Useless Machine

A simple desk toy that switches itself off. While the idea is non-unique, the design and 3D print files are.

The lid and arm are meant to be 3D printed and fitted to a box of dimensions 7x7x14cm.

The two switches (main switch and reverse stop switch) are soldered to a PCB which is mounted to the enclosure by the nuts included with the main switch. Note: the main switch shown in the photos is red, switches available for purchase are blue. There is no difference.

The main driving arm is mounted to a 9G servo, and designed to hit the main switch at one extension, and hit the reverse stop switch at the other.


3D CAD File


  • Main switch – available from
  • Reversing switch – available from
  • Continuous rotation servo
  • PCB – order online or etch at home
  • Arm – 3D print online or locally
  • Lid – 3D print (as above) or make a simple lid from wood or a material of your choice (I used foam board)
  • Case – build a simple box out of your material of choice (I used foam board) to the dimensions specified above.