On Hackaday three years ago, architect Ekaggrat Singh Kalsi–a designer who also 3D prints with light–shared a robotic writing clock, also referred to as the Doodle Clock, that he has now updated and posted for all interested parties. The biggest improvement is with how time is marked by the clock.
There are several general improvements on this clock compared to the first one. The first version of the clock used a marker, which proved to be a problem since the marker would dry up after only 30 minutes of use. Then Ekaggrat got a good idea and substituted the marker for a magnetic doodling board inspired by the Fisher Price ones. In this case, he used 2 mm cylindrical magnets inside a solenoid (a coil wound up into a tightly packed helix) to write and then erase the time.
Another general improvement from the first prototype is that the second version has a much smoother and quieter sound since Ekaggrt used small gear steppers instead of servos this time around. All clock parts were designed and 3D printed. In addition to the 3D printed parts, the following components are also required to build this clock yourself: an artmega 644 p; two stepsticks; 1293dd; two 1:100 15mm stepper motors; two 12 x 18 mm solenoids; two 2mm diameter x 10mm magnets; and one ds1307.