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Low Self-Discharge, High-Voltage Supercapacitors Using Porous Carbon

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Supercapacitors rely mostly on double-layer capacitance to bridge the divide between chemical batteries and traditional capacitors, but they come with a number of weaknesses. Paramount among these are their relatively low voltage of around 2.7 V before their electrolyte begins to decompose, as well as their relatively high rates of self-discharge. Here a new design using lignin-derived porous carbon electrodes and a fluorinated diluent was demonstrated by [Shichao Zhang] et al., as published in Carbon Research , that seems to address these issues. Most notable are the relatively high voltage of 4 V, an energy density of 77 Wh/kg and a self-discharge rate that’s much slower than that of conventional supercapacitors. In comparison with these supercapacitors, these demonstrated versions are also superior in terms of recharge cycles with 90% of capacity remaining after 10,000 cycles, which together with their much higher energy density should prove to be quite useful. This feat is acc...
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PicoZ80 is a Drop-in Replacement for Everyone’s Favorite Zilog CPU

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The Z80 has been gone a couple of years now, but it’s very much not forgotten. Still, the day when new-old-stock and salvaged DIP-40 packaged Z80s will be hard to come by is slowly approaching, and [eaw] is going to be ready with the picoZ80 project. You can probably guess where this is going: an RP2350B on a DIP-40 sized PCB can easily sit on the bus and emulate a Z80. It can do so with only one core, without breaking a sweat. That left [eaw] a second core to play with, allowing the picoZ80 to act as a heck of an accelerator, memory expander, USB host, disk emulator– you name it. He even tossed in an ESP32 co-processor to act as a WiFi, Bluetooth, and SD-card controller to use as a virtual, wirelessly accessible disk drive. The onboard ram that comes with an RP2350B would be generous by 1980s standards, but [eaw] bumped that up with an 8 MB SPRAM chip–accessed in 64 pages of 64 kB each, naturally. If more RAM than a very pricey hard drive wasn’t luxury enough, there’s also 16 MB of...
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Acoustic Drone Detection On the Cheap with ESP32

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We don’t usually speculate on the true identity of the hackers behind these projects, but when [TN666]’s accoustic drone-detector crossed our desk with the name “Batear” , we couldn’t help but wonder– is that you, Bruce? On the other hand, with a BOM consisting entirely of one ESP32-S3 and an ICS-43434 I2S microphone, this isn’t exactly going to require the Wayne fortune to pull off. Indeed, [TN666] estimates a project cost of only 15 USD, which really democratizes drone detection. It’s not a tuba–  Imperial Japanese aircraft detector being demonstrated in 1932. Image Public Domain via rarehistoricalphotos.com The key is what you might call ‘retrovation’– innovation by looking backwards. Most drone detection schema are looking to the ways we search for larger aircraft, and use RADAR. Before RADAR there were acoustic detectors, like the famous Japanese “war tubas” that went viral many years ago. RADAR modules aren’t cheap, but MEMS microphones are– and drones, especially quad-c...
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Build This Open-Source Graphics Calculator

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Graphics calculators are one of those strange technological cul-de-sacs. They rely on outdated technology and should not be nearly as expensive as they are, but market effects somehow keep prices well over $100 to this day. Given that fact, you might like to check out an open-source solution instead. NumOS comes to us from [El-EnderJ]. It’s a scientific and graphic calculator system built to run on the ESP32-S3 with an ILI9341 screen. It’s intended to rival calculators like the Casio fx-991EX ClassWiz and the TI-84 Plus CE in terms of functionality. To that end, it has a full computer algebra system and a custom math engine to do all the heavy lifting a graphic calculator is expected to do, like symbolic differentiation and integration. It also has a Natural V.P.A.M-like display—if you’re unfamiliar with Casio’s terminology, it basically means things like fractions and integrals are rendered as you’d write them on paper rather than in uglier simplified symbology. If you’ve ever want...
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Building a Laser-Driven Photoacoustic Speaker

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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...
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The 3DFX Voodoo Lives Again In An FPGA

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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 curi...
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Hackaday Links: March 22, 2026

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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...
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