2026-04-01 02:30:04
It’s likely that Hackaday has a readership with the highest percentage of oscilloscope ownership among any in the world, and we’re guessing that most of you who fit in that bracket have a modern digital instrument on your bench. It’s a computer with a very fancy analogue front end, and the traces are displayed in software. Before those were a thing though, a ‘scope was an all-analogue affair, with a vacuum-tube CRT showing the waveform in real time. [Joshua Coleman] has made one of these CRT ‘scopes from scratch, and we rather like it.
Using a vintage two inch round tube, it includes all the relevant power supplies and input amplifiers for the deflection plates. It doesn’t include the triggers and timebase circuitry you’d expect from a desktop instrument though, so unless you add a sawtooth on its X input it’s only good for some Lissajous figures. But that’s not the point of a project like this one, because it’s likely even the cheapest of modern ‘scopes way exceeds any capabilities it would have even if it were fully formed. It’s a talking point and an attractive demonstration of a bit of early-20th-century physics, which probably many of us would appreciate if it were ours.
A video of the device is below the break, meanwhile we’ve taken a look in the past at the prehistory of the oscilloscope.
2026-04-01 01:00:01
Keeping your filament safely away from moisture exposure is one of the most crucial aspects of getting a good 3D print, with equipment like a filament dryer a standard piece of equipment to help drive accumulated moisture out of filament prior to printing or storage. Generally such filament dryers use hot air to accomplish this task over the course of a few hours, but this is not very efficient for a number of reasons. Increasing the vaporization rate of water without significantly more power use should namely be quite straightforward.
The key here is the vapor pressure of a liquid, specifically the point at which it begins to transition between its liquid and gaseous phases, also known as the boiling point. This point is defined by both temperature and atmospheric pressure, with either factor being adjustable. In a pressure cooker this principle is for example used to increase the boiling temperature of water, while for our drying purposes we can instead reduce the pressure in order to lower the boiling point.
Although a lower pressure is naturally more effective, we can investigate the best balance between convenience and effectiveness.
The main thing that determines whether or not a substance is in a liquid or gaseous state is pressure from the surrounding gas, specifically the surrounding air or equivalent. Although some of the liquid’s molecules will gradually make their way into these surroundings, at e.g. atmospheric pressure at sea level you do not expect to see water instantly boil-off, whereas nitrogen and oxygen are fortunately all in a gaseous state until either very high pressures, very low temperatures or both.
How easy it is for a liquid to transition to a gas depends on its volatility, which itself is related to the strength of its intermolecular interactions. If these are rather weak then a liquid will transition into a gaseous state relatively easily, meaning at lower temperatures and lower pressures. For water this transition point at sea level is at about 100°C, but for people who live a km or more above sea level, this boiling point starts dropping rapidly.
These principles are used in a variety of ways, with many kitchens featuring a pressure cooker: this is a special pressurized pan that increases the boiling point of water by increasing the pressure inside the vessel, thus speeding up cooking times.
Increasing pressure of a gas can also turn it back into a liquid, as is the case with for example liquefied petroleum gas (LPG) which is generally stored in pressurized containers. Similarly, in the case of liquefied natural gas (LNG), natural gas is gaseous at atmospheric pressure and room temperature, but is a liquid at -162°C, with some level of pressure above that atmospheric pressure also required. LNG superseded purely pressure-based storage methods in the form of CNG, which requires pressures over 200 bar (>20 MPa).
What we’re trying to do with heating up 3D printer filament and bags of forbidden candy is thus to increase the energy in the system, bringing it closer to the point where the trapped moisture can overcome the vapor pressure of the surrounding air and escape. Logically this means that if we can reduce the surrounding pressure by removing as much of the atmospheric gas as possible, this moisture can escape significantly easier.
Essentially what we need is a pressure cooker, just one that reduces pressure.
The relation between pressure and temperature as far as the vapor pressure of water is concerned is well-documented. Intuitively at 0 Pa water will boil off practically instantaneously, as there is no vapor pressure from a surrounding atmosphere. The question for our purposes is however just how much we need to reduce the pressure to make a difference, i.e. how deep of a vacuum we need.
Looking at a relevant graph, such as this one from the Engineering Toolbox site, we can see that the relationship between pressure and temperature is fairly linear below atmospheric pressure at sea level at 100 kPa (1 bar). Rather than trying to hit some arbitrary point on this curve, we should instead look at what off-the-shelf options we have available that may work for us here.
Since there’s no need for us to hit some kind of ultra-high vacuum, it would be plenty to hit something below 1 kPa, which is absolutely achievable with even a consumer-grade roughing pump like a rotary vane pump. This type of pump is commonly used for silicone and resins in hobbyist applications, making it a solid first target. Theoretically these can vacuum dry filament and more at room temperature.
Another option we have are diaphragm pumps, which come in piston- and eccentric variants. These have the advantage of not requiring oil, and do not produce vaporized oil on their output that has to be captured or vented. They do not hit quite the same vacuum levels as rotary vane pumps, but they can be quite easily staged to improve the final vacuum.
Even with most of the gases evacuated around the material that we’re trying to extract moisture from, we still have the option to add thermal energy to hurry the water molecules along. If, for example, we can only hit a pressure of around 100 mbar, we would still need to raise the temperature significantly above room temperature to get the intended effect.
Even with the same PTC-type heater as used in off-the-shelf filament dryers, we could still save significant power and time as now the boiling temperature of the trapped water is less than 50°C. Whether or not this is a very significant difference is something which can be ascertained experimentally after we first get a baseline on what difference just changing the environmental pressure makes.
Thus, all that remains is obtaining some data by firing up a gaggle of vacuum pumps and writing down the results.
The most straightforward experiment involves the use of a budget rotary vane pump and associated vacuum chamber. Here I picked up a Vevor 3.5 CFM single-stage rotary vane pump (model KQ-1K) rated for 150 Watt along with an 11 L vacuum chamber. Unfortunately the first pump that I received was defective and sounded like someone had lost a bag of spanners inside it while running, while only hitting a sad final vacuum of ~400 mbar.
Fortunately the replacement unit seemed to work a lot better and hit -1 bar on the chamber’s vacuum gauge along with a happy burst of nebulized oil from the pump’s air-oil separator. It was finally time to load up the chamber with some wet things.
As testing the moisture content in a spool of filament is tricky at best, I instead opted for two much easier indicators of vacuum drying chops: a bag of color-changing (cobalt(ii) chloride-containing) silica desiccant and juicy pieces of fruit (apple and banana). The latter items being mostly because it’s a fun experiment and dried fruit is tasty, plus it’s another way to judge drying capacity.
After loading in the samples, the chamber had a vacuum pulled, with the pump managing 10-20 mbar. This is approximately one light-year away from the advertised 5 Pa, but then nobody trusts marketing on non-laboratory equipment. Other than there being clear bubbling/boiling of fluids being visible on the apple piece as the vacuum formed there was little to observe.
After letting it rest for approximately 24 hours the chamber was checked and confirmed to have retained its vacuum level. Ignoring physical changes, the samples’ weight were compared to their pre-vacuum exposure. This gave the following results:
This shows that the fruit definitely lost some moisture, while the silica desiccant wasn’t saturated yet and kept doing its thing. As for the effect on the fruit, the apple looked fresh and other than a slightly dryer outer layer was still moist and tasty. The piece of banana had however turned gooey and was not very appetizing any more.
As an aside, the Vevor pump also got rather hot after a few minutes, with cloudy oil in the reservoir, so the best way forward here might be to invest in a second-hand twin-stage lab-level pump instead.
With those results in hand, we still got two more vacuum setups: the two types of diaphragm pumps. Both are readily available via any online shopping platform, with the micropumps available for about $5 a pop, as they’re commonly used in e.g. vacuum packaging devices. The larger eccentric pumps are also found everywhere, but come in significantly pricier, even if they can pump a much larger volume per minute.
Here the micropumps are connected in a four-stage configuration, while the eccentric pumps feature a two-stage configuration. Both use the same vacuum chamber, being a repurposed glass jam container. Not only is jam rather tasty, their glass jars are also designed to maintain a vacuum for extended periods of time as part of the preservation process, making them excellent small vacuum chambers.
We run the same experiment as before, but only with the silica desiccant. This shows a rather similar outcome, just with these pumps not hitting quite the same final vacuum. For the twin-stage eccentric pump setup the final vacuum was about 100 mbar, and the quad-stage micropump system hit 60 mbar.
Much like with the rotary vane pump experiment, there was no clearly visible color change to the desiccant. The weight remained unchanged from an initial 3.26 grams, taking into account the variability of those cheap ‘precision’ scales, even after calibration.
What these experiments make clear is that merely having a low vapor pressure isn’t a silver bullet when you want to remove moisture from silica desiccant or unsuspecting pieces of fruit. It also shows why vacuum packing foodstuffs is a good way to keep them fresh for longer, as leaving a piece of apple lying around on a kitchen counter for a day would result in a far less tasty result.
The application of thermal energy is thus apparently not just a good idea, but might be the best way to make moisture hurry up in evacuating from a sample, especially when water is bound to e.g. a desiccant. For the next stage of this vacuum drying adventure we’ll thus be looking at putting vacuum chambers into some kind of thermal chamber, like a confused mixture of an autoclave and pressure cooker. Here the main question is the selection of the optimal heating solution, which is where again there are many choices.
This should reveal whether the <100 mbar of the cheaper, 12 VDC-powered diaphragm pump setup is enough to make it a competitor to the mains-powered rotary vane pump for this purpose. Beyond this there is also the question in how far existing filament dryers could be retrofitted to support some level of vacuum, as well as potential vacuum storage.
Any thoughts, notes, references and more on this topic are most welcome.
2026-03-31 23:30:39
There are plenty of drones (and other gadgets) you can buy online that use proprietary control protocols. Of course, reverse-engineering one of these protocols is a hacker community classic. Today, [Zac Turner] shows us how this GPS drone can be autonomously controlled by a simple Arduino program or Python script.
What started as [Zac] sniffing some UDP packets quickly evolved into him decompiling the Android app to figure out what’s going on inside. He talks about how the launch command needs accurate GPS, how there’s several hidden features not used by the Android app, et cetera. And it’s not like it’s just another Linux SoC in there, either. No, there’s a proper Real-Time Operating System (RTOS) running, with a shell and a telnet interface. The list of small curiosities goes on.
After he finished reverse-engineering the protocol, he built some Python scripts, through which you can see the camera feed and control the drone remotely. He also went on to make an Arduino program that can do the latter using an Arduino Nano 33 IoT.
2026-03-31 22:00:09
Solar power has been around for a long time now. Once upon a time, it was mostly the preserve of research projects and large-scale municipal installations. Eventually, as the technology grew ever cheaper, rooftop solar came along, and cashed-up homeowners rushed to throw panels on their homes to slash their power bills and even make money in some cases.
Those in apartments or rented accommodations had largely been left out of the solar revolution. That was, until the advent of balcony solar. Popular in Germany, but little known in the rest of the world, the concept has brought home power generation to a larger market than ever.
Photovoltaic solar panels were very expensive to manufacture, a long time ago. This made it difficult for solar power to compete with traditional energy sources like fossil fuels. High install costs and limited power output made the business case difficult, even if the energy from the sun itself was effectively free. However, as the desire for cleaner sources of energy ramped up over the years, solar panel production ramped up in turn. Economies of scale did their thing, and panels grew cheap enough for individuals to consider installing them on their own homes. This led to the widespread uptake of rooftop solar, with installations commonly in the 5 kW to 10 kW range with inverter hardware to allow feeding energy back into the grid in a safe and controlled manner.
The problem with rooftop solar is that not everybody owns their roof. A great many people around the world live in apartments, or rent, and are not in a position to make permanent adjustments to their home. These groups were largely left out of the solar revolution. That was, until solar panels grew so cheap and power bills grew high enough that even small-scale installs started to make financial sense.
In Germany in particular, small solar installs have become quite popular, and the country has become a hotbed for so-called “balcony” solar installations. These involve simple setups of one or two solar panels which are designed to be easily mounted on a balcony or other outdoor area of a home, rather than permanently installed on a rooftop.
They come with small inverters to convert the DC output of the solar panels into AC power, which plug straight into an existing home power socket. This do-it-yourself install method eliminates the need for hiring an electrician, further improving the affordability of the system. The inverters used with these systems include anti-islanding protection so that the solar system does not power any circuits if the grid has been deenergized for service or repair.
Balcony solar does have some limitations compared to rooftop installs. Often, installation angles are imperfect for making the most of the sun available. There are also limitations to how much power you can get out of such a system. Germany’s initial regulations for “balkonkraftwerk” systems stated that feed in power had to be limited to 600 watts to avoid potential issues with household wiring and sockets that were never designed for feed-in solar power.
Updated regulations allow up to 800 watts of feed-in, with an additional regulation that the installed panels do not exceed a level of 2000 watts peak output. It might sound like a mismatch, but it’s possible to use the excess power from the panels to charge a battery when the output exceeds the 800-watt limit. Having larger panels with higher peak output is useful, too, for when the sun isn’t shining so bright. A 2000 watt peak panel setup will be outputting 800 watts or more far more often than a set of panels that only delivers 800 watts in peak conditions.
Despite the limitations, or perhaps because of them, it’s a cinch to get yourself going with solar in Germany. Just head to your local big box store, purchase a kit, and hang it off the side of your house. Once you plug it in to the wall, you’re pretty much done. Most kits come with some sort of app for monitoring the system so you can keep an eye on how much your panels are generating. The ease of access has led to an explosion in installs, with over 1 million balcony solar setups already operating in the country.
Thus far, balcony solar has been largely a German thing. However, other parts of the world are catching on. Other European nations like Spain, France, and Belgium have all got on board the train already. In the United States, the state of Utah has already approved a framework for balcony solar installs, and Virginia is following close behind. The key has been carving out special measures to allow easy, cheap DIY installs for small solar systems.
Typically, setting up rooftop solar in most states requires signing an agreement with the local utility regarding power feed-in to the grid, as well as hiring professional contractors for the installation. This adds a huge amount of cost which a small solar system would never recoup in a reasonable amount of time. By eliminating these hurdles for small-scale plug-in setups, they become viable and far more accessible to more of the community.
Balcony solar is unlikely to be an instant gamechanger that drastically shakes up the power grid. Most installs are low power. Their juice is mostly sucked up to run a fridge and a TV or two, and few make major feed-in contributions to the broader grid. However, their popularity in Europe shows that there is a serious eagerness amongst the broader community to get on board the solar train any which way or how. At the very least, balcony solar is a grand business opportunity and one that is bringing sustainability to more corners of the urban and suburban landscape than ever before.
Featured image: “Sogenanntes Balkonkraftwerk” by [Triplec85]
2026-03-31 19:00:39
The Eufymake E1 is a recently-released prosumer UV printer that can print high-resolution color images onto pretty much anything. It also uses proprietary ink cartridges (which integrate a magnetic stirrer, nice) which are far more expensive than UV ink in bulk. So [charliex] set out to figure out how to refill the ink cartridges, including the cleaning cartridge.
UV printing in general is a bit of a maintenance hog, which has helped keep it from hobbyist use. UV ink doesn’t really like sitting idle in a machine, but the E1 automates cleaning and flushing of the print head as well as having swappable cartridges for each ink. This makes it a lot more user-friendly than UV printing has historically been.
The cartridge hardware can have a longer serviceable life than the ink inside, so it makes sense to try to refill them. There are more reasons to do this than just limiting costs. What if one wishes to print and the parent company is sold out of cartridges? What if they shut down? Refilling cartridges, and emptying waste from the cleaning cartridge, would become imperatives — lest an expensive prosumer UV printer turn into a paperweight. Thankfully software DRM control of the cartridges seems limited, at least so far.
Refilling cartridges can be carefully done with syringes combined with manual bypass of spring-loaded valve mechanisms. Emptying the cleaning cartridge can similarly be done by syringe, and it even has a hidden refill port under some plastic at its top.
[charliex] approaches all of this from a reverse-engineering perspective, indeed, he has a whole separate blog post about the software for the printer. So his solution is much more informed and elegant than, for example, just melting a new refill hole in the side of the things. It’s an interesting read, so check it out.
Our own Tom Nardi took a close, hands-on look at the E1 printer last year and came away pretty impressed with its capabilities. The cartridges are a big part of the user-friendliness of the system, but we hope there remains a viable option for manual refill for those of us who want to control costs or don’t wish to be locked in, and don’t mind violating a warranty or two in the process.
2026-03-31 16:00:10
As literally everything ought to be able to play DOOM in some fashion, [Adam Rice] recently set out to make the venerable DNS finally play the game after far too many decades of being DOOM-less. You may be wondering how video games and a boring domain records database relate to each other. This is where DNS TXT records come into play, which are essentially fields for arbitrary data with no requirements or limitations on this payload, other than a 2,000 character limit.
Add to this the concept of DNS zones which can contain thousands of records and the inkling of a plan begins to form. Essentially the entire game (in C#) is fetched from TXT records, loaded into memory and run from there. This is in some ways a benign form of how DNS TXT records can be abused by people with less harmless intentions, though [Adam] admits to using the Claude chatbot to help with the code, so YMMV.
The engine and WAD file with the game’s resources are compressed to fit into 1.7 MB along with a 1.2 MB DLL bundle, requiring 1,966 TXT records in Base64 encoding on a Cloudflare Pro DNS zone. With a free Cloudflare account you’d need to split it across multiple zones. With the TXT records synced across the globe, every DNS server in the world now has a copy of DOOM on it, for better or worse.
You can find the project source on GitHub if you want to give this a shake yourself.
Thanks to [MrRTFM] for the tip.
