Building an electromagnetically-assisted pendulum

For an upcoming clock project, Stephen Hobley is experimenting with an electromagnetic pendulum. The goal is to keep a pendulum swinging at a constant speed, in order to use it as a timing reference. By adding a permanent magnet to the bottom of a pendulum, and placing a coil of wire at the bottom of the pendulum’s path, he is able to use the coil both to sense the motion of the pendulum, and to give it an electromagnetic boost every cycle to keep it swinging.