A Dual-Zone Clock Tells the Time Here... and There

Writing for Hackster and other fine maker technology outlets, I often have to work with people in other time zones. While this can mean anywhere, PST, or California time seems to come up quite a bit. Rather than continue to subtract 3 hours from my EST location — while trying to mentally confirm this was the correct procedure over and over — I created a mechanical clock with two hour hands. These linked hands, or gears, can then be offset as needed in order to tell time in multiple locations at an instant.

The device is powered by an Arduino Nano, which triggers an 28BYJ-48 motor to advance 1/60th of a revolution every minute. Timing is fed to the Nano via a DS3231 RTC module, and the unit can be set with a single button to advance the wheels, or unplugged to let time catch up as needed.

Code is available here. Notably, the number of steps needed for 28BYJ-48 motors to make a full revolution is almost, but not exactly 2,038. So in reality, each minute move isn’t quite 1/60th of a revolution, and steps must be skipped intermittently, though this procedure still needs a bit of work. One other interesting bit in the code comes at the end, where the coils are de-energized to save power and heat generation. This would allow some steppers to rotate freely, but given the unit's internal gear reduction, this doesn't seem to be a problem.