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Hackaday Links: December 14, 2025

Fix stuff, earn big awards? Maybe, if this idea for repair bounties takes off. The group is dubbed the FULU Foundation, for “Freedom from Unethical Limitations on Users,” and was co-founded by right-to-repair activist Kevin O’Reilly and perennial Big Tech thorn-in-the-side Louis Rossman. The operating model works a bit like the bug bounty system, but in reverse: FULU posts cash bounties on consumer-hostile products, like refrigerators that DRM their water filters or bricked thermostats. The bounty starts at $10,000, but can increase based on donations from the public. FULU will match those donations up to $10,000, potentially making a very rich pot for the person or team that fixes the problem.

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A graph showing the poisoning success rate of 7B and 13B parameter models

It Only Takes A Handful Of Samples To Poison Any Size LLM, Anthropic Finds

It stands to reason that if you have access to an LLM’s training data, you can influence what’s coming out the other end of the inscrutable AI’s network. The obvious guess is that you’d need some percentage of the overall input, though exactly how much that was — 2%, 1%, or less — was an active research question. New research by Anthropic, the UK AI Security Institute, and the Alan Turing Institute shows it is actually a lot easier to poison the well than that.

We’re talking parts-per-million of poison for large models, because the researchers found that with just 250 carefully-crafted poison pills, they could compromise the output of any size LLM. Now, when we say poison the model, we’re not talking about a total hijacking, at least in this study. The specific backdoor under investigation was getting the model to produce total gibberish.

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Finally, A Pipe Slapophone With MIDI

If you live in a major city, you’ve probably seen a street performer with some variety of slapophone. It’s a simple musical instrument that typically uses different lengths of PVC pipe to act as resonant cavities. When struck with an implement like a flip-flop, they release a dull but pleasant tone. [Ivan Miranda] decided to build such an instrument himself and went even further by giving it MIDI capability. Check it out in the video below.

[Ivan’s] design uses a simple trick to provide a wide range of notes without needing a lot of individual pipes. He built four telescoping pipe assemblies, each of which can change length with the aid of a stepper motor and a toothed belt drive. Lengthening the cavity produces a lower note, while shortening it produces a higher note. The four pipe assemblies are electronically controlled to produce notes sent from a MIDI keyboard, all under the command of an Arduino. The pipes are struck by specially constructed paddles made of yoga mats, again controlled by large stepper motors.

The final result is large, power-hungry, and vaguely playable. It’s a little unconventional, though, because moving the pipes takes time. Thus, keypresses on a MIDI keyboard set the pipes to a given note, but don’t actually play it. The slapping of the pipe is then triggered with a drum pad.

We love weird instruments around these parts.

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A circuit diagram in a book on a desk with computers and microcontrollers

Taking Electronics To A Different Level

One part wants 3.3V logic. Another wants 5V. What do you do? Over on the [Playduino] YouTube channel, there’s a recent video running us through a not-so-recent concern: various approaches to level-shifting.

In the video, the specific voltage domains of 3.3 volts and 5 volts are given, but you can apply the same principles to other voltage domains, such as 1.8 volts, 2.5 volts, or nearly any two levels. Various approaches are discussed depending on whether you are interfacing 5 V to 3.3 V or 3.3 V to 5 V.

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Printing With PHA Filament As Potential Alternative To PLA

PLA (polylactic acid) has become the lowest common denominator in FDM 3D printing, offering decent performance while being not very demanding on the printer. That said, it’s often noted that the supposed biodegradability of PLA turned out to be somewhat dishonest, as it requires an industrial composting setup to break it down. Meanwhile, a potential alternative has been waiting in the wings for a while, in the form of PHA. Recently, [JanTec Engineering] took a shot at this filament type to see how it prints and tests its basic resistance to various forms of abuse.

PHA (polyhydroxyalkanoates) are polyesters that are produced by microorganisms, often through bacterial fermentation. Among their advantages are biodegradability without requiring hydrolysis as the first step, as well as UV-stability. There are also PLA-PHA blends that exhibit higher toughness, among other improvements, such as greater thermal stability. So far, PHA seems to have found many uses in medicine, especially for surgical applications where it’s helpful to have a support that dissolves over time.

As can be seen in the video, PHA by itself isn’t a slam-dunk replacement for PLA, if only due to the price. Finding a PHA preset in slicers is, at least today, uncommon. A comment by the CTO of EcoGenesis on the video further points out that PHA has a post-printing ‘curing time’, so that mechanical tests directly after printing aren’t quite representative. Either you can let the PHA fully crystallize by letting the part sit for ~48 hours, or you can speed up the process by putting it in an oven at 70 – 80°C for 6-8 hours.

Overall, it would seem that if your goal is to have truly biodegradable parts, PHA is hard to beat. Hopefully, once manufacturing capacity increases, prices will also come down. Looking for strange and wonderful printing filament? Here you go.

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Teardown Of A 5th Generation Prius Inverter

The best part about BEV and hybrid cars is probably the bit where their electronics are taken out for a good teardown and comparison with previous generations and competing designs. Case in point: This [Denki Otaku] teardown of a fifth-generation Prius inverter and motor controller, which you can see in the video below. First released in 2022, this remains the current platform used in modern Prius hybrid cars.

Compared to the fourth-generation design from 2015, the fifth generation saw about half of its design changed or updated, including the stack-up and liquid cooling layout. Once [Otaku] popped open the big aluminium box containing the dual motor controller and inverters, we could see the controller card, which connects to the power cards that handle the heavy power conversion. These are directly coupled to a serious aluminium liquid-cooled heatsink.

At the bottom of the Prius sandwich is the 12VDC inverter board, which does pretty much what it says on the tin. With less severe cooling requirements, it couples its heat-producing parts into the aluminium enclosure from where the liquid cooling loop can pick up that bit of thermal waste. Overall, it looks like a very clean and modular design, which, as noted in the video, still leaves plenty of room inside the housing.

Regardless of what you think of the Prius on the road, you have to admit it’s fun to hack.

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Need For Speed Map IRL

When driving around in video games, whether racing games like Mario Kart or open-world games like GTA, the game often displays a mini map in the corner of the screen that shows where the vehicle is in relation to the rest of the playable area. This idea goes back well before the first in-vehicle GPS systems, and although these real-world mini maps are commonplace now, they don’t have the same feel as the mini maps from retro video games. [Garage Tinkering] set out to solve this problem, and do it on minimal hardware.

Before getting to the hardware, though, the map itself needed to be created. [Garage Tinkering] is modeling his mini map on Need For Speed: Underground 2, including layers and waypoints. Through a combination of various open information sources he was able to put together an entire map of the UK and code it for main roads, side roads, waterways, and woodlands, as well as adding in waypoints like car parks, gas/petrol stations, and train stations, and coding their colors and gradients to match that of his favorite retro racing game.

To get this huge and detailed map onto small hardware isn’t an easy task, though. He’s using an ESP32 with a built-in circular screen, which means it can’t store the whole map at once. Instead, the map is split into a grid, each associated with a latitude and longitude, and only the grids that are needed are loaded at any one time. The major concession made for the sake of the hardware was to forgo rotating the grid squares to keep the car icon pointed “up”. Rotating the grids took too much processing power and made the map updates jittery, so instead, the map stays pointed north, and the car icon rotates. This isn’t completely faithful to the game, but it looks much better on this hardware.

The last step was to actually wire it all up, get real GPS data from a receiver, and fit it into the car for real-world use. [Garage Tinkering] has a 350Z that this is going into, which is also period-correct to recreate the aesthetics of this video game. Everything works as expected and loads smoothly, which probably shouldn’t be a surprise given how much time he spent working on the programming. If you’d rather take real-world data into a video game instead of video game data into the real world, we have also seen builds that do things like take Open Street Map data into Minecraft.

Thanks to [Keith] for the tip!

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