Electronic Dice
I made this pair of electronic dice many years ago (probably about 15!). It was a present for my then girlfriend - now my wife (she was not put off by extreme geekiness - thankfully)
They use a single character LCD dot matrix display, the display is about 75mm x 50mm (3" x 2" for non-European readers) and has 5 by 7 pixels.To make the two dice separate and different colours I peeled off the polarising film from the front of the display, cut out two squares and reattached using clear sticky back plastic to hold in place. (To make the black die I rotated {or turned upside down - I can't remember} the piece of polarising lens)
It uses a PIC chip to drive the display directly. The PIC chip is powered at 3V by a lithium coin cell (still the original battery from 15 years ago!)
The common pin of the LCD is driven with a 50% duty cycle square wave from one PIC port line and each pixel is driven by another square wave - either in phase to give 0V across the pixel, or 90 degrees out of phase to give the 6V p-p 50% duty cycle square wave needed to drive the LCD.
The 50% duty cycle is important apparently to avoid damaging the display
The tactile switch on the back stands proud of the rest of the circuitry allowing a press on the corner of the display to roll the dice (or turn on and off using a long press)