The DIY 1982 Picture Phone

April 29, 2025 by 15 Comments

If you’ve only been around for the Internet age, you may not realize that Hackaday is the successor of electronics magazines. In their heyday, magazines like Popular Electronics, Radio Electronics, and Elementary Electronics brought us projects to build. Hacks, if you will. Just like Hackaday, not all readers are at the same skill level. So you’d see some hat with a blinking light on it, followed by some super-advanced project like a TV typewriter or a computer. Or a picture phone.

In 1982, Radio Electronics, a major magazine of the day, showed plans for building a picture phone. All you needed was a closed-circuit TV camera, a TV, a telephone, and about two shoeboxes crammed full of parts.

Like many picture phones of its day, it was stretching the definition a little. It actually used ham radio-style slow scan TV (SSTV) to send a frame of video about once every eight seconds. That’s not backwards. The frame rate was 0.125 Hz. And while the resulting 128 x 256 image would seem crude today, this was amazing high tech for 1982.

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PCBs of two continuous glucose monitors

Peeking At Poking Health Tech: The G7 And The Libre 3

April 29, 2025 by 8 Comments

Continuous glucose meters (CGMs) aren’t just widgets for the wellness crowd. For many, CGMs are real-time feedback machines for the body, offering glucose trendlines that help people rethink how they eat. They allow diabetics to continue their daily life without stabbing their fingertips several times a day, in the most inconvenient places. This video by [Becky Stern] is all about comparing two of the most popular continuous glucose monitors (CGMs): the Abbott Libre 3 and the Dexcom G7.

Both the Libre 3 and the G7 come with spring-loaded applicators and stick to the upper arm. At first glance they seem similar, but the differences run deep. The Libre 3 is the minimalist of both: two plastic discs sandwiching the electronics. The G7, in contrast, features an over-molded shell that suggests a higher production cost, and perhaps, greater robustness. The G7 needs a button push to engage, which users describe as slightly clumsy compared to the Libre’s simpler poke-and-go design. The nuance: G7’s ten-day lifespan means more waste than the fourteen-day Libre, yet the former allows for longer submersion in water, if that’s your passion.

While these devices are primarily intended for people with diabetes, they’ve quietly been adopted by a growing tribe of biohackers and curious minds who are eager to explore their own metabolic quirks. In February, we featured a dissection of the Stelo CGM, cracking open its secrets layer by layer.

Continue reading “Peeking At Poking Health Tech: The G7 And The Libre 3” →

Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Protractor Keyboard

April 29, 2025 by 9 Comments

Don’t you love it when the title track is the first one on the album? I had to single out this adjustable keyboard called the Protractor, because look at it! The whole thing moves, you know. Go look at the gallery.

The Protractor, an adjustable monoblock split keyboard with sliding angles.
Image by [BFB_Workshop] via reddit
If you use a true split, even if you never leave the house, you know the pain of losing the good angle and/or separation you had going on for whatever reason. Not only does this monoblock split solve that simply by being a monoblock split, you can always find the right angle you had via the built-in angle finder.

[BFB_Workshop] used a nice!nano v2, but you could use any ZMK-supported board with the same dimensions. This 5 x 12 has 60 Gateron KS-33 switches, which it was made for, and has custom keycaps. You can, of course, see all the nice, neat ribbon cable wiring through the clear PLA, which is a really great touch.

This bad boy is flat enough that you can use the table as your palm rest. To me, that doesn’t sound so comfortable, but then again, I like key wells and such. I’d still love to try a Protractor, because it looks quite interesting to type on. If you want to build one, the files and instructions are available on Printables.

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Hydrogen Trains: Not The Success Germany Hoped They Would Be

April 29, 2025 by 90 Comments

As transport infrastructure in Europe moves toward a zero-carbon future, there remain a number of railway lines which have not been electrified. The question of replacing their diesel traction with greener alternatives, and there are a few different options for a forward looking railway company to choose from. In Germany the Rhine-Main railway took delivery of a fleet of 27 Alstom hydrogen-powered multiple units for local passenger services, but as it turns out they have not been a success (German language, Google translation.). For anyone enthused as we are about alternative power, this bears some investigation.

It seems that this time the reliability of the units and the supply of spare parts was the issue, rather than the difficulty of fuel transport as seen in other failed hydrogen transport problems, but whatever the reason it seems we’re more often writing about hydrogen’s failures than its successes. We really want to believe in a hydrogen future in which ultra clean trains and busses zip around on hydrogen derived from wind power, but sadly that has never seemed so far away. Instead trains seem inevitably to be following cars, and more successful trials using battery units point the way towards their being the future.

We’re sure that more hydrogen transport projects will come and go before either the technological problems are overcome, or they fade away as impractical as the atmospheric railway. Meanwhile we’d suggest hydrogen transport as the example when making value judgements about technology.

Weird And Wonderful VR/MR Text Entry Methods, All In One Place

April 29, 2025 by 5 Comments

Are you a developer or experimenter pondering options for text entry in virtual or mixed reality? If that’s the case (or you’re merely curious) then here’s the resource you need: TEXT, or the Text Entry for XR Trove. It’s a collection of all the things people have tried when it comes to creating text entry interfaces for virtual and mixed reality (VR/MR) systems, all in a searchable list, complete with animated demonstrations.

There are a lot of different ways to approach this problem, ranging from simple to strange.

VR and MR are new frontiers, and optimal interfaces are still very much a work in progress. If one wishes to avoid reinventing the wheel, it’s a good idea to research prior art. This resource makes it very easy to browse all the stuff people have tried when it comes to text entry.

It’s also fun just to browse and see what kinds of unusual solutions people have come up with that go pretty far beyond “floating over-sized virtual keyboard”. Lenstouch for example involves tapping directly on the touch-sensitive front of the headset, and PalmType reminds us somewhat of the Palm Pilot’s Graffiti system.

It’s a treasure trove of creativity with a nice, searchable interface. Have you come up with your own, or know of a method that isn’t there? Submit it to the collection so others can find it. And if you’re in the process of cooking something up yourself, we have some DIY handwriting recognition resources you might find useful.

Pi Pico Throws Us For A (MIDI) Loop

April 28, 2025 by 3 Comments

Modern micro-controllers are absolute marvels, but it isn’t too many projects use one and nothing else. For an example of such simplicity, take a look at [oyama]’s Pi Pico MIDI looper.

It uses the PicoW to interface with a synth via MIDI-BLE, which can be anything from pro equipment to an app on your smartphone. The single control button is already provided by the Pico W– the bootsel button is wearing a lot of hats here, allowing one to select betwixt 4 tracks (all different drums), set the tempo, and input notes on the selected track.

The action is simple: pound out the rhythm for each track, and it will repeat forever, or at least until you press the single button again to change it. There’s also a nice serial interface so you can see what’s going on via UART or USB. For what it does, it is amazingly simple: the BOM is one item, the Pi Pico W. To see it in action, check out the demo video below.

Given the ADC chops on the Pico, it would probably be easy to extend this build with a speaker to make a tiny stand-alone, one-button synth. Or you could add more buttons buttons, but then it’s no longer the beautifully simple single-line BOM project that [oyama] showed us.

Of course, everything is open-source on GitHub, under the BSD license, and forking is encouraged, so [oyama] would doubtless be more than happy to see you go nuts hacking and extending this tiny MIDI looper.

We’ve actually seen the MIDI-BLE standard used before, like this hack adding it to a Eurorack. If you like synths, you may be interested to see what it takes to design one from scratch, sans microcontroller. Continue reading “Pi Pico Throws Us For A (MIDI) Loop” →

Deriving The Reactance Formulas

April 28, 2025 by 9 Comments

If you’ve dealt with reactance, you surely know the two equations for computing inductive and capacitive reactance. But unless you’ve really dug into it, you may only know the formula the way a school kid knows how to find the area of a circle. You have to have a bit of higher math to figure out why the equation is what it is. [Old Hack EE] wanted to figure out why the formulas are what they are, so he dug in and shared what he learned in a video you can see below.

The key to understanding this is simple. The reactance describes the voltage over the current through the element, just like resistance. The difference is that a resistance is just a single number. A reactance is a curve that gives you a different value at different frequencies. That’s because current and voltage are out of phase through a reactance, so it isn’t as easy as just dividing.

If you know calculus, the video will make a lot of sense. If you don’t know calculus, you might have a few moments of panic, but you can make it. If you think of frequency in Hertz as cycles per second, all the 2π you find in these equations convert Hz to “radian frequency” since one cycle per second is really 360 degrees of the sine wave in one second. There are 2π radians in a circle, so it makes sense.

We love developing intuition about things that seem fundamental but have a lot of depth to them that we usually ignore. If you need a refresher or a jump start on calculus, it isn’t as hard as you probably think. Engineers usually use vectors or imaginary numbers to deal with reactance, and we’ve talked about that too, if you want to learn more.