Mysterious Files PH

When life gives you lemons, you make lemonade. What if life gives you a pile of old e-book readers? Well, when [spiritplumber] got box of old Nook Simple Touch devices, he decided to design solar-powered cases to help boost the old batteries. It makes perfect sense to us: sunlight readable screen, sunlight chargeable battery.

It looks like he’s got a pair of panels built into the 3D printed case. He recommends using any TP4056-based charger, and tying into the battery test points, not the 5 V supply. It won’t hurt anything if you do, apparently, but the device will think it’s plugged in an refuse to turn off the WiFi. That’s no big deal when you’ve got a continental power grid on the other end of the cable, but charging from a small panel on the back of the case doesn’t always give you enough juice to waste on unneeded radio activity. Especially indoors — these panels are apparently big enough to trickle-charge the device under artificial light, which is a nice, if doubtless slow feature.

The design is open source, and includes SketchUp design files as well as the exported .STL, so if you’ve got a hankering to edit this to fit a different e-book reader, you can. He also provides a handy-dandy guide to root this model of Nook, and if you’re on Hackaday we probably don’t need to explain why you might want to.

We’ve seen the Nook Simple Touch go some interesting places — like into the clouds as a glider computer — but solar power is a new hack for this device, at least on this site. We don’t know if [spiritplumber] has a green thumb, but he’s evidently got some environmental bones in his body: his last featured project was about improving quadcopter efficiency with a wing and a prayer.

The ionosphere is of great importance to shortwave radio transmissions, since it allows radio waves to be refracted and reflected over the horizon, and it’s therefore unfortunate that the height and thickness of the ionosphere depends on the time of day or night, weather, season, and the solar cycle. To get a better idea of current transmission conditions, [mircemk] built this shortwave propagation monitor.

The monitor provides a basic measure of ionosphere conditions by measuring the strength of received shortwave signals: if the conditions for transmission are good, it should receive a relatively high level of existing signals, and a weak signal if conditions are bad. It has an external antenna connected to a signal strength indicator circuit based on the CA3089, which amplifies signals in the 1-40 MHz range and outputs a smoothed voltage indicating the RF energy in this range. The output signal can be read by any voltmeter, in this case an Arduino Nano with an OLED display. Assuming the same antenna is always used, the signal should noticeably fluctuate between night and day as the solar wind affects the ionosphere.

Of course, the distance at which you’ll be receiving a signal means nothing unless you have a receiver, which can range from the antique to the modern.

Making stuff cool and keeping it that way has been a pretty essential part of human civilization for thousands of years, with only in the past few hundred years man-made methods having become available that remove the reliance on the whims of nature and lugging around massive blocks of ice. The most important cooling method is undoubtedly that of vapor-compression refrigeration, but this is hardly the only method to transfer thermal energy from one location to another.

For example, we recently covered an elastocaloric cooling project by a group of scientists that uses strips of NiTi metal. By flexing these they induce a cooling effect which when put in a number of stages serves to transfer a significant amount of thermal energy between both sides, much like a vapor-compression system but without the gases and compressor. Meanwhile the Seebeck effect is relatively well-known from Peltier thermocouple devices, and features heavily in portable refrigerators and kin where these solid-state devices can also transfer thermal energy.

Of course, along with how they function the major question with all of these cooling technologies is how efficient they are, as this determines when you’d want to even consider them for a specific application.

The Science Of Cold

Although as animals we have an intuitive understanding of what concepts like ‘cold’ and ‘hot’ are in the sense of comfort levels, on a fundamental level the related concept of temperature is about the kinetic energy of the particles in a system. Essentially, the more kinetic energy exists in the system, the higher the temperature of said system is, regardless of whether it’s a liquid, gas, solid or plasma. Hence a temperature of zero Kelvin is the complete absence of any such kinetic energy in the system, also known as the Third Law of thermodynamics:

As the temperature of a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.

When we talk about moving thermal energy from one location to another – as in refrigeration – this thus means transferring said energy from one system to another in some fashion, something which is covered by the First Law of thermodynamics:

In a process without transfer of matter, the change in internal energy, , of a thermodynamic system is equal to the energy gained as heat, , less the thermodynamic work, , done by the system on its surroundings.

In the case of a hot water bottle or ice bag we are actively changing the energy balance of a system by transferring matter. This makes such transfers rather lossy, which is not a quality that is generally desirable in a refrigeration system. Thus we prefer a closed system in which the matter is ideally never lost, and thus all the energy transfer occurs via reversible processes.

Vapor-Compression

In vapor-compression refrigeration a liquid – the refrigerant – is circulated through the system, alternately changing state into a gas by absorbing thermal energy from the environment, before shedding this energy again while condensing back into a liquid.

A key component in this system is the compressor, which takes in the saturated vapor. This means that said vapor contains enough energy to effect the liquid-gaseous transition, but is still pretty close to the condensing point.

By compressing this vapor into a smaller volume its temperature increases since roughly the same amount of kinetic energy exists within the system. This superheated vapor then passes through the condenser, like the radiator found at the back of the average kitchen refrigerator. Here the superheated vapor condenses back into a liquid, with the higher temperature and pressure helping to make the condensing process more efficient. This is also why said refrigerator radiator can feel so warm to the touch.

The role of the expansion valve is effectively the opposite of the compressor: as the name suggests this is where the liquid refrigerant at high pressure suddenly transitions back to a low pressure, causing adiabatic flash evaporation of part of the liquid into a vapor. This reduces the temperature of the refrigerant, making it colder than e.g. the inside of the refrigerator and drawing in kinetic energy from the air inside said refrigerator before the vapor makes its way to the compressor again.

Elastocaloric Cooling

With elastocaloric cooling (ECC) there is no liquid refrigerant or a pressure differential. Instead they rely on the elastocaloric effect, which is thermomechanical in nature.

Similar to how the refrigerant with vapor-compression refrigeration can absorb energy as it transitions from liquid to vapor and vice versa, with the elastocaloric effect it is the material itself that absorbs thermal energy from its environment when it’s mechanically loaded.

The aforementioned NiTi alloy is also known as a shape-memory alloy (SMA), which are generally known to be heat sensitive, finding use in applications like thermal fuses and sensors.

While the application of heat or cold can cause the deformation, this also works the other way around when mechanical force is applied. This is readily demonstrated with a strip of NiTi SMA and a thermal camera, as in this video by Helge Wurst:

As the strip is bent, the area experiencing the deformation becomes rather warm to the touch, with subsequent relaxation causing the same area to become cold to the touch.

Using such strips and mechanical actuators capable of applying 900 MPa of pressure, Guoan Zhou et al. were able to achieve freezing temperatures. They did this by combining multiple of such elastocaloric stages with CaCl₂ as heat-exchange fluid. This is not a mainstream cooling method so far, but it should be quite reliable and low-maintenance.

Magnetocaloric Cooling

The magnetocaloric effect (MCE) was first observed in 1881 by German physicist Emil Warburg, with the early 20th century seeing significant progress towards using it for cooling applications. This particular effect as the name suggests consists of exposing a material to a magnetic field, with this material then drawing in thermal energy. Upon removal of the magnetic field the material sheds this gained energy as well as some additional energy, thus cooling down relative to its environment.

Similar to the elastocaloric effect, this relies on an adiabatic process: without the transfer of any matter or entropy. This makes it a fully reversible process that can be repeated by successive applications of said magnetic field.

The biggest disadvantage with this effect for cooling purposes is that it’s only a very strong effect (giant MCE, or GMCE) in a limited number of alloys discovered so far. The first significant here was a rare-earth gadolinium-based alloy, Gd₅(Si₂Ge₂), that showed GMCE at 270 K. This relatively low temperature and the use of rare-earths made this a tough sell.

More recently discovered alloys like Ni₂Mn-X, where X is a variety of additives, display the GMCE near room temperature and even saw GE demonstrate an Ni-Mn-based magnetic refrigerator in 2014. So far commercialization of GMCE-based refrigeration is still rather limited but there is a push to make it work for generally less efficient vapor-compression-based home refrigerators.

Electrocaloric Cooling

Although easy to confuse with the magnetocaloric effect, the electrocaloric effect (ECE) pertains to the application of an electric field in dielectric materials. The effect is roughly the same, with the dipoles in the material either assuming an ordered or disordered state, depending on whether the field is respectively applied or turned off.

So far ECE-based cooling hasn’t seen commercialization yet either, though the past years there have been a range of breakthroughs, with for example Xin Chen et al. demonstrating ECE polymer films in 2023 that was subsequently used to create a thin-film refrigerator prototype with. This was claimed to achieve a Coefficient of Performance (COP) of a rather astounding 24, which compared to traditional heat pumps would make it a rather interesting solution if it can be commercialized.

Thermoelectric Cooling

The thermoelectric effect and the associated Peltier cooling devices are probably the most well-known and most heavily commercialized on this list along with vapor-compression. Within the thermoelectric effect, the Peltier effect concerns thermocouples and their associated temperature differences, thus lending its name to what are alternatively called ‘Peltier coolers’ as well as ‘thermoelectric coolers’, or TECs.

Rather than a refrigerant or rearranging of dipoles here the transfer of kinetic energy is performed using charge carriers within the TEC. On average charge carriers move to the ‘cool’ side, allowing them to transfer heat away from the other side.

As is well-known, this Peltier effect is rather limited when used as a heat pump, with very low efficiency and strict limitations on temperature differences. This is why their use in dehumidifiers and portable refrigerators is at best questionable.

The main reason why TECs are so popular can be said to be due to vapor-compression refrigeration being so bulky and neither elastocaloric, nor MCE, nor ECE solid-state coolers being quite ready for prime-time yet at the low-low price level that TECs can achieve due to being dead-simple semiconductor devices.

Pulse Tube Cooling

Another interesting, partially solid-state cooling method is the pulse tube refrigerator (PTR), which has seen limited use in commercial and other applications. Its main advantage is that it can be used as a cryocooler, making it ideal for space telescopes where sensors have to remain super-cold.

At its core it’s reminiscent of vapor-compression refrigerating, in that it uses a gas and a compressor, yet there’s no circulating loop of refrigerant. Inside the tube a piston alternately compresses the gas – often helium – which forces it through the regenerator. As the compression raises the temperature of the gas, this heat is then passed onto the material of the regenerator. On its way back through the regenerator this heat is then returned to the gas, explaining the name of this component.

The hot and cold sides of the regenerator are hereby used for cooling, though other PTR configurations are possible, such as the coaxial design. The relatively straightforward mechanical design and low temperatures achievable are why hobbyists are tinkering with PTRs in order to do things like making their own liquid nitrogen.

Chill Choices

Ultimately the question of what the right cooling method is for your particular task depends on a range of factors, including the required efficiency, available space and whether or not that big research grant budget just became available.

In terms of commercially available options that aren’t outrageously expensive, your options are somewhat limited, especially if you do not have a lot of space available. It’s possible that in a number of years these alternate technologies will be commercialized and wipe the floor with TECs in particular, but unless you’re currently heavily into tinkering with strips of NiTi SMA to build your own cooler, the primary options would seem to be either vapor-compression or TECs.

That said, considering that only a hundred years ago we were only just beginning to transition from iceboxes to vapor-compression refrigeration, it’s already pretty neat that we have some rather chill options to use today, and absolutely cool ones to look forward to.

Featured image: “Frosted Flakes“, National Park Service photo by [Neal Herbert]. Thumbnail image: “Frost” by [XoMEoX].

Solarpunk is sometimes thought of as the “good ending” to cyberpunk– there’s technology, but it’s community-focused instead of in the hands of evil conglomerates, and– if the name doesn’t give it away– renewably powered. [Victor Frost] found that image of the future inspiring enough to create this ESP32-hosted community hub. Yes, it looks like a lantern, but it’s actually a very-local webserver.

Local webserver sounds like an oxymoron, but this device does serve a page over HTTP… just, not on the world-wide web. Instead the only way to access it is via its own Wireless Network– he’s using the ‘captive portal’ that forces you to log into public wifi to direct people to a community message board.

It’s unmoderated, and unfiltered– users can post what they like, but given that they have to be within a few meters of the device, it’s not exactly anonymous. It’s a lot like the community center corkboard brought into the 21st centruy, which is very in keeping with the solarpunk ethos.

For ease of updates, he’s subdivided the ESP32’s flash into three partitions: one for the data, and two for the software, using LittleFS. This allows live updates and keeping a known-good backup for the quickest possible turnaround and/or rollback. One interesting thing is that his who UI– the actual web site, HTML, CSS, and JS– is all crammed into a single string in PROGMEM rather than files on the little file system. It’s an interesting choice, and makes for quick updates, firmware and UI in one go. Not everyone will like it, but it works for [Victor]. The code is, of course, on GitHub under the GPL— there’s a lot of overlap between the open source and solarpunk ethos, after all.

It’s a bit of a pity that he missed our Green Powered Challenge, as this project would have fit right in to the PV category, considering it runs on a 6W panel. For all the cyberpunk and solar power you see on this website, you’d think the “solarpunk” tag would be more popular, but no– all we have is this stained-glass robot.

Thanks to [Victor] for the tip! If you missed our contest, too, no worries– we take projects of all colours, green or otherwise, all the time. Just drop us a tip. 

Although the ReactOS project is in no rush to dethrone Windows as the desktop operating system of choice, this doesn’t mean that some real changes aren’t happening. Most recently two big changes got merged, the first pertaining to the separate boot- and live CD images that are now merged into a single image, and the second being a new PnP-aware ATA storage stack for ATA and AHCI devices, with NT6+ compatibility.

Although there is still a separate live CD for now, this first change means that testing and installing ReactOS becomes easier, and that the old-school text-based installer may soon be on its way out as well.

Having the new ATA storage stack in place will translate into much better compatibility with real hardware, including the ability to use more hardware to install on and boot from compared to the old UniATA driver.

Combined, these two changes should bring the ReactOS installation and usage experience a lot closer to that of Windows, as well as many Linux distros. If you had issues with the OS on real hardware, this might be just the right time to give it another shake and provide detailed feedback to the developers if any remaining issues are encountered.

Thanks to [jeditobe] for the tip.

Software that collects public data from the Internet and uses it to provide half-assed answers to your questions might seem like a modern craze, but today we bid farewell to a website that helped pioneer pretend conversations all the way back in 1997 — as of May 1st, Ask Jeeves is no more.

Well, technically they dropped the “Jeeves” part back in 2006. Since then it’s just been Ask.com, but as the name implies the idea was more or less the same. Rather than the relatively rigid parameters and keywords required by traditional search engines, you could ask Jeeves questions about the world using natural language. Early advertisements showed the virtual valet answering arbitrary questions like “How many calories in a banana?,” which of course today seems commonplace and utterly unimpressive, but was a pretty wild for the 1990s.

It might seem surprising that a site designed from day one to offer a human-like Q&A experience should fold right as such technology is becoming commonplace. But of course, that commonality is the problem. When Google can answer your questions just as well (or poorly…) as Jeeves or anyone else, what’s the benefit for the average Internet user to seek out another service? But it’s still somewhat ironic, which is probably why the farewell message on Ask.com ends with the line “Jeeves’ spirit endures.”

While on the subject of technology that’s potentially ahead of its time, MacRumors is reporting that Apple is giving up on their Vision Pro augmented reality googles. They haven’t been formally discontinued as of yet, but sources indicate that the internal development team for the entire product line has been disbanded and reassigned to other projects within the company. This comes after a October 2025 refresh of the hardware still failed to connect with consumers. Insiders have said that not only were sales sluggish on the ~$3,500 headsets, but that they were getting returned at a far higher rate than any of Apple’s other hardware products.

Now, we’re hardly Apple apologists here at Hackaday. It sort of goes without saying that the whole “Walled Garden” thing doesn’t really fit our ethos. But we can’t deny that the Vision Pro is an impressive piece of technology. After years of sticking our phones in crappy plastic headsets, or trying to force hardware designed for VR gaming to do literally anything else, the Vision Pro offered a practical way to put augmented reality to work. But even for a company known for producing expensive hardware, the price tag was just too much for most consumers.

We’ll go out on a limb here and predict that the Vision Pro will one day be looked back on like the Newton — a product that was too expensive and niche to be a commercial success when it came out, but still a technical milestone that gave us a glimpse into the shape of things to come.

Speaking of a technology that will inevitably become more common, the European Patent Office (EPO) released a report this week showing a seven-fold increase in the number of inventions intended for battery reuse and recycling over the last decade. Given our insatiable demand for rechargeable batteries, it should come as no surprise that there’s a huge push for new methods of squeezing more use out of cells. As noted several times by the EPO, it’s not purely about saving money either. Even if Europe produces the batteries domestically, they need to import the raw materials. Relying on foreign countries to provide critical infrastructure can be precarious in the best of times, and is likely to only become more politically onerous in the future.

Finally, we’ll leave you with a fun way to waste some time on a Sunday evening: Visible Zorker. Created by Andrew Plotkin, this website allows you to not only play through all three installments of Zork, but presents a debugger-style view of the source code as the game is running. Even if you’re not terribly interested in seeing how your responses are parsed, the map that shows your progress through the world is certainly handy. The project was actually started back in 2025, but Andrew just completed the trilogy by adding support for Zork III a couple days ago so now is the perfect time to check it out.

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.

Triple monitor workstations are pretty common these days, particularly for those wishing to maximise screen space for greater productivity. [Will It Work?] has put together a sillier take on this concept, however, hooking the diminutive iPod Nano up to three monitors instead.

The 6th-generation iPod nano brought forth a new form factor – it’s the postage stamp-sized one that you could clip to your workout gear. It’s not typically what you’d call a productivity device, but there is a way to get more out of it. The trick is to grab a 30-pin Keyboard Dock, which allows access to the composite video signal from the iPod. It was originally designed for the iPad, but it works with the iPad nano too with a 30-pin spacer adapter – just don’t expect the keys to do anything. This setup also allows access to the 3.5mm four-pole jack, which handles audio input and output. With a bunch of additional cables and adapters, the iPod was able to be hooked up to three screens, a set of Apple Pro speakers, and three Sharp LCD monitors.

What can you do with this setup? Fundamentally, not a whole lot. You can’t use the keyboard with the iPod Nano, so you’re limited to interacting with the tiny touchscreen. There also aren’t exactly a lot of apps to run on the platform, either. You can basically listen to music, watch a slide show, or record voice memos, while looking at the iPod’s display spread identically across three TVs. Still, it’s a fun joke build, because at a glance it genuinely looks like you’ve set up a triple-monitor workstation running off a tiny iPod from over a decade ago.

If you want to blow the mind of your next podcast guest, consider recording your next episode on this rig. Alternatively, explore some of the other hacks we’ve seen for the platform. Video after the break.