39C3: Hacking Washing Machines

December 29, 2025 by 18 Comments

Many of us have them, few of us really hack on them: well, here we’re talking about large home appliances. [Severin von Wnuck-Lipinski] and [Hajo Noerenberg] were both working on washing machines, found each other, and formed a glorious cooperation that ended in the unholy union of German super-brands Miele and B/S/H — a Miele washer remote controlled by Siemens’ web app.

This talk, given at the 39th Chaos Communication Congress (39C3), is about much more than the stunt hack, however. In fact, we covered [Severin]’s work on the very clever, but proprietary, Miele Diagnostic Interface a little while ago. But now, he’s got it fully integrated into his home automation system. It’s a great hack, and you can implement it without even opening the box.

About halfway through the talk, [Hajo] takes over, dissecting the internal D-Bus communication protocol. Here, you have to open up the box, but then you get easy access to everything about the internal state of the machine. And D-Bus seems to be used in a wide range of B/S/H/ home appliances, so this overview should give you footing for your own experimentation on coffee machines or dishwashers as well. Of course, he wires up an ESP32 to the bus, and connects everything, at the lowest level, to his home automation system, but he also went the extra mile and wrote up a software stack to support it.

It’s a great talk, with equal parts humor and heroic hacking. If you’re thinking about expanding out your own home automation setup, or are even just curious about what goes on inside those machines these days, you should absolutely give it a watch.

Editor Note: The “S” is Siemens, which is Hackaday’s parent company’s parent company. Needless to say, they had nothing to do with this work or our reporting on it.

The Birotary Engine Explained

December 28, 2025 by 34 Comments

Everyone generally knows about piston and rotary engines, with many a flamewar having been waged over the pros and cons of each design. The “correct” answer is thus to combine both into a single engine design. The resulting birotary engine comes courtesy of Czech company [Knob Engines] which makes their special engine for the aviation market. The workings of this engine and why it makes perfect sense for smaller airplanes is explained by [driving 4 answers] in a recent video.

Naturally, it’s at best confusing to call an engine a “rotary”, as this covers many types of engines. One could consider the birotary engine perhaps a cross between the traditional rotary piston engines that powered early aircraft and the Wankel rotary engines that would appear much later. The fact that both the housing and the crankshaft rotate reinforces this notion of a piston rotary, while it keeps the fixed ports and glow plugs on the housing that is typical of a Wankel-style engine. Having both the housing and crankshaft rotate is also why it’s called the ‘birotary’.

The claimed benefits of this design include a small size, low vibrations, reduced gyroscopic effect due to counter-rotation, no apex seals, and less mechanically complex than a piston engine. This comes at the cost of a very short stroke length and thus the need for a relatively high RPM and slow transition between power output levels, but those disadvantages are why small airplanes and UAVs are being targeted.

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Streaming Music To Cassette

December 28, 2025 by 13 Comments

In almost every measurable way, a lossless digital audio file is superior to any analog media. This doesn’t mean that analog audio isn’t valuable though; plenty of people appreciate the compression, ambiance, and other side-effects of listening to a vinyl record or a cassette tape despite the technical limitations. To combine the audio technology of the modern world with these pleasant effects of old analog media, [Julius] built a cassette-based media streamer.

The music playback device takes input from a Bluetooth stream of some sort, converts the digital stream to analog, combines the stereo signal into a mono signal, and then records it to a cassette tape. The tape is then looped through to a playback device which outputs the sound to a single speaker. This has the effect of functioning as a tape delay device, and [Julius] did add input and output jacks to use it as such, but in its default state it has the effect of taking modern streaming through a real analog device and adding the compression and saturation that cassette tapes are known for.

The design of the device is impressive as well, showing off the tape loop and cassette front-and-center with a fluorescent vu meter on the side and a metal case. Getting all of this to work well together wasn’t entirely smooth, either, as [Julius] had to sort out a number of issues with the electronics to keep various electric noises out of the audio signal. Retro analog music players are having a bit of a resurgence right now, whether that’s as a revolt against licensed streaming services or as a way to experience music in unique ways, and our own [Kristina Panos] recently went down an interesting rabbit hole with one specific type of retro audio player.

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A photo of the circuit on a breadboard

Retro Semiconductors: The Silicon Controlled Rectifier

December 28, 2025 by 9 Comments

Over on YouTube [Lockdown Electronics] reviews an old bit of kit known as the Silicon Controlled Rectifier (SCR). Invented in the 1950s the SCR is a type of thyristor and they were popular back in the 1970s. They are often replaced these days by the TRIAC and the MOSFET but you might still find some old schematics that call for them and you can still buy them.

The SCR is a three terminal electronic switch which latches on. You apply a signal at the gate which allows the other two pins, the anode and cathode, to conduct; and they continue to do so until power is removed. The silicon inside the device is comprised of three semiconductor junctions, as: PNPN. The P on the left is the anode, the N on the right is the cathode, and the P in the right middle is the gate.

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Create Aerated Concrete Using Xanthan Gum And Dishwashing Liquid

December 28, 2025 by 29 Comments

To make aerated concrete, add a foam-forming agent and stir in a significant amount of air. This serves to make the concrete significantly lighter, better insulating, and more resilient to fire. Making it can however be a bit of an issue, often requiring ingredients that aren’t purchased at the average DIY store. This is where [NightHawkInLight]’s method seems rather promising, requiring effectively only xanthan gum and dishwashing detergent.

For the small-scale demonstration, 15 grams of the thickening agent xanthan gum is mixed with enough alcohol to create a slurry. To this 60 mL of the detergent and 1 liter of water is added and mixed until the xanthan gum has absorbed all the moisture, which takes about 5-10 minutes. This mixture is then added to Portland cement with two parts cement to one part xanthan gum/detergent mixture and mixed for a while.

Of importance here is that this mixture will keep expanding in volume while mixing, so you have to have to keep an eye on the amount of air relative to concrete, as this will determine the strength and other properties of the final aerated concrete. If you continue past a certain point you will even create open-celled aerated concrete that’s completely porous, so you have to know what kind of concrete you want before you start mixing up a big batch.

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Moving Mousepad Is An Elegant Aimbot

December 27, 2025 by 12 Comments

These days, it can be hard to remain competitive in online shooters without spending your entire life dedicated to the sport. This leads some to explore the world of competitive aids. (AKA: cheating.) A great example is [Nick], who built a mechanical aimbot to help in this regard.

[Nick’s] build moves a mousepad underneath the mouse opposite to the desired movement direction, in order to simulate the mouse movements required to aim at targets in game. This is achieved with the aid of a XDraw A4 pen plotter, which served as a cheap prebuilt X-Y motion platform. The plotter responds to simple serial commands, which makes it easy to control. The X-Y gantry was mounted underneath the desk so the mousepad sits seamlessly on top of the desk, sliding neatly on low-friction mouse skate stickers.

With the mousepad control system built, it was then necessary to figure out how to turn it into an aimbot. [Nick] already had a machine vision tool to detect enemies in shooting game, so it was merely modified to make the right mousepad movements to get the crosshairs right where they needed to be before firing. In testing, it proved more than capable at helping a new player achieve far superior aim, as a good aimbot should.

We’ve featured similar projects before that use complex mechanical contraptions to aim for you. Yes, it’s still cheating, but it’s a lot harder to detect than a traditional aimbot. That doesn’t make it right, per se, just more subtle. Video after the break. Continue reading “Moving Mousepad Is An Elegant Aimbot” →

What To Do When Your Foucault Pendulum Stops Swinging

December 27, 2025 by 41 Comments

At the Houston Museum of Natural Science they recently made a disturbing discovery: their Foucault pendulum had stopped swinging for the first time since its installation in the 1970s. (Video, embedded below.)

While some might take this as yet another sign of the end times, here it is simply a sign that the electromagnetic system that kicks the pendulum developed a fault and will need to be fixed.

Their explainer video of this Herzstein Foucault pendulum is also worth watching, as it explains both the underlying physics and this particular pendulum’s construction. Every 48 hours the 81.6 kg heavy pendulum completes a full rotation, like clockwork, with pins along the circumference being tipped over one by one as the pendulum precesses.

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