Coil Inside Pulse Motor: Trifecta Wave Coil on Stator Adds Speed

Hook

I finally got a coil inside the main set circuit on the stator of my pulse motor and it made a huge difference in how fast everything spins. The trifecta wave coil sits right in there with the trigger and you can hear the squeak when it's working.

Watch this experiment

I started the pulse motor at 2.16 volts. Both motors caught and you could hear the little squeaking coming from the trigger coil inside. Turned it up to 8.61 volts and the smaller 2222-turn coil really got the big rotor flying. The flywheel effect on that nine-magnet rotor is wild — it kept spinning for 40-50 minutes after I cut the power.

What you'll learn

How a trifecta wave coil performs when placed inside the set circuit, why the squeak tells you it's triggering correctly, and how the smaller high-turn coil helps ramp up speed once the big coil gets the rotor moving. All straight from the bench with real voltage numbers.

From the bench

All my coils are wound counterclockwise. The trifecta coil is wired in series and feeds the TIP142 transistor on the breadboard. I'm using 100 ohm 5% tolerance resistors — they blow out now and then but swapping one brings it right back. The rotor has nine magnets at 40° separation and that seems to give it better flywheel action than the toroid magnet version. I ran out of 18 gauge wire so the next one might be 14 gauge.

How it works / what we changed

The two trigger coils are separate from the three coils they're triggering. You only need a set and an offset trigger. I ran the trigger coil inside the main coil and when you get the voltage right it makes that squeaky noise. At 2.16 volts both pulse motors started turning. I turned it up to 8.61 volts and the little coil with 2222 turns started squeaking louder and really accelerated the big rotor. The nine-magnet rotor at 40° separation has fantastic coasting — 40-50 minutes of slow spin after power off.

fan coil

The fan coil is the smaller one with 2222 turns. It sits on the stator and makes most of the squeaking noise. Once the big trifecta coil gets the rotor up to speed, the fan coil kicks in harder and you see a serious jump in rpm. It seems to be the one that really drives the final speed even though the big coil does the heavy lifting to get it started. I noticed the fan coil is what makes the whole thing take off once it's triggered properly.

Builder checklist

• Two separate trigger coils (set and offset)
• Trifecta wave coil wired in series to TIP142 transistor
• 100 ohm 5% resistors on the breadboard
• All coils wound counterclockwise
• Nine magnets on rotor at 40° separation for best flywheel
• Trigger coil placed inside the main coil for squeak feedback
• 18 gauge or 14 gauge wire for the power coils

Troubleshooting

If it won't start, check the resistors — they blow periodically. Swap the bad one and it usually fires right up. Make sure the trigger coil is sitting inside the main coil and you hear the squeak; no squeak usually means no triggering. If speed won't increase, the little 2222-turn coil might not be getting enough rpm from the big coil yet. Balance the rotor dead center or it will shake the table.

Safety

These circuits can pop resistors and transistors. Keep voltages low when you first test — I started at 2.16 V. Watch for hot components on the breadboard. The spinning rotor with strong magnets can pinch fingers if you're not careful. Always disconnect power before swapping parts.

FAQ

Why does it squeak? That's the trigger coil inside the main coil picking up the magnetic field and switching the transistor fast. More voltage makes it louder.

How long does the rotor coast? The nine-magnet rotor at 40° keeps turning 40-50 minutes after power is removed.

Can I chain the coils? I think wiring them so the first charges the second and so on could make it run longer without extra input, but I haven't tested that yet.

What gauge wire next? I'm out of 18 gauge so the next trifecta coil will probably be 14 gauge.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Best Wire Gauge for Pulse Motor Coils (AWG Guide)
• Pulse Motor vs Bedini Motor: What's the Difference?
• How to Wind Coils for a Pulse Motor (Step by Step)

Watch this experiment on YouTube

• ▶ Watch full on YouTube