YouTube content creator [Playful Technology] wanted to understand how ubiquitous analog clock modules worked and undertook a project to control the hands of a module directly using an Arduino microcontroller to find out.
Inside these modules, a crystal oscillator drives an electromagnet that turns a small plastic gear with a magnetic ring clockwise or anti-clockwise via magnetic pulses depending on the polarity of the electromagnet.
The gear is meshed with other gears to provide the correct rotation rate for the minute, hour and second hands of the clock.
The Arduino can easily take over control of the hands by disconnecting the electromagnet from the crystal oscillator circuit, allowing the microcontroller to move the hands at any speed and in either direction.
The creator is looking to improve reliability and also plans to replace the module’s original drive mechanism with a servo motor.
