I Finally Got My Reed Switch Motor Running (With Big Transistor Self-Runner Tests)

Hook

I spun the 8-coil rotor as a reed switch motor self-runner and the cog when the drive coil passes those neodymium magnets is wild. One coil driving everything, counter rotating magnets to test both directions, and a big transistor instead of the usual tiny reed switch — here’s exactly what happened on the bench.

Watch this experiment

I fire the rotor by hand while the 9V battery is connected and you can instantly see it counter rotate and try to keep going once I let go. The same thing happens without the battery but it slows down faster. Every time the drive coil passes a magnet you get this pronounced physical kick — boom, boom, boom.

What you'll learn

You’ll see how one coil can interact with all the rotor magnets in a Bedini-style setup, why counter rotating magnets helps test self-running, and how drive coil passes feel when you’ve only got a single drive coil active. Plus the difference between a big transistor and the cheap little reed switches I usually use.

From the bench

This is my eight coil rotor. Every coil has part of it on the generator half. Three bridge rectifiers: one for the 26, one for the 30, and one shared for the 28 and 32 gauge wires. The drive coil is 28 gauge plus a 26 gauge trigger strand. Everything rectifies into a cap bank made of 9400 microfarad 50V caps plus an 11V 10 farad supercapacitor. The 9V battery also feeds that same cap bank through a diode. The rotor has four magnets on it right now and it’s heavy, lopsided, and wobbles a bit.

How it works / what we changed

I’m using a Bedini setup on the drive coil. There’s a diode on the green breadboard that seems to help but I couldn’t remember exactly where it was connected. Earlier experiments with a reed switch let it spin a lot longer. The big transistor needs more juice so it doesn’t run as long on the cap bank. I spin it outside first, then inside first to get counter rotation going. When everything slows down you can see the cogging and the lens kick in at the same time.

Counter rotating magnets

I deliberately spin the rotor several different ways — outside first, inside first — so the counter rotating magnets show how the setup reacts in both directions. With the 9V connected it instantly counter rotates and tries to keep spinning from the cap bank. Without the battery it still tries but slows down quicker. You can see it trying to work; it definitely wants to self-run but the heavy rotor and transistor draw make it tough.

Drive coil passes

I keep my hand on the rotor at first so I can feel exactly when the drive coil passes by a magnet. It is very pronounced. You get a really strong cog every time the drive coil passes the neodymium magnets. On camera you see the rotor jump and hear the boom-boom-boom as it cogs. That single drive coil is passing all six magnets and the physical feedback is unmistakable.

One coil

There’s only one coil on here that’s a drive coil. I did that so it could interact with all six. You can see how it’s kind of just one coil — four magnets on the stator at the moment and it still picks up and tries to run. The power going through that single coil is obvious; it’s rudimentary but it works. The generator strands (26, 28/32, 30) each have their own bridge rectifier feeding the cap bank separately.

Builder checklist

• 8-coil rotor with one dedicated drive coil (26ga trigger + 28ga drive)
• Three bridge rectifiers feeding a shared cap bank
• 9400µF 50V caps plus 10F 11V supercapacitor
• 9V battery connected through diode to the cap bank
• Four neodymium magnets on rotor for initial tests
• Stable stator preferred — mine wobbles so self-running is harder
• Reed switch vs big transistor — reed switches run longer on same bank

Troubleshooting

It doesn’t spin as long with the transistor as it does with the little 7mm reed switches. I’m guessing the reed switch costs a lot less to run. The rotor is heavy and lopsided so it wobbles; a stable stator would help. Cogging is strong but once speed drops the back-emf lens kick and cog happen together. If it won’t self-run, try counter rotating magnets both ways and check diode placement on the breadboard.

Safety

Big cap banks hold charge even after power is removed. The 10 farad supercap and 9400µF banks can deliver serious current. Watch your fingers around the spinning rotor — those neodymium magnets and the strong cog can pinch. 9V battery is low voltage but still treat all connections carefully.

FAQ

Why does the reed switch version run longer?

The tiny 7mm reed switches are very inexpensive to run compared with the big transistor.

Can one coil really drive all the magnets?

Yes — in this test the single drive coil interacts with all six magnets and you can see it pick up and counter rotate on its own.

What are drive coil passes like?

Very pronounced physical cog you can feel by hand and see on camera every time the coil passes a magnet.

Do you need the 9V battery?

It helps get it spinning faster but the cap bank alone will still show counter rotating magnets and cogging once it slows down.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Bedini Motor & SSG Circuit Guide (Beginner Bedini Explained)
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Which Transistor for Your Pulse Motor? (2N3055, TIP31, and More)
• I Finally Got My Pulse Motor Running (Reed Switch)
• Counter-Rotating Device: Troubleshooting Resonance & Safety Relay Upgrade

Watch this experiment on YouTube

• ▶ Watch full on YouTube