Yaydio, A Music Player For Kids

March 29, 2025 by Jenny List 6 Comments

Music consumption has followed a trend over the last decade or more of abandoning physical media for online or streaming alternatives. This can present a problem for young children however, for whom a simpler physical interface may be an easier way to play those tunes. Maintaining a library of CDs is not entirely convenient either, so [JakesMD] has created the Yaydio. It’s a music player for kids, that plays music when a card is inserted in its slot.

As you might expect, the cards themselves do not contain the music. Instead they are NFC cards, and the player starts the corresponding album from its SD card when one is detected. The hardware is simple enough, an Arduino Nano with modules for MP3 playback, NFC reading, seven segment display, and rotary encoder. The whole thing lives in a kid-friendly 3D printed case.

Some thought has been given to easily adding albums and assigning cards to them, making it easy to keep up with the youngster’s tastes. This isn’t the first such kid-friendly music player we’ve seen, but it’s certainly pretty neat.

DIY Split Keyboard Made With A Saw

March 29, 2025 by Maya Posch 17 Comments

Split keyboards are becoming more popular, but because they’re still relatively niche, they can be rather expensive if you want to buy one. So why not make your own? Sure, you could assemble one from a kit, but why not take a cheap mechanical keyboard, slice it in half and just waves hands connect the two halves back together? If this thought appeals to you, then [nomolk]’s literal hackjob video should not be ignored. Make sure to enable English subtitles for the Japanese-language video.

Easy split keyboard tip: just reconnect both halves... (Credit: nomolk, YouTube) — Easy split keyboard tip: just reconnect both halves… (Credit: nomolk, YouTube)

In it, the fancy (but cheap) mechanical keyboard with Full RGB™ functionality is purchased and tested prior to meeting its demise. Although the left side with the cable and controller still works, the right side now needs to be connected, which is where a lot of tedious wires have to be soldered to repair traces.

Naturally this will go wrong, so it’s important to take a (sushi) break and admire the sunset before hurling oneself at the tracing of faulty wiring. This process and the keyboard matrix is further detailed on the blog entry (in Japanese) for this process.

Although this was perhaps easier than the other split keyboard project involving a membrane keyboard, this tongue-in-cheek project demonstrates the limits of practicality with this approach even if it could be cleaned up more with fancier wiring.

We give it full points for going the whole way, however, and making the keyboard work again in the end.

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An ESP32 Pomodoro Timer

March 29, 2025 by Jenny List 12 Comments

The Pomdoro technique of time management has moved on a little from the tomato-shaped kitchen timer which gave it a name, as [Rukenshia] shows us with this nifty ESP32 and e-paper design. It’s relatively simple in hardware terms, being a collection of off-the-shelf modules in a 3D printed case, but the software has a custom interface for the friend it was built for.

At its heart is a NodeMCU board and a Waveshare display module, with a rotary encoder and addressable LED as further interface components. A lot of attention has been paid to the different options for the interface, and to make the front end displayed on the screen as friendly and useful as possible. Power comes via USB-C, something that should be available in most working environments here in 2025.

We’ve tried a variant on this technique for a while now with varying success, maybe because a mobile phone doesn’t make for as good a timer as a dedicated piece of hardware such as this. Perhaps we should follow this example. If we did, the Hackaday timer couldn’t possibly use an ESP32.

AMSAT-OSCAR 7: The Ham Satellite That Refused To Die

March 29, 2025 by Maya Posch 41 Comments

When the AMSAT-OSCAR 7 (AO-7) amateur radio satellite was launched in 1974, its expected lifespan was about five years. The plucky little satellite made it to 1981 when a battery failure caused it to be written off as dead. Then, in 2002 it came back to life. The prevailing theory being that one of the cells in the satellites NiCd battery pack, in an extremely rare event, failed open — thus allowing the satellite to run (intermittently) off its solar panels.

In a recent video by [Ben] on the AE4JC Amateur Radio YouTube channel goes over the construction of AO-7, its operation, death and subsequent revival are covered, as well as a recent QSO (direct contact).

The battery is made up of multiple individual cells.

The solar panels covering this satellite provided a grand total of 14 watts at maximum illumination, which later dropped to 10 watts, making for a pretty small power budget. The entire satellite was assembled in a ‘clean room’ consisting of a sectioned off part of a basement, with components produced by enthusiasts associated with AMSAT around the world. Onboard are two radio transponders: Mode A at 2 meters and Mode B at 10 meters, as well as four beacons, three of which are active due to an international treaty affecting the 13 cm beacon.

Positioned in a geocentric LEO (1,447 – 1,465 km) orbit, it’s quite amazing that after 50 years it’s still mostly operational. Most of this is due to how the satellite smartly uses the Earth’s magnetic field for alignment with magnets as well as the impact of photons to maintain its spin. This passive control combined with the relatively high altitude should allow AO-7 to function pretty much indefinitely while the PV panels keep producing enough power. All because a NiCd battery failed in a very unusual way.

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Open Source Framework Aims To Keep Tidbyt Afloat

March 29, 2025 by Tom Nardi 10 Comments

We recently got a note in the tips line from [Tavis Gustafson], who is one of the developers of Tronbyt — a replacement firmware and self-hosted backend that breaks the Tidbyt smart display free from its cloud dependency. When they started the project, [Tavis] says the intent was simply to let privacy-minded users keep their data within the local network, which was itself a goal worthy enough to be featured on these pages.

But now that Tidbyt has been acquired by Modal and has announced they’ll no longer be producing new units, things have shifted slightly. While the press release says that the Tidbyt backend is going to stay up and running for existing customers, the writing is clearly on the wall. It’s now possible that the Tronbyt project will be able to keep these devices from ending up in landfills when the cloud service is inevitably switched off, especially if they can get the word out to existing users before then.

What’s that? You say you haven’t heard of Tidbyt? Well, truth be told, neither had we. So we did some digging, and this is where things get really interesting.

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Contagious Ideas

March 29, 2025 by Elliot Williams 8 Comments

We ran a story about a wall-mounted plotter bot this week, Mural. It’s a simple, but very well implemented, take on a theme that we’ve seen over and over again in various forms. Two lines, or in this case timing belts, hang the bot on a wall, and two motors drive it around. Maybe a servo pulls the pen in and out, but that’s about it. The rest is motor driving and code.

We were thinking about the first such bot we’ve ever seen, and couldn’t come up with anything earlier than Hektor, a spray-painting version of this idea by [Juerg Lehni]. And since then, it’s reappeared in numerous variations.

Some implementations mount the motors on the wall, some on the bot. There are various geometries and refinements to try to make the system behave more like a simple Cartesian one, but in the end, you always have to deal with a little bit of geometry, or just relish the not-quite-straight lines. (We have yet to see an implementation that maps out the nonlinearities using a webcam, for instance, but that would be cool.) If you’re feeling particularly reductionist, you can even do away with the pen-lifter entirely and simply draw everything as a connected line, Etch-a-Sketch style. Maslow CNC swaps out the pen for a router, and cuts wood.

What I love about this family of wall-plotter bots is that none of them are identical, but they all clearly share the same fundamental idea. You certainly wouldn’t call any one of them a “copy” of another, but they’re all related, like riffing off of the same piece of music, or painting the same haystack in different lighting conditions: robot jazz, or a study in various mechanical implementations of the same core concept. The collection of all wall bots is more than the sum of its parts, and you can learn something from each one. Have you made yours yet?

(Fantastic plotter-bot art by [Sarah Petkus] from her write-up ten years ago!)

Recreating The Analog Beauty Of A Vintage Tektronix Oscillator

March 29, 2025 by Dan Maloney 11 Comments

Tektronix must have been quite a place to work back in the 1980s. The company offered a bewildering selection of test equipment, and while the digital age was creeping in, much of their gear was still firmly rooted in the analog world. And some of the engineering tricks the Tek wizards pulled off are still the stuff of legend.

One such gem of analog design was the SG505, an ultra-low-distortion oscillator module that [Paul] is trying to replicate with modern parts. That’s a tall order since not only did the original specs on this oscillator call for less than 0.0008% total harmonic distortion over a frequency range of 20 Hz to 20 kHz, but a lot of the components it used are no longer manufactured. Tek also tended to use a lot of custom parts, especially mechanical ones like the barrel switch used to select attenuation levels in the SG505, leaving [Paul] no choice but to engineer his way around them.

So far, [Paul] has managed to track down most of the critical components or source suitable substitutes. One major win was locating the original J-FET Tek used in the oscillator’s AGC circuit. One part that’s proven more elusive is the potentiometer that Tek used to adjust the frequency; who knew that finding a dual-gang precision wirewound 10k single-turn pot with no physical stop would be such a chore?

[Paul] still seems to be very much in the planning stages of this project yet, and that’s probably for the best since projects such as these live and die on proper planning. We’re keen to see how this develops, and we’re very much looking forward to seeing the FFT results. We also imagine he’ll be busting out his custom curve tracer at some point in the build, too.