Clocks, as we’ve often seen, come in a wide range of shapes and sizes. Proving, however, that there’s yet another way to tell time, Davide Di Gloria has come up with a robotic plotter which uses a Magna Doodle for a display.
The device features a pair of NEMA 17 stepper motors to control the position of an electromagnet "drawing pen" via a 2D SCARA arm and inverse kinematics. The drawing implement itself is an electromagnet originally from a 12V relay, activated by a MOSFET. When passed over the Magna Doogle it’s able to write out the time and date quite nicely. When it’s time for new characters, a third servo on the back — a smaller 28BYJ-48 — sweeps an eraser over the toy's surface, creating a nice clean area on which to plot.
The Roboclock is controlled by a Creality Melzi 1.1.4 3D printer board, with custom firmware developed in Arduino. Parts for the device are 3D-printed, and the Fusion360 project is available here and here for your perusal.
One would suppose Di Gloria has another printer/control board somewhere that he used to actually make parts for it. On the other hand, he could have theoretically made needed parts on the Melzi-based printer, then disassembled it to provide components. Likely not what happened, but if you have an old printer sitting around, the project could provide a few ideas on how to reuse it!