Perpetual Spinning Top

This project was inspired by the spinning top from the film Inception; ever since watching the film, I have wanted a top that spins forever. While there are many commercial perpetual tops, I was not happy with any of them. They require power cords, noisy mechanisms, or large bases that destroy the illusion.

In this Instructable, I will show you how to build my perpetual top design that is nearly silent, wireless, and has a base that is only 10mm thick.

Hidden inside the ordinary-looking display base is an electromagnetic circuit and a battery that keep the top spinning. The base is powered by a long-range induction charger under the desk, meaning no visible wires, ports, or switches. When placed on the base, the top will spin indefinitely with the wireless charging and for around 4 days on battery.

How It Works

The system relies on a pulse-feedback circuit (a concept popularized by John Bedini and vintage electromagnetic motor toys):

1. The Top: The top houses a powerful N52 neodymium magnet, and it spins on an ultra-low-friction ceramic silicon nitride bearing ball tip to minimize mechanical drag.
2. The Sensor & Driver: Hidden beneath the concave surface of the base is a custom dual-wound electromagnet containing two concentric coils: a pickup (sensing) coil and a drive coil.
3. The Kick: As the spinning top spins over the base, its rotating magnet induces a tiny voltage spike in the pickup coil. This tiny spike triggers a high-gain BC517 Darlington transistor, which instantly dumps a pulse of current from the battery into the drive coil.
4. Perpetual Motion (Almost): The resulting magnetic pulse delivers a micro-kick to the top's magnet at the exact right millisecond of every revolution—replacing the energy lost to air resistance and surface friction.
5. Power: A thin 5W wireless charging receiver sits inside the base. An under-desk charger mounted below the tabletop continuously keeps the internal 1000 mAh battery topped off through up to 20 mm of solid wood.

I'm working on a YouTube video to show the working principle in more detail, and will add a link to it once it's finished.

Current Issues

The wireless charging board and the battery charging board get very hot during charging (around 90 C), fotunalty they only heat up when charging the battery after it's discharged, so during continuous operation with the wireless charging, everything stays at a safe temperature. The only way I see to fix this is to create a custom pbc that handles everything, but I don't know how to make a PCB that complex.

More information about the project can be found on my website

All files can be found on the project's Thingiverse page: https://www.thingiverse.com/thing:7414257

Electronics

x1 523450 1000mAh Battery (5.2 mm thick × 34 mm wide × 50 mm long)

x1 TP4056 Step-up Boost Battery Charger

x1 5W Wireless Charger Receiver

x1 Under-desk Wireless Charger (40mm range)

0.31 mm Magnet Wire

Silicone Wire

Hardware

x1 7/16 x 1/4 Inch N52 Magnet (Axially magnetised)

x1 Ferrite Sheet

x1 3/16" Ceramic Silicon Nitride Bearing Balls

1 mm Steel Wire

Other

PVA/School Glue

Superglue

Hotglue

Paint

x1 Filler Primer

x1 Light Brown Spray Paint

x1 Brown Alcohol Ink Set

x1 Chip Bristle Paint Brush

x1 Satin Clearcoat

Black Paint

PCB

x1 Custom PCB

x1 BC517 Transistor

x1 10k resistor

3d printed parts

x1 Inception Top - Top Lower

x1 Inception Top - Top Upper

x1 Inception Top - Base Upper

x1 Inception Top - Base Lower

Tools

Soldering iron & solder

3D printer & filament

Wire strippers/flush cutters

Sandpaper (220, 400, 800+ grit)

Multimeter (to verify coil continuity and output voltage)

Lighter or craft knife (for stripping magnet wire enamel)

The electromagnet can be wound with a drill or any motor that can spin slowly; you just need to adapt the spool to work with your motor. I set up a simple coil winder for my motor, which you can find here, along with the files for the spool: https://www.thingiverse.com/thing:7414258

Place some thin, smooth plastic, like transparency sheets, over the spools to prevent them from getting stuck to the coil.

Assemble the two spool sections using the steel wire to connect them, leaving a 4mm gap between them.(You can print an extra Spool_Side_2 to use as a spacer)

Place the end of the magnet wire through the first hole on the spool.

Wind the magnet wire around the spool as neatly as possible until the spool diameter is just over 30 mm.

Take about 8 inches of wire, fold it in half, and feed it through the center hole on the spool, then keep winding.

When the spool reaches a final diameter of just under 40mm cut the wire and feed the end through the third hole on the spool.

Coat the outside circumference of the electromagnet with PVA glue.

Once that glue dries, remove the spools. Then, one side at a time, carefully remove the protective plastic so the electromagnet does not come undone, Coat the face of the electromagnet in glue, put the plastic back on, and place something heavy on it.

Once the coil is finished, cut the loop we fed through the second hole in the spool.

Download the Gerber files from the project's Thingiverse page and upload them to any PCB service like JLCPCB or PCBWay and select a 2-layer 1.6 mm board.

Solder the resistor and transistor to the PCB as shown, ensuring the transistor has its flat side facing away from the board.

Wire everything up according to the diagram.

Be sure to strip the enamel off the last 1/2in. of all 4 electromagnet wires.

The wireless charger connects to the IN+ and IN- pads on the underside of the battery charger board.

Pads 1 and 2 on the PCB connect to the larger inner coil in the electromagnet, and pads 3 and 4 connect to the outer coil.

Test whether the circuit keeps the top spinning, and adjust the potentiometer on the battery charging board to set the power of the spin.

If your top slows down or gets actively stopped when spinning over the base:

Ensure the battery is charged

Make sure the battery charging board's potentiometer is turned up

Check your wire connections

Make sure the magnet wire is making a proper connection (it must have the enamel stripped off)

If you can hear or feel the electromagnet pulsing when you bring the top near it, but the top stops spinning, the coil polarity is inverted: Swap the connections for Pad 3 and Pad 4 (or Pad 1 and Pad 2) to reverse the phase.

Print all of the parts from the Thingiverse page

For the Top Upper and Top Lower, use 100% infill and a fine layer height

For the Base Lower, use a first layer height of 0.24 mm, or first layer + layer height * n = 0.24. n = an arbitrary number

For the Base Upper, print at as fine a layer height as you can with no supports, and follow the same layer height rule as Base Lower

Assemble the two halves of the top around the magnet and superglue them together. Try to get the gap between the two halves as small as possible.

Place all the components in the base and route the wires through the channels.

Place a layer of ferrite sheet over the charging coil, and add as many layers of ferrite as you can fit under the electromagnet.

Add a small drop of hot glue to each component to prevent it from rattling.

Before you seal it up, add a way to identify the location of the charging coil after the base is assembled. I added a small black line above it that slightly shows through the paint.

Place the Base Upper on and twist to lock it in place; optionally, add a dab of superglue.

Coat the assembled base and top with filler primer, then sand smooth, and repeat until the surface is free of lines or divots. Ensure the top dished side of Base Upper is as smooth as possible to reduce friction with the top. I have found that very heavy coats of filler primer work best.

Paint the top with black or dark grey paint, taking care to keep the surface smooth. Try to avoid getting paint in the hole at the bottom where the ceramic ball will go.

I chose to paint the base in a wood effect; the easiest way to achieve a wood effect is done by applying a base coat of light brown and then brush on alcohol inks. See this video for a more detailed explanation of the technique: https://www.youtube.com/watch?v=5NBW7uJnJGo

Clearcoat both the top and base to protect them from scratches. Any clearcoat will work; I went with a satin-finish clearcoat, although the top spinning has polished a small portion of it, so I would recommend a gloss coat for the base so the top doesn't change its appearance.

Superglue the ceramic ball into the bottom of the Top, being careful not to get superglue on the exposed side of the ball. (If the ball does not go in all the way, you can heat it first so it melts into the plastic; be careful to keep it perfectly centered)

Attach the under-desk charger to the bottom of your desk and place the base over it, ensuring the charging coil is directly above the charger. This can take some trial and error to align, so I recommend adding a subtle mark to the top of the desk once you have it aligned for future reference. Once it's charging, give the top a spin.