The meaning of Inception’s ending famously revolves around a top which spins forever in dreams, but in real life comes to a stop like any other top. Any other top, that is, except for [Aaed Musa]’s self-spinning top, which can continuously spin for about two hours before coming to a stop.

The one constraint was that every functional component had to be contained within the top’s shell, and [Aaed]’s first approach was to build a reaction wheel into the top. When a motor accelerates a weighted wheel, conservation of angular momentum applies an equal and opposite torque to the motor. The problem is that motors eventually reach a top speed and stop accelerating, which puts an end to the torque. This is known as saturation, and the only way to desaturate a reaction wheel is to slow it down, which counteracts the originally generated torque. [Aaed] originally planned to mount the motor in a one-way bearing, which would let it bleed off speed without producing torque against the rest of the top, but it was rather choppy in practice.

The solution occurred to [Aaed] while watching the aforementioned final scene, when it occurred to him that the wobbling of a top could actually generate rotation. A prototype proved that an off-center weight rotating at a constant speed did successfully spin the top by rotating the center of mass, and after that, it was a matter of incremental testing and improvement. A higher moment of inertia worked better, as did a lower center of gravity and a tip made from a hard, low-friction silicon nitride ball bearing. He made housings out of both 3D-printed plastic and CNC-milled aluminium, which each contained a tiny brushless motor, an electric speed controller, a microcontroller, and a small rechargeable lithium battery.

If you allow for external power, you can make the top itself the rotor of a motor, and drive it from a base. Alternatively, if you levitate your top in a vacuum, it could spin for longer than recorded history.

The balance bikes toddlers are rocking these days look like great fun, but not so great in the snow. Rather than see his kid’s favourite toy relegated to shed until spring, [John Boss] added electric power, and an extra wheel to make one fun-looking snow trike. Like a boss, you might say.

Physically, the trike is a delta configuration: two rear wheels and one front, though as you can see the front wheel has been turned into a ski. That’s not the most stable configuration, but by shifting the foot pegs to the front wheel and keeping the electronics down low, [John] is able to maintain a safe center of gravity. He’s also limiting the throttle so kiddo can’t go dangerously fast– indeed, the throttle control is in the rear electronics component. The kid just has a big green “go” button.

Bit-banging the throttle, combined with the weight of the kiddo up front, creates a strong tendency towards wheel-spin, but [John] fixes that with a some cleverly printed TPU paddles zip-tied to the harbor-freight wheels and tires he’s hacked into use. Those wheels are fixed to a solid axle that’s mounted to flat plate [John] had made up to attach to the bike frame. It’s all surprisingly solid, given that [John] is able to demonstrate the safety factor by going for a spin of his own. We would have done the same.

We particularly like the use of a tool battery for hot-swappable power. This isn’t the first time we’ve seen a kid’s toy get the tool battery treatment, but you aren’t limited to mobile uses. We’ve seen the ubiquitous 18V power packs in everything from fume extractors to a portable powerpack that can even charge a Tesla.

The Tamagotchi Connection is a series of Tamagotchi toys that took the original portable pet concept and mixed things up with a wireless connection, which allowed you to interact with the pets of other proud Tamagotchi owners. This wireless connection is implemented using an infrared transceiver, somewhat like IrDA, but as [Zach Resmer] discovered while reverse-engineering this connection, it’s actually what is called ‘Nearly NEC’ by [Natalie Silvanovich], who has a GitHub repository full of related Tamagotchi hacking tools and ROM dumps.

With the protocol figured out, creating a transceiver for low-bitrate infrared communication isn’t particularly hard. In this case, it was implemented using an RP2040 MCU and an appropriate IR LED and receiver pair. This Tamagometer project was also implemented as an app for the Flipper Zero, and a custom PCB called the Pico TamaBadge by [Daniel Weidman].

There’s a web application associated with [Zach]’s project using a Web Serial-enabled browser (i.e. Chrome). The serial protocol is somewhat documented in the patent for the device’s connection feature, which makes it relatively easy to implement yourself.