I Put One Magnet in the Center to Run My Pulse Motor (N/S Array)

Hook

I wanted north south array of magnets on the outside — six north, six south alternating — but my pulse motor wouldn't run it. The suggestion was put one magnet in the center and use a stick to adjust the RPMs. That's exactly what I did and it worked.

Watch this experiment

The rotor now spins with six inner magnets of the same polarity timed to the outer ones. Instead of twelve hits it's six stronger hits and the whole setup feels smoother.

What you'll learn

How a single central magnet can trigger a reed switch for an alternating N/S array, why an aluminum core makes the drive coil gentler, and how three 120 degree generator coils behave when you first fire the motor up.

From the bench

I used a bifilar coil with a 13 inch aluminum core on the drive side. The aluminum is added last — it's the finishing piece. I only had this size core that fit my bobbin so that's what we got. The goal was just enough kick to get rotation without a ton of extra flux.

How it works / what we changed

Previously I had twelve same-polarity magnets on the inside. Now it's six, timed under the reed switch with the outer alternating magnets. The central magnet on a stick lets me adjust position easily. When I gave it power the rotor took off right away. The light on the bench blew out but the motor kept going.

North south array

The outer ring is six north and six south alternating. That was the predicament. With the central magnet and reed switch it now fires at the right intervals so the drive coil pushes at the correct times. It feels completely different from the old all-same-polarity setup.

Reed switch

The reed switch sits above the rotor and the six inner magnets pass under it. Each inner magnet matches the polarity of the outer one at that moment. Six hits instead of twelve means stronger pulses and simpler timing. I can tweak the stick to fine-tune RPM without holding anything by hand.

Aluminum core

We used aluminum for the drive coil core because we don't want a lot of magnetic flux. It closes the field and gives a smooth ride. The core is added last to the coil, not first. I haven't cut the big core yet but I'm thinking about sawing it into shorter pieces for even faster spins.

120 degree coil

All three generator coils are wound 120 degrees apart and clockwise. The first is 34 gauge with 5000 turns per coil. Next is 32 gauge and then 14 gauge for the amps. I marked front and back on each. Polarity isn't fully checked yet but I plan to test it by running the motor and watching if it helps or hurts RPM.

Pulse motor generator

This setup is now a pulse motor generator. The drive circuit uses the reed switch and the three 120 degree coils act as generator phases. I'm testing what each circuit puts out alone, in series, and in parallel after bridge rectifying. The 14 gauge especially should give interesting readings once it goes through a capacitor and feeds back.

Magnet array on rotor

The rotor carries the alternating north south array on the outside plus the six inner magnets. The central magnet on the adjustable stick completes the timing. It replaced the old twelve-magnet inner ring and now everything moves with six hits. The makeshift stick holder works great and I can turn it while running.

Bedini

This is very much in the Bedini style — reed switch, drive coil, generator coils, and thinking about dumping energy back. I used to have one drive coil and eleven generator coils but switched to three-phase 120 degree layout for better control. Might even add switches between phases later.

Coil winding

The 34 gauge circuit has 5000 turns in each coil, all clockwise. The other two phases are 32 gauge and 14 gauge. I haven't measured exact turns on the heavier wires yet. All coils are marked front and back. The aluminum core slides in last on the drive bifilar. I'm still deciding how to connect the finish ends — one-two-three then parallel or series into the bridge rectifiers.

Builder checklist

• Rotor with 12 outer alternating N/S magnets
• Six inner same-polarity magnets timed to outer
• One central magnet on adjustable stick for reed switch
• Bifilar drive coil with aluminum core added last
• Three 120 degree generator coils (34ga 5000 turns, 32ga, 14ga)
• Reed switch positioned over inner magnets
• Bridge rectifiers ready for each phase
• Capacitor for possible dump back to drive circuit
• Multimeter and scope for polarity and output checks

Troubleshooting

If the motor runs worse after adding a coil, the polarity is probably backwards. You can tell right away without extra tools. Light load on the bench can blow bulbs when the rotor spins fast. The aluminum core keeps things from getting too sticky. If timing feels off, just nudge the stick that holds the central magnet.

Safety

Watch for spinning rotor — keep fingers clear. The reed switch can get hot if current is too high. Capacitors hold charge after running so discharge them before touching. The 14 gauge coil might produce higher currents than expected once rectified. Always start with low voltage on a new configuration.

FAQ

Why put one magnet in the center? It lets the reed switch fire at the exact intervals needed for the alternating outer array without needing twelve inner magnets.

Does the aluminum core reduce power? Yes, on purpose. We want a smooth gentle kick instead of strong flux for this experiment.

Can I use different wire gauges? Absolutely. I'm testing 34ga, 32ga and 14ga to see what each phase produces alone and together.

How do you connect the three phases? Still figuring that out on the bench. Bridge rectifying each then deciding series or parallel dump back to the drive circuit.

Will it charge batteries? That's the next test once we get clean output through the capacitor.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Using a Hall Effect Sensor in Your Pulse Motor Build
• Best Neodymium Magnets for Pulse Motor Rotors
• I Finally Got My Pulse Motor Running (Reed Switch)
• 24-Node Magnet Array Pulse Motor — Single Solenoid Design

Watch this experiment on YouTube

• ▶ Watch full on YouTube