I Finally Measured Eddy Currents in My Pulse Motor Setup

Hook

I wanted to see eddy currents without building a whole new spinning-disc AC generator, so I kept the aluminum disc stationary on top of my pulse motor and spun the magnets underneath instead. The pickup coils gave small but measurable voltage and the results felt like a win.

Watch this experiment

I set up an axial flux style pulse motor with a stationary aluminum disc on top and two coils positioned just out of the main magnetic field but in range of the eddy current fields. We measured voltage with the disc in place, removed it, added a plastic spacer, and tried different rotor magnets. The disc stayed mostly steady while the magnets spun below.

What you'll learn

You’ll see real bench readings from 0.7 V up to about 3 V depending on air gap and coil position. We talk about how the aluminum yokes the permanent magnets, why moving the coils to the edge increases voltage, and what happens when you flip the drive coil orientation to get the motor running smoothly.

From the bench

The motor uses a mix of 32 gauge, 26 gauge, 22 gauge and 20 gauge wire. The pickup coils are 32 and 26 gauge wired in series, going through a bridge rectifier because the voltage is AC. One test lit a small LED through a random resistor I found on the table. The drive side is a tri-coil arrangement and I had to flip the whole thing around so the power went into the table instead of the wrong direction.

How it works / what we changed

Instead of spinning the aluminum disc I kept it fixed and spun the magnets below it. That creates changing magnetic fields that induce eddy currents in the stationary disc. The coils pick up a small induced voltage from those currents. I swapped the big magnets for a six-position Fate magnet rotor that ended up running on three poles. I also removed the blue 3D-printed part to bring everything closer. The disc has a tiny bit of movement but the blue tape marker shows it stays pretty steady.

Aluminum disc pulse motor

I tried an aluminum disc pulse motor approach by holding the disc stationary on top of the spinning magnet rotor. With a quarter inch of aluminum between the magnets and the coils we still saw voltage, though it was low. When I removed the disc and replaced it with a 1/16 inch plastic spacer the output jumped because we lost the yoking effect of the aluminum. The disc itself stayed mostly still while the magnets moved underneath, which felt easier than building a whole new spinning-disc rig.

Pickup coil eddy current

My pickup coil eddy current setup used two coils (32 and 26 gauge) wired in series, resting on top of the aluminum or the plastic spacer. We measured roughly 0.7 V with the disc in place and up to 1.5 V when I dragged the coils over the edge. Without the aluminum the reading climbed to about 3 V at the closer gap, showing the magnets were contributing more than I first thought. Even at 0.007 V in one configuration I still counted it as a win because the coils were clearly reacting to the moving field through the disc.

Builder checklist

• Stationary aluminum disc (about 1/4 inch thick) mounted above magnet rotor
• Two pickup coils (32 ga + 26 ga) in series, placed just outside direct magnet field
• Bridge rectifier on pickup output because voltage is AC
• Fate magnet rotor or similar, running on three poles instead of six
• Drive coil flipped so power flows in the correct direction
• Plastic spacer ready for comparison tests
• Multimeter or scope to watch voltage while adjusting coil position toward the edge

Troubleshooting

If voltage is almost zero, check that the coils are not too far from the eddy current field. I had to flip the drive coil orientation because all the power was going into the table instead of driving the rotor. When the magnetically inclined clips interfered I swapped to a different rotor. If the disc wobbles too much, tape it lightly to keep it steadier while still allowing minimal movement. Low readings like 0.007 V can improve by moving coils to the outer edge or reducing the air gap.

Safety

Keep fingers clear of the spinning rotor and magnets. The voltages here are low but the circuit still uses a bridge rectifier and capacitors in some tests. Watch for hot coils on the drive side. Always unplug power before moving wires or changing the rotor. The hex nuts are small; make sure they are tight so nothing flies off.

FAQ

Is the voltage really from eddy currents or just the magnets?

Both play a part. With the aluminum disc in place and a quarter-inch gap the yoking effect is strong and we saw about 0.7 V. Removing the disc and closing the gap gave roughly 3 V, so the magnets contribute more than I first assumed. Still, the difference when the disc is present points to eddy currents doing work.

Why is the output so low?

We used thin 32 and 26 gauge wire with a modest number of turns. The coils sit just out of the strongest field on purpose. Moving them farther over the edge raised the reading to 1.5 V, but the whole setup was more about proving the concept than making usable power.

Can this charge a capacitor?

I thought about feeding the rectified output to a capacitor but the voltages stayed too small in most tests. The LED lit through a random resistor, so there is real current, just not a lot.

Does the disc have to spin?

In this build I kept it stationary on purpose. It does move a tiny bit but the blue tape shows it stays mostly fixed while the magnets spin underneath. That made the experiment simpler than building a full spinning-disc generator.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Best Wire Gauge for Pulse Motor Coils (AWG Guide)
• Pulse Motor vs Bedini Motor: What's the Difference?
• DIY Magnetic Induction Motor: Hobbyists in 2026

Watch this experiment on YouTube

• ▶ Watch full on YouTube