The small coil wants 5v, which is easy to get using any USB cable. I found an old USB mini cable in the bottom of the drawer and decided to upcycle it into my power supply for this project.

Cut the small end off and expose the wires. A good pair of wire strippers is really helpful here.

Normal USB cables have 5 wires inside: look for a red and black wire as well as a few colored data wires. You can just ignore these for this project. Trim them to get them out of the way.

Some USB cables are charge-only cables. If you have a charge-only cable, there will be just 2 wires in there: red and black. You're golden.

Solder the red to the red wire on the coil and the black to the black wire.

If you prefer a no-solder version of this project, use one of our 2.1mm screw terminals with a 5v power supply. Insert the red and black wires into the screw terminal and screw them down tightly. Then you can plug your coil into the wall with any 5v power supply with a 2.1mm jack.