Drive a Stepper Motor with... a Stepper Motor

A couple months ago, we saw YouTuber "Tech Build" drive a stepper motor via an Arduino Leonardo, along with a touchpad acting as a PS/2 mouse input. This lets you swipe up and down as you would with a smartphone to physically control the stepper in response. In this new hack, Tech Build shows how to drive a stepper without any microcontroller whatsoever, instead using a second stepper as the input method.

To get this working, he hooked up the controlling stepper motor to the input pins of a ULN2003 driver board, which is connected to external power as well. Outputs are connected to the driven motor, and when the input is spun, the output motor and gear assembly spins in response. The trick here is that when the input is spun, it induces a current across its coils in the exact same sequence that’s used to actually drive this type of motor.

This process won’t work at lower speeds, and isn’t extremely accurate, but it’s a fun experiment that you may be able to do with parts on-hand. The experiment focuses on using a unipolar steper, but you could also move a bipoloar stepper motor with the appropriate driver, such as the L298N.