The late 1950s were such an optimistic time in America. World War II had been over for less than a decade, the economy boomed thanks to pent-up demand after years of privation, and everyone was having babies — so many babies. The sky was the limit, especially with new technologies that promised a future filled with miracles, including abundant nuclear power that would be “too cheap to meter.”

It didn’t quite turn out that way, of course, but the whole “Atoms for Peace” thing did provide the foundation for a lot of innovations that we still benefit from to this day. This 1958 film on “The Armour Research Reactor” details the construction and operation of the world’s first privately owned research reactor. Built at the Illinois Institute of Technology by Atomics International, the reactor was a 50,000-watt aqueous-homogenous design using a solution of uranyl sulfate in distilled water as its fuel. The core is tiny, about a foot in diameter, and assembled by hand right in front of the camera. The stainless steel sphere is filled with 90 feet (27 meters) of stainless tubing to circulate cooling water through the core. Machined graphite reflector blocks surrounded the core and its fuel overflow tank (!) before the reactor was installed in “biological shielding” made from super-dense iron ore concrete with walls 5 feet (1.5 m) thick — just a few of the many advanced safety precautions taken “to ensure completely safe operation in densely populated areas.”

While the reactor design is interesting enough, the control panels and instrumentation are what really caught our eye. The Fallout vibe is strong, including the fact that the controls are all right in the room with the reactor. This allows technicians equipped with their Cutie Pie meters to insert samples into irradiation tubes, some of which penetrate directly into the heart of the core, where neutron flux is highest. Experiments included the creation of radioactive organic compounds for polymer research, radiation hardening of those new-fangled transistors, and manufacturing radionuclides for the diagnosis and treatment of diseases.

This mid-century technological gem might look a little sketchy to modern eyes, but the Armour Research Reactor had a long career. It was in operation until 1967 and decommissioned in 1972, and similar reactors were installed in universities and private facilities all over the world. Most of them are gone now, though, with only five aqueous-homogenous reactors left operating today.

There’s been a lot of buzz about Meshtastic lately, and with good reason. The low-power LoRa-based network has a ton of interesting use cases, and as with any mesh network, the more nodes there are, the better it works for everyone. That’s why we’re excited by this super-affordable Meshtastic kit that lets you get a node on the air for about ten bucks.

The diminutive kit, which consists of a microcontroller and a LoRa module, has actually been available from the usual outlets for a while. But [concretedog] has been deep in the Meshtastic weeds lately, and decided to review its pros and cons. Setup starts with flashing Meshtastic to the XIAO ESP32-S3 microcontroller and connecting the included BLE antenna. After that, the Wio-SX1262 LoRa module is snapped to the microcontroller board via surface-mount connectors, and a separate LoRa antenna is connected. Flash the firmware (this combo is supported by the official web flasher), and you’re good to go.

What do you do with your new node? That’s largely up to you, of course. Most Meshtastic users seem content to send encrypted text messages back and forth, but as our own [Jonathan Bennett] notes, a Meshtastic network could be extremely useful for emergency preparedness. Build a few of these nodes, slap them in a 3D printed box, distribute them to willing neighbors, and suddenly you’ve got a way to keep connected in an emergency, no license required.

Just about any 3D printer can be satisfying to watch as it works, but delta-style printers are especially hypnotic. There’s just something about the way that three linear motions add up to all kinds of complex shapes; it’s mesmerizing. Deltas aren’t without their problems, though, which led [Bruno Schwander] to undertake a trio of interesting mods on his Anycubic Kossel.

First up was an effort to reduce the mass of the business end of the printer, which can help positional accuracy and repeatability. This started with replacing the stock hot-end with a smaller, lighter MQ Mozzie, but that led to cooling problems that [Bruno] addressed with a ridiculously overpowered brushless hairdryer fan. The fan expects a 0 to 5-VDC signal for the BLDC controller, which meant he had to build an adapter to allow Marlin’s 12-volt PWM signal to control the fan.

Once the beast of a fan was tamed, [Bruno] came up with a clever remote mount for it. A 3D-printed shroud allowed him to mount the fan and adapter to the frame of the printer, with a flexible duct connecting it to the hot-end. The duct is made from lightweight nylon fabric with elastic material sewn into it to keep it from taut as the printhead moves around, looking a bit like an elephant’s trunk.

Finally, to solve his pet peeve of setting up and using the stock Z-probe, [Bruno] turned the entire print bed into a strain-gauge sensor. This took some doing, which the blog post details nicely, but it required building a composite spacer ring for the glass print bed to mount twelve strain gauges that are read by the venerable HX711 amplifier and an Arduino, which sends a signal to Marlin when the head touches the bed. The video below shows it and the remote fan in action.

The current generation of USB-powered soldering irons have a lot going for them, chief among them being portability and automatic start and stop. But an iron that turns off in the middle of soldering a joint is a problem, one that this capacitive-touch replacement control module aims to fix.

The iron in question is an SJ1 from Awgem, which [DoganM95] picked up on Ali Express. It seems well-built, with a sturdy aluminum handle, a nice OLED display, and fast heat-up and cool-down. The problem is that the iron is triggered by motion, so if you leave it still for more than a second or two, such as when you’re soldering a big joint, it turns itself off. To fix that,[DoganM95] designed a piggyback board for the OEM controller with a TTP223 capacitive touch sensor. The board is carefully shaped to allow clearance for the existing PCB components and the heater cartridge terminals, and has castellated connections so it can connect to pads on the main board. You have to remove one MOSFET from the main board, but that’s about it for modifications. A nickel strip makes contact with the inside of the iron’s shell, turning it into the sensor plate for the TTP223.

[DoganM95] says that the BA6 variant of the chip is the one you want, as others have a 10-second timeout, which would defeat the purpose of the mod. It’s a very nice bit of design work, and we especially like how the mod board nests so nicely onto the OEM controller. It reminds us a little of those Quansheng handy-talkie all-band mods.

Jack of all trades, master of none, as the saying goes, and that’s especially true for PCB prototyping tools. Sure, it’s possible to use a CNC router to mill out a PCB, and ditto for a fiber laser. But neither tool is perfect; the router creates a lot of dust and the fiberglass eats a lot of tools, while a laser is great for burning away copper but takes a long time to burn through all the substrate. So, why not put both tools to work?

Of course, this assumes you’re lucky enough to have both tools available, as [Mikey Sklar] does. He doesn’t call out which specific CNC router he has, but any desktop machine should probably do since all it’s doing is drilling any needed through-holes and hogging out the outline of the board, leaving bridges to keep the blanks connected, of course.

Once the milling operations are done, [Mikey] switches to his xTool F1 20W fiber laser. The blanks are placed on the laser’s bed, the CNC-drilled through holes are used as fiducials to align everything, and the laser gets busy. For the smallish boards [Mikey] used to demonstrate his method, it only took 90 seconds to cut the traces. He also used the laser to cut a solder paste stencil from thin brass shim stock in only a few minutes. The brief video below shows the whole process and the excellent results.

In a world where professionally made PCBs are just a few mouse clicks (and a week’s shipping) away, rolling your own boards seems to make little sense. But for the truly impatient, adding the machines to quickly and easily make your own PCBs just might be worth the cost. One thing’s for sure, though — the more we see what the current generation of desktop fiber lasers can accomplish, the more we feel like skipping a couple of mortgage payments to afford one.

It’s been quite a week for asteroid 2024 YR4, which looked like it was going to live up to its “city killer” moniker only to be demoted to a fraction of a percent risk of hitting us when it swings by our neighborhood in 2032. After being discovered at the end of 2024, the 55-meter space rock first popped up on the (figurative) radar a few weeks back as a potential risk to our home planet, with estimates of a direct strike steadily increasing as more data was gathered by professional and amateur astronomers alike. The James Webb Space Telescope even got in on the action, with four precious hours of “director’s discretionary” observation time dedicated to characterizing the size and shape of the asteroid before it gets too far from Earth. The result of all this stargazing is that 2024 YR4 is now at a Level 1 on the Torino Scale of NEO collision risk, with a likely downgrade to 0 by the time the asteroid next swings through again in 2028. So, if like us you were into the whole “Fiery Space Rock 2032” thing, you’ll just have to find something else to look forward to.

On the other hand, if you’re going to go out in a fiery cataclysm, going out as a trillionaire wouldn’t be a bad way to go. One lucky Citibank customer could have done that if only an asteroid had hit during the several hours it took to correct an $81 trillion credit to their account back in April, a mistake that only seems to be coming to light now. You’d think a mistake 80% the size of the global economy would have caused an overflow error somewhere along the way, or that somebody would see all those digits and think something was hinky, but apparently not since it was only the third person assigned to review the transaction that caught it. The transaction, which falls into the “near-miss” category, was reversed before any countries were purchased or fleets of space yachts were commissioned, which seems a pity but also points out the alarming fact that this happens often enough that banks have a “near-miss” category — kind of like a Broken Arrow.

We all know that near-Earth space is getting crowded, with everyone and his brother launching satellite megaconstellations to monetize our collective dopamine addiction. But it looks like things are even starting to get crowded around the Moon, at least judging by this lunar photobomb. The images were captured by the Lunar Reconnaisance Orbiter, which has been orbiting the Moon and studying the landscape for the last 16 years but stretched its capabilities a bit to capture images of the South Korean Danuri. The two probes are in parallel orbits but opposite directions and about 8 kilometers apart at the time, meaning the relative velocity between the two was an unreasonably fast 11,500 km/h. The result is a blurred streak against the lunar surface, which isn’t all that much to look at but is still quite an accomplishment. It’s not the first time these two probes have played peek-a-boo with each other; back in 2023, Danuri took a similar picture when LRO was 18 kilometers below it.

We don’t do much air travel, but here’s a tip: if you want to endear yourself to fellow travelers, it might be best to avoid setting up a phone hotspot named “I Have a Bomb.” That happened last week on American Airlines flight 2863 from Austin, Texas to Charlotte, North Carolina, with predictable results. The prank was noticed while the flight was boarding, causing law enforcement officers to board the plane and ask the prankster to own up to it. Nobody volunteered, so everyone had to deplane and go back through screening, resulting in a four-hour delay and everyone missing their connections. We’re all for fun SSIDs, mind you, but there’s a time and a place for everything.

And finally, we wanted to share this fantastic piece from Brian Potter over at Construction Physics on “Why it’s so hard to build a jet engine.” The answer might seem obvious — because it’s a jet engine, duh — but the article is a fascinating look at the entire history of jet propulsion, from their near-simultaneous invention by the principal belligerents at the end of World War II right through to their modern incarnations. The article is an exploration into the engineering of complex systems, and shows how non-obvious the problems were that needed to be solved to make jet engines practical. It’s also a lesson in the difficulties of turning a military solution into a practical commercial product. Enjoy!

FR4 is FR4, right? For a lot of PCB designs, the answer is yes — the particular characteristics of the substrate material don’t impact your design in any major way. But things get a little weird up in the microwave range, and having one of these easy methods to measure the dielectric properties of your PCB substrate can be pretty handy.

The RF reverse-engineering methods [Gregory F. Gusberti] are deceptively simple, even if they require some fancy test equipment. But if you’re designing circuits with features like microstrip filters where the permittivity of the substrate would matter, chances are pretty good you already have access to such gear. The first method uses a ring resonator, which is just a PCB with a circular microstrip of known circumference. Microstrip feedlines approach but don’t quite attach to the ring, leaving a tiny coupling gap. SMA connectors on the feedline connect the resonator to a microwave vector network analyzer in S21 mode. The resonant frequencies show up as peaks on the VNA, and can be used to calculate the effective permittivity of the substrate.

Method two is similar in that it measures in the frequency domain, but uses a pair of microstrip stubs of different lengths. The delta between the lengths is used to cancel out the effect of the SMA connectors, and the phase delay difference is used to calculate the effective permittivity. The last method is a time domain measurement using a single microstrip with a couple of wider areas. A fast pulse sent into this circuit will partially reflect off these impedance discontinuities; the time delay between the reflections is directly related to the propagation speed of the wave in the substrate, which allows you to calculate its effective permittivity.

One key takeaway for us is the concept of effective permittivity, which considers the whole environment of the stripline, including the air above the traces. We’d imagine that if there had been any resist or silkscreen near the traces it would change the permittivity, too, making measurements like these all the more important.

Ho-hum — another week, another high-profile bricking. In a move anyone could see coming, Humane has announced that their pricey AI Pin widgets will cease to work in any meaningful way as of noon on February 28. The company made a splash when it launched its wearable assistant in April of 2024, and from an engineering point of view, it was pretty cool. Meant to be worn on one’s shirt, it had a little bit of a Star Trek: The Next Generation comm badge vibe as the primary UI was accessed through tapping the front of the thing. It also had a display that projected information onto your hand, plus the usual array of sensors and cameras which no doubt provided a rich stream of user data. Somehow, though, Humane wasn’t able to make the numbers work out, and as a result they’ll be shutting down their servers at the end of the month, with refunds offered only to users who bought their AI Pins in the last 90 days.

How exactly Humane thought that offering what amounts to a civilian badge cam was going to be a viable business model is a bit of a mystery. Were people really going to be OK walking into a meeting where Pin-wearing coworkers could be recording everything they say? Wouldn’t wearing a device like that in a gym locker room cause a stir? Sure, the AI Pin was a little less obtrusive than something like the Google Glass — not to mention a lot less goofy — but all wearables seem to suffer the same basic problem: they’re too obvious. About the only one that comes close to passing that hurdle is the Meta Ray-Ban smart glasses, and those still have the problem of obvious cameras built into their chunky frames. Plus, who can wear Ray-Bans all the time without looking like a tool?

Good news for everyone worried about a world being run by LLMs and chatbots. It looks like all we’re going to have to do is wait them out, if a study finding that older LLMs are already showing signs of cognitive decline pans out. To come to that conclusion, researchers gave the Montreal Cognitive Assessment test to a bunch of different chatbots. The test uses simple questions to screen for early signs of impairment; some of the questions seem like something from a field sobriety test, and for good reason. Alas for the tested chatbots, the general trend was that the older the model, the poorer they did on the test. The obvious objection here is that the researchers aren’t comparing each model’s current score with results from when the model was “younger,” but that’s pretty much what happens when the test is used for humans.

You’ve got to feel sorry for astronomers. Between light pollution cluttering up the sky and an explosion in radio frequency interference, astronomers face observational challenges across the spectrum. These challenges are why astronomers prize areas like dark sky reserves, where light pollution is kept to a minimum, and radio quiet zones, which do the same for the RF part of the spectrum. Still, it’s a busy world, and noise always seems to find a way to leak into these zones. A case in point is the recent discovery that TV signals that had been plaguing the Murchison Wide-field Array in Western Australia for five years were actually bouncing off airplanes. The MWA is in a designated radio quiet zone, so astronomers were perplexed until someone had the bright idea to use the array’s beam-forming capabilities to trace the signal back to its source. The astronomers plan to use the method to identify and exclude other RFI getting into their quiet zone, both from terrestrial sources and from the many satellites whizzing overhead.

And finally, most of us are more comfortable posting our successes online than our failures, and for obvious reasons. Everyone loves a winner, after all, and admitting our failures publicly can be difficult. But Daniel Dakhno finds value in his failures, to the point where he’s devoted a special section of his project portfolio to them. They’re right there at the bottom of the page for anyone to see, meticulously organized by project type and failure mode. Each failure assessment includes an estimate of the time it took; importantly, Daniel characterizes this as “time invested” rather than “time wasted.” When you fall down, you should pick something up, right?

“World’s best” is a mighty ambitious claim, regardless of what you’ve built. But from the look of [Marius Hornberger]’s tricked-out miter fence, it seems like a pretty reasonable claim.

For those who have experienced the torture of using the standard miter fence that comes with machine tools like a table saw, band saw, or belt sander, any change is likely to make a big difference in accuracy. Miter fences are intended to position a workpiece at a precise angle relative to the plane of the cutting tool, with particular attention paid to the 90° and 45° settings, which are critical to creating square and true joints.

[Marius] started his build with a runner for the T-slot in his machine tools, slightly undersized for the width of the slot but with adjustment screws that expand plastic washers to take up the slack. An aluminum plate equipped with a 3D printed sector gear is attached to the runner, and a large knob with a small pinion mates to it. The knob has 120 precisely positioned slots in its underside, which thanks to a spring-loaded detent provide positive stops every 0.5°. A vernier scale also allows fine adjustment between positive stops, giving a final resolution of 0.1°.

Aside from the deliciously clicky goodness of the angle adjustment, [Marius] included a lot of thoughtful touches. We particularly like the cam-action lock for the angle setting, which prevents knocking your fine angle adjustment out of whack. We’re also intrigued by the slide lock, which firmly grips the T-slot and keeps the fence fixed in one place on the machine. As for the accuracy of the tool, guest meteorologist and machining stalwart [Stefan Gotteswinter] gave it a thumbs-up.

[Marius] is a veteran tool tweaker, and we’ve featured some of his projects before. We bet this fence will see some use on his much-modified drill press, and many of the parts for this build were made on his homemade CNC router.

If you think sonic booms from supersonic aircraft are a nuisance, wait until the sky is full of planes propelled by up-scaled versions of this interesting but deafening audio resonance engine.

Granted, there’s a lot of work to do before this “Sonic Ramjet” can fly even something as small as an RC plane. Creator [invalid_credentials] came up with the idea for a sound-powered engine after listening to the subwoofers on a car’s audio system shaking the paint off the body. The current design uses a pair of speaker drivers firing into 3D printed chambers, which are designed based on Fibonacci ratios to optimize resonance. When the speakers are driven with a low-frequency sine wave, the chambers focus the acoustic energy into powerful jets, producing enough thrust to propel a small wheeled test rig across a table.

It’s fair to ask the obvious question: is the engine producing thrust, or is the test model moving thanks to the vibrations caused by the sound? [invalid_credentials] appears to have thought of that, with a video showing a test driver generating a powerful jet of air. Downloads to STL files for both the large and small versions of the resonating chamber are provided, if you want to give it a try yourself. Just be careful not to annoy the neighbors too much.

Thanks to [cabbage] for the tip via [r/3Dprinting].

While not impossible, replicating the machines and processes of a modern semiconductor fab is a pretty steep climb for the home gamer. Sure, we’ve seen it done, but nanoscale photolithography is a demanding process that discourages the DIYer at every turn. So if you want to make semiconductors at home, it might be best to change the rules a little and give something like this pulsed laser deposition prototyping apparatus a try.

Rather than building up a semiconductor by depositing layers of material onto a silicon substrate and selectively etching features into them with photolithography, [Sebastián Elgueta]’s chips will be made by adding materials in their final shape, with no etching required. The heart of the process is a multi-material pulsed laser deposition chamber, which uses an Nd:YAG laser to ablate one of six materials held on a rotating turret, creating a plasma that can be deposited onto a silicon substrate. Layers can either be a single material or, with the turret rapidly switched between different targets, a mix of multiple materials. The chamber is also equipped with valves for admitting different gases, such as oxygen when insulating layers of metal oxides need to be deposited. To create features, a pattern etched into a continuous web of aluminum foil by a second laser is used as a mask. When a new mask is needed, a fresh area of the foil is rolled into position over the substrate; this keeps the patterns in perfect alignment.

We’ve noticed regular updates on this project, so it’s under active development. [Sebastián]’s most recent improvements to the setup have involved adding electronics inside the chamber, including a resistive heater to warm the substrate before deposition and a quartz crystal microbalance to measure the amount of material being deposited. We’re eager to see what else he comes up with, especially when those first chips roll off the line. Until then, we’ll just have to look back at some of [Sam Zeloof]’s DIY semiconductors.

To the extent that you’re familiar with magnetostriction, you probably know that it’s what makes big transformers hum, or that it’s what tips you off if you happen to walk out of a store without paying for something. But magnetostriction has other uses, too, such as in this clever linear position sensor.

Magnetostriction is just the tendency for magnetic materials to change size or shape slightly while undergoing magnetization, thanks to the tiny magnetic domains shifting within the material while they’re aligning. [Florian B.]’s sensor uses a side effect of magnetostriction known as the Wiedenmann effect, which causes a wire to experience a twisting force if a current pulse is applied to it in a magnetic field. When the current pulse is turned off, a mechanical wave travels along the wire to a coil, creating a signal. The difference in time between sending the pulse and receiving the reflection can be used to calculate the position of the magnet along the wire.

To turn that principle into a practical linear sensor, [Florian B.] used nickel wire stretched tightly down the middle of a PVC tube. At one end is a coil of copper magnet wire, while the other end has a damper to prevent reflections. Around the tube is a ring-shaped cursor magnet, which can move up and down the tube. An exciter circuit applies the current pulse to the wire, and an oscilloscope is used to receive the signal from the wire.

This project still appears to be in the prototype phase, as evidenced by the Fischertechnik test rig. [Florian] has been working on the exciter circuit most recently, but he’s done quite a bit of work on optimizing the cursor magnet and the coil configuration, as well as designs for the signal amplifier. It’s a pretty neat project, and we’re looking forward to updates.

If you need a deeper dive into magnetostriction, [Ben Krasnow] points the way.

We’ve all got our health-related crosses to bear, and even if you’re currently healthy, it’s only a matter of time before entropy catches up to you. For [Markus Bindhammer], it caught up to him in a big way: liver disease, specifically cirrhosis. The disease has a lot of consequences, none of which are pleasant, like abnormally high ammonia concentration in the blood. So naturally, [Markus] built an ammonia analyzer to monitor his blood.

Measuring the amount of ammonia in blood isn’t as straightforward as you think. Yes, there are a few cheap MEMS-based sensors, but they tend to be good only for qualitative measurements, and other solid-state sensors that are more quantitative tend to be pretty expensive since they’re mostly intended for industrial applications. [Marb]’s approach is based on the so-called Berthelot method, which uses a two-part reagent. In the presence of ammonia (or more precisely, ammonium ions), the reagent generates a dark blue-green species that absorbs light strongly at 660 nm. Measuring the absorbance at that wavelength gives an approximation of the ammonia concentration.

[Marb]’s implementation of this process uses a two-stage reactor. The first stage heats and stirs the sample in a glass tube using a simple cartridge heater from a 3D printer head and a stirrer made from a stepper motor with a magnetic arm. Heating the sample volatilizes any ammonia in it, which mixes with room air pumped into the chamber by a small compressor. The ammonia-laden air moves to the second chamber containing the Berthelot reagent, stirred by another stepper-powered stir plate. A glass frit diffuses the gas into the reagent, and a 660-nm laser and photodiode detect any color change. The video below shows the design and construction of the micro lab along with some test runs.

We wish [Markus] well in his journey, of course, especially since he’s been an active part of our community for years. His chemistry-related projects run the gamut from a homebrew gas chromatograph to chemical flip flops, with a lot more to boot.

Just when you thought the saga of the Bitcoin wallet lost in a Welsh landfill was over, another chapter of the story appears to be starting. Regular readers will recall the years-long efforts of Bitcoin early adopter James Howells to recover a hard drive tossed out by his ex back in 2013. The disk, which contains a wallet holding about 8,000 Bitcoin, is presumed to be in a landfill overseen by the city council of Newport, which denied every request by Howells to gain access to the dump. The matter looked well and truly settled (last item) once a High Court judge weighed in. But the announcement that the Newport Council plans to cap and close the landfill this fiscal year and turn part of it into a solar farm has rekindled his efforts.

Howells and his investment partners have expressed interest in buying the property as-is, in the hopes of recovering the $780 million-ish fortune. We don’t think much of their odds, especially given the consistently negative responses he’s gotten over the last twelve years. Howells apparently doesn’t fancy his odds much either, since the Council’s argument that closing the landfill to allow him to search would cause harm to the people of Newport was seemingly made while they were actively planning the closure. It sure seems like something foul is afoot, aside from the trove of dirty diapers Howells seeks to acquire, of course.

When all else fails, blame the monkey. The entire nation of Sri Lanka suffered a blackout last Sunday, with a hapless monkey being fingered as the guilty party. The outage began when a transformer at a substation south of the capital city of Colombo went offline. Unconfirmed reports are that a troop of monkeys was fighting, as monkeys do, and unadvisedly brought their tussle over the fence and into the substation yard. At some point, one of the warring animals sought the high ground on top of a transformer, with predictable results. How turning one monkey into air pollution managed to bring down an entire country’s grid is another question entirely.

From the enshittification files comes this horrifying story of in-dashboard ads. Stellantis, maker of Jeep, Dodge, Chrysler, and other brands that can reliably be counted upon to be littered with bad grounds, has decided to start putting full-screen pop-up advertisements on infotainment systems. As if that’s not atrocious enough, the ads will run not just when the car is first started, but every time the vehicle comes to a stop in traffic. The ads will hawk things like extended warranties, at least initially, but we predict it won’t be long before other upsell attempts are made. It would be pretty easy to pull in other data to customize ads, such as an offer to unlock heated seats if the outside temperature gets a little chilly, or even flog a pumpkin spice latte when the GPS shows you’re near a Starbucks. The possibilities are endless, and endlessly revolting, because if one car company does it, the rest will quickly follow. Ad-blocking wizards, this may be your next big target.

And finally, calling all hams, or at least those of us with an interest in digital modes. Our own Al Williams will be making an appearance on the DMR Tech Net to talk about his Hackaday recent article on Digital Mobile Radio. The discussion will be on Monday, February 17 at 00:30 UTC (19:30 EST), on Brandmeister talk group 31266. If you’ve got a DMR-capable radio, DMR Tech Net has a handy guide to getting the talk group into your code plug. If none of that makes any sense, relax — you can still tune in online using this link and the Player button in the upper right. Or, if ham radio isn’t your thing, Al will be making a second appearance the next night but on a Zoom call to discuss “How to Become Rich and (almost) Famous on Hackaday,” which is his collection of tips and tricks for getting your project to catch a Hackaday writer’s eye.

Anyone who has ever had the misfortune of a blown head gasket knows that the old saying “oil and water don’t mix” is only partially true. When what’s coming out of the drain plug looks like a mocha latte, you know you’re about to have a very bad day.

[SpankRanch Garage] recently found himself in such a situation, and the result was this clever vacuum dehydrator, which he used to clean a huge amount of contaminated hydraulic fluid from some heavy equipment. The machine is made from a retired gas cylinder welded to a steel frame with the neck pointing down. He added a fill port to the bottom (now top) of the tank; as an aside, we had no idea the steel on those tanks was so thick. The side of the tank was drilled and threaded for things like pressure and temperature gauges as well as sight glasses to monitor the process and most importantly, a fitting for a vacuum pump. Some valves and a filter were added to the outlet, and a band heater was wrapped around the tank.

To process the contaminated oil, [Spank] glugged a bucket of forbidden milkshake into the chamber and pulled a vacuum. The low pressure lets the relatively gentle heat boil off the water without cooking the oil too badly. It took him a couple of hours to treat a 10-gallon batch, but the results were pretty stark. The treated oil looked far better than the starting material, and while it still may have some water in it, it’s probably just fine for excavator use now. The downside is that the vacuum pump oil gets contaminated with water vapor, but that’s far easier and cheaper to replace that a couple hundred gallons of hydraulic oil.

Never doubt the hacking abilities of farmers. Getting things done with what’s on hand is a big part of farm life, be it building a mower from scrap or tapping the power of the wind.

Most of us see the world in a very narrow band of the EM spectrum. Sure, there are people with a genetic quirk that extends the range a bit into the UV, but it’s a ROYGBIV world for most of us. Unless, of course, you have something like this ESP32 antenna array, which gives you an augmented reality view of the WiFi world.

According to [Jeija], “ESPARGOS” consists of an antenna array board and a controller board. The antenna array has eight ESP32-S2FH4 microcontrollers and eight 2.4 GHz WiFi patch antennas spaced a half-wavelength apart in two dimensions. The ESP32s extract channel state information (CSI) from each packet they receive, sending it on to the controller board where another ESP32 streams them over Ethernet while providing the clock and phase reference signals needed to make the phased array work. This gives you all the information you need to calculate where a signal is coming from and how strong it is, which is used to plot a sort of heat map to overlay on a webcam image of the same scene.

The results are pretty cool. Walking through the field of view of the array, [Jeija]’s smartphone shines like a lantern, with very little perceptible lag between the WiFi and the visible light images. He’s also able to demonstrate reflection off metallic surfaces, penetration through the wall from the next room, and even outdoor scenes where the array shows how different surfaces reflect the signal. There’s also a demonstration of using multiple arrays to determine angle and time delay of arrival of a signal to precisely locate a moving WiFi source. It’s a little like a reverse LORAN system, albeit indoors and at a much shorter wavelength.

There’s a lot in this video and the accompanying documentation to unpack. We haven’t even gotten to the really cool stuff like using machine learning to see around corners by measuring reflected WiFi signals. ESPARGOS looks like it could be a really valuable tool across a lot of domains, and a heck of a lot of fun to play with too.

Thanks to [Buckaroo] for the tip.

Starting a new microcontroller project can be pretty daunting. While you have at least a rough idea of where you want to end up, there are so many ways to get there that you can get locked into “analysis paralysis” and never get the project off the ground. Or arguably worse, you just throw whatever dev board you have in the junk bin and deal with the consequences.

While it’s hard to go wrong with relying on a familiar MCU and toolchain, [lcamtuf] argues in this recent guide to choosing microcontrollers that it’s actually not too much of a chore to make the right choice. Breaking the microcontroller universe down into three broad categories makes the job a little easier: simple process control, computationally intensive tasks, and IoT products. Figuring out where your project falls on that spectrum narrows your choices considerably.

For example, if you just need to read some sensors and run a few servos or solenoids, using something like a Raspberry Pi is probably overkill. On the other hand, a Pi or other SBC might be fine for something that you need wireless connectivity. We also appreciate that [lcamtuf] acknowledges that intangible considerations sometimes factor in, such as favoring a new-to-you MCU because you’ll get experience with technology you haven’t used before. It might not override technical considerations by itself, but you can’t ignore the need to stretch your wings once in a while.

There’s nothing earth-shattering here, but we enjoy think pieces like this. It’s a bit like [lcamtuf]’s recent piece on rethinking your jellybean op-amps.

Fair warning: watching this hybrid manufacturing method for gear teeth may result in an uncontrollable urge to buy a fiber laser cutter. Hackaday isn’t responsible for any financial difficulties that may result.

With that out of the way, this is an interesting look into how traditional machining and desktop manufacturing methods can combine to make parts easier than either method alone. The part that [Paul] is trying to make is called a Hirth coupling, a term that you might not be familiar with (we weren’t) but you’ve likely seen and used. They’re essentially flat surfaces with gear teeth cut into them allowing the two halves of the coupling to nest together and lock firmly in a variety of relative radial positions. They’re commonly used on camera gear like tripods for adjustable control handles and tilt heads, in which case they’re called rosettes.

To make his rosettes, [Paul] started with a block of aluminum on the lathe, where the basic cylindrical shape of the coupling was created. At this point, forming the teeth in the face of each coupling half with traditional machining methods would have been tricky, either using a dividing head on a milling machine or letting a CNC mill have at it. Instead, he fixtured each half of the coupling to the bed of his 100 W fiber laser cutter to cut the teeth. The resulting teeth would probably not be suitable for power transmission; the surface finish was a bit rough, and the tooth gullet was a little too rounded. But for a rosette, this was perfectly acceptable, and probably a lot faster to produce than the alternative.

In case you’re curious as to what [Paul] needs these joints for, it’s a tablet stand for his exercise machine. Sound familiar? That’s because we recently covered his attempts to beef up 3D prints with a metal endoskeleton for the same project.

Thanks to [Ziggi] for the tip.

Unless you work for the government or a large corporation, constrained designs are a fact of life. No matter what you’re building, there’s likely going to be a limit to the time, money, space, or materials you can work with. That’s good news, though, because constrained projects tend to be interesting projects, like this airborne polarimetric synthetic aperture radar.

If none of those terms make much sense to you, don’t worry too much. As [Henrik Forstén] explains, synthetic aperture radar is just a way to make a small radar antenna appear to be much larger, increasing its angular resolution. This is accomplished by moving the antenna across a relatively static target and doing some math to correlate the returned signal with the antenna position. We saw this with his earlier bicycle-mounted SAR.

For this project, [Henrik] shrunk the SAR set down small enough for a low-cost drone to carry. The build log is long and richly detailed and could serve as a design guide for practical radar construction. Component selection was critical, since [Henrik] wanted to use low-cost, easily available parts wherever possible. Still, there are some pretty fancy parts here, with a Zynq 7020 FPGA and a boatload of memory on the digital side of the custom PCB, and a host of specialized parts on the RF side.

The antennas are pretty cool, too; they’re stacked patch antennas made from standard FR4 PCBs, with barn-door feed horns fashioned from copper sheeting and slots positioned 90 to each other to provide switched horizontal and vertical polarization on both the receive and transmit sides. There are also a ton of details about how the radar set is integrated into the flight controller of the drone, as well as an interesting discussion on the autofocusing algorithm used to make up for the less-than-perfect positional accuracy of the system.

The resulting images are remarkably detailed, and almost appear to be visible light images thanks to the obvious shadows cast by large objects like trees and buildings. We’re especially taken by mapping all combinations of transmit and receive polarizations into a single RGB image; the result is ethereal.