This is a CNC pen device made out of parts from an old printer and a scanner.
This was also my first significant programming project. It accepted input in the form of a bitmap line drawing from which it generated instructions to drive the stepper motors and pen solenoid.
This was before my introduction to microcontrollers which made the hardware more complecated then it need to be. I used the computer's parallel port for communication but because there was not enough pins to drive all the motors they are indirectly driven through a mess of discrete transistors that translated the parallel port pin patterns into the stepper motor commands.
These are some test input images:
And here the machine draws them:
Here is logic and power circuits. The thick cable near the top is the
comes from the parallel port.