Sketch the current time with this Magna Doodle clock
The Magna Doodle is a classic children’s toy that works by embedding a layer of iron shavings just below the surface of a canvas and then using a magnetic pen to pull them up, thus showing whatever lines might have been drawn. Steve Turner had the idea to automate this drawing process by converting his Magna Doodle into a clock for displaying the current time in almost any TrueType font.
To begin, Turner created a simple wooden frame with several cut slots for its three NEMA17 stepper motors, the electronics housing, and the Magna Doodle itself. At the bottom of the frame sits a timing belt loop that, when pulled in one direction by the stepper motor’s pulley, drags the erasing head in order to reset the canvas for the next drawing cycle. Meanwhile, the top has a pair of stepper motors arranged in a SCARA design, which uses a couple of arms joined at a single point to move the magnetic head over the area.
Driving this combination of stepper motors is a Nano Every board that sends movement commands to a set of three TMC2130 stepper motor drivers and a micro servo. When the device draws a number, the Arduino reads the font file from an SD card and plots it according to the time given by a DS3231 RTC module.
To see Turner’s project in action, you can watch its demonstration video below and check out his tutorial on Hackster.io.