[Open Frime TV] has a video addressing this in a novel way, by creating the windings for a switch-mode power supply transformer using stacked PCB coils instead of wire (Russian language ...

And so we have this example of reclaiming copper from ... But the transformer is not the only source of the red metal; [eWaste Ben] also harvests it from relay coils and the main coil and shading ...

A standard flashlight was modified by soldering the flashlight bulb in series with a coil of wire. The coil consists of many turns of 24 gague copper wire. When constructing, add turns to the coil ...