Reed Switch Pulse Motor: One Magnet, Magnetic Field Lines & More

Hook

I’m juggling a few projects right now and the one that’s got my attention is the Utron running on a reed switch. One magnet underneath is doing most of the work while I try to favor magnetic field lines over brute pull.

Watch this experiment

You’ll see the three-level disc spin smoothly on a 12-V battery, the Utron maglev rotor with four neo magnets, and a quick peek at the cactus that grew like crazy during a 4 kHz piezo test.

What you'll learn

How a single magnet can couple to a multi-magnet rotor, why slow startup helps, the difference between magnetic field lines and direct pull, and how tricky it is to nail the exact reed switch spot when everything keeps changing.

From the bench

Right now I’ve got the three-level discs with a pole in the back. The bottom disc carries 12 magnets. I’m planning 12 on the top disc too for stronger coupling but I’m taking it one step at a time. The Utron has four rectangular neodymium magnets arranged at 90°. I’m using a 7-mm reed switch in the north position and a 20-gauge coil. Power comes from a 12-V SLA battery and I may add a second. The whole thing is currently maglev.

How it works / what we changed

I start the rotor slow so it has a better chance of coupling at the half-inch gap I’m running. I could close the gap more but I want it to work more on the magnetic field than the physical pull of the magnet. There’s a difference in how those two feel and I’m favoring the field approach. The reed switch sits in the north slot of the 90° layout. I can move it around in that zone but hitting exactly the right spot is tough because coil resistance, battery voltage, and heat all keep changing.

One magnet

Right now one magnet underneath is doing all the action on the three-level disc. Even though the bottom has 12 magnets, a single magnet can drive the rotor if the coupling is strong enough and you start slow. Surface area matters and I’m looking for magnets that will couple properly in the vertical setup.

Magnet right there

The magnet’s right there on the Utron rotor. You can see the field extending out from it while I position the 7-mm reed switch. The reed reacts to that exact location and small movements change the timing drastically. I’m setting the range so I can tweak it without pulling the whole thing apart.

Magnetic field lines magnet

I’m trying to run this more on magnetic field lines than the actual pull of the magnet. There’s a terminology difference and I can feel it when the rotor spins. At half an inch the field does the work before the physical attraction takes over. That’s the zone I want to stay in while I dial in the reed switch.

Builder checklist

• 7-mm reed switch mounted in north position of 90° layout
• Four rectangular neodymium magnets on Utron rotor
• 20-gauge coil (option for three coils later)
• 12-V SLA primary battery (charge battery for true Bedini)
• Half-inch starting gap, slow rotor spin for coupling
• Magnets with enough surface area for vertical coupling on three-level disc
• Patience to find reed sweet spot while variables stay as constant as possible

Troubleshooting

If the reed switch triggers too early or late, move it within the north slot; small changes make big differences. Battery voltage drops before you lock in the perfect spot; keep a second SLA ready. Coupling feels weak; try slower startup or stronger surface-area magnets. Too many variables changing at once; stabilize battery voltage and coil temperature first. Rotor won’t stay maglev; check balance of the four neo magnets.

Safety

Use proper eye protection around spinning rotors and strong neodymium magnets. Reed switches can weld if current is too high; start low. SLA batteries can vent if over-charged in a Bedini setup; monitor voltage. Keep the cactus away from the spinning parts.

FAQ

Can one magnet really drive 12 magnets on the disc?

Yes, it’s doing the action right now. Strong coupling and slow startup help.

Why favor magnetic field lines over direct pull?

I can feel a difference and I want the rotor to spin more on the field at the half-inch gap.

How do you find the perfect reed switch position?

You get close by feel but exact magic spot is hard because voltage, heat, and coil resistance keep changing.

Do you need a charge battery for this?

True Bedini needs the SLA charge battery. I’m limited to two working ones right now so balancing is part of the experiment.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor vs Bedini Motor: What's the Difference?
• Using a Hall Effect Sensor in Your Pulse Motor Build
• Best Neodymium Magnets for Pulse Motor Rotors
• Magnetic Levitation on a Pole – Experiment 1

Watch this experiment on YouTube

• ▶ Watch full on YouTube