This project uses RGB LEDs to create a clock face. Each hand is assigned a colour and as the hands overlap on the face of the clock it mixes the colours.
The clock uses a single AA battery to power the display which is boosted to 5 volts with a switching mode power supply. The power supply should be able to use any AA battery that is at 0.7 volts or higher, which means that it should still work fine with AA batteries that may be “dead” when used in other devices.
The heart of the clock is a DS1307 realtime clock with a CR2032 coin cell battery backup. The battery should be sufficient to keep the time for at least a couple of years.
LED Desktop Clock - [Link]