Mysterious Files PH

Heat pumps are great, because they pump heat around, and we often don’t want heat where it is. Need it somewhere else? Pump it! It’s great. It’s also a bit pricey if you’re buying new, but [Craftsman Chris] over on YouTube realized that the window air conditioning unit he found in a dumpster is, in fact, a heat pump. Normally it’s an air-source heat pump, but with a delightful series of hacks, he gets it automated and hooked into a ground loop in his latest YouTube video.

The heat sink is provided by a bunch of PEX tubing [Chris] buried in his back yard. After experimenting with using the water loop for cooling directly, he realized that pumping heat out of his house into the cold ground would go much better with a heat pump. That’s where the window A/C came in. After cleaning and servicing it, it was time to convert it to dump heat into water rather than outside air. To do that, [Chris] welded up a tank made of scrap metal around the existing heat exchanger. It’s designed for air, sure, but water takes its heat just fine. The nice thing about this is that by keeping the internals of the air conditioner mostly stock, he doesn’t let out any of the tasty, tasty CFCs that may be hiding inside.

Connecting this unit to his thermostat is equally hacky– he takes an old Programmable Logic Controller that looks fit to run a small factory, and hooks it to a single linear actuator to poke the A/C unit’s stock power button. Is it elegant? No. Does it work? Yes. Is it a hack? Indubitably!

We’ve seen window units pressed into whole-house A/C service before, but adding the water loop is a great hack. We saw a window A/C used as a ground-source pump before, too, but that was a Canadian project and so sensibly turned the machine around to provide heating for the maple mansion.

One of the most fun challenges in paleontology is determining characteristics of long-dead species like their behavior and body temperature based on nothing but some fossils and traces that are usually millions of years old. Something that has long vexed the paleontological community for example has been the question whether non-avian dinosaurs like the well-known Tyrannosaurus rex was cold- or warm-blooded, and if the latter, what temperature this was. Cue a recent study by [Randon J. Flores] et al. in Science Advances in which they seek to answer this question.

Although modern-day dinosaurs in the form of birds are all warm-blooded – meaning capable of regulating their body temperature – species like crocodiles, who also lived alongside non-avian dinosaurs, are cold-blooded and have to cycle between sun-basking and a cool dip in a nearby river to maintain their body temperature.

By looking at the temperature-dependent formation of carbonate clumped isotopes in three T. rex teeth from the Late Cretaceous Hell Creek Formation, they were able to deduce that these dinosaurs had a body temperature of 36.3 ± 2.5°C, comparable to modern-day endotherms. This was also much higher than that of contemporary crocodilian teeth found in the same area.

When popular dinosaur movies like Jurassic Park showed T. rex and other non-avian dinosaurs as being active, warm-blooded hunters, this was pretty much based on cutting-edge science at the time. Fortunately for its creators, later paleontological findings have largely confirmed that portrayal, although these days non-avian dinosaurs have often gained more feathers and other details – even outside of feathered theropods that became birds – that were absent in these early 90s reconstructions.

Hacking on Raspberry Pi board internals is one of my favourite topics. I know a bunch of obscure things about these cute little boards. Three years ago, I covered a Raspberry Pi 4 RAM upgrade story. Getting a BGA RAM chip and swapping it in seemed like a no-brainer to me – apart from all the numerous uncertain parts about it, you know. It was a joy to see hackers pull it off, and for it to function as well as it did!

Things changed. You can’t really get RAM chips anymore. You also can’t get RAM sticks. You can’t get even SSDs with RAM chips on them. Even getting Raspberry Pi boards can be hard unless you know where to look. This is where a recent three-minute video by [Jeff Geerling] finds us.

Turns out, Raspberry Pi Foundation pushed binary-blob bootloader changes that limit your ability to upgrade RAM. I’ve known about it since last year through the grapevine, and somehow, as I read about it, this didn’t bother me at all. Not enough to write a Hackaday article about it, even, much less talk about it more widely. Why didn’t it bother me? Today, I sat down and pondered this for a bit.

Here’s my conclusion: I don’t think it’s a big deal at all, even if it seems that many people would disagree. Come in, as you are, and I hope you find my thoughts on the situation entertaining.

How It’s Made

First, some ground facts. This change restricts upgrading the RAM chip on your Pi 4 and Pi 5, as well as Compute Modules. By the looks of it, it does not restrict replacing the RAM chip with a chip of a similar size, quote, “locking devices to their original RAM size”. As such, this does not prevent repair of your Raspberry Pi board, but does somewhat limit your repair part choice, at most.

This restriction is easily bypassable. The bootloader is stored in the SPI flash chip, which can be reflashed using the built-in mask ROM over USB and rpiboot, and you are not prevented from flashing older versions of the bootloader, so far. This means even if you manually swap the RAM chip, all you need to do is to also downgrade the bootloader to the last known good release — 2024-09-10 — and then your Pi board or Compute Module will function with upgraded RAM. If you have the skills to upgrade your RAM, you most certainly have the skills to downgrade the Raspberry Pi bootloader.

For most regular use, having a two-year old bootloader version won’t really matter. There have been about 15 releases since the 2024-09-10 one, so I went and read through the patchnotes. Checking quickly, the important features like NVMe boot have been available for a fair bit before this release, maybe you will miss out on a few quality of life fixes or more obscure hardware configuration problems, but that’s it. Hopefully I’m not missing something, please point it out if I am. You know what is an issue, by the way? The patch notes for the 2024-09-23 release don’t mention the RAM size check addition at all, maybe they should fix that.

What’s funny is, I am checking reports and it seems that the board will boot and function well with newer bootloaders (mostly 2025 versions), and in other cases (mostly but not always 2026 bootloader versions) it will outright refuse to boot with a 8 or 9 flash failure code. I haven’t compared details on what exactly might be causing this yet, but it might be that you don’t even need to downgrade bootloader all that badly – though I’d definitely start with the oldest known-good release.

How It Happened

This is the first reason I can’t bring myself to care. If you can upgrade your RAM, you can downgrade the bootloader. However, here’s the point of contention – did this change really need to happen?

For the reference, this bootloader change happened almost exactly two years ago, at some point between September 10 and September 23, 2024. This was exactly a year and a half after we covered the first Raspberry Pi RAM upgrade. What changed?

The Raspberry Pi Foundation (RPF) justifies this as follows: they saw third-party resellers sourcing low-RAM Compute Modules, upgrading them with RAM from unknown source and unknown stability. My observation is that they’d also be reselling the modules at a markup for purely commercial gain, while undercutting RPF who would otherwise direct that money into RnD, something I much enjoy to see them do. This creates perverse incentives and risk for people buying Raspberry Pi boards online, and RPF decided to limit this primarily for their users’ benefit, plus, if you ask me, some of theirs.

Is this justification true? I can’t know, but I went to check for signs of this happening, and the non-consensual RAM switcheroos seems to be happening all over the place! The related GitHub issues have a fair few pingbacks, and exploring them makes the problem look grim to me.

Off the cuff, I spent 15-20 minutes checking, and I can easily find fifteen different people on GitHub alone complaining about this failure. [(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)] As far as failure modes in popular hardware go, this is a surprisingly large number that suggests at least hundreds of hackers and hobbyists affected, if not more. None of them appear to have performed the upgrade themselves, hot air and flux way, the Hackaday way – all of them seemingly simply bought a “8 GB” version from either Aliexpress or Amazon. In at least one case, the seller immediately lied to the buyer about the issue and did not at all admit that an upgrade took place, even though it clearly did.

How It Makes Sense

This seems to map exactly to what RPF says happened. I can very much see why they would be worried. For instance – at the time they made this change, if my memory isn’t failing me, CM5 or CM4 2 GB boards went for $30-$40, 8 GB boards went for $100ish, and 4 GB boards were somewhere inbetween. As far as the intersection of hacker gadgets and industrial-lite hardware goes, that price is more than fair.

At this point, we’re no longer talking about people upgrading RAM on their boards for fun, and remember, you can still do all of that. Instead, that’s a fair bit of margin for someone to grab for 20 minutes of hot air work, someone who hasn’t done any of the RnD that RPF has put in. I personally much rather would see that margin go to RPF, and I’d like to have them deal with none of the headache, too.

Creating incentives for this kind of switcheroo business, unimpeded, seems deeply corrosive to me. For one, there’s zero repercussions for someone equipping those boards with substandard and harvested chips. RPF, as any experienced hardware company, would know about sourcing harvested or otherwise shady-origin RAM and other chips. A third party on Amazon/Aliexpress passing on those chips undisclosed to unqualified end users, now that goes far beyond the usual harvested chip horror stories. It turns into a game of “will/won’t the user notice the weirdness and ask the seller for a refund on time”, and at $100-$200, together with the ship-item-back requirement these prices bring, the answer will generally be “no”. Now, the buyer finds out about the tampering almost immediately, since Raspberry Pi boards auto-update the firmware.

If you don’t agree that this alone is corrosive – notice how this kind of “upgraded” board clearly requires sellers to misrepresent what they’re selling? You’re not going to find about this “upgrade” in the listing, there won’t be a “8GB reworked” label, clearly that would require lowering the price and/or cutting into the margins. Just like there’s no incentive for using a fresh RAM chip instead of a harvested one, there’s also zero incentive to be open about the mod. That’s no way to sell a pen, much less a full computer.

How RPF Does Things

Here’s the most confusing part to me. I’m seeing [Jeff] and others say that this is out of character for RPF to do. This does not seem true to me, at all? I don’t recall a time when Raspberry Pi has put effort into giving users freedom to hack on the board itself as soon as any sort of legal or competition issue arose.

Raspberry Pi puts cryptographic EEPROMs on Pi Camera boards, v2 and beyond, to thwart clone cameras that became so prolific and cheap with v1, I own at least five of those clones in different form-factors. I don’t like it, but at least the authenticity checks are disabled for Compute Module versions, as far as I remember. They still don’t sell the MLX7704 PMIC that immediately dies if you accidentally short-circuit GPIO header 5 V to 3.3 V, two male pins that are right on the side of the board and exceptionally easy to short-circuit from three sides simultaneously.

Raspberry Pi only ever publishes “reduced” schematics, ever since 2013, and they haven’t even released those for Pi 5. Neither have they published Pi 4 USB-C issue fix schematics despite having promised to do so. Half of the chips on a modern Raspberry Pi board are single-source and board-specific, the aforementioned PMIC being a fun example. Raspberry Pi boards ship closed-source software, from the bootloader to the GPU code whipping the CPU, to all the onboard wireless chips they have used so far, and this brings real issues you’ll stumble upon as you push the limits. The JTAG port has always been locked down, and even the bootloader is cryptographically signed – no patching out the RAM check code, sorry to spoil it.

I’m far from done listing ways in which Raspberry Pi prevents or works against low-level board tinkering, there’s at least five more things I could list from memory if I were bothered to check them thoroughly enough right now. Point is, if anyone came to Raspberry Pi for the low-level hackability of the hardware, there was never a shortage of reasons to look elsewhere. That was never the upside.

I don’t think low-level board hackery is what people genuinely expect from Raspberry Pi at all, even if they might say that they do – because it was never really there. You can’t genuinely expect something that was barely ever present. In contrast, there’s plenty of competition that publishes full board schematics, sometimes even gerbers, uses as much open code as possible, doesn’t sign bootloaders, and so on. Raspberry Pi is not open or hackable hardware by those metrics, and it never was. It’s not hackable hardware anywhere as much as it’s hardware made for hackers to use, and there’s clearly a big difference.

How Did We Get Here?

In practice, people clearly come to Raspberry Pi because of their community in the millions, meticulously explored and documented hardware, unmatched availability of boards and software alike, having solutions for nigh every little niggle and nitpick, RPF’s ability to experiment and release new cool hardware year after year, and even new standards they create along the way. Most of low-level problems get papered over through sheer scale – say, last year [Jonathan Clark] reverse-engineered the Raspberry Pi Zero 2 W, and then [TubeTime] reverse-engineered the Compute Module 5, how cool is that?

I could agree with [Jeff Geerling] that it could instead benefit from a “warranty bit” type of mechanism, but really, the bootloader downgrade isn’t that hard of a penalty, and “board autoupdates firmware, fails on next boot” is a much stronger indicator that you should go get a refund at haste. A refund is also way easier to get if you say “hey, the board stopped working immediately”, and who knows, maybe you’ll get a refund and get to keep the board so that you can downgrade its firmware and still use it! Win-win, seller loses out on selling you a shady board, and you get a shady board that might just work, for free. Chances are, we wouldn’t even be talking about the RAM swap restrictions if it weren’t for the RAM shortage, and that is not RPF’s fault at all whatsoever.

My advice: don’t lament Raspberry Pi RAM upgrades, especially given they’re only slightly harder to perform now. Very few hackers ever performed them, the main audience for them turned out to be dodgy hardware resellers online, and in most cases, repair doesn’t seem to be impeded at all, either.

Think of the users that will no longer be fooled by a shady seller on Amazon, especially now that the perverse incentives for board mods and reusing harvested RAM chips are at their highest. RAM shortages might make any RAM topic hurt deeper than usual, which to me is the most likely reason we’re discussing this in 2026 instead of 2025, but this change is far more likely to help a hacker in practice, than it is to hurt.

Even if the world has already settled on plain old propellers as the way to make quadcopter drones fly, this doesn’t mean that you cannot give other designs a shake to see what kind of flying performance they result in. For example impeller designs that depart radically from standard propellers – themselves a sub-category of axial impellers – and go radically radial instead as in this design by [quadmovr] with accompanying demonstration video.

This is itself a remix of a design by [Baba] to make it fit the target 1750KV T-mount motor. As for whether this is a design that you want to slap on your own quadcopter, the obvious disadvantage is that it’s much heavier than regular propellers.

Weighing [quadmovr]’s drone without battery pack and with these 3D-printed PETG impellers shows them to weigh 189 grams. This compares to 141 grams with the standard three-bladed propellers, or a hefty 12.8 gram weight penalty per impeller. Naturally this translates into less flying time, so what are the advantages?

The noise profile of the impeller design is definitely more pleasant, and much like novice quadcopters with the protective ring around the propellers these impellers should be more robust. On the other hand increased mass adds to inertia, and there is a lot more surface area with the air to add drag, so despite the absolutely sick moves that [quadmovr] pulls off with both impeller configurations in the video one has to admit that regular three-blade propellers do have the edge here.

In the US, among other places, housing costs are skyrocketing. It can sometimes be difficult to get a feel for the scale of the issue and how it hits neighborhoods differently. [Justin Blinder] has designed a device to help people get a more visceral understanding of the problem.

In New York City, Citi Bikes are everywhere in the city’s transportation landscape. [Blinder] used a GPS module plugged into an ESP32S3 to vary the amount of resistance on one of these bikes by actuating the front brake with a servo. As a rider takes the bike through different neighborhoods, the resistance varies in proportion to the rent burden experienced there.

[Blinder] explains, “One of the main technical challenges was calibrating this relationship so that the changes were physically noticeable without feeling abrupt or unsafe.” As rent burden is merely the percentage of income taken up by rent in an area (by the block in this dataset), it is only one indicator of the additional friction a family might feel in an area, but a useful one to at least begin to convey the disparities in the urban environment. We really like how this connects abstract statistics to something more experiential.

If you’re looking for some other bike hacks, how about wireless brakes or a sleeper e-bike with a solenoid display?

via Next City

Nuclear power really hit its stride in the 1950s. In the post-war period, there was a rush to develop peaceful uses for splitting the atom, beyond its application as a weapon of war. Soon enough, nuclear reactors were hooking up to power grids and helping propel ships and submarines around the globe.

Eventually, this led to an obvious idea—what if a ship with a reactor could serve as a floating nuclear power station? That question would be answered in the mid-1960s, with an American project of some strategic importance.

Whatever Floats Your Boat

You might think that the first floating nuclear power plant would have been a US or Soviet navy project, but you’d be quite wrong. Instead, it was actually the US Army which was responsible for achieving this feat. The project began as part of the US Army Nuclear Power Program, which was intended to develop small reactors that could be deployed to remote regions to supply electricity. One of the results of that program was MH-1A, the nuclear reactor abord the vessel otherwise known as the USS Sturgis.

The contract for the Sturgis’ reactor was awarded to Martin Marietta in 1961. Termed the MH-1A, standing for Mobile, High Power, the reactor was a pressurized water unit running on low-enriched uranium, built inside a 350-ton containment vessel. Nameplate capacity was a healthy 10 megawatts. The ship itself was not a clean-sheet design; instead, it was built out of a converted Liberty Ship left over from World War II. The former cargo vessel was formerly known as the SS Charles H. Cugle. As part of its conversion, it had its propulsion system removed, since it was intended to operate from fixed moorings or anchorage for extended periods of time. It was deemed uneconomical to otherwise maintain the capacity for independent propulsion.

The MH-1A reactor was installed in the Sturgis while it was moored at Gunston Cove, near the Fort Belvoir facility that hosted the Army’s very first nuclear reactor, the SM-1. The reactor first went critical in January 1967, and was accepted into Army service six months later in July. The Sturgis would remain at Gunston Cove for the following 11 months, where it supplied electricity to Fort Belvoir in lieu of any required operational use.

The Sturgis did not have to wait long to be called into service. It was initially considered for deployment in the Vietnam theatre, but instead, it would wind up serving in Central America—but not for entirely unrelated reasons. In 1968, the Panama Canal was

facing somewhat of a crisis. The dry season led to water shortages, with authorities forced to ration what was ran through the Gatun Hydroelectric Station for local energy needs, and what was used to run the locks to allow ships to transit the Panama Canal. To aid in keeping the canal open, the US Army deployed both the Sturgis, as well as the Andrew J. Weber, a diesel-powered power barge of some 20 MW capacity. The two ships were hooked up to support the power needs of the Canal Zone, in turn freeing up water resources for the locks of the Panama Canal. This allowed the passage of an additional 15 ships through the canal per day. The deployment wasn’t entirely altruistic, of course. Keeping traffic flowing through the canal was undoubtedly an aid to US logistics during the Vietnam War, with much materiel passing through this route during the conflict. The Sturgis ultimately stayed on station until 1975, eventually being replaced by Hitachi turbine generators instead.

Beyond its trip to Panama, the Sturgis didn’t have much else to do. It was retired from service in 1976, since the Army Reactor Program had been ended and its generation capacity had been replaced with more practical solutions at the canal. It returned to the US in 1977, where its fuel was removed at Fort Belvoir. It was then moored as part of the James River Reserve Fleet for long-term storage. Eventually, a $35 million contract was awarded in 2014 to decommission and dispose of the reactor, with the rest of the ship then to be scrapped as per usual shipbreaking practices. The process was completed by 2019, and the world’s first floating nuclear power station was no more.

The story of the Sturgis is rather a strange one. Military planners conceived that a floating nuclear power plant could be incredibly useful, and not long after it was completed, they found the perfect application for it. Once that application was no longer important, the ship was mothballed in short order.

Since then, the world hasn’t seen a whole lot of floating nuclear power stations. Russian efforts netted a single nuclear-powered barge in 2019, but plans to produce more have not yet come to fruition. Ultimately, it seems hard enough for our modern civilization to put together new reactors for use on land, let alone portable floating units that can be deployed at will. It seems like there just isn’t quite enough demand to justify their existence in greater numbers than one at a time.

Featured image: “MH-1A, STURGIS Nuclear Barge”, US Army Corps of Engineers

Coaxing a DVI signal out of a microcontroller to drive a DVI or HDMI screen has been possible for a while now, but limitations in what the devices can do has, in turn, placed a limit on the resolution that can be delivered. Now [Aaron Gayle] has broken through a barrier by generating 1080p video from an RP2350. The previous best from Raspberry Pi Pico-class microcontrollers was 720p, which an RP2040 could deliver. The 2350 is faster and has faster peripherals, but even then, to reach this resolution he had to overclock it to 372 MHz. For all the impressive achievement, there’s still a limitation. Lacking space for a framebuffer, he generates scanline by scanline, a technique we associate more with 8-bit computers from the 1980s.

The 1080p video code is part of a package called TVtop, a board game in which the game board is displayed on the TV and whose players interact from their phones via Wi-Fi. For that reason, there’s an ESP32 in the project too, though it has nothing to do with the video hack.

Now that an RP2350 has been shown to generate 1080p, we look forward to seeing others building upon this achievement in terms of what video can be delivered. If you do something, be sure to let us know.

Meanwhile, Aaron tells us he was inspired by this Hackaday story, which asked if it was possible.

Header image: Raspberry Pi, CC BY-SA 4.0.