A person with blonde hair and light skin in a black t-shirt points at an image of a large QR code with what appear to be pictographic humans dancing in place of the usual blocky squares between the finding squares.

Reading QR Codes By Hand

October 21, 2026 by No comments

QR codes can be a handy way to send a link or contact details without all that tedious mucking about with typing in a link, but they aren’t very useful without a smartphone to decode them. [Noel Friedrich] wondered if there was a way to do it by hand.

If it all seems a bit daunting at first, [Friedrich]’s write-up helps you work through copying a QR code to paper and then decoding it, as long as it’s version 1-5. Slashes in the template tell you where error correction has been applied to the code and you need to flip the bit back to what it was.

[Friedrich] then goes into some more details with a practical example of how the error correction works and how to exploit the ways QR codes are generated and read to make artistic QR codes. This even works to make human readable codes (without the worksheet), although the quality of the text still makes it somewhat challenging.

This isn’t the first time we’ve featured reading QR codes without a computer, but once you learn, maybe this QR code clock will be a bit more useful!

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Making A Five-Segment Display With Platinum-Titanium Cathodes

October 21, 2026 by 4 Comments

Before the advent of effective semiconductor LEDs many display types existed to display things like numbers and other characters. The Nixie tube is a well-known one, along with VFDs and there are also lesser known ones such as Burrough’s Panaplex, which all saw plentiful use in everything from calculators to audio equipment. The design that [Witchcraft and Alchemy] made appears to lean heavily on this Panaplex design.

Rather than neon, this uses argon as the gas. The anode is formed by the indium-tin oxide layer on a piece of glass, with the cathode sputtered onto the other side in the form of first a titanium layer followed by platinum. This combination helps to prevent the latter from flaking off due to incompatibilities between the molecular matrices of the glass and platinum.

Since this is an early prototype, only five segments were sputtered onto the glass and driven with a 74141 Nixie driver IC, creating the expected purple glow in a vacuum chamber. Following this a self-contained prototype was created, but this proved to be less successful, with the prototype quickly failing to light up as expected.

For a next attempt no tape or epoxy for sealing the device will be used, but rather a gasket instead of gluing the front glass onto the device. The use of conductive vias should make the device’s vacuum more permanent, and enable those last two segments to make it a seven-segment display. The final change should be to use a Penning mixture instead of pure argon.

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Every Type Of Current Sensor Explained

October 21, 2026 by No comments

Measuring electric currents is an essential element of many electrical systems, but doing so in a way that is as nonintrusive as possible is not an easy problem to solve. Due to this we got a wide variety of current sensors to choose from for any given application, with [ElectrArc240] running us through these variants in a recent video.

The fairly low-tech, cheap and quite reliable method of using a shunt resistor is first demonstrated. This sees a lot of use in fairly low-voltage and low-current applications, with for example videocards using it to limit the amount of power the GPU can use, a feature that modders will happily bypass. Here simply the voltage drop across a known resistance value is measured, from which the current can be derived.

Of course, you got higher voltage and higher current applications too, as well as direct- and alternating current, with the latter especially allowing for easy current measurements simply from the electromagnetic field, or flux. Anyone who has used a clamp meter can attest to that such contact-free current sensing works, even for DC applications.

Beyond the basic transformer type you got many variants including Hall-Effect, TMR and fluxgate sensors, as well as the fiber-optic current sensor that uses an interferometer to measure the phase-change induced by the magnetic field – the Faraday effect – to the transmitted electromagnetic radiation. These more exotic types will improve resolution, at the cost of a rapidly increasing void in your project budget.

These various sensor types and their construction are demonstrated and discussed in the video, including when you’d want to use a specific type, and what the potential gotchas are with each type. Even if for many applications a simple shunt resistor suffices, it’s a good idea to know these different types, as well as their underlying theory of operation.

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Sega Genesis Controllers On The Philips CD-i

October 21, 2026 by 2 Comments

The Philips CD-i was not popular upon its launch in 1991, and is barely acknowledged today. In the opinion of [MattKC], it had a particularly poor selection of controllers, too, and it’s often hard to find used examples anyway. To rectify this situation, he whipped up an adapter to let him use Sega Genesis controllers instead.

The benefit of the Genesis controller is that it uses DB-9 connectors that are readily available, and it’s got a simple pinout that is compatible with the Atari joystick port, too. It makes interfacing the controllers supremely easy. Converting the controllers required using a Arduino Pro Micro to read the Genesis pad and translate it into something suitable for the CD-i.

On the Sega controller side, the microcontroller just has to strobe one pin while reading the state of others to determine what all the buttons are doing. The CD-i, however, expects a serial data stream from the original Philips controllers. Thus, the microcontroller is set up to poll the Genesis controller, and then translate this into the serial commands for the CD-i. It gets a little complicated, because the CD-i wasn’t really built for game controllers, but mouse-like inputs instead. But it’s not too hard to get things working once you understand what the weird Philips console is looking for.

There aren’t really any good games on the CD-i, so this isn’t a project that the retro gaming masses will be flocking to. Still, if you have a CD-i and you want to hook up some controllers on the cheap, this might come in handy. Alternatively, you could also try the BlueRetro project.

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Knitting Yarn And Filament With FilaLoom

October 21, 2026 by 6 Comments

We don’t generally think of 3D printing and knitting in the same sentence. One uses threads and fine motor control, while the other requires great knowledge of pressing buttons and plastics. That said, they both entail stacking material over and over until a finished product emerges. So why not blend the two crafts together? [Joram de Haas] decided to work on just that in the form of FilaLoom.

2D, 3D, and even embedded mechanisms!

This isn’t the first time we have seen additional elements embedded into 3D printed parts here on Hackaday. However, this particular implementation has some extra features which allow the embedded structures to grow larger than most examples prior. Instead of placing any implements directly into a structure by hand, all thread is placed by a tool head not so different from tool-changer printers. Using both the 3D printing tool head and the thread tool, some truly interesting properties can emerge from the finished product. If you aren’t interested in the weird webbing properties themselves, you surely could appreciate the possibilities demonstrated by the 3D knits.

You might not have a specific use case for thread printing, but why not check out some other fancy 3D printing techniques? Here’s a group of various design techniques that will certainly make you think twice in your next design!

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Building A Simple Internet Radio

October 21, 2026 by 23 Comments

Broadcast radio isn’t as popular as it once was, its popularity suffering in turn due to technologies like MP3 players and music streaming services. If you don’t fancy either of those, you might like to listen to some internet radio stations, using a rig like the one [CodersCafeTech] built.

It’s a simple desktop radio set, but instead of tuning in to AM or FM broadcast bands, it has an antenna for 2.4 GHz instead. That’s because inside this radio is an ESP32-S3 development board, which is equipped with onboard WiFi hardware that lets it connect to the internet. It’s hooked up to a 1.3-inch OLED display over I2C, which acts as a user interface in concert with a rotary encoder. Sound is handled with a MAX98357 I2S audio amplifier, hooked up to a small 3 W speaker. Once programmed appropriately, all the unit needs is a WiFi SSID and password, and the URL for the internet radio station you’d like to listen to.

We’ve featured a few internet radio builds over the years, as well as a rather fun build that saw a Macintosh SE/30 hooked up to Spotify. If you’re tinkering with something along those lines, don’t hesitate to let us know on the tipsline!

The Age Of Altair

October 21, 2026 by 11 Comments

I recently got the Amazon Christmas toy book in the mail, and it is definitely the modern version of the Sears Christmas Wish Book for last century’s youth. Or at least the majority of last century’s youth. For the true hacker, we had a different set of wishes. Recently, I found something I’ve clung to for over 50 years: the 1975 “The Age of Altair” catalog from MITS. Now that was a wish book!

The poor thing has been dragged around for decades and, I’m sad to say, it looks it. It isn’t totally trash, but I decided I should scan it. Then I realized that Bitsavers has already done it for me and with a much nicer copy, too. The images in this post are from their scan instead.

About the Altair

The magazine that started it all (World Radio History).

If your first computer ran Windows, you might not get the significance of the Altair. Back in 1974, the idea of having your own computer was practically ludicrous. Sure, Radio Electronics had published plans for the Mark 8 in July of that year. But it used an anemic 8008 CPU, and it wasn’t easy to get all the parts you’d need to build one. Other limited computers, like the Kenbak-1 or the occasional surplus minicomputer, ended up in personal hands. But you couldn’t just decide you wanted a real computer, plunk down some money, and have one delivered unless you had extremely deep pockets.

To stay on magazine stands longer, old print mags would come out earlier than their cover date suggested. The January 1975 Popular Electronics arrived, actually, in December of 1974 — just in time for the holidays. It showed a computer you could buy as a kit or assembled: the Altair 8800. Many of us were mesmerized by the idea of owning an actual useful computer.

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