Coil generator in practice

Question

I am trying to create something like gyroball. Which features LED lights, so the faster the spinning, the more light LEDs emit. This seems like a simple scenario of a coil generator.

As an experiment, I 3D printed a wheel, which can hold feromagnets I bought. I don't know their exact specs, but they seem quite powerfull. The wheel was fastened to my cordless drill and magnets were inserted in alternating polarities (and since I miscalculated during modeling the print, there are 9 compartments so the last two has same polarity).

Then I salvaged the coil from old PSU (I dont know the exact specs), connected multimeter to its leads and spinned magnets near the coil.

I tried spinning magnets from the side, with and without touching the coil. I measured the continuity of the coil's leads (beeped). But the multimeter stayed at 0.00 no matter what (I tried almost all settings of the multimeter DC and AC).

After some research and finding this and this questions, I've added a resistor as a load.

But that didn't make any change. I took apart the gyroball I have, to see there are two coils as well.

Spinning the printed wheel close to them did not light them up.

• What could be the cause?
• Are the two magnets of the same pols somehow messing with the whole thing?
• Is my salvaged coil a bad type (wire too thick)?
• Does my resistor have too much resistance to properly work (I tried more types than this one)?

EDIT: Thanks for your answers! I tried self made coil from old solenoid and paper tube, the ends are scraped and whole small circuit has continuity, but still no luck.

Answer 1

The coil you are using is wound on a toroidal core. Such a coil does not pick up external magnetic fields efficiently. You should use a coil with an air gap, or simply an open wound coil. That will be more affected by the changing magnetic field created by your rotating magnets.

Answer 2

What could be the cause?

and

Is my salvaged coil a bad type (wire too thick)?

The toroid coil you used in your experiment has a closed-path magnetically so, ideally it can neither produce an external magnetic field nor receive an external magnetic field. That's why you measured no induced voltage when you brought a magnet near it.

The coils in the picture of the thing that works are not closed-path toroids hence they can both produce an external magnetic field and be influenced by an external magnetic field.

When you find a non-closed-path inductor, make sure you alternate the magnets so that the field changes north-south etc.. It won't be as good as it can be with only 9 magnet positions because it means two of the magnets next to each other will have the same polarity of field.