2025-12-27 17:00:12
Visualizers used to be very much in vogue, something you’d gasp in at amazement when you’d fire up Winamp or Windows Media Player. They’re largely absent from our modern lives, but [Arnov Sharma] is bringing them back. After all, who doesn’t want a cool visualizer hanging on the wall in their living room?
The build is based around the Raspberry Pi Pico 2. It’s paired with a small microphone hooked up to a MAX9814 chip, which amplifies the signal and offers automatic gain control to boot. This is a particularly useful feature, which allows the microphone to pick up very soft and very loud sounds without the output clipping. The Pi Pico 2 picks up the signals from the mic, and then displays the waveforms on a 64 x 32 HUB75 RGB matrix. It’s a typical scope-type display, which allows one to visualize the sound waves quite easily. [Arnov] demonstrates this by playing tones on a guitar, and it’s easy to see the corresponding waveforms playing out on the LED screen.
It’s a fun project, and it’s wrapped up in a slick 3D printed housing. This turns the visualizer into a nice responsive piece of wall art that would suit any hacker’s decor. We’ve featured some other great visualizers before, too.
2025-12-27 14:00:10
Not every impulsive purchase on eBay leads to possession of a wooden Dalek, but when a friend did exactly that, [Tony Goacher] did his part to turn ‘Dalek Bob’ into a motorized and remote-controlled unit of impressive stature.
The purchased Dalek is made of wood and, with the help of two bolts, is of sufficient size to trap a human inside. There’s a bench of sorts upon which the captive can sit, and with some effort, shuffle the surrounding frame awkwardly about. The scale of the Dalek is impressive, but it was clear the effect of human-powered locomotion was lacking. The solution was to install wheelchair motors, tires, and an ESP32-based remote control.
Quite a lot of work went into mounting the motors and wheels, and the challenges will be familiar to anyone who has done hobby robotics. One can choose ideal motors and wheels, but making them fit one another can be an entirely different story. Shafts and hubs are of different sizes, motor mounting doesn’t quite match the platform, and it’s all a bit like fitting a square peg into a round hole. But with access to the right tools, it’s nothing a little metalwork and welding can’t solve.
For the control system, the ESP32 (with a beautiful CNC-routed custom PCB) sets itself up as a wireless access point that serves a web-based control panel for piloting, and controls two H-bridges to drive the motors. What’s more, it also provides a sound board from which a second operator can trigger appropriate phrases and sounds from the Dalek.
Some folks prefer their remote-controlled Daleks plush and cute instead of large and looming, but we like the smooth movement and imposing stature of this one. Watch it all in action in the video, embedded below.
2025-12-27 11:00:40
Physics simulations using classical mechanics is something that’s fairly easily done on regular consumer hardware, with real-time approximations a common feature in video games. Moving things to the quantum realm gets more complex, though with equilibrium many-body systems still quite solvable. Where things get interesting is with nonequilibrium quantum systems.
These open systems are subject to energy gains and losses that disrupt its equilibrium. The truncated Wigner approximation (TWA) is used as a semi-classical method to solve these, but dissipative spin systems proved tricky. Now however [Hosseinabadi] et al. have put forward a TWA framework (PR article) for driven-dissipative many-body dynamics that works on consumer hardware.
Naturally, even with such optimizations there is still the issue that the TWA is only an approximation. This raises questions such as about how many interactions are required to get a sufficient level of accuracy.
Using classical computers to do these kind of quantum physics simulations has often been claimed to the ideal use of qubit-based quantum computers, but as has been proven repeatedly, you can get by with a regular tensor network or even a Commodore 64 if you’re in a pinch.
2025-12-27 08:00:02
When you think of air conditioners, you tend to think of rather bulky units, with the window-mounted appliances probably among the most compact. There’s however no real minimum size limit to these AC units, as long as you can get an appropriate compressor. If you also manage to pick up a small, DC-powered compressor like [Hyperspace Pirate] did, then you might be tempted to make a hand-portable, battery-powered AC unit.
At their core vapor-compression AC units are very simple, featuring the aforementioned compressor, a condensing coil, expansion valve and the evaporator coil. Or in other words, some radiators looted out of other devices, various plumbing supplies and the refrigerant gas to charge the AC unit with.
Since the compressor uses a BLDC motor, it has three terminals that a typical ESC connects to, along with two 2200 mAh Li-on battery packs that can keep the portable AC unit running for a while.
As for the refrigerant gas, although the compressor lists R134a, this is both quite expensive and illegal in parts of the world like the EU. Alternatives are butane (R600) as well as isobutane (R600a), but due to unfortunate circumstances the use of propane (R290) was forced. Fortunately this worked fine, and after some testing and running of numbers it was found that it had about 42 Watt cooling power, with a coefficient of performance (COP) of around 1.
Considering that most AC units have a COP of 3.5 – 5, this shows that there’s still some room for increased efficiency, but at the very least this portable, battery-powered AC unit provides cold air on one side, and hot air on the other while completely blowing Peltier thermocouples out of the water in terms of efficiency.
2025-12-27 05:00:03
[Nicholas Murray]’s Composite Test Pattern Generator is a beautifully-made, palm-sized tool that uses an ESP32-based development board to output different test patterns in PAL/NTSC. If one is checking out old televisions or CRTs, firing up a test pattern can be a pretty handy way to see if the hardware is healthy or not.
The little white add-on you see attached to the yellow portion is a simple circuit (two resistors and an RCA jack) that allows the microcontroller to output a composite video signal. All one needs to do is power on the device, then press the large button to cycle through test patterns. A small switch on the side toggles between NTSC and PAL video formats. It’s adorable, and makes good use of the enclosures that came with the dev board and proto board.
In a pinch a hacker could use an original Raspberry Pi, because the original Pi notably included a composite video output. That feature made it trivial to output NTSC or PAL video to a compatible display. But [Nicholas]’s device has a number of significant advantages: it’s small, it’s fast, it has its own battery and integrated charger, and the little color screen mirroring the chosen test pattern is a great confirmation feature.
This is a slick little device, and it’s not [Nicholas]’s first test pattern generator. He also created a RP2040-based unit with a VGA connector, the code of which inspired a hacker’s home-grown test pattern generator that was used to service a vintage arcade machine.
2025-12-27 02:00:00
Optical Character Recognition (OCR) forms the bridge between the analog world of paper and the world of machines. The modern-day expectation is that when we point a smartphone camera at some characters it will flawlessly recognize and read them, but OCR technology predates such consumer technology by a considerable amount, with IBM producing OCR systems as early as the 1950s. In a 1960s promotional video on the always delightful Periscope Film channel on YouTube we can get an idea of how this worked back then, in particular the challenge of variable quality input.
What drove OCR was the need to process more paper-based data faster, as the amount of such data increased and computers got more capable. This led to the design of paper forms that made the recognition much easier, as can still be seen today on for example tax forms and on archaic paper payment methods like checks in countries that still use it. This means a paper form optimized for reflectivity, with clearly designated sections and lines, thus limiting the variability of the input forms to be OCR-ed. After that it’s just a matter of writing with clear block letters into the marked boxes, or using a typewriter with a nice fresh ink ribbon.
These days optical scanners are a lot more capable, of course, making many of such considerations no longer as relevant, even if human handwriting remains a challenge for OCR and human brains alike.
