2026-02-11 11:00:04
Airport runways seem pretty simple, just another strip of asphalt or concrete not unlike the roads that our cars drive upon every day. We can even use these same highways as landing strips in a pinch, so you’d assume that the engineering for either isn’t that dissimilar. Of course, you can use a highway for an occasional emergency, but a runway that sees the largest and heaviest airplanes taxi, take off and land on a constant basis is a whole other challenge, as detailed in a recent [Practical Engineering] video and its transcript.
When you consider that an Airbus A380 the take-off weight is up to 550 ton, it’s quite clear what the challenge is for larger airports. Another major issue is that of friction, or lack thereof, as the speeds and kinetic energy behind it are so much higher. One only has to look at not only runway overruns but also when one skids off sideways due issues like hydroplaning and uneven friction. Keeping the surface of a runway as high-friction as possible and intact after hundreds of take-offs, tail-strikes and other events is no small feat.
Of course, the other part of runway engineering is for when things do go wrong and an airplane enters the runway safety areas, or overrun zones. This usually provides some flat and clear space where an airplane can safely bleed off its kinetic energy, with the collapsing surface of the EMAS technology being one of the best demonstrations of how this can be safely and dramatically shortened.
Another aspect not covered here that is part of these overrun zones are frangible structures, such as any localizer antennae of ILS, lighting, etc. Frangible here means that the structure easily collapses when a heavy airplane crashes into it without causing significant damage to the airplane.
It was the failure of such a design process that doomed the crew and passengers of Jeju Air Flight 2216 in December of 2024, when the airplane during an emergency belly landing skidded over the end of the runway. Although there was a lot of open space after the ILS localizer array with just a flimsy wall and further level fields, the ILS array’s base contained a poured concrete base on which the airplane effectively pulverized.
2026-02-11 08:00:20
A common sight in ‘smart homes’, door sensors allow you to detect whether a door is closed or open, enabling the triggering of specific events. Unfortunately, most solutions for these sensors are relatively bulky and hard to miss, making them a bit of a eyesore. This was the case for [Dillan Stock] as well, who decided that he could definitely have a smart home, yet not have warts sticking out on every single doorframe and door. There’s also a video version of the linked blog post.
These door sensors tend to be very simple devices, usually just a magnet and a reed relay, the latter signaling a status change to the wireless transmitter or transceiver. Although [Dillan] had come across recessed door sensors before, like a Z-wave-based unit from Aeotec, this was a very poorly designed product with serious reliability issues.
That’s when [Dillan] realized that he could simply take the PCB from one of the Aqara T1 door sensors that he already had and stuff them into a similar 20 mm diameter form factor as that dodgy sensor unit. Basically this just stuffs the magnet and PCB from an existing wart-style sensor into a recessed form factor, making it a very straightforward hack, that only requires printing the housings for the Aqara T1 sensor and some intimate time between the door and a drill.
2026-02-11 05:00:43
When [101 Things] didn’t want to copy Morse code, he decided to build a Pi Pico system to read it for him. On the face of it, this doesn’t seem particularly hard, until you look at the practical considerations. With perfectly timed dots and dashes, it would be trivial. But in real life, you get an audio signal. It has been mangled and mixed with noise and interference as it travels through the air. Then there’s the human on the other end who will rarely send at a constant speed with no errors.
Once you consider that, this becomes quite the project, indeed. The decoder captures audio via the Pi’s analog-to-digital converter. Then it resamples the input, applies an FFT, and converts the output via a complex classification pipeline that includes, among other things, Bayesian decoding. Part of the pipeline makes simple typo corrections. You can see the device do its thing in the video below.
Another issue with the code is that it decodes multiple channels in real time. So looking up spelling corrections, for example, has to be done rapidly. The device can also send code and show stats and graphics on an LCD screen.
If you know the code is arriving at a known speed, you could do something much simpler. The Pico has lots of memory which makes it easy to use complex algorithms. When you are memory-limited, you need different tricks.
2026-02-11 03:30:31
As popular as the game of chess is, it has one massive flaw. This being that it requires two participants, which can be a challenge. Although playing chess on a computer against an AI has been a thing for many decades, it’s hard to beat physical chess boards that give you all the tactile pleasure of handling and moving pieces, yet merging the two is tricky. You can either tell the player to also move the opponent’s pieces, or use a mechanism to do so yourself, which [Joshua Stanley] recently demonstrated in a video.
There are a few ways that you can go about having the computer move and detect the pieces. Here [Joshua] chose to use Hall magnetic sensors to detect the magnets that are embedded in the 3D printed chess pieces as well as their absence. These sensors are mounted to the back side of a PCB which is also the playing field, thus using the silkscreen for the board markings.
For the electromagnet that moves the chess pieces core x/y kinematics were used to move it underneath the PCB, engaging when moving pieces but otherwise deactivated. This is all controlled by an ESP32 MCU, while the computer runs the open-source Stockfish chess engine. As the human player changes piece positions this is detected by the magnet’s presence, with the change input into Stockfish.
As the demonstration at the end of the video shows, it definitely works, yet some issues remain. Ignoring the mistake with making the near-right corners black instead of white, the pieces are large enough that e.g. moving a knight piece between others pushes them to the side, requiring these to be put back in place.
There is also no way for the computer to detect which piece is placed where, which can be incredibly helpful on some commercial self-playing chess boards like this for new players, as well as to detect invalid moves, but this might be on the list for a potential V2 of this build.
Best part of this build is probably the use of a PCB for the playing field, which would allow you to go pretty crazy with custom designs and colors, especially now that some PCB places are offering multi-color silkscreens that allow for custom graphics.
2026-02-11 00:30:10
There are many adapters, dongles, and cables designed for interfacing display standards, and no doubt some of you have them in the glue of your entertainment system or work space. They’re great for standards, but what about something that’s not quite standard? [Stephen] has an arcade cabinet with a CRT that runs at an unusual 336 by 262 pixel resolution. It can be driven as 320 by 240 but doesn’t look great, and even that “standard” resolution isn’t supported by many dongles. He’s shared the story of his path to a unique USB to VGA converter which may have application far beyond this arcade machine.
We follow him on a path of discovery, through RP2040 PIOs, simple resistor ladder DACs, and home-made kernel modules, before he arrives at GUD, a USB display protocol with its own upstreamed Linux kernel driver. It’s designed to be used with a Raspberry PI deriving an LCD or HDMI display, but for his task he implemented the protocol on one of the more expensive STM32 series microcontrollers. The result after several false starts and some fiendish PCB routing is a standalone GUD-based USB-to-VGA converter that delivers perfect 34-bit colour at this unusual resolution, and also presumably others if required. It’s a worthwhile read for the many hints it gives on the subject of driving displays, even if you’re not driving an odd cabinet monitor.
2026-02-10 23:00:20
When it comes to knowledge there are things you know as facts because you have experienced them yourself or had them verified by a reputable source, and there are things that you know because they are common knowledge but unverified. The former are facts, such as that a 100mm cube of water contains a litre of the stuff, while the latter are received opinions, such as the belief among Americans that British people have poor dental care. The first is a verifiable fact, while the second is subjective.
In our line there are similar received opinions, and one of them is that you shouldn’t print with old 3D printing filament because it will ruin the quality of your print. This is one I can now verify for myself, because I was recently given a part roll of blue PLA from a hackerspace, that’s over a decade old. It’s not been stored in a special environment, instead it’s survived a run of dodgy hackerspace premises with all the heat and humidity that’s normal in a slightly damp country. How will it print?
In the first instance, looking at the filament, it looks like any other filament. No fading of the colour, no cracking, if I didn’t know its age it could have been opened within the last few weeks. It loads into the printer, a Prusa Mini, fine, it’s not brittle, and I’m ready to print a Benchy.
My first surprise on printing the Benchy is that it’s a pretty good print. Received Opinion tells me that PLA is hydrophobic, and if you leave some out for a decade it will absorb so much moisture as to be unusable. In fact I was expecting a very stringy print indeed because I’ve seen that before with filament left out for about a year in the damp British climate. But this Benchy had almost no hairiness, its only flaw was a little bit of collapse along its prow line. I know the Mini isn’t at fault here as I’ve seen it print a flawless Benchy with new PLA, so that’s strike one to the ancient plastic.
Manipulating the Benchy, I found strike two. This is a reasonable print, but with not-too-hard pressure on the cabin I could snap it. The layer adhesion wasn’t as much as it is with a new-filament Benchy, and it has broken cleanly along the layer lines in the cabin pillars. Since snapping a Benchy isn’t a quantitative measure of how much the layer adhesion had degraded, I decided to formulate a test for layer adhesion. If I print something designed for measuring layer adhesion failure in both this old PLA and some new PLA, I can compare the two. It’s not perfect as I don’t have a new reel of the same formulation as the old stuff, but it’ll be close enough.
What I have come up with is a 150 mm long box section with a 2 mm wall. If I clamp the first 5 0mm to the edge of a table, I can apply a force to the far end of the 100 mm poking out into free space, and find its breaking point. To that end I’ve printed two, one in my blue old PLA, and another in brand new grey PLA. I’m dangling a collection of angle brackets each of which weighs 130 g from the end of the box section, and adding brackets until it breaks.
I had only twenty brackets, and as expected the old PLA broke first, at ten brackets, or a 1.3 kg load. My back of the envelope calculation from high school physics gives me about a 130 N force on the top edge of the layer boundary over the fulcrum on the edge of the table to do this. I ran out of brackets and other hardware to try to break the grey box section, and finally admitted defeat when it refused to break with a 3 kg piece of rail I’ve been hoarding to make an anvil dangling from its end. I have proved that layer adhesion with ancient PLA is more than three times weaker than on the same printer with new PLA. It’s interesting when examining the break, the layers have parted very cleanly, this is not tearing of the PLA but simply poor adhesion between layers.
In doing these experiments I’ve discovered, not unexpectedly, that ancient PLA isn’t as good as new PLA. I am assuming that this was as good a PLA as the modern stuff when it was new — indeed I remember printing back in the day and my prints seemed just as good as today. What does surprise me though is that how it’s deteriorated isn’t what I expected. It produces good prints in terms of their physical form, without the hairiness I was expecting. In turn I didn’t expect the prints with this stuff to be weak, so what’s going on?
PLA filament is not pure PLA, instead it has chemicals added to modify its properties. The most obvious one in this reel is the blue pigment, but others might modify its plasticity or melting characteristics, to name two possibilities. These are not going to be stable solids like the polymer, instead they will be volatile compounds which are capable of evaporating over time.
I’m no polymer chemist, so I’ll draw my engineer’s conclusions here and prepare for a roasting from the chemists if I’m wrong. What I think has happened is that the volatile additives in the filament have departed over the years, and both the stringiness in damp newer PLA and the strength in prints made with new PLA are as much due to their presence or absence as to the PLA itself. In my tests here I think I have seen something closer to PLA alone with the additive chemistry absent, and along the way I may have touched on why the manufacturers add it in the first place.
It’s likely few of you are printing using ancient PLA, so while interesting, these results have limited direct relevance to your printing. But I have to wonder whether there’s a lesson to be learned in filament storage, and perhaps using a warm environment to stave off moisture might hasten the departure of those volatiles. Perhaps the best thing is not to be a hoarder, and to use your filament up as quickly as you can. Meanwhile, this isn’t the first time we’ve ventured into backyard physical measurements.
