Two sides of a business-card shaped device are shown. On the left, it’s clear that the device is about half a centimeter thick, with a large scroll wheel visible in the center. The device cover is 3D-printed in black plastic, and has cutouts to mark where three buttons ar. On the right, the underside of the device is visible. It is a black PCB, with white text giving contact information.

Building A Macro Pad Into A Business Card

August 31, 2025 by Aaron Beckendorf 10 Comments

A business card is a convenient way to share your contact information, but it’s unfortunately prone to being thrown away or forgotten. PCB business cards try to get around this problem, but while impressive, most won’t keep the recipient engaged for a very long time. [Cole Olsen]’s macro pad business card, on the other hand, might actually get regular use.

The card has three buttons and a rotary encoder as controls, with an RGB LED to indicate the card’s current mode. It can perform three sets of functions: general productivity, serving as a presentation remote, and controlling music. The scroll wheel is the main control, and can switch through windows, desktops, and tabs, page through slides, and control music volume.

The card itself is made out of a PCB, the exposed side of which contains [Cole]’s contact information, and the other side of which is covered by a 3D-printed case. As thick as it is, this might be stretching the definition of “card” a bit, but as a mechanical engineer, [Cole] did want to demonstrate some mechanical design. A nice!nano wireless keyboard development board running ZMK firmware reads the sensors and sends commands. Conveniently for a presentation remote, the card is powered by a rechargeable battery and can work wirelessly (as a side benefit, if a recipient were minded to get rid of this card, the lithium-polymer battery would probably substantially delay disposal).

[Cole] writes that he was inspired by many of the other impressive business cards we’ve covered. Some of the macro pads we’ve seen have been marvels of miniaturization in their own right.

LEDs That Flow: A Fluid Simulation Business Card

August 12, 2025 by Matt Varian 18 Comments

Fluid-Implicit-Particle or FLIP is a method for simulating particle interactions in fluid dynamics, commonly used in visual effects for its speed. [Nick] adapted this technique into an impressive FLIP business card.

The first thing you’ll notice about this card is its 441 LEDs arranged in a 21×21 matrix. These LEDs are controlled by an Raspberry Pi RP2350, which interfaces with a LIS2DH12TR accelerometer to detect card movement and a small 32Mb memory chip. The centerpiece is a fluid simulation where tilting the card makes the LEDs flow like water in a container. Written in Rust, the firmware implements a FLIP simulation, treating the LEDs as particles in a virtual fluid for a natural, flowing effect.

This eye-catching business card uses clever tricks to stay slim. The PCB is just 0.6mm thick—compared to the standard 1.6mm—and the 3.6mm-thick 3.7V battery sits in a cutout to distribute its width across both sides of the board. The USB-C connection for charging and programming uses clever PCB cuts, allowing the plug to slide into place as if in a dedicated connector.

Inspired by a fluid simulation pendant we previously covered, this board is just as eye-catching. Thanks to [Nick] for sharing the design files for this unique business card. Check out other fluid dynamics projects we’ve featured in the past.

Hands On: The Hacker Pager

July 31, 2025 by Tom Nardi 27 Comments

It should come as no surprise that the hacker community has embraced the Meshtastic project. It’s got a little bit of everything we hold dear: high quality open source software, fantastic documentation, a roll-your-own hardware ethos, and just a dash of counterculture. An off-grid communications network cobbled together from cheap parts, some of which being strategically hidden within the urban sprawl by rogue operators, certainly sounds like the sort of thing you’d read about it in a William Gibson novel.

But while the DIY nature of Meshtastic is one of its most endearing features for folks like us, it can also be seen as one of its weak spots. Right now, the guidance for those looking to get started is to pick a compatible microcontroller development board, 3D print a case for it, screw on an antenna from AliExpress, flash your creation with the latest firmware, and then spend some quality time with the documentation and configuration tools to actually get it on the air. No great challenge for the average Hackaday reader, but a big ask for the weekend adventurer that’s just looking for a way to keep in touch with their friends while camping.

Quality hardware that offers a turn-key experience will be critical to elevating Meshtastic from a hobbyist’s pastime to something that could actually be fielded for applications such as search and rescue. Plus, let’s be honest, even those of us who like to put together our own gadgets can appreciate a more consumer-oriented piece of hardware from time to time. Especially if that hardware happens to be open source and designed to empower the user rather than hold them back.

Enter the Hacker Pager from exploitee.rs. As the name implies, it’s still very much a device intended for hackers — a piece of hardware designed for the halls of DEF CON rather than trekking through the wilderness. But it’s also an important step towards a new generation of Meshtastic hardware that meets the high standard of quality set by the software itself.

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ATtiny-Powered Business Card Plays Cracktro Hits

July 29, 2025 by Matt Varian 11 Comments

PCB business cards are a creative way to show your tech skills while getting your name out there. This take on a PCB business card, sent in by [VCC], tackles one of the big challenges with them: making them in such a way that they are cheap enough to not feel bad about handing them out.

These cards plug into a USB port for power and have over a dozen small LEDs that light up the stars on the front, and a small buzzer that can play over ten minutes of cracktro music. To keep the cost down, [VCC] went with an ATtiny1616 microcontroller costing under 50 cents and still having plenty of outputs to drive the buzzer and LEDs. The final per-unit cost prior to shipping came out to only 1.5 euros, enabling them to be handed out without worrying about breaking the bank.

To aid in the assembly of the cards, [VCC] 3D printed a jig to apply material to the back of the USB connector, building up its thickness to securely fit in the USB port. He also wrote a small script for assembly-line programming the cards, getting the programming process down to around ten seconds per card and letting him turn through prepping the cards. Thanks, [VCC], for sending in your project—it’s a great addition to other PCB business cards we’ve featured.

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A Very Tidy Handheld Pi Terminal Indeed

July 27, 2025 by Jenny List 30 Comments

As single board computers have become ever smaller and more powerful, so have those experimenting with them tried to push the boundaries of the machines they can be used in. First we had cyberdecks, and now we have handheld terminals. Of this latter class we have a particularly nice example from [Random Alley Cat]. It takes a Raspberry Pi Zero 2W and a handful of other parts, and makes them with a 3D printed case into something very professional indeed.

One of the problems with these designs has always been tidily packing away all the parts with their cables, and it’s one she solves by making a chassis to hold all the parts, and a case which fits around that. In a stroke the case no longer has to provide a dual function, allowing for a much easier internal layout. Her screen is a Pimoroni Hyperpixel, the keyboard is an Xbox 360 accessory, and the power supply is an off the shelf Pi UPS board and battery.

We particularly like the accesses on the underside of this machine to access the Pi ports, and the ventilation holes and external case details. It’s not perfect, as she says in the video below it’s not the best Linux keyboard. but we could really see ourselves using this.

If you follow handheld cyberdecks, we have a few treats for you on these pages. Not all of them run Linux, for example.

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Video Tape Hides Video Player

July 22, 2025 by Tyler August 16 Comments

While it might not be accurate to say VHS is dead, it’s certainly not a lively format. It continues on in undeath thanks to dedicated collectors and hobbyists, some of whom may be tempted to lynch Reddit user [CommonKingfisher] for embedding a video player inside a VHS tape.

Miniaturization in action. The video player probably cost about the same as the original VHS when you account for inflation.

The hack started with a promotional video card via Ali Express, which is a cheap enough way to get a tiny LCD player MP4 playing micro. As you can see, there was plenty of room in the tape for the guts of this. The tape path is obviously blocked, so the tape is not playable in this format. [CommonKingfisher] claims the hack is “reversible” but since he cut a window for the LCD out of the casing of the cassette, that’s going to be pretty hard to undo. On the other hand, the ultrasonic cutter he used did make a very clean cut, and that would help with reversibility.

The fact that the thing is activated by a magnetic sensor makes us worry for the data on that tape, too, whether or not the speaker is a peizo. Ultimately it doesn’t really matter; in no universe was this tape the last surviving copy of “The Matrix”, and it’s a lot more likely this self-playing “tape” gets watched than the VHS was going to be. You can watch it yourself in the demo video embedded below.

VHS nostalgia around here usually involves replicating the tape experience, rather than repurposing the tape. We’re grateful to [George Graves] for the tip. Tips of all sorts are welcome on our friendly neighborhood tips line.

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An image of a light grey graphing calculator with a dark grey screen and key surround. The text on the monochrome LCD screen shows "Input: ENEB Result 1: BEEN Confidence 1: 14% [##] Result 2: Good Confidence 2: 12% [#] Press ENTER key..."

A Neural Net For A Graphing Calculator?

July 17, 2025 by Navarre Bartz 3 Comments

Machine learning and neural nets can be pretty handy, and people continue to push the envelope of what they can do both in high end server farms as well as slower systems. At the extreme end of the spectrum is [ExploratoryStudios]’s Hermes Optimus Neural Net for a TI-84 Plus Silver Edition.

This neural net is setup as an autocorrect system that can take four character inputs and match them to a library of twelve words. That’s not a lot, but we’re talking about a device with 24 kB of RAM, so the little machine is doing its best. Perhaps more interesting than any practical output is the puzzle solving involved in getting this to work within the memory constraints.

The neural net “employs a feedforward neural network with a precisely calibrated 4-60-12 architecture and sigmoid activation functions.” This leads to an approximate 85% accuracy being able to identify and correct the given target words. We appreciate the readout of the net’s confidence as well which is something that seems to have gone out the window with many newer “AI” systems.

We’ve seen another TI-84 neural net for handwriting recognition, but is the current crop of AI still headed in the wrong direction?

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