I had converted my mini-mill to CNC last year and had a leftover motor controller
board, some nema17 stepper motors, a 12v power supply and an Adruino microcontroller.
I loaded GRBL 1.1 (a CNC GCode server) into the Arduino, 3D printed some pulley
"covers" for the Etch-A-Sketch knobs (the X & Y axes) which I printed with a 2mm
gear tooth pitch so I could use standard 6mm W x 280mm L toothed belts (commonly
used for 3D printer builds) and made similar toothed pulleys to fit over the nema17
motor spindles. I wired the motors into the motor controller board which sits as a
daughterboard plugged into the Arduino (an old Uno). I then used quick-clamps to
clamp the Etch-A-Sketch to the sheet of 1/4" plywood I mounted everything else on.
I can now connect to the Arduino GRBL server via USB cable and using the UGS (Universal
GCode Sender) I can send text, images etc to be rendered on the Etch-A-Sketch -- now
basically a 2-axis CNC device, the knobs being twiddled by the stepper motors.
I plan to use this to introduce and explain to the kids in my family how computer CNC
control works in a fun and easy-to-understand way, drawing Marvel and Star Wars pix
and the like...