Improving Aluminium-Ion Batteries With Aluminium-Fluoride Salt

February 11, 2025 by 43 Comments

There are many rechargeable battery chemistries, each with their own advantages and disadvantages. Currently lithium-ion and similar (e.g. Li-Po) rule the roost due to their high energy density at least acceptable number of recharge cycles, but aluminium-ion (Al-ion) may become a more viable competitor after a recently published paper by Chinese researchers claims to have overcome some of the biggest hurdles. In the paper as published in ACS Central Science by [Ke Guo] et al. the use of solid-state electrolyte, a charge cycle endurance beating LiFePO4 (LFP) and excellent recyclability are claimed.

It’s been known for a while that theoretically Al-ion batteries can be superior to Li-ion in terms of energy density, but the difficulty lies in the electrolyte, including its interface with the electrodes. The newly developed electrolyte (F-SSAF) uses aluminium-fluoride (AlF3) to provide a reliable interface between the aluminium and carbon electrodes, with the prototype cell demonstrating 10,000 cycles with very little cell degradation. Here the AlF3 provides the framework for the EMIC-AlCl3 electrolyte. FEC (fluoroethylene carbonate) is introduced to resolve electrolyte-electrode interface issues.

A recovery of >80% of the AlF3 during a recycling phase is also claimed, which for a prototype seems to be a good start. Of course, as the authors note in their conclusion, other frameworks than AlF3 are still to be investigated, but this study brings Al-ion batteries a little bit closer to that ever-elusive step of commercialization and dislodging Li-ion.

Hearing What The Bats Hear

February 11, 2025 by 9 Comments

[Iftah] has been exploring the sounds beyond what we can hear, recording ultrasound and pitching it down. He made a short video on the practice, and it’s like a whole new world of sounds exists just outside of our hearing.

For instance, a dropped toothpick sounds like you’ve just dropped a piece of lumber, a broken lightbulb sounds like a shattered window, and a blackbird sounds like a blue whale. Besides simply sounding super, [Iftah] speculates that there’s some regularity here: that as you slow down the sound it sounds like it came from sources that are physically bigger. He follows this up in a second video, but if you just think about the basic physics, it makes sense.

If you’re interested in recording your own ultrasound, there are a bunch of options on the market. With modern audio processors running up to 192 kHz or even 384 kHz out of the box, all that’s missing is the high-frequency-capable microphone. Those aren’t unobtainable anymore either with many MEMS mics performing well above their rated frequency response specs. Recording ultrasound sounds like a fun and not-too-expensive project to us!

Of course, most of the ultrasound recording we’ve seen has been about the bats. Check out the Pipistrelle or this pair of DIY bat detectors for some good background. But after watching [Iftah]’s video, we’re no longer convinced that the cute little insectivores are the coolest thing going on in the ultrasound.

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The Science Behind Making Buildings Comfortably Non-Combustible

February 11, 2025 by 33 Comments

Although the most fire-resistant building is likely a windowless, concrete bunker, this tends to be not the vibe that most home owners go for. This is why over the years construction of buildings in areas prone to bush- and wildfires – i.e. an uncontrolled fire in an area with combustible vegetation – has adapted to find a happy medium between a building that you’d enjoy living in and a building that will not instantly combust the moment an ember from a nearby wildfire gently touches down upon any part of it.

To achieve this feat, the primary means include keeping said combustible vegetation and similar away from the building, and to make the house as resistant to ember attacks as possible. That this approach is effective has been demonstrated over the course of multiple wildfires in California during the past years, whereby houses constructed more recently with these features had a much higher chance of making it through the event unscathed.

Naturally, the devil is in the details, which is why for example the Australian standard for construction in bushfire-prone areas (AS 3959, last updated in 2018, 2009 version PDF) is rather extensive and heavy on details, including multiple Bushfire Attack Level (BAL) ratings that define risk areas and legally required mitigation measures. So what does it take exactly to survive a firestorm bearing down on your abode?

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Precision Reference Puts Interesting Part To Work

February 11, 2025 by 8 Comments

Interesting parts make for interesting projects, and this nifty precision voltage reference has some pretty cool parts, not to mention an interesting test jig.

The heart of [Gaurav Singh]’s voltage reference is an ADR1399, precision shunt reference from Analog Devices. The datasheet makes for pretty good reading and reveals that there’s a lot going on inside the TO-49 case, which looks unusually large thanks to a thick plastic coat. The insulation is needed for thermal stability for the heated Zener diode reference. The device also has a couple of op-amps built in, one that provides closed-loop voltage control and another that keeps the internal temperature at a toasty 95°C. The result is a reference that’s stable over a wide range of operating conditions.

[Gaurav]’s implementation maximizes this special part’s capabilities while making it convenient to use. The PCB has a precision linear regulator that accepts an input voltage from 16 V to 20 V, plus a boost converter that lets you power it from USB-C. The board itself is carefully designed to minimize thermal and mechanical stress, with the ADR1399 separated from the bulk of the board with wide slots. The first video below covers the design and construction of an earlier rev of the board.

One problem that [Gaurav] ran into with these boards was the need to age the reference with an extended period of operation. To aid in that, he built a modular test jig that completed PCBs can be snapped into for a few weeks of breaking in. The jigs attach to a PCB with pogo pins, which mate to test points and provide feedback on the aging process. See the second video for more details on that.

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Make A Secret File Stash In The Slack Space

February 10, 2025 by 15 Comments

Disk space is allocated in clusters of a certain size. When a file is written to disk and the file size is smaller than the cluster(s) allocated for it, there is an unused portion of varying size between the end of the file’s data and the end of the allocated clusters. This unused space is the slack space, it’s perfectly normal, and [Zachary Parish] had an idea to write a tool to hide data in it.

The demo uses a usb drive, using the slack space from decoy files to read and write data.

[Zachary]’s tool is in Python and can map available slack space and perform read and write operations on it, treating the disparate locations as a single unified whole in which to store arbitrary files. A little tar and gzip even helps makes things more efficient in the process.

There’s a whole demo implemented on Linux using a usb drive with some decoy files to maximize the slack space, and you can watch it in action in the video embedded below. It’s certainly more practical than hiding data in a podcast!

Note that this is just a demo of the concept. The approach does have potential for handling secret data, but [Zachary] points out that there are — from a serious data forensics point of view– a number of shortcomings in its current form. For example, the way the tool currently structures and handles data makes it quite obvious that something is going on in the slack space.

[Zachary] created this a few years ago and has some ideas about how to address those shortcomings and evolve the tool, so if you have ideas of your own or just want to try it out, the slack_hider GitHub repository is where you want to go.

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Screenshot of Linux in a PDF in a browser

Nice PDF, But Can It Run Linux? Yikes!

February 10, 2025 by 21 Comments

The days that PDFs were the granny-proof Swiss Army knives of document sharing are definitely over, according to [vk6]. He has managed to pull off the ultimate mind-bender: running Linux inside a PDF file. Yep, you read that right. A full Linux distro chugging along in a virtual machine all encapsulated within a document. Just when you thought running DOOM was the epitome of it. You can even try it out in your own browser, right here. Mind-boggling, or downright Pandora’s box?

Let’s unpack how this black magic works. The humble PDF file format supports JavaScript – with a limited standard library, mind you. By leveraging this, [vk6] managed to compile a RISC-V emulator (TinyEMU) into JavaScript using an old version of Emscripten targeting asm.js instead of WebAssembly. The emulator, embedded within the PDF, interfaces with virtual input through a keyboard and text box.

The graphical output is ingeniously rendered as ASCII characters – each line displayed in a separate text field. It’s a wild solution but works astonishingly well for something so unconventional.

Security-wise, this definitely raises eyebrows. PDFs have long been vectors for malware, but this pushes things further: PDFs with computational power. We know not to trust Word documents, whether they just capable of running Doom, or trash your entire system in a blink. This PDF anomaly unfolds a complete, powerful operating system in front of your very eyes. Should we think lightly, and hope it’ll lead to smarter, more interactive PDFs – or will it bring us innocent looking files weaponized for chaos?

Curious minds, go take a look for yourself. The project’s code is available on GitHub.

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Blinds Automated With Offline Voice Recognition

February 10, 2025 by 7 Comments

Blinds are great for keeping light out or letting light in on demand, but few of us appreciate having to walk over and wind them open and shut on the regular. [DIY Builder] resented this very task, so set about creating an automated system to do the job for him.

The blinds in question use a ball chain to open and close, which made them relatively easy to interface with mechanically. [DIY Builder] set up a NEMA 17 stepper motor with an appropriate 3D-printed gear to interface with the chain, allowing it to move the blinds accurately. The motor is controlled via an Arduino Nano and an A4988 stepper motor driver.

However, that only covered the mechanical side of things. [DIY Builder] wanted to take the build a step further by making the blinds voice activated. To achieve this, the Arduino Nano was kitted out with a DFRobot Gravity voice recognition module. It’s a super simple way to do voice recognition—it’s an entirely offline solution with no cloud computing or internet connection required. You just set it up to respond to simple commands and it does the rest.

The result is a voice activated blind that works reliably whether your internet is up or not. We’ve seen some other great projects in this space, too. Video after the break.

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