This Handy Synth Packs An ESP32

May 2, 2026 by 2 Comments

Since the first electronic hobbyist wired up a multivibrator to a keyboard many decades ago, electonic synthesisers have been a staple of home-made projects. Now with the proliferation of significantly powerful microcontrollers it’s possible to make a synth that surpasses many of the high-end models from days gone by.

Among those we’ve seen of late perhaps none does this better than [Povle] with their Spark portable keyboard. It’s a tiny thing that reminds us of those little Casio synths of the 1980s, but in its 3D printed case it packs a load of features.

Hardware wise it’s an ESP32 with a 3D printed keyboard using keyswitches. There are a load of pots for sound adjustment, and buttons for functions. A small OLED display shows what’s going on. Software wise it relies upon the AMY synth library, and there are repositories for both its hardware and software.

There’s a demo video we’ve placed below, and in it you hear the keyboard at work. And here maybe we’ve saved the best until last, because alongside being a fully featured synth, it’s also a sampler and a Bluetooth MIDI keyboard. Is there nothing this thing can’t do!

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Debugging A Stopped Foucault Pendulum’s Electronics

May 2, 2026 by 2 Comments

After the Foucault pendulum at the Houston Museum of Natural Science stopped working a while back after maintenance on the building, workers set out to determine what was wrong with the mechanism that normally keeps it in motion. Fortunately, it turned out that all they had to do was fiddle with some knobs to get everything dialed back in proper-like.

When we previously covered this dire event, it was claimed that this was a one-off system, hacked together by some random bloke. But as can be seen in the video and further detailed in the comments to the video the reality is far more interesting.

This particular Foucault pendulum is one of many that were created by the California Academy of Sciences, with hundreds of them installed throughout the US and possibly elsewhere. That said, since a pendulum of any description will never be a perpetual motion device, the electromagnet installed near the top of the installation has to carefully add some kinetic energy back that was lost due to friction as the pendulum moves around.

Sadly the video doesn’t go into much detail on what exactly was wrongly configured with this particular pendulum. Keeping a weight at the end of a long cable moving around at a set velocity is a tricky business, so it’s little wonder that getting some parameters wrong would engage and disengage the electromagnets at the wrong times and making the pendulum stop swinging.

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Rust Helps Make A $1 Handheld Console

May 1, 2026 by 4 Comments

These days, even an old Game Boy will set you back $100 or more, and a new handheld console will be many multiples of that. However, you can build a really cheap handheld gaming toy if you follow [Chris Dell’s] example.

In [Chris]’s own words, he used Rust to build a $1 handheld gaming console. How is that possible? Well, it all comes down to the CH32V003—a microcontroller cheaper than just about anything else out there. It sells for just 9 cents in bulk, and it’s no slouch either. The RISC-V device is a fully-fledged 32-bit chip running at 48 MHz, though with only 2 KB of RAM and 16 KB of flash. Still, that’s more than enough to make some little games. To this end, [Chris] paired the CH32V003 with an SSD1306 OLED display, and three tactile pushbuttons. He then whipped up some code in Rust with the aid of the ch32-hal project, implementing a neat platform game that ran at a healthy 25 fps.

The CH32V003 probably won’t be starring in a new handheld gaming revolution anytime soon. Still, it’s always interesting to see just what can be achieved with one of the cheapest microcontrollers on the market.

[Thanks to Kian Ryan for the tip!]

3D Printed Orrery Runs On A Single Motor

May 1, 2026 by 6 Comments

The solar system is kind of hard to observe in motion all at once. Sometimes, it’s nice to have a little model to look at, so you can see the relative motions of celestial bodies play out in front of you. Such a device is called an orrery, and [illusionmanager] has built rather a nice example of their own.

The build represents all the planets in the solar system, plus the sun and our very own Moon. An ESP32 lives at the heart of the build, running an astronomical simulation to calculate the proper positions of all the celestial objects. It then drives a small stepper motor via a TMC2209 driver, turning the mechanism back and forth until all the pieces are positioned correctly, using a reed switch and magnet to detect the initial zero position. The orrery is able to be driven by a single motor in this manner thanks to an ingenious mechanism, wherein the rings interlock with each other using small tabs. The Moon is controlled by a separate geared mechanism connected to the main rotation.

It’ s a nice decoration that also serves as a great conversation piece, particularly if you like talking about the heavens. We’ve featured some fine works from [illusionmanager] before, too, like this exquisite reverse sundial. Video after the break.

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Magnetic Induction Heats Water

May 1, 2026 by 19 Comments

Producing hot water off-grid is a surprisingly energy-intensive activity, and although it looks simple on its surface it can get quite complicated especially when used in large scale for something like providing hot water for an entire home. When using combustion to heat the water there needs to be proper venting as well as control of the fuel, and even storage of the hot water needs to be meticulous to avoid certain pathogens. [Greenhill Forge] has built an off-grid solution for heating hot water that doesn’t necessarily rely on any combustion, though, provided he can find something to spin his custom electric machine.

The machine in question is, of course, an induction heater. It works similar to any simple electric motor, generator, or transformer except in this case the eddy currents generated are exploited rather than minimized. Normally these currents, generated when a magnet passes by a metal, are wasted heat in other machines but in this induction heater it’s the goal. The machine’s stator is built from copper tube wound in a spiral which allows water to flow through and absorb heat. The tube is soldered into one electrically solid mass to maximize the eddy currents. The rotor is taken from a previous generator built by [Greenhill Forge] which holds the permanent magnets.

During the initial tests using a power drill to drive the generator, he was able to heat 1.5 liters of water from 7.9C to about 24.4 C in three minutes. The math works out to providing 575 watts of power to the heater, and with something that could spin the generator faster it might have the potential to provide around 14.5 kW. Provided that there’s a source of energy around, such as a wind or water turbine, this could be a fairly sustainable way of generating hot water in off-grid situations. Some of [Greenhill Forge]’s other projects are centered around this idea as well, like one of his builds which uses waste sawdust to heat his workshop with a custom-built stove.

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Adapting A 100-Year-Old Lens To A Modern Camera

May 1, 2026 by 3 Comments

You can get all kinds of fancy lenses for modern cameras, with all sorts of mechanical and electronic wizardly to make them shoot better images. But what if you paired a vintage lens with a modern camera? It would take some work, as [Mathieu] found out, but you’d also get some interesting results.

The optic in question is a 100-year old lens—a Foth 50 mm f2.5 to be precise, originally used with a folding film camera. It was sourced from a market for just 3 euros. Notably, the lens was not designed for modern cameras, and so lacks an aperture and focusing mechanism. [Mathieu] thus had to fabricate something to fit the lens to a Sony FX3. A first attempt used an aperture adapter from Amazon and an elcoid adapter, but there were vignetting problems due to the lens placement in this case. Ultimately, [Mathieu] went with a special macro adapter that allowed him to control focus and tuck in an ND filter behind the lens, which made up for the lack of an aperture.

The vintage glass isn’t the sharpest lens out there, but that’s kind of what’s fantastic about it. The center of the frame is certainly focused, but it fades out softly towards the edges of the image, giving a cinematic, dreamlike effect. The bokeh in the background are particularly charming, too. As far as 3 euro lenses go, this one was a hit.

You can slap just about any lens on anything if you get creative with how you do it. Video after the break.

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Running DOOM On A Travel Router With Touch Screen

May 1, 2026 by 7 Comments

Continuing his quest to put DOOM on literally everything that has a capable enough processor and a screen, [Aaron Christophel]’s most recent target is a Slate 7 Pro travel router. With a generous 2.8″ touch screen and a lot of onboard processing power to handle all the advertised networking and routing features via its WAN and (W)LAN interfaces, it should be able to run the game really quite well. As usual the main question is how to get the game to run on it first.

The port of choice is fbdoom, with instructions on how to run it on this router provided on the GitHub project page. The reason for the touch screen is so that you can see the status of interfaces and interact with it without having to open the web interface. Boringly, this router has an SSH daemon ready to connect to, giving you full root access to the Linux-based firmware.

It’s just your typical AArch64 ARM-based system, with the gl_screen process running for the touch screen display. From there it was easy enough to deduce the settings to jot into fbdoom so that it too could use the same screen and touch inputs. After copying the compiled binary with SCP over to the router, it can then be started like any application. With touch inputs somewhat awkwardly mapped to certain areas of the touch screen, it’d be nice to see the USB 2.0 port used for USB HID inputs, but it does show how easy things can be when it runs something like Linux and you got full root access.

Incidentally this also heavily blurs the lines between something like a Valve Steamdeck and a router, with the latter just missing some gamepad controls on the side to do some on-the-go gaming when you’re not using it for routing network traffic.

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