This ATmega328P-powered device is like a tiny modern-day telegraph printer.
YouTuber Et Discover built a miniature printer that’s controlled by his phone over Bluetooth. The device uses a pen as the marking device and a micro servo and linkage system to move it back and forth. The small strip of paper is advanced by a 24BYJ-48 stepper motor, along with a ULN2003 driver, allowing for sequential control over pen placement.
What’s interesting from a mechanical standpoint is that the pen doesn’t descend to the paper to make each dot, but instead the rig employs an electromagnet to bounce the paper up to hit the pen. A neodymium magnet is embedded in the small printed platform that rises up to receive a dot, and a boost converter is used to produce 24 volts for actuation.