A DIY Toroidal Coil Winding Machine Built with an Arduino

A typical electric coil is cylindrical with copper wire wound around a solid ferromagnetic core. Those are difficult enough to make since they usually have hundreds or thousands of turns, but at least it is a relatively simple task to wind wire around a cylinder. Toroidal coils, which are shaped like donuts, are a lot more difficult to wind. Imagine trying to cover a hula hoop in hundreds of turns of rope and you have a pretty good idea of the challenge involved. That’s why YouTuber Mr Innovative built this DIY toroidal coil winding machine with an Arduino.

Toroidal coils perform better than standard cylindrical coils because of their symmetry, which helps to eliminate leakage flux and reduces the amount of electromagnetic interference emitted by the coil. The core of a toroidal coil is a solid ferromagnetic ring. In order to wind wire around that ring, a machine has to pass wire through the inside of the ring, around the outside, and back inside again—and then repeat that process many times. The easiest way to achieve that is by mounting your spool of wire on the edge of spinning hoop the travels through the center of your toroidal core. That means the hoop needs some sort of hinge mechanism so that it can be opened and fed through the core.

That’s how this DIY toroidal coil winding machine works. That hoop, along with most of the other mechanical components, is made of wood. There is a hinged opening on one side and a wire spool on the other. When the toroid core is in place, both it and the hoop spin simultaneously. Their relative speeds determine the distance between each wire turn. The core is turned by a stepper motor and the hoop is turned by a belt connected to a DC motor. An Arduino is used to control those motors, and the user can use a rotary encoder to set the number of turns required and their density. If you have a need for custom toroidal coils, you’ll almost certainly want to create a machine like this.