Getting a magnetic field to balance on ... and a handful of current regulation ICs. The coils can be made in house if necessary, with each winding getting about 800 turns of enameled wire.

A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.

With coils printed right on the board, you don’t need to worry about fussy winding jobs ... use four-layer PCBs which allow for more magnetic strength out of the coils made with traces.

A coil of wire, or solenoid, consists of a wire coiled up into a spiral shape. When an electric current flows, the shape of the magnetic field is very similar to the field of a bar magnet.