I Finally Got My Pulse Motor Running with a 180 Degree Rotor

Hook

I ditched the trigger coil and went with two reed switches on my motor 180-degree rotor. The waveform got choppy but that chop is torque and the spikes look promising for flyback charging.

Watch this experiment

I fire up one circuit first so the rotor can settle, then flip the second. You can see the oscilloscope switch from a saw-blade induction wave to sharp spikes the moment both circuits are active. Turning one circuit off makes the spikes disappear and the wave widens as the rotor slows.

What you'll learn

How reed switches behave differently than a trigger coil on a pulse motor, what 10-38 V flyback spikes look like on the scope, why a 180 degree rotor helps separate drive and charge phases, and the weird little bearing I added under the rotor for extra spin.

From the bench

All my coils are one-of-a-kind: 20 gauge with exactly 666 turns and 30 gauge wound parallel but counterclockwise. The 30 gauge strand on one coil broke at the seam but there was still enough to use. I ran the whole thing on a 24 V 20 A power supply first, then switched to two 12 V batteries. A T-Energy charger sits nearby in case the flyback charging doesn't keep them topped up.

How it works / what we changed

The reed switches give a much choppier signal than the old trigger coil but that chop equals torque. Once both circuits are on you see clean flyback spikes instead of the magnetic induction wave. I added a toggle switch and diodes on each 30 gauge strand so the coils can charge each other's batteries in parallel. The 180 degree layout is key: when one reed is closed the opposite coil is not under load so its battery can accept the spike.

motor 180 degree rotor

I built this around a motor 180 degree rotor with magnets spaced 180 degrees apart. That spacing lets one reed switch fire while the opposite coil sits in the float zone. The result is drive on one side and charging opportunity on the other without fighting the battery at the same time. I ran it on 12 V and 24 V; the spikes get stronger and gap-free at 24 V.

180 degree rotor reed

The 180 degree rotor reed timing is what makes the flyback loop possible. When this magnet hits one reed the opposite coil is not being energized so its battery can take the spike through the diodes. I saw the waveform switch instantly from a spiky saw blade to sharp 10-38 V peaks the moment the second circuit joined in.

degree rotor reed switches

These degree rotor reed switches are mounted so each controls its own drive coil and battery circuit. They produce a less smooth but much torquier pulse than a trigger coil. When I kill one switch the rotor slows, the spikes mellow into a wider wave, and the scope shows fewer events per rotation. I still need to add the final toggle and diode orientation but the bench test already looks promising.

Builder checklist

• 180 degree magnet rotor on a good low-friction bearing
• Two reed switches timed 180 degrees apart
• Two independent drive coils (20 ga 666 turns + 30 ga parallel)
• Separate 12 V battery per circuit with toggle switch
• Diodes on each 30 ga strand facing the battery to pass flyback
• Oscilloscope hooked to watch spike vs wave behavior

Troubleshooting

Scope readings went weird until I noticed a clip had come undone on the probe. After fixing it the spikes showed up between 10-38 V. If your waveform looks off, double-check every connection and try cycling power. The rotor sometimes needs a few seconds to settle after starting one circuit.

Safety

Use proper diodes rated for your spike voltages. Keep batteries fully charged before testing. Watch for heating in the 30 gauge strands. Always use an on-off switch so you can kill power instantly. I laughed when I said it would run forever but these batteries do last a long time even without charging.

FAQ

Why is the waveform so choppy? That's the reed switches. They give torque instead of the smooth trigger-coil feel.

How big are the spikes? I measured 10 to 38 volts peak-to-peak on this setup. Bigger at 24 V.

Will the batteries charge each other? That's the plan. The 180 degree rotor reed timing should let one coil's flyback charge the other battery while its own circuit rests.

What if the 30 gauge wire breaks? I had enough left on the broken coil to keep testing. You can always wind another but this one still worked.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Placement & First Spin
• Pulse Motor: What It Is & How It Works (Beginner Guide)
• Understanding Back EMF in Pulse Motors
• Can a Pulse Motor Charge Batteries? What Experiments Show
• Pulse Motor Rotor Design: Magnets, Materials and Balance

Watch this experiment on YouTube

One soft line only — site UI owns subscribe/membership.

▶ Watch full on YouTube