Electromagnetic clock
Short and sweet little video to show off my latest project, an electromagnetic flip clock, inspired by vintage commercial clocks, and other projects seen here and there.
This uses 28 bifilar coils made with the coil winder from my previous video, and controlled by an Arduino Nano, with MCP23017 chips and transistor arrays. All the main parts are custom designed and 3D printed. It's pretty big, at 16 inches wide. The clock sets itself to the correct time automatically on power-up using GPS, and keeps itself exactly on time that way.
With the bifilar coils, it becomes easy to reverse the polarity of each electromagnet, by feeding 12V into the central tap then briefly applying higher voltage at either end.
Each segment is fitted with 2 magnets with opposite polarity, and the alternating current applied via the transistors will in turn repulse one and attract the other. The code keeps track of those positions so it only moves what needs to be.
The transistor arrays used here are Toshiba TBD62083APG, which are limited to a 500mA output current per channel. Applying more than that will burn a channel immediately. This made selection and position of the magnets a little tricky since they need to be able to be repulsed and attracted by the coils but without being too strong for the electromagnets’ power to overcome. Same goes for how each segment is mounted, the amount of friction that must not be too great to block movement while not being too loose, distance between magnet and coil etc.
But overall very fun to make. It’s so noisy and clicky!
Designing PCBs can also be sort of a little artistic exercise :)