motor rotor magnets: I Finally Got My Pulse Motor Running at 3V

Hook

I finally got the pulse motor to spin cleanly using three motor rotor magnets. Three volts, 120 milliamps, and it took off. The induction coil underneath lit up with 4.1 AC volts just from sitting there. Then I pushed it to 9 volts and watched the numbers climb while I sorted out the Bedini wiring that had been confusing me for months.

Watch this experiment

I set the power supply at 3 volts and the current hovered around 120–130 mA. The three drive coils (16 gauge in front, 20 gauge on the sides) are wired in series. As the motor rotor magnets swing past they each get a solid kick and the rotor keeps turning. You can see the cap-bank LEDs flashing fast as energy moves between stages.

What you'll learn

You’ll see exactly how motor rotor magnets behave on a balanced rotor at low voltage, how much AC voltage an induction coil picks up from proximity alone, and why the common-ground connection matters so much when you add a charge battery. No theory overload, just bench measurements and what actually worked.

From the bench

The rotor is well balanced with good bearings so the magnets stay put even as speed builds. At 3 volts I measured 4.1 AC volts on the induction coil sitting directly under the drive coil. When I raised the supply to 9 volts the induction reading jumped to 26–28 volts while current sat between 1.03 and 1.15 amps. One of the coils is 26 turns, another 24; the bottom line looks like it will stay above 300 mA if I extend it. The multimeter jumped around too much on amps so I switched to the three-in-one scope meter. The cap bank fills and dumps quickly; the LEDs flash so fast it almost looks continuous.

How it works / what we changed

I finally nailed the Bedini hookup. The primary battery negative connects straight to the charge battery negative. Everything else follows the schematic I could barely read. Earlier I had the charge-battery negative going back to the emitter instead and that killed the negative spike. Once the negatives are paralleled the radiant spike shows up and the system starts charging. The three motor rotor magnets line up with the drive coils for a strong punch every rotation. I left the two rear coils and the three unused front coils out of the circuit for this test.

pulse motor

This whole build is a pulse motor. It runs on timed pulses to the drive coils instead of continuous current. The motor rotor magnets provide the moving magnetic field that interacts with the coil field. At 3 volts it already spins smoothly. I’m curious how much faster it will go once I add the Hall-effect or reed-switch timing and clean up the current draw.

Bedini SSG

We ran a proper Bedini SSG setup with primary and charge battery. Once the common ground was correct we saw the charging effect. The cap bank fills from the spikes and then dumps into the charge battery. It’s not massive current but it was charging at least a tenth to two hundredths of a volt per second in earlier runs. That felt like real progress after all the failed attempts.

pulse motor rotor

The rotor itself is the star here. Three motor rotor magnets spaced evenly give a solid punch every time they line up with the drive coils. Balance is excellent; the bearings are smooth and nothing has flown off yet. I keep thinking about adding more magnets or trying a different magnet orientation, but for now this simple three-magnet setup is working better than anything I tried before.

back emf

When the coils fire you get the back emf spike. That’s what charges the cap bank and eventually the second battery. In the wrong hookup the spike disappears. Once I connected the negatives in parallel the negative spike returned and the LEDs started flashing fast. That back emf is the whole reason these motors interest me.

induction coil

I stuck a big induction coil right under the drive coil. Even though the rotor isn’t spinning fast enough to push the field all the way through, the changing current in the drive coil still imprints on the induction coil. At 3 volts I read 4.1 AC volts. At 9 volts it climbed to 28–30 volts. A little voltage also comes from the passing magnets but it’s weak compared with the coil induction.

pulse motor coil

The drive side uses three 16-gauge coils in front and two 20-gauge coils, all hooked in series. That gives a pretty strong punch to the motor rotor magnets. I may need to bring in more of the spare coils because the current climbs fast at 9 volts. The induction coil underneath is a different gauge and turn count; it’s purely there to harvest the changing field.

neodymium magnets pulse motor

These look like neodymium magnets on the rotor. They’re strong enough to give a solid kick without needing huge current. The balance is good and they stay seated at speed. I’m still learning which pole orientation works best, but the current arrangement is already spinning the rotor nicely at low voltage.

pulse motor battery charging

With the correct Bedini common-ground connection the charge battery actually sees voltage gain. It’s not huge, but we were gaining at least 0.1 to 0.2 volts per second in the earlier tests. The cap bank acts as a buffer, filling from the spikes and then feeding the charge battery. That symbiotic transfer is what keeps me coming back to these experiments.

pulse motor rpm

I didn’t get a clean RPM reading because the multimeter was jumping all over on the sporadic signal. The rotor is clearly turning fast enough that the LEDs look almost solid. At 9 volts it definitely wants to go quicker; I’ll need better timing (maybe the signal generator or Hall sensor) and possibly more coils to keep the current from running away while chasing higher rpm.

Builder checklist

• Three motor rotor magnets spaced at 120 degrees on a balanced rotor
• Drive coils: three 16 AWG + two 20 AWG in series
• Induction coil placed directly under drive coil for proximity pickup
• Primary battery negative tied directly to charge battery negative
• Cap bank with visible LED flash to monitor energy transfer
• Multimeter or scope on induction coil to watch AC voltage
• Good bearings so magnets stay seated at speed

Troubleshooting

If you don’t see the negative spike, double-check that the charge-battery negative is paralleled with the primary negative. My earlier emitter connection killed the radiant energy. If current runs away at 9 volts, add more coils or lower the voltage. Sporadic amp readings usually mean the signal is too fast for the meter; switch to a scope or clamp meter. If the rotor won’t start, make sure the magnets line up with the coil cores at rest.

Safety

Running at 9 volts and over 1 amp means things can get warm. Keep an eye on coil temperature. The spinning rotor with strong neodymium magnets can pinch fingers if it grabs something metal. Use a proper power supply with current limit. Capacitors in the cap bank hold charge after power is removed; discharge them before touching. Always wear eye protection around spinning magnets.

FAQ

How many motor rotor magnets did you use? Three, spaced evenly. That gave a strong punch every rotation at 3 volts.

Why did the induction coil read 4.1 volts at only 3 volts input? The changing current in the drive coil imprints on the pickup coil through proximity even when the rotor isn’t screaming fast.

What fixed the Bedini charging? Connecting the two battery negatives together so they share a common ground. The earlier emitter-only connection removed the radiant spike.

Can this really charge a battery? In my tests we saw small but steady voltage gain on the charge battery once the hookup was correct.

Will it run faster at higher voltage? It definitely sped up at 9 volts but current also climbed; more coils or better timing will be needed to push rpm safely.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Bedini Motor & SSG Circuit Guide (Beginner Bedini Explained)
• Understanding Back EMF in Pulse Motors
• Best Neodymium Magnets for Pulse Motor Rotors
• Can a Pulse Motor Charge Batteries? What Experiments Show

Watch this experiment on YouTube

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