One of the coolest things about old hi-fi hardware is that it often came with flickety needles that danced with the audio level. You can still buy these if you want, or you can simulate the same look on a screen, as [mircemk] demonstrates.

It isn’t [mircemk]’s first rodeo in this regard. An earlier project involved creating simulated VU meters on round displays, but they were somewhat limited. Using the Adafruit GFX library on an ESP32 netted a working setup, but it was jerky and very jagged and digital-looking. It was more akin to a fake needle display running on an 8-bit computer than something that looked like a real vintage VU meter.

[mircemk] didn’t give up and figured the ESP32 microcontroller and GC9A01 round display could surely deliver better results. The trick was to leverage the LVGL graphics library instead, along with the Squarelinestudio UI editor. The library was able to display far richer graphics that look like an actual vintage VU meter, even appearing glowing and backlit like the real thing. The moving needle animates far more smoothly as well, pulsing with the music in a way that feels far more realistic compared to the earlier attempt.

It’s nice to see this simple project revisited and so boldly improved just a year later. If you’re looking to implement real-looking gauges while retaining the flexibility of a small LCD screen, you might like to try the LVGL library for yourself. With that said, sometimes you just can’t beat the real analog gauges themselves. Video after the break.

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An MRI scan is never a pleasant occasion – even if you aren’t worried about the outcome, lying still in a confined, noisy space for long periods of time is at best an irksome experience. For hearing protection and to ameliorate boredom or claustrophobia, the patient wears headphones. Since magnets and wires can’t be used inside an MRI machine, the headphones have to literally pipe the sound in through tubes, which gives them poor sound quality and reduces the amount of noise they can block. [SomethingAboutScience], however, thinks that photoacoustic speakers could improve on these, and built some to demonstrate.

These speakers use the photoacoustic effect, which is mostly caused by surface heating when exposed to an intense light, then transferring the heat to the surrounding air, which expands. If the surface can transfer heat to the air quickly enough, and if the light source is modulated quickly, the rapid expansions and contractions in the surrounding air create sound waves. As a test, [SomethingAboutScience] shone a modulated 5-Watt laser on a piece of gold leaf, which produced recognizable music.

Gold leaf works because it absorbs blue light well and is thin enough to transfer heat to the air quickly. To cut out the absorbing surface, [SomethingAboutScience] also shone the laser directly into orange nitrogen dioxide gas, which produced a somewhat cleaner sound (in a purely auditory sense; nitrogen dioxide is quite dangerous, and calling it “a little toxic” is an understatement). Soot-coated glass also worked rather well, though a soot-coated glass smoking pipe didn’t provide the desired acoustics. He also 3D-printed an earphone shape with a gold leaf-lined cavity inside it, then used a fibre-optic cable to direct the laser light into it. We would be personally reluctant to couple a 5-Watt laser into a reflective cavity centimeters from our eardrums, but it didn’t appear to damage its surroundings.

We’ve seen the photoacoustic effect used before to perform long-range, almost silent command injection to voice assistants. It’s also possible to use lower-power lasers and beam sound directly into people’s ears.

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Thanks to [Marble] for the tip!

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The 3DFX Voodoo was not the first dedicated 3D graphics chipset by any means, but it became the favourite for gamers among the early mass-market GPUs. It would be found on a 3D-processing-only PCI card that sat on the feature connector of your SVGA card. The Voodoo took any game that supported its Glide API into the world of (for the time) smooth and beautiful 3D. They’re worth a bit now, but if you don’t fancy forking out for mid-’90s silicon in 2026, there’s another option. [Francisco Ayala Le Brun] has implemented the 3DFX Voodoo 1 in SpinalHDL for FPGAs.

The write-up goes into the Voodoo’s architecture. Where the parts of a modern GPU are programmable for the various functions it can do, in this part they are dedicated hardware functions for the various graphics tricks the chip can perform. Implementing such an architecture on an FPGA led to bugs and timing problems, and the write-up deals with that in detail.

The whole thing can be found in a GitHub repository if you’re curious, and is definitely worth a read for anyone interested in 1990s retrocomputing. 3DFX themselves would eventually be swallowed by Nvidia, a rival whose offerings would overtake them at the end of the ’90s, but they still represent a somewhat special moment. Don’t forget, if you have the real thing, you can probably upgrade its memory.

Header image: Konstantin Lanzet, GFDL.

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On Friday, Reuters reported that Amazon is going to try to get into the smartphone game…again. The Fire Phone was perhaps Amazon’s biggest commercial misstep, and was only on the market for about a year before it was discontinued in the summer of 2015. But now industry sources are saying that a new phone code-named “Transformer” is in the works from the e-commerce giant.

At this point, there’s no word on how much the phone would cost or when it would hit the market. The only information Reuters was able to squeeze out of their contacts was that the device would feature AI heavily. Real shocker there — anyone with an Echo device in their kitchen could tell you that Amazon is desperate to get you talking to their gadgets, presumably so they can convince you to buy something. While a smartphone with even more AI features we didn’t ask for certainly won’t be on our Wish List, if history is any indicator, we might be able to pick these things up cheap on the second-hand market.

On the subject of AI screwing everything up, earlier this week, the Electronic Frontier Foundation reported that The New York Times had started blocking the Internet Archive’s crawlers, citing concerns over their content being scraped up by bots for training data. The EFF likens this to a newspaper asking libraries to stop storing copies of their old editions, and warns that in an era where most people get their news via the Internet, not having an archived copy of sites like The Times will put holes in the digital record. They also point out that mirroring web pages for the purposes of making them more easily searchable is a widely accepted practice (ask Google) and has been legally recognized as fair use in court.

Assuming we take the NYT’s side of the story at face value, there’s a tiny part of our cold robotic heart that feels some sympathy for them. Over the last year or so, we’ve noticed some suspicious activity that we believe to be bots siphoning up content from the blog and Hackaday.io, and it’s resulted in a few technical headaches for us. On the other hand, what’s Hackaday here for if not to share information? Surely the same could be said for any newspaper, be it the local rag or The New York Times. If a chatbot learning some new phrases from us is the cost of doing business in 2026, so be it. Can’t stop the signal.

Switching gears to the world of aerospace, NASA’s X-59 supersonic research aircraft had to abort a test flight on Friday after just nine minutes in the air. The plane is designed to demonstrate techniques which promise to reduce or eliminate the sonic booms heard on the ground during supersonic flight, and is currently being put through its paces at Armstrong Flight Research Center in Edwards, California.
NASA’s very pointy X-59 aims to make supersonic flight more commercially viable.
The space agency hasn’t clarified exactly what the issue was, but after the pilot saw a warning indicator in the cockpit, the decision was made to end the flight early so engineers could take a look at the problem. Given that the X-59 went on to make an uneventful landing, it sounds like things weren’t too dire. Hopefully, that means it won’t be long before the sleek experimental aircraft is back in the air.

Friday also saw the towering Space Launch System rocket return to the launch pad ahead of a potential April 1st (no, really) liftoff for Artemis II. There are about a million things that could further delay the mission, from technical issues to suspicious looking cloud formations over Cape Canaveral, but we’re certainly in the final stretch now. The 10-day mission will see four astronauts run through a packed schedule of experiments and demonstrations as they become the first humans to swing by the Moon since the Apollo program ended in 1972.

Finally, the National Museum of the U.S. Air Force has released a video taken by a drone flying around their collection of Cold War era aircraft. Seasoned FPV pilots will probably notice it’s not the most technically impressive flight out there, but it does provide some viewpoints that simply wouldn’t be possible otherwise. It’s also a bit surreal to see these aircraft, once the absolute state-of-the-art and developed at an unimaginable cost, collecting dust while a $300 drone that packs in higher resolution optics and far more processing power literally flies circles around them.

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See something interesting that you think would be a good fit for our weekly Links column? Drop us a line, we’d love to hear about it.

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Odds are, you’ve taken pills before; it’s a statistical certainty that some of you reading this took several this morning. Whenever you do, you’re at the mercy of the manufacturer: you’re trusting that they’ve put in the specific active ingredients in the dosage listed on the package. Alas, given the world we live in, that doesn’t always happen. Double-checking actual concentrations requires expensive lab equipment like gas chromatography. It turns out checking for counterfeit pills is easier than you’d think, thanks to a technique called Disintegration Fingerprinting.

The raw voltage signal from the sensor is stored as a “disintegration fingerprint” of particles detected per minute.
It’s delightfully simple: all you need is a clear plastic cup, a stir plate, and a handful of electronic components — namely, a microcontroller, a servo, and an IR line-following sensor. You’ve probably played with just such a sensor: the cheap ones that are a matched pair of LED and photodetector. It works like this: the plastic cup, filled with water, sits upon the stir plate. To start the device, you turn on the stir plate and actuate the servo to drop the pill in the water. The microcontroller then begins recording the signal from the photo-diode. As the pill breaks up and/or dissolves in the water, the swirling bits are going to reflect light from the IR LED. That reflectance signal over time is the Disintegration Fingerprint (DF), and it’s surprisingly effective at catching fakes according to the authors of the paper linked above. Out of 32 different drug products, the technique worked on 90% of them, and was even able to distinguish between generic and brand-name versions of the same drug.

Of course, you do need a known-good sample to generate a trustworthy fingerprint, and there’s that pesky 10% of products the technique doesn’t work on, but this seems like a great way to add some last-mile QA/QC to the drug distribution chain, particularly in low and middle-income countries where counterfeit drugs are a big problem.

We’ve featured pill-identifiers before, but machine vision is going to be much more easily fooled by counterfeits than this method. If your problem isn’t worrying that your pills are fake, but forgetting to take them, we’ve had projects to help with that, too.

Thanks to [Zorch] for the tip!

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Thermal energy storage is pretty great, as phase-change energy storage is very consistent with its energy output over time, unlike chemical batteries. You also get your pick from a wide range of materials that you can either heat up or cool down to store energy. Here, the selection is mostly dependent on how you wish to use that energy at a later date. [Hyperspace Pirate] is mostly interested in cooling down a house, on account of living in Florida.

As can be seen in the top image, the basic setup is pretty straightforward. PV solar power charges a battery until it’s fully charged. Then an MCU triggers a relay on the AC inverter, which then starts the cooling compressor on the water reservoir. This proceeds to phase change the water from a liquid into ice. The process can later be reversed, which will draw thermal energy out of the surrounding air and thus provide cooling.

Although water is not the most interesting substance to pick for the
The cool side of the thermal storage system, chilling a car. (Credit: Hyperspace Pirate, YouTube)
thermal energy storage, it can provide 1 kWh of cooling power in 10.8 kg, or 92.8 kWh in a mere m³. This makes it much more compact as well as cheaper than chemical storage using batteries.

After charging the main compressor loop with R600 (N-butane), the system is trialed with a small PV solar array that manages to freeze the entire bucket of water. Courtesy of insulation, it’s kept that way for a few days, giving plenty of time for the separate glycol-filled loop to dump thermal energy into it and push cold air into the surrounding environment. This prototype managed to cool down [Hyperspace Pirate]’s car in just two hours, which is good enough for a proof-of-concept.

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The 8051 was an 8-bit Harvard-architecture microcontroller first put out by Intel in 1980. They’ve since discontinued that line, but it lives on in the low-cost STC8 family of chips, which is especially popular in Asia. They’re cheap as, well, chips — under 1$ — but lack compatibility with modern toolchains. If you’re happy with C, then you’re fine, but if you want to plus-plus it up and use all those handy-dandy shortcuts provided by the Arduino ecosystem, you’re out of luck. Or rather, you were, until [Bùi Trịnh Thế Viên] aka [thevien257] came up with a workaround.

The workaround is delightfully Hack-y. One could, conceivably, port a compiler for Arduino’s Wiring to the 8051, but that’s not what [Viên] did, probably because that would be a lot of work. There isn’t even a truly modern toolchain to put plain C on this chip. Instead, [Viên] started with rv51, a RISC-V emulator written in 8051 assembly language by [cryozap]. RISC-V is a lot easier to work with and, frankly, a more useful skill to build up.

Now emulation does come with a cost: 8kB of flash memory and a 100x to 1000x slowdown in the emulated application code. For that reason, anything timing critical, like interrupts, should probably be handled the old-fashioned way. He’s targeting the STC8H8K64U specifically, so if you happen to have other STC8-based dev boards lying around, you’ll have some extra work ahead of you.

Of course, you can get ultra-cheap microcontrollers that are natively RISC V already– and they’re good enough to act as microcomputers of the era the 8051 hails from, so this hack is likely going to stay fairly niche. Still, if you’re in that niche, teaching an 8051 to speak RISC might be a handy trick to have in your back pocket.

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Although the RTL-SDR is cheap, accessible, and capable enough for many projects, it does have some important limitations. In particular, its bandwidth is limited to about 3.2 MHz, and the price of SDRs tends to scale rapidly with bandwidth. [Anders Nielsen], however, is building a modular SDR with a target price of $50 USD, and has already reached a bandwidth of almost 20 MHz.

If this project looks familiar, it’s because we’ve covered an earlier iteration. At the time, [Anders] had built the PhaseLoom, which filters an incoming signal, mixes it down to baseband, and converts it to I/Q signals. The next stage is the PhaseLatch, a board housing a 20-MHz, 10-bit ADC, which samples the in-phase and quadrature signals and passes them on to a Cypress FX2LP microcontroller development board. [Anders] had previously connected the ADC to a 6502 microprocessor instead of the FX2LP, but this makes it a practical SDR. The FX2LP was a particularly good choice for this project because of its USB 2.0 interface, large buffers for streaming data, and parallel interface. It simply reads the data from the SDR and dumps it to the computer.

The FX2LP didn’t support the ADC’s clock rate, and overclocking the ADC led to issues, so [Anders] connected the ADC to an independent 20 MHz oscillator. The frequency spectrum of the SDR was oddly bell-shaped, which turned out to be due to the limited analogue bandwidth of the PhaseLoom (about 650 kHz) falling behind the digital bandwidth of 20 MHz. The PhaseLoom’s bandwidth seemed to be limited mostly by an amplifier, and decreasing its gain greatly improved matters. The SDR doesn’t yet have a 20 MHz bandwidth according to the normal definition, but it’s close enough to be practical, and further improvements will have to wait on an updated PhaseLoom board.

The Cypress development board used here is surprisingly capable – we’ve previously seen it used to build an SDR GPS decoder. Most of the custom-built SDRs we see don’t focus on technical performance, but do use such interesting components as a tube-based receiver or a custom silicon chip.

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Belkin charger standby power. (Credit: Denki Otaku, YouTube)
A well-known property of wall warts like power bricks and USB chargers is that they always consume some amount of power even when there’s no connected device drawing power from them. This feels rather wasteful when you have a gaggle of USB chargers constantly plugged in, especially on a nation-sized scale. This is where a new USB-C wall charger by Belkin, the BoostCharger Pro, is interesting, as it claims ‘zero standby power’, which sounds pretty boastful and rather suspect. Fortunately, [Denki Otaku] saw fit to put one to the test and even tear one down to inspect the work of Belkin’s engineers.

Naturally, no laws of physics were harmed in the construction of the device, as ‘zero standby power’ translated from marketing speak simply means ‘very low standby power usage’, or about 3 milliwatt with 0.3 mA at the applied 100 VAC.

Fascinatingly, plugging in an e-marker equipped USB-C cable with no device on the other end caused this standby usage to increase to about 30 mW, clearly disabling the ‘zero standby’ feature. With that detail noted, it was time to tear down the charger, revealing its four PCBs.

The boring answer here is that Belkin didn’t do anything special, but rather followed the Renesas application note for a 65W USB-C adapter with Zero Standby Power:
Zero Standby Power Application Note. (Credit: Renesas)
As can be surmised from the effect of a non-e-marked versus e-marked USB-C cable being inserted, the USB-PD controller IC detects the presence or absence of a cable, and signals the flyback section to mostly shut down. This then leaves a trickle of current for the charger’s ICs as they wait for something to happen. In the (unfortunately restricted) datasheet for the Renesas iW9870 flyback controller IC, we can see this feature described, including how plugging in a USB cable disables the feature.

This feature appears to be somewhat related to how USB power banks work, with them shutting down the outputs if idle, though there are some issues with it backfiring. Some power banks have a ‘trickle charge’ mode where even low amounts of current being drawn doesn’t shut off the output. In the case of this Renesas ‘zero standby power’ feature, it seems to rely on USB cable detection as an equivalent to an active power device.

As noted in the video, this seems to cause issues when inserting an e-marked cable, and some users have reported the charger randomly turning off the output while actively charging from it. Here we’d like to pitch an absolutely bonkers suggestion, and pitch putting a physical on/off switch on the charger – as well as on power banks – rather than try to do more smart guessing.

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We have to admit, we didn’t know that we wanted a desktop electric jellyfish until seeing [likeablob]’s Denki-Kurage, but it’s one of those projects that just fills a need so perfectly. The need being, of course, to have a Bladerunner-inspired electric animal on your desk, as well as having a great simple application for that Cheap Yellow Display (CYD) that you impulse purchased two years ago.

Maybe we’re projecting a little bit, but you should absolutely check this project out if you’re interested in doing anything with one of the CYDs. They are a perfect little experimentation platform, with a touchscreen, an ESP32, USB, and an SD card socket: everything you need to build a fun desktop control panel project that speaks either Bluetooth or WiFi.

We love [likeablob]’s aesthetic here. The wireframe graphics, the retro-cyber fonts in the configuration mode, and even the ability to change the strength of the current that the electric jellyfish is swimming against make this look so cool. And the build couldn’t be much simpler either. Flash the code using an online web flasher, 3D print out the understated frame, screw the CYD in, et voila! Here’s a direct GitHub link if you’re interested in the wireframe graphics routines.

We’ve seen a bunch of other projects with the CYD, mostly of the obvious control-panel variety. But while we’re all for functionality, it’s nice to see some frivolity as well. Have you made a CYD project lately? Let us know!

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Although the CRT has largely disappeared from our everyday lives, there was a decades-long timeframe when this was effectively the only display available. It’s an analog display for an analog world, and now that almost everything electronic is digital, these amazing pieces of technology are largely relegated to retro gaming and a few other niche uses. [Maurycy] has a unique CRT that’s small enough to fit in a handheld television, but since there aren’t analog TV stations anymore, he decided to build his own with nothing but an 8-bit microcontroller and a few other small parts.

The microcontroller in question is a fairly standard 8-bit AVR. These microcontrollers have one major limitation when generating the VHF and UHF radio signals needed for analog TV: their natural clock speed is much too low. The maximum output frequency of a pin on this microcontroller is only 6 MHz, and [Maurycy] needs something about two orders of magnitude faster. To solve this problem, [Maurycy] uses a quirk of the square wave generated by toggling a pin at its maximum frequency, which is that a wide range of harmonics will be generated, some of which will have a high enough frequency to be picked up on the handheld analog TV. The microcontroller is configured to use two pins. Toggling the pins into various states allows the humble AVR to generate a usable TV signal.

The scan rate for CRTs is comparably low as well. At the beginning of each frame, there’s enough processing power left on the microcontroller to play Conway’s Game of Life, which is then sent out over the airwaves to the TV. [Maurycy] notes that his harmonics-based video generation method is extremely noisy and probably wouldn’t pass FCC muster. However, the signal Power is so low that it’s unlikely to interfere with anything. If you’re curious about these unusual sideways-built CRTs, though, we recently saw someone take two apart and use them to build a CRT-based VR headset.

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