DIY TENS Machine Is A Pain-Relief PCB

November 22, 2025 by Tyler August 36 Comments

Transcutaneous Electrical Nerve Stimulation (TENS) is one of those things that sounds like it must be woo when you first hear of it. “A trickle of current that can deal with chronic pain better than the pills we’ve been using for decades? Yeah, and what chakras do you hook this doo-hickie up to?” It seems too good to be true, but in fact it’s a well-supported therapy that has become part of scientific medicine. There are no crystals needed, and you’re applying electrodes to the effected area, not your chakras. Like all medical devices, it can be expensive if you have to buy the machine out-of-pocket… but it is just a trickle of current. [Leon Hillmann] shows us its well within the range of hackability, so why not DIY?

[Leon]’s TENS machine is specifically designed to help a relative with hand problems, so breaks out electrodes for each finger, with one on the palm serving as a common ground. This type of TENS is “monophasic”– that is, DC, which is easier than balancing current flowing in two directions through quivering flesh. The direct current is provided at 32 V to the digit electrodes, safely kept to a constant amperage with a transistor-based current limiting circuit. The common ground in the palm is pulsed at a rate set by an ATmega32U4 and thus controllable: 14 Hz is given as an example.

Obviously if you want to reproduce this work you’re doing it at your own risk and need to consult with relevant medical professionals (blah blah blah, caveat gluteus maximus) but this particular sort of medical device is a good fit for the average hacker. Aside from prosthetics, we haven’t seen that much serious medical hacking since the pandemic. Still, like with synthesizing medical drugs, this is the kind of thing you probably don’t want to vibe code.

A Precisely Elegant Cyberdeck Handheld

February 27, 2025 by Donald Papp 15 Comments

[Nicholas LaBonte] shows off a Cyberdeck Handheld that demonstrates just how good something can look when care and attention goes into the design and fabrication. He wanted to make something that blended cyberpunk and nautical aesthetics with a compact and elegant design, and we think he absolutely succeeded.

On the inside is a Raspberry Pi and an RTL-SDR. The back of the unit is machined from hardwood, and sports a bronze heat sink for the Raspberry Pi. The front has a prominent red PSP joystick for mouse input and a custom keyboard. The keyboard is especially interesting. On the inside it’s a custom PCB with tactile switches and a ATmega32U4 running QMK firmware — a popular choice for DIY keyboards — and presents to the host as a regular USB HID device.

The keys are on a single plate of little tabs, one for each key, that sits between the front panel and press on the tact switches inside.

How did he make those slick-looking keys? It’s actually a single plate that sits between the front panel and the switches themselves. [Nicholas] used a sheet of polymer with a faux-aluminum look to it and machined it down, leaving metal-looking keys with engraved symbols as tabs in a single panel. It looks really good, although [Nicholas] already has some ideas about improving it.

On the right side is the power button and charging port, and astute readers may spot that the power button is where a double-stack of USB ports would normally be on a Raspberry Pi 5. [Nicholas] removed the physical connectors, saving some space and connecting the USB ports internally to the keyboard and SDR.

As mentioned, [Nicholas] is already full of ideas for improvements. The bronze heat sink isn’t as effective as he’d like, the SDR could use some extra shielding, and the sounds the keyboard ends up making could use some work. Believe it or not, there’s still room to spare inside the unit and he’d maybe like to figure out a way to add a camera, GPS receiver, or maybe a 4G modem. We can’t wait! Get a good look for yourself in the video, embedded below.

Continue reading “A Precisely Elegant Cyberdeck Handheld” →

Tiny Mouse Ring Uses Prox Sensors

February 10, 2025 by Lewin Day 11 Comments

A traditional computer mouse typically fits in the palm of your hand. However, with modern technology, there’s no need for mice to be so large, as demonstrated by [juskim]’s neat little mouse ring. Check it out in the video below.

The concept is simple—it’s a tiny mouse that sits neatly on the end of one of your fingers. You then get the slightly surreal experience of pointing on your computer just by moving a single finger instead of your whole hand.

The project uses a typical optical mouse sensor for movement, as you might expect. However, there are no conventional switches for the left and right mouse buttons. Instead, [juskim] realized a more compact design was possible by using proximity sensors instead. The sensors detect the presence of his fingers on either side of the ring mouse. When one of the fingers is lifted, the absence of the finger triggers a mouse click, either left or right, depending on the finger.

The build started with junk box parts, but hooking up an Arduino Pro Micro dev board and other modules proved too cumbersome to use effectively. Instead, the build relies on an ATTO board, a tiny PCB featuring the same ATmega32U4 microcontroller. Similarly, the build relies on tiny proximity sensors from STM to fit in the “ring” form factor. It’s all wrapped up in a 3D-printed enclosure that fits snugly on the user’s finger.

We’ve seen some other neat mouse rings before, too. Or, if you want something really different, grab some keychains and make a 6DOF mouse.

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A keyboard built into a commercial foot rest.

Floorboard Is A Keyboard For Your Feet

September 4, 2024 by Kristina Panos 8 Comments

Whether you have full use of your hands or not, a foot-operated keyboard is a great addition to any setup. Of course, it has to be a lot more robust than your average finger-operated keyboard, so building a keyboard into an existing footstool is a great idea.

When [Wingletang]’s regular plastic footrest finally gave up the ghost and split in twain, they ordered a stronger replacement with a little rear compartment meant to hold the foot switches used by those typing from dictation. Settling upon modifiers like Ctrl, Alt, and Shift, they went about designing a keyboard based on the ATmega32U4, which does HID communication natively.

For the switches, [Wingletang] used the stomp switches typically found in guitar pedals, along with toppers to make them more comfortable and increase the surface area. Rather than drilling through the top of the compartment to accommodate the switches, [Wingletang] decided to 3D print a new one so they could include circuit board mounting pillars and a bit of wire management. Honestly, it looks great with the black side rails.

If you want to build something a little different, try using one of those folding stools.

A very tiny keyboard with RGB backlighting.

Tiny Custom Keyboard Gets RGB

August 23, 2024 by Lewin Day 12 Comments

Full-size keyboards are great for actually typing on and using for day-to-day interfacing duties. They’re less good for impressing the Internet. If you really want to show off, you gotta go really big — or really small. [juskim] went the latter route, and added RGB to boot!

This was [juskim]’s attempt to produce the world’s smallest keyboard. We can’t guarantee that, but it’s certainly very small. You could readily clasp it within a closed fist. It uses a cut down 60% key layout, but it’s still well-featured, including numbers, letters, function keys, and even +,-, and =. The build uses tiny tactile switches that are SMD mounted on a custom PCB. An ATmega32U4 is used as the microcontroller running the show, which speaks USB to act as a standard human interface device (HID). The keycaps and case are tiny 3D printed items, with six RGB LEDs installed inside for the proper gamer aesthetic. The total keyboard measures 66 mm x 21 mm.

Don’t expect to type fast on this thing. [juskim] only managed 14 words per minute. If you want to be productive, consider a more traditional design.

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A Planck-inspired 40% ortholinear keyboard.

DIY Keyboard Can Handle Up To Three Host Devices

May 10, 2024 by Kristina Panos 16 Comments

Here’s a story that may be familiar: [der-b] is a Linux developer who is forced two carry two laptops — one for work with unavoidable work stuff on it, and one for software development. Unfortunately this leads to keyboard confusion between the two when one is connected to an external display.

In an attempt to overcome this, [der-b] designed a keyboard that can be connected to more than one device at a time, despite ultimately thinking that this will lead to another layer of confusion. The point was to try to make something as lightweight as possible, since carrying two laptops is already a struggle. As a bonus, this project was a learning experience for soldering SMD parts.

The keyboard itself is based on the Planck and uses an ATMega32u4 running QMK firmware, so that means it’s a 40% ortholinear with 48 keys total. [der-b] used low-profile Cherry MX switches to keep things sleek.

In order to switch between different host devices, [der-b] uses shortcuts as you’ll see in the short video after the break. This is accomplished with a FSUSB36 IC on the USB connections between the ATMega and the host.

[der-b] encountered a spate of issues while building this keyboard, which you can read all about in the blog post. We love to see transparency when it comes to your write-ups, especially when the projects become learning experiences. (Aren’t they all?) But if 48 keys aren’t nearly enough for you, check out this learning-experience keyboard build.

Continue reading “DIY Keyboard Can Handle Up To Three Host Devices” →

the dongle developed by Marcel, with a USB-A plug on one end and an SMD antenna on the other

Hackaday Prize 2022: House Ventilation Reverse-Engineered And Automated

June 1, 2022 by Arya Voronova 5 Comments

[Marcel] thought – what if he had more control over his house ventilation system? You could add some nifty features, such as automatically ventilating your house in the mornings when everyone’s away, only creating noise when nobody’s around to hear it. Sadly, most ventilation systems are not automation-friendly at all – he was lucky, however, as his system came with a wireless remote. [Marcel] reverse-engineered this remote, created a USB dongle speaking the same protocol, and tied it into his Home Assistant setup!

The remote in question is Orcon R15, with an Atmel MCU talking to a CC1101 chip through SPI. He sniffed the SPI communications when pressing different buttons, figured out the protocol by comparing the recordings, and built a test setup with a spare Arduino and CC1101 module. It worked, and he set out to design a separate dongle, using an ATMega32U4. The dongle looks pretty neat, and fits a Hammond enclosure – what’s not to like?

Then he set out to develop the firmware, and didn’t disappoint on that front either. His code doesn’t just imitate the original remote perfectly in terms of control, it also has user-friendly pairing flow, keeps track of the system’s current state, and still lets the original remote be used in parallel. Eagle files for the PCB are available on the project page, with the code and a PDF schematic available in the GitHub repo. This entire journey is described in the Hackaday.io page, and we would recommend you check it out for all the insights it provides!

Ventilation systems don’t tend to be designed for automation, and it’s endearing to see hackers working on conquering this frontier. Last time we’ve seen a ventilation system hack, it had the additional challenge of being landlord-friendly, and we think the hacker nailed it!