Making a Hidden Door Status Sensor

The door sensor in its new enclosures. (Credit: Dillan Stock)
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.

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hackaday.com/2026/02/10/making…

Building a Self-Playing Chess Board Robot

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.

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hackaday.com/2026/02/10/buildi…

The Best USB To VGA Converter For The Job

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.

hackaday.com/2026/02/10/the-be…

Is That Ancient Reel Of PLA Any Good?

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?

It Ain’t Stringy

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.

A wobbly print from our old filament.
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.

Punishing Prints, And Risking Holes In The Floor

My 3D print stress test setup
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 couldn’t even break the new filament print with a floor-damaging 3Kg piece of rail!
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?

When The Volatiles Depart, What’s Left?

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.

hackaday.com/2026/02/10/is-tha…

ReMemory is the Amnesia-hedging Buddy Backup You Didn’t Know You Needed

What would happen if you lost your memory, even partially? With so much of our lives being digital, forgetting your passwords (or the master key to your password manager) could be disastrous. Haunted by that specter after a concussion, [eljojo] created ReMemory, a tool based on Shamir’s Secret Sharing to help your friends help you.

Shamir’s Secret Sharing, for the uninitiated, is a way to split up important data between parties so that the full picture is only available when a quorum comes together. The classic example is giving everyone a couple of digits out of the combination to the bank vault, but no one the full combination. Together, they can open the vault.

ReMemory works the same way. Rather than the combination to a bank vault, the locally-hosted, browser-based interface splits the encryption key to your sensitive data. If you’re old fashioned that might be a plaintext list of passwords, or for the more modern the recovery codes to your password manager. It could be literally anything, like your Aunt Edna’s famous cupcake recipe, which surely should not be lost to time.
Aunt Edna could probably handle this.
You can chose how many friends to split your data betwixt, and how many will be required to meet quorum– the minimum, of course, being two, but the suggested default is to split the data five ways, and allow decryption from any three parties. Each bundle includes the complete recovery tool, so anyone in your circle of trust can start the process of decrypting your data if they get the others on board. Since it’s self-hosted and browser based, those friends don’t have to be particularly tech-savvy, as long as they can be trusted to hold onto the files. Everything is explained in the readme included in each bundle.

This does have the downside of requiring you to have multiple close friends, at least some of whom you trust to come through in a crunch, and all of whom you trust not to collude behind your back. Still, if you’re the social type, this seems like it might be a useful tool. The code is available under an Apache 2.0 license, so you can audit it for yourself — a must for any tool you plan on entrusting your secrets to.

The best part of the sharing algorithm is that it’s not vulnerable to quantum computing. While [eljojo] was thinking of amnesia when he put the tool together, we can’t help but think this also solves the postmortem password problem.

hackaday.com/2026/02/10/rememo…

Gaming on an Arduino Uno Q in Linux

After Qualcomm’s purchase of Arduino it has left many wondering what market its new Uno Q board is trying to target. Taking the ongoing RAM-pocalypse as inspiration, [Bringus Studios] made a tongue-in-cheek video about using one of these SoC/MCU hybrid Arduino boards for running Linux and gaming on it. Naturally, with the lack of ARM-native Steam games, this meant using the FEX x86-to-ARM translator in addition to Steam’s Proton translation layer where no native Linux game exists, making for an excellent stress test of the SoC side of this board.
Technically, this is a heatsink. (Credit: Bringus Studios, YouTube)
We covered this new ‘Arduino’ board previously, which features both a quad-core Cortex-A53 SoC and a Cortex-M33 MCU. Since it uses the Uno form factor, all SoC I/O goes via the single USB-C connector, meaning that a USB-C docking station is pretty much required to use the SoC, though there’s at least 16 GB of eMMC to install the OS on. A Debian-based OS image even comes preinstalled, which is convenient.

With a mere 2 GB of LPDDR4 it’s not the ideal board to run desktop Linux on, but if you’re persistent and patient enough it will work, and you can even play 3D video games as though it’s Qualcomm’s take on Raspberry Pi SBCs. After some intense gaming the SoC package gets really quite toasty, so adding a heatsink is probably needed if you want to peg its cores and GPU to 100% for extended periods of time.

As for dodging the RAM-pocalypse with one of these $44 boards, it’s about the same price as the 1 GB Raspberry Pi 5, but the 2 GB RPi 5 – even with the recent second price bump – is probably a better deal for this purpose. Especially since you can skip the whole docking station, but losing the eMMC is a rawer deal, and the dedicated MCU could be arguably nice for more dedicated purposes. Still, desktop performance is a hard ‘meh’ on the Uno Q, even if you’re very generous.

Despite FEX being a pain to set up, it seems to work well, which is promising for Valve’s upcoming Steam Frame VR glasses, which are incidentally Qualcomm Snapdragon-based.

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hackaday.com/2026/02/10/gaming…