You use limit switches to switch off a motor if it reaches one of its two end positions. Even if you build a microprocessor-based motor controller, you should switch off a motor with hardware by ...

To solve the problem without sourcing a new switch, [Jean-Noel] built his own Arduino based Dahlander switch. This consists of three relays that select the wiring configuration for each speed mode.

They also discuss some of their favorite ways to control the motors ranging from a light switch to an Arduino. They even mention how to turn one into a big servo thanks to a project on Hackaday.io ...