Building A Functional Aliens Motion Tracker

October 2, 2025 by Lewin Day 5 Comments

Aliens is the second film from the legendary science-fiction series about, well… aliens. Naturally, it featured some compelling future-tech — such as the M314 Motion Tracker. [RobSmithDev] wanted to recreate the device himself, using modern technology to replicate the functionality as closely as possible.

While a lot of cosmetic replicas exist in the world, [Rob] wanted to make the thing work for real. To that end, he grabbed the DreamHAT+ Radar HAT for the Raspberry Pi. It’s a short-range radar module, and thus is useless for equipping your own air force or building surface-to-air weaponry. However, it can detect motion in a range of a few meters or so, using its 60 GHz transmitter and three receivers all baked into the one chip.

[Rob] does a great job of explaining how the radar works, and how he integrated it into a viable handheld motion tracker that works very similarly to the one in the movie. It may not exactly keep you safe from alien predators, but it’s always fun to see a functional prop rather than one that just looks good.

This isn’t the first time we’ve seen somebody try to replicate this particular prop, but the modern electronics used in this build definitely bring it to the next level.

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TekaSketch: Where Etch A Sketch Meets Graph Theory

September 29, 2025 by Heidi Ulrich 6 Comments

The Etch A Sketch was never supposed to meet a Raspberry Pi, a camera, or a mathematical algorithm, but here we are. [Tekavou]’s Teka-Cam and TekaSketch are a two-part hack that transforms real photos into quite stunning, line-drawn Etch A Sketch art. Where turning the knobs only results in wobbly doodles, this machine plots out every curve and contour better than your fingertips ever could.

Essentially, this is a software hack mixed with hardware: an RPi Zero W 2, a camera module, Inkplate 6, and rotary encoders. Snap a picture, and the image is conveyed to a Mac Mini M4 Pro, where Python takes over. It’s stripped to black and white, and the software creates a skeleton of all black areas. It identifies corner bridges, and unleashes a modified Chinese Postman Algorithm to stitch everything into one continuous SVG path. That file then drives the encoders, producing a drawing that looks like a human with infinite patience and zero caffeine jitters. Originally, the RPi did all the work, but it was getting too slow so the Mac was brought in.

It’s graph theory turned to art, playful and serious at the same time, and it delivers quite unique pieces. [Tekavou] is planning on improving with video support. A bit of love for his efforts might accellerate his endeavours. Let us know in the comments below!

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Surprisingly Refined Perpetual Motion Device Teardown

September 25, 2025 by Maya Posch 5 Comments

Perpetual motion devices are either a gag, a scam, or as in the case of this particular toy that [Big Clive] bought on AliExpress, a rather fascinating demonstration of a contact-free inductive sensor combined with a pulsed magnet boost for the metal ball. A cool part about the device is that it comes with a completely clear enclosure, so you can admire its internals while it’s operating. Less cool was that after unboxing the device wasn’t working as the detector wasn’t getting the 12 V it needs to operate, requiring a bit of repairing first.

The crucial part of the perpetual motion device schematic with the sensor, MCU and coil. (Credit: bigclivedotcom, YouTube)

Based on the label on the bottom of the device with the creative model identifier P-toy-002, its standby current is 10 µA which ramps up to 3 A when it’s operating. This makes sense when you look at the two core components: the industrial inductive detector, and a rather big electromagnet that’s driven by a bank of three 10 mF, 35V capacitors, turning it into something akin to a coilgun. Annoyingly, an attempt was made to erase most of the IC package markings.

The circuitry isn’t too complex, fortunately, with an adjustable electromagnet coil voltage circuit combined with a MOSFET to provide the pulse, and a 78L12 regulator to generate the 12 VDC from the coil’s voltage rail for the sensor that is monitored by a MCU.

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Estes Wants You To 3D Print Their New Model Rocket

September 5, 2025 by Tom Nardi 46 Comments

The Estes line of flying model rockets have inspired an untold number of children and adults alike, thanks in part to their simplicity. From the design and construction of the rockets themselves to the reliability and safety of the modular solid-propellant motors, the company managed to turn actual rocket science into a family activity. If you could glue fins onto a cardboard tube and stick a plastic nosecone on the end, you were nearly ready for launch.

But what if you’re looking for something a bit more challenging? That’s where the new Estes Scorpio 3D comes in. Unlike the classic Estes kit, which included the fins, nosecone, and other miscellaneous bits of the rocket, the Scorpio kit requires you to 3D print your own parts. Do it right, and the company says you can send your creation to heights of 1,000 feet (305 m).

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Silent Speak And Spell Gets Its Voice Back

August 18, 2025 by Al Williams 4 Comments

While talking computers are old hat today, in 1978, a talking toy like the Speak and Spell was the height of novel tech. [Kevin] found a vintage one, but it didn’t work. It looked like someone had plugged in the wrong power adapter, leading to, undoubtedly, one or more unhappy children. There was some damage that suggests someone had already tried to repair it, but without success.

In addition to effecting the repair, [Kevin] took lots of pictures, so if you ever wanted to peek inside one of these, this is your chance. The case had no screws, just clips, although apparently some of the newer models did have some screws.

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A Second Chance For The Single Wheel Monorail?

August 16, 2025 by Heidi Ulrich 27 Comments

Lately, this peculiar little single wheel monorail came to our attention. Built by [extraglide1976], all from Meccano. His build started with modest tests: one gyro obviously flopped. Two gyros geared together ran slightly better. But when he adds active gimbal control, things suddenly come to life – the model shudders, catches itself, and carries on. The final green-roofed locomotive, with LEDs signalling ‘system go’, trundles smoothly along a single rail on [extraglide1976]’s deck.

To be fair, it houses a lot of mechanics and engineering which we don’t find in the monorails of today. We do have quite a few monorails in our world, but none of them balance on a single wheel like this one. So, where did this invention derail?

Outside of theme parks, Japan is one of the few countries where monorails are still used as serious urban transport: though Germany’s century-old Wuppertal Schwebebahn, the lesser-known C-Bahn, China’s sprawling Chongqing and Shanghai systems, Malaysia’s Kuala Lumpur line, Brazil’s São Paulo network, the US links in Seattle and Las Vegas, and India’s Mumbai Monorail prove the idea has quietly taken root elsewhere.

The thing you’ll see in nearly all these monorails is how the carriages are designed to clamp onto the tracks. This is of course the most safe option, but it loses out on speed to the ones that sit on top of the tracks, balancing on one wheel. Such a train was actually invented, in 1910, by Louis Brennan. His original monorail promised faster, cheaper transport, even using existing rails. The carriages leaned into turns like a motorbike, without any intervention from the driver. Two counter-rotating gyroscopes kept the carriage upright, cancelling precession forces like a mechanical Jedi trick.

Back then, it failed commercially, but today? With cheap sensors, brushless motors, and microcontrollers, and intelligent software, why not let it make a comeback? It could carry freight through narrow urban tunnels. With high-speed single-rail pods?

Investors killed Brennan’s idea, but we live in a different time now. You could start out with a gimmicky ‘snacks and beer’ highline from your fridge to your garage. Share your take on it in the comments!

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[Ben] at workbench with 3D-printed sea scooter

Watertight And Wireless In One Go: The DIY Sea Scooter

August 11, 2025 by Heidi Ulrich 26 Comments

To every gadget, tool, or toy, you can reasonably think: ‘Sure I could buy this… but can I make it myself?’ And that’s where [Ben] decided he could, and got to work. On a sea scooter, to be exact.

This sea scooter was to be a fully waterproof, hermetically sealed 3D-printed underwater personal propulsion device, with the extreme constraint that the entire hull and mechanical interfaces are printed in one go. No post-printing holes for shafts, connectors, or seals. It also meant [Ben] needed to embed all electronics, motor, magnetic gearbox, custom battery pack, wireless charging, and non-contact magnetic control system inside the print during the actual print process.

As [Ben] explains, both Bluetooth and WiFi ranges are laughable once underwater. He elegantly solves this with a reed-switch-based magnetic control system. The non-contact magnetic drive avoids shaft penetrations entirely. Power comes from a custom 8S LiFePO₄ pack, charged wirelessly through the hull. Lastly, everything’s wrapped in epoxy to make it as watertight as a real submarine.

The whole trick of ‘print-in-place’ is that [Ben] pauses the builder mid-print, and drops in each subsystem like a secret ingredient. Continuing, he tweaks the printer’s Z-offset, and onwards it goes. It’s tense, high-stakes work; a 14-hour print where one nozzle crash means binning hundreds of dollars’ worth of embedded components.

Still, [Ben] took the chance, and delivered a cool, fully packed and fully working sea scooter. Comment below to discuss the possibilities of building one yourself.

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