Free Pendulum Clock

Forum user Cyclist recently built a free pendulum clock.

The cool thing about a free pendulum is that it has no mechanical linkage, escapement mechanism, or direct mechanical power to keep it going.

A small magnet on the bottom of the pendulum induces a voltage on a coil mounted beneath as it swings past. The voltage is detected by Teensy’s a/d converter and triggers a propulsion pulse applied to the coil from a digital output pin. This gives the pendulum a tiny nudge to keep it going. The pendulum defies the senses, swinging in eerie silence.

Cyclist reported that the accuracy is all about the pendulum.¬† He had it going for about a week and it was running slow by a consistent 1 second per day. He’s working on trying to refine the pendulum¬† and pivot design for easier, finer adjustment.