Using an Arduino Micro Pro module along with a real time clock and a darlington driver array I created a working Topsy Turvy Clock.
The electronics was not particularly challenging, I effectively wired 3 off the shelf components together using a motherboard/module approach. The stepper motors had a gearbox so to know the absolute position I added a clear disk with a segment marked off with tape which passed through a slotted opto sensor. On startup the clock homes each of the motors before moving to the correct locations.
If you've any questions about the electronics or anything else about the clock, please leave a comment.
I've entered it into the Atmel Simply AVR Design Contest, you can see the other entrants here - Atmel Simply AVR Design Contest