Arduino Uno-driven plotter uses rulers for arms
When you see a plastic ruler, you wouldn’t normally assume it was destined to become part of a CNC plotter. Maker “lingib,” however, realized their potential to be combined to form plotter arms, in this case actuated by two stepper motors.
The resulting build can expand and contract the resulting shape, allowing a pen at the end point of the two sets of rulers to move back and forth across a piece of paper. Necessary spaces in the plot are provided by a micro servo that can lift the pen/ruler off of the writing surface.
The device is powered by an Arduino Uno, which controls the two NEMA 17 stepper motors via a pair of EasyDriver Modules. You can find more details about how to create one of these, including code and how the geometry behind it works, on its Instructables page.