Electromagnetic Marble Dropper

This is designed for a CPO Physics stand that has mounting holes 5 cm apart. The bolts that attach it to the base stand are 1/4 in.-20 nuts. The electromagnet is wound around a carriage bolt with a 1/4 inch-20 acorn nut. The acorn nut is good for centering the marble.


The circuit is simple — it is a an electromagnet, AA battery case, switch, and optional a flyback diode.