Counter-Rotating Device: Troubleshooting Resonance & Safety Relay Upgrade

Not every experiment goes smoothly — and that's exactly the point. In this video, Papa Bale takes us through the honest reality of running a complex counter-rotating device: things go wrong, resonance creeps in, and you have to figure out why. But he doesn't leave it there. By the end of the video, he's not just solved the immediate problems — he's revealed a serious hardware upgrade that will make the machine safer and smarter.

Component Reference: Counter-Rotating Device Build

The Counter-Rotating Device: What It Is and What It's Doing

The machine at the center of this video is a counter-rotating device — two rotors spinning in opposite directions, driven by separate circuits. Papa Bale is running it at 3.72V at the time of filming, with the system charging into a 5.5V parallel 20-farad supercapacitor bank. The goal is to accumulate DC voltage in the supercaps through proximity induction.

The induction mechanism uses a trifiler coil wound with 28-gauge strand, connected in series and feeding a bridge rectifier. The rectifier converts the AC-like pulsed output from the coil's proximity to the spinning rotor magnets into DC voltage, which then charges the two parallel supercapacitors. It's an elegant approach to harvesting rotational energy without brushes or direct electrical contact — purely through magnetic proximity.

The Problem: Resonance and Humming

When Papa Bale hooks up all the capacitor banks, the system starts to resonate. There's an audible hum — and that hum gets louder with each additional circuit added. Each new element steps up the resonation further. It's not catastrophic; the system still works, the caps still charge, and the voltage continues to climb. But the hum is a symptom of something worth understanding and ideally fixing.

Isolating the cause takes some experimenting. When the cap banks are disconnected and only two drive circuits are running, the device operates cleanly — except for the green circuit, which resonates on its own. This tells Papa Bale the resonance has at least two sources: the interaction between the capacitive load and the coil's natural frequency, and an inherent resonance issue specific to the green circuit's tuning.

He tests using three 12V batteries to saturate the 28-gauge trifiler strand through the bridge rectifier, driving the charging harder. Even under these conditions, the voltage climbs steadily — reaching 4.07V and heading toward the supercap bank's 5.5V capacity ceiling. So the resonance is an annoyance, not a dealbreaker.

Circuit Comparisons: Red, Black, and Green

Papa Bale does something instructive here: he tests each drive circuit individually to compare their behavior. The red circuit runs "nice and smooth, quiet" — almost no resonance, clean operation. The black circuit is even better — "extremely smooth," his words — and functions with minimal vibration. The rotor shaft itself is solid during both tests, with only natural resonant vibration (the kind present in any rotating mechanical system) rather than the problematic electrical resonance.

The green circuit, by contrast, resonates even in isolation. This is useful diagnostic information: it means the fix for the green circuit is likely a component-level or timing adjustment, not a fundamental architectural problem. Papa Bale doesn't panic. He documents it and moves on to the larger point of the video.

The Upgrade: Latching Relay, Infrared Sensor, MOSFET, and PCB

Here's where the video shifts from troubleshooting to forward engineering. Papa Bale reveals a set of components he's planning to integrate into the machine: a 12V latching relay, an infrared sensor and receiver, a MOSFET, and a purpose-built PCB board.

Together, these components will form an automatic power-cut safety mechanism. The infrared sensor will monitor the rotor's speed. When the machine reaches a speed threshold — the point where continued acceleration could be dangerous — the sensor triggers the MOSFET, which activates the latching relay to cut power automatically. The latching design means the relay stays in the off position until manually reset, rather than cycling on and off continuously.

This is a genuinely important safety feature. As Papa Bale's counter-rotating device gets more efficient and better tuned, it will naturally want to spin faster. Without a speed limiter, a loose magnet (like the one he's been cautious about in previous videos) could become a projectile. The infrared cutoff addresses this risk directly — it's the kind of safety engineering that separates a well-thought-out experimental build from a dangerous one.

Why This Video Matters

There are two kinds of build videos: the polished demos where everything works perfectly, and the real ones where problems surface and get solved in real time. This video is the second kind, and it's far more valuable for it. Papa Bale doesn't edit out the hum. He doesn't skip past the resonance. He documents it, tests it, and shares what he learns — and then caps it off with a hardware upgrade that meaningfully improves the machine.

If you're building multi-circuit pulse motor systems or exploring supercapacitor charging through proximity induction, this video is required watching. The resonance behavior Papa Bale encounters is something you'll almost certainly run into yourself, and his systematic approach to isolating it is a model for how to troubleshoot complex electromagnetic systems.

Deep Dive: How Proximity Supercapacitor Charging Works

The elegance of the supercapacitor charging mechanism in this build deserves more explanation. Traditional motor energy harvesting uses brushes or slip rings to extract electrical energy from a spinning rotor. These introduce friction, wear, and complexity. Papa Bale's proximity approach eliminates all of that — the coil simply sits close to the spinning rotor magnets without touching, and the rapidly changing magnetic flux induces a voltage in the coil by Faraday's law of induction.

Because the induced voltage alternates as each magnet pole passes (first north, then south, then north again), it can't directly charge a DC capacitor. The bridge rectifier solves this — it converts the alternating pulse polarity into a consistent DC output. Four diodes arranged in a bridge pattern ensure that regardless of which direction the induced voltage swings, the current always flows in the same direction into the supercapacitor.

Supercapacitors (also called ultracapacitors) are ideal for this application because they can accept rapid charge pulses — unlike chemical batteries, which need time for ion diffusion. A 20-farad bank at 5.5V can store 0.5 × 20 × 5.5² = 302 joules, which is a substantial amount of energy for a bench experiment. Papa Bale's 4.07V charge level in the video represents about 166 joules — meaningful stored energy from purely inductive coupling.

Electromagnetic Resonance: What Causes It and How to Suppress It

The resonance hum Papa Bale encounters is a classic interaction between inductance and capacitance in a circuit — an LC resonance. Every coil has inductance (L) and every capacitor bank has capacitance (C). When connected, they form an LC tank circuit that wants to ring at a natural frequency determined by f = 1/(2π√LC).

If the motor's pulsing frequency happens to be near this natural resonant frequency, the circuit rings loudly — the audible hum Papa Bale hears. Solutions include: adding resistance to dampen the oscillation (at the cost of efficiency), changing the capacitor bank size to shift the resonant frequency away from the operating frequency, or adjusting the motor speed to move the drive frequency away from resonance.

The green circuit's independent resonance suggests it has a different LC product than the red and black circuits, possibly due to different coil winding or a component value variation. This is common in hand-built systems. The diagnostic approach Papa Bale uses — isolating each circuit to find the resonant culprit — is exactly the right methodology.

Common Mistakes When Building Counter-Rotating Systems

Mismatched circuit timing: If the two counter-rotating circuits fire at slightly different rates, they'll periodically beat against each other, creating both mechanical and electrical resonance. Identical circuit components and matched coil positions help prevent this.

Unshielded coil leads near IR sensors: The magnetic fields from drive coils can interfere with infrared proximity sensors if the leads run parallel and close together. Route coil wires away from sensor circuits or use shielded cable for sensor leads.

No flyback protection on relay coils: When a relay coil de-energizes, it produces a voltage spike that can damage MOSFETs. Always include a flyback diode across any relay coil driven by a transistor or MOSFET — a small detail Papa Bale's PCB layout should incorporate.

Supercap polarity: Supercapacitors are polarity-sensitive. Reverse-connect them even briefly and you risk damage. The bridge rectifier in Papa Bale's circuit helps, but double-check polarity markings during initial assembly.

Frequently Asked Questions

More on This Topic

Related experiments and concepts from Papa Bale's pulse motor research:

• 26AWG litz wire pickup coil achieving 220mA — proximity induction output measurement
• How back-EMF recovery works in Bedini-style pulse motor circuits
• Budget trifiler coil winding for pulse motor drive circuits
• Bridge rectifier explained: converting pulsed coil output to DC
• MOSFET switching in pulse motor safety and trigger circuits
• Trifiler coil construction for supercapacitor charging applications