The clock served as two purposes: to learn how gear systems like planetary gear sets work, and to practice Arduino programming to accurately control the speed of a stepper motor. The idea for the design was to display the inherent beauty of a complex mechanical system.
The original design
This was the original design, when I still had a basic understanding of gear design. The issue with this design was getting the geometry right such that the final gear turning the hour hand turns clockwise, at the right rate, and coaxial to the minute hand. Figuring out a way to rigidly mount two independently rotating arms on the same axis proved to be very challenging. The solution was to use a timing belt on the back to provide the final ratio without reversing the rotation. However, I was unsatisfied with the elegancy of the solution and the overall look of the clock.