When you buy—or even salvage—limit switches for electronics projects, you expect them to work again and again, producing normally open (NO) and normally closed (NC) signals as needed. Generally, they do work quite well, but if you want to test things for a little extra assurance, you might want to check out this project by Mr Innovative.

The automated device spins a NEMA17 stepper motor however many times you choose with a rotary encoder, registering the NO and NC signals that are sent to its Arduino Nano controller in response. The unit then gives a pass or fail output via a small OLED screen to let you know everything is functioning properly.