Building Festival Badges That Sync Themselves Up

May 20, 2026 by 3 Comments

Lots of music events these days hand out various glowing tchotchkes that flash and sync up with the performance. [Tony Goacher] has whipped up his own badges that can do just that, all without needing any sort of pairing or infrastructure to speak of.

The CrowdClock badges each feature a ring of 16 addressable RGB LEDs. Running the LEDs is an ESP32 microcontroller, which has lots of neat wireless capability baked in from the factory. [Tony] decided to leverage the ESP-NOW wireless communication protocol to enable each badge to broadcast its current local clock tick. Each device also listens out for clock ticks from other badges in the area, and updates its current clock tick value if it receives a higher one from another badge. This behaviour allows a bunch of badges within radio range to all sync up automatically in short order, and then run their LED sequences in sync. There’s no need for a master designation or anything, the devices just all sync to whichever badge has the highest clock value and go from there.

It’s a really neat way to create propagating self-syncing behaviour in distributed wireless nodes. Files are on Github for those curious to learn more. Meanwhile, if you’ve ever wondered how those concert wristbands work, we’ve looked at that too. Video after the break.

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A DIY 3D Printing Filament Dryer

May 20, 2026 by 20 Comments

In a recent video [Saša Karanović] revisits the DIY filament dryer that he gave a shot a couple of years ago. Back then he reused an existing filament dryer, adding a custom controller and such to improve its performance.

This technically-not-fully-DIY dryer got some feedback since then, and thus the V2 version is an example of how to better DIY such a dryer, including a custom PCB and a GitHub project for all the details.

Those who just want to dive into the documentation for assembly and the BOM can look at the available documentation. At its core the whole assembly consists of some kind of container like the shown 5L food storage type, along with an SHT30 temperature and humidity sensor and 100 K NTC temperature sensor. These connect to the controller board which then switches on or off the 12 V polyimide resistive heater.

One thing that could be improved here is that the saturated warm air has nowhere to go. This is a common issue with filament dryers and why it’s recommended with even commercial filament dryers like the common Sunlu types to leave them slightly ajar so that the moist air can be replaced with cooler air that can much more readily absorb moisture.

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DIY Potentiometer Is A Great Teaching Aid

May 20, 2026 by 15 Comments

A potentiometer is a simple electrical device that allows resistance to be varied at will. Most everyone in the electronics field is intimately familiar with how they work on a fundamental level. Of course, we all had to be taught once, though, and a great way to do that would be with a teaching tool like the one [DiscoLapy] built.

What you’re looking at here is a very simple potentiometer that bares its function for all to see. It consists of a 3D printed base and knob, which form the mechanical part of the device. A paper track is then laid on top to act as the main resistive element, once properly covered with graphite from a regular old pencil. From there, it’s as simple as adding the necessary contacts and wiper to the device, and you’ve got a potentiometer sitting in front of you.

What’s great about this build is that it’s very intuitive. Just by looking at it or putting it together, you get a straightforward understanding of everything that’s going on. By drawing the resistive trace, and by turning the knob, particularly if hooked up to an LED or something like in the demonstration, it’s easy to see how the potentiometer varies its resistance and affects a circuit.

We’ve featured some other fantastic teaching tools in the past, too. If you’ve got your own educational gems, be sure to let us know.

Spy Tech: A Quiet Radio For Spies

May 20, 2026 by 9 Comments

Normally, when you think of a radio transmitter, you want the strongest signal and range. But if your radio operator is secretly operating as a spy, broadcasting their position isn’t a feature; it is a liability. This fact didn’t escape World War II radio designers.

In late 1942, the British realized they needed a way for Special Operation Executive agents, resistance members, and other friendly forces to communicate with an aircraft without attracting undue attention. Two engineers from the Royal Corps of Signals developed a pair of transceivers — the S-Phone — operating around 380 MHz just for this purpose. Frequencies this high were unusual at the time, which further deterred enemy detection.

The output power was below 200 mW, and the ground equipment consisted of a dipole strapped to the operator. No transistors, so with rechargable batteries, the rig weighed about fifteen pounds and reused some parts of a paratrooper radio, Wireless Set Number 37. The other side of the connection was installed in an airplane.

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A render of the moon, on a circular display.

Put The Moon On Your Desk

May 20, 2026 by 8 Comments

Most people take the Moon for granted, not considering its slow cycle where the sun gradually illuminates different parts of it. A recent project from [Karsten Mueller] helps you keep our nearest celestial neighbor in mind by putting a tiny version on your desk. (German)

The device itself is made with a circular display, an ESP32-S3, and a simple 3D printed case. But the interesting part is the software — it’s not just a moon phase display, it actually takes your local time, latitude and longitude into account. The resulting image is an approximation of what the moon looks like if you were to look at it, even if you wouldn’t actually be able to see it, such as when it is obscured by the Earth or barely visible during the daylight sky. Initially the project actually used a photograph of the Moon that [Karsten] personally snapped, but there’s also an option to pull the imagery from NASA.

The original write-up is in German, but there’s also an English page for the project on Hackaday.io, and the source is available on GitHub if you’d like to put one together yourself.

Between-Device Sharing Still Sucks

May 20, 2026 by 109 Comments

Once upon a time, computing was simple. You had files on a floppy disk. If you wanted to take them to a different computer, you ejected the disk from one machine and put it in another. It wasn’t fast, but it was easy and intuitive. Besides, you probably only had one computer of your own, anyway.

Life has since gotten a lot more complex. You’ve got a desktop, a laptop, a work laptop, your personal and business phones, and a smart watch to boot. You live amongst a swirling maelstrom of terabytes of data. Despite all the technical advances that got you here, it’s still a pain to get a file from one device to another, even when they’re sitting on the same desk. Why?!

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Bring Back That Aged Scanner, In Your Browser

May 20, 2026 by 36 Comments

We have probably all at some point had to replace a peripheral not because it is faulty, but because it is no longer supported by our operating system. It’s especially bad for Windows users, but for older hardware this is increasingly a part of the Linux experience too. [George MacKerron] is here with what may prove to be a valuable technique to keep these devices active. He’s running a minimalist x86 computer in the browser, with just enough OS to support the device.

In this case the hardware is a USB scanner, and the resulting software takes a WebAssembly x86 emulator and adds a bit of glue software allowing it to use WebUSB to talk to the real-world hardware. It runs a minimal Alpine Linux environment with SANE — something that’s normal for Linux users but which has never been there on a Windows machine. The result is something which needs no installation, but can be run on any machine with a powerful enough web browser.

While such an approach might at first seem like overkill, we’re told it runs surprisingly quickly. In this case it’s for scanner, but we can see it could find a use with many other pieces of aged hardware.

If WebAssembly is new to you, we gave it a primer a few years ago.

Header image: Fir0002/Flagstaffotos, GFDL 1.2.