3D file for electromagnetic holder

A round plastic cap (bottle cap) with a small central indent was glued flush to the electromagnet and used to center the steel ball onto the magnet correctly. The electromagnet could be turned off through the Arduino app (see .ino file), and the steel balls would free-fall onto the top of the plate.

For the non-magnetic ruby ball, a paper cone was used as a pin-sized funnel to manually drop the ruby ball from the top center of the acrylic tube.