Hans Summers has an amazing collection of projects. His most popular project is the binary clock. It runs off of mains, uses a bunch of TTL logic chips and a binary counter. He has posted links to ...

The 4060 binary counter slowly counts up to 8,196 on a 1.11 Hz or 0.83 Hz clock, for four hour or 5.5 hour operation respectively. When it hits that threshold, it fires the gear motor.