Quote Printer Keeps Receipts

January 3, 2026 by 7 Comments

In the world of social media, “keeping receipts” refers to the practice of storing evidence that may come in handy for a callout post at a later date. For [Teddy Warner], though, it’s more applicable to a little printer he whipped up to record the very best banter from his cadre of friends.

[Teddy’s] idea was simple. He hoped to capture amusing or interesting quotes his friends made in his apartment, and store them in a more permanent form. He also wanted to allow his friends to do the same. To that end, he whipped up a small locally-hosted web interface which his friends could use to record quotes, along with proper attribution. Hosted on a Raspberry Pi 5, the web interface can then truck those quotes out to an 80 mm thermal receipt printer. The anecdote, epithet, or witticism is then spat out with a timestamp in a format roughly approximating a receipt you might get from your local gas station. What’s neat is that [Teddy] was also able to install the entire system within the housing of the Miemieyo receipt printer, by 3D printing a custom base that could house the Pi and a suitable power supply.

Beyond being fun, this system also serves a critical purpose. It creates a paper trail, such that in-jokes, rumors, and insults alike can be traced back to their originating source. No more can Crazy Terry claim to have invented “the Malaga bit,” because the server and the receipt clearly log that Gerald dropped it first at the Boxing Day do.

We’ve seen similar projects before, too. There’s just something neat about holding a bit of paper in your hand.

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FPGA Dev Kit Unofficially Brings MSX Standard Back

January 3, 2026 by 8 Comments

In the 1980s there were an incredible number of personal computers of all shapes, sizes, and operating system types, and there was very little interoperability. Unlike today’s Windows-Mac duopoly, this era was much more of a free-for-all but that didn’t mean companies like Microsoft weren’t trying to clean up all of this mess. In 1983 they introduced the MSX standard for computers, hoping to coalesce users around a single design. Eventually it became very successful in Japan and saw some use in a few other places but is now relegated to the dustbin of history, but a new FPGA kit unofficially supports this standard.

The kit is called the OneChip Book and, unlike most FPGA kits, includes essentially everything needed to get it up and running including screen, keyboard, and I/O all in a pre-built laptop case. At its core it’s just that: and FPGA kit. But its original intent was to recreate this old 80s computer standard with modern hardware. The only problem is they never asked for permission, and their plans were quickly quashed. The development kit is still available, though, and [electricadventures] goes through the steps to get this computer set up to emulate this unofficially-supported retro spec. He’s also able to get original MSX cartridges running on it when everything is said and done.

Although MSX is relatively unknown in North America and Western Europe, it remains a fairly popular platform for retro computing enthusiasts in much of the rest of the world. We’ve seen a few similar projects related to this computer standard like this MSX-inspired cyberdeck design, but also others that bring new hardware to this old platform.

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A photo of the thrust meter from the Apollo lunar module

Apollo Lunar Module Thrust Meter Lives Again

January 3, 2026 by 7 Comments

[Mike Stewart] powers up a thrust meter from an Apollo lunar module. This bit of kit passed inspection on September 25, 1969. Fortunately [Mike] was able to dig up some old documentation which included the pin numbers. Score! It’s fun to see the various revisions this humble meter went through. Some of the latest revisions are there to address an issue where there was no indication upon failure, so they wired in a relay which could flip a lamp indicator if the device lost power.

This particular examination of this lunar thrust module is a good example of how a system’s complexity can quickly get out of hand. Rather than one pin there are two pins to indicate auto or manual thrust, each working with different voltage levels; the manual thrust is as given but the auto thrust is only the part of the thrust that gets added to a baseline thrust, so they need to be handled differently, requiring extra logic and wiring for biasing the thrust meter when appropriate. The video goes into further detail. Toward the end of the video [Mike] shows us what the meter’s backlights look like when powered.

If you’re interested in Apollo mission technology be sure to check out Don Eyles Walks Us Through The Lunar Module Source Code.

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Teardown Of Boeing 777 Cabin Pressure Control System

January 3, 2026 by 21 Comments

Modern passenger airliners are essentially tubes-with-wings, they just happen to be tubes that are stuffed full with fancy electronics. Some of the most important of these are related to keeping the bits of the tube with humans inside it at temperatures and pressures that keeps them alive and happy. Case in point the Boeing 777, of which [Michel] of Le Labo de Michel on YouTube recently obtained the Cabin Pressure Control System (CPCS) for a teardown.

The crucial parts on the system are the two Nord-Micro C0002 piezo resistive pressure transducers, which measure the pressure inside the aircraft. These sensors, one of which is marked as ‘backup’, are read out by multiple ADCs connected to a couple of FPGAs. The system further has an ARINC 429 transceiver, for communicating with the other avionics components. Naturally the multiple PCBs are conformally coated and with vibration-proof interconnects.

Although it may seem like a lot of hardware just to measure air pressure with, this kind of hardware is meant to work without errors over the span of years, meaning significant amounts of redundancy and error checking has to be built-in. Tragic accidents such as Helios Airways Flight 522 involving a 737-300 highlight the importance of these systems. Although in that case human error had disabled the cabin pressurization, it shows just how hard it can be to detect hypoxia before it is too late.

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Scientific staff members working on the computing machine Setun

The Setun Was A Ternary Computer From The USSR In 1958

January 3, 2026 by 41 Comments

[Codeolences] tells us about the FORBIDDEN Soviet Computer That Defied Binary Logic. The Setun, the world’s first ternary computer, was developed at Moscow State University in 1958. Its troubled and short-lived history is covered in the video. The machine itself uses “trits” (ternary digits) instead of “bits” (binary digits).

When your digits have three discrete values there are a multiplicity of ways of assigning meaning to each state, and the Setun uses a system known as balanced ternary where each digit can be either -1, 0, or 1 and otherwise uses a place-value system in the normal way.

An interesting factoid that comes up in the video is that base-3 (also known as radix-3) is the maximally efficient way to represent numbers because three is the closest integer to the natural growth constant, the base of the natural logarithm, e, which is approximately 2.718 ≈ 3.

If you’re interested to know more about ternary computing check out There Are 10 Kinds Of Computers In The World and Building The First Ternary Microprocessor.

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Pickle Diodes, Asymmetric Jacobs Ladders, And Other AC Surprises

January 3, 2026 by 15 Comments

While we’re 100 years past Edison’s fear, uncertainty, and doubt campaign, the fact of the matter is that DC is a bit easier to wrap one’s head around. It’s just so honest in its directness. AC, though? It can be a little shifty, and that results in some unexpected behaviors, as seen in this video from [The Action Lab].

He starts off with a very relatable observation: have you ever noticed that when you plug in a pickle, only half of it lights up? What’s up with that? Well, it’s related to the asymmetry he sees on his Jacobs ladder that has one side grow hotter than the other. In fact, it goes back to something welders who use DC know about well: the Debye sheath.

The arc of a welder, or a Jacobs ladder, or a pickle lamp is a plasma: ions and free electrons. Whichever electrode has negative is going to repel the plasma’s electrons, resulting in a sheath of positive charge around it. This positively-charged ions in the Debye sheath are going to accelerate into the anode, and voila! Heating. That’s why it matters which way the current goes when you’re welding.

With DC, that makes sense. In AC, well — one side starts as negatively charged, and that’s all it takes. It heats preferentially by creating a temporary Debye sheath. The hotter electrode is going to preferentially give off electrons compared to its colder twin — which amplifies the effect every time it swings back to negative. It seems like there’s no way to get a pure AC waveform across a plasma; there’s a positive feedback loop at whatever electrode starts negative that wants to introduce a DC bias. That’s most dramatically demonstrated with a pickle: it lights up on the preferentially heated side, showing the DC bias. Technically, that makes the infamous electric pickle a diode. We suspect the same thing would happen in a hot dog, which gives us the idea for the tastiest bridge rectifier. Nobody tell OSHA.

[The Action Lab] explains in more detail in his video, and demonstrates with ring-shaped electrode how geometry can introduce its own bias. For those of us who spend most of our time slinging solder in low-voltage DC applications, this sort of thing is fascinating.  It might be old hat to others here; if the science of a plain Jacobs ladder no longer excites you, maybe you’d find it more electrifying built into a blade.

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A bed of metal powder is visible through a green-tinted window. A fused metal pattern, roughly square, is visible, with one corner glowing white and throwing up sparks.

Printing In Metal With DIY SLM

January 3, 2026 by 5 Comments

An accessible 3D printer for metals has been the holy grail of amateur printer builders since at least the beginning of the RepRap project, but as tends to be the case with holy grails, it’s proven stubbornly elusive. If you have the resources to build it, though, it’s possible to replicate the professional approach with a selective laser melting (SLM) printer, such as the one [Travis Mitchell] built (this is a playlist of nine videos, but if you want to see the final results, the last video is embedded below).

Most of the playlist shows the process of physically constructing the machine, with only the last two videos getting into testing. The heart of the printer is a 500 Watt fiber laser and a galvo scan head, which account for most of the cost of the final machine. The print chamber has to be purged of oxygen with shielding gas, so [Travis] minimized the volume to reduce the amount of argon needed. The scan head therefore isn’t located in the chamber, but shines down into it through a window in the chamber’s roof. A set of repurposed industrial servo motors raises and lowers the two pistons which form the build plate and powder dispenser, and another servo drives the recoater blade which smooths on another layer of metal powder after each layer.

As with any 3D printer, getting good first-layer adhesion proved troublesome, since too much power caused the powder to melt and clump together, and too little could result in incomplete fusion. Making sure the laser was in focus improved things significantly, though heat management and consequent warping remained a challenge. The recoater blade was originally made out of printed plastic, with a silicone cord along the edge. Scraping along hot fused metal in the early tests damaged it, so [Travis] replaced it with a stainless steel blade, which gave much more consistent performance. The final results looked extremely promising, though [Travis] notes that there is still room for redesign and improvement.

This printer joins the very few other DIY SLM machines we’ve seen, though there is an amazingly broad range of other creative ideas for homemade metal printers, from electrochemical printers to those that use precise powder placement.

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