Flip card

LEDs That Flow: A Fluid Simulation Business Card

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.

3D-Printing A Full-Sized Kayak In Under A Day

If you want to get active out on the water, you could buy a new kayak, or hunt one down on Craigslist, Or, you could follow [Ivan Miranda]’s example, and print one out instead.

[Ivan] is uniquely well positioned to pursue a build like this. That’s because he has a massive 3D printer which uses a treadmill as a bed. It’s perfect for building long, thin things, and a kayak fits the bill perfectly. [Ivan] has actually printed a kayak before, but it took an excruciating 7 days to finish. This time, he wanted to go faster. He made some extruder tweaks that would allow his treadmill printer to go much faster, and improved the design to use as much of the belt width as possible. With the new setup capable of extruding over 800 grams of plastic per hour, [Ivan] then found a whole bunch of new issues thanks to the amount of heat involved. He steps through the issues one at a time until he has a setup capable of extruding an entire kayak in less than 24 hours.

This isn’t just a dive into 3D printer tech, though. It’s also about watercraft! [Ivan] finishes the print with a sander and a 3D pen to clean up some imperfections. The body is also filled with foam in key areas, and coated with epoxy to make it watertight. It’s not the easiest craft to handle, and probably isn’t what you’d choose for ocean use. It’s too narrow, and wounds [Ivan] when he tries to get in. It might be a floating and functional kayak, just barely, for a smaller individual, but [Ivan] suggests he’ll need to make changes if he were to actually use this thing properly.

Overall, it’s a project that shows you can 3D print big things quite quickly with the right printer, and that maritime engineering principles are key for producing viable watercraft. Video after the break.

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2025 One Hertz Challenge: Abstract Aircraft Sculpture Based On Lighting Regulations

The 2025 One Hertz Challenge is really heating up with all kinds of projects that do something once every second. [The Baiko] has given us a rather abstract entry that looks like a plane…if you squint at it under the right conditions.

It’s actually quite an amusing abstract build. If you’ve ever seen planes flying in the night sky, you’ve probably noticed they all have similar lights. Navigation lights, or position lights as they are known, consist of a red light on the left side and a green light on the right side. [The Baiko] assembled two such LEDs on a small sliver of glass along with an ATtiny85 microcontroller.

Powered by a coin cell, they effectively create a abstract representation of a plane in the night sky, paired with a flashing strobe that meets the requirements of the contest. [The Baiko] isn’t exactly sure of the total power draw, but notes it must be low given the circuit has run for weeks on a 30 mAh coin cell.

It’s an amusing piece of PCB art, though from at least one angle, it does appear the red LED might be on the wrong side to meet FAA regulations. Speculate on that in the comments.

In any case, we’ve had a few flashers submitted to the competition thus far, and you’ve got until August 19 to get your own entry in!

Design Review: LattePanda Mu NAS Carrier

It is a good day for design review! Today’s board is the MuBook, a Lattepanda Mu SoM (System-on-Module) carrier from [LtBrain], optimized for a NAS with 4 SATA and 2 NVMe ports. It is cheap to manufacture and put together, the changes are non-extensive but do make the board easier to assemble, and, it results in a decent footprint x86 NAS board you can even order assembled at somewhere like JLCPCB.

This board is based on the Lite Carrier KiCad project that the LattePanda team open-sourced to promote their Mu boards. I enjoy seeing people start their project from a known-working open-source design – they can save themselves lots of work, avoid reinventing the wheel and whole categories of mistakes, and they can learn a bunch of design techniques/tips through osmosis, too. This is a large part of why I argue everyone should open-source their projects to the highest extent possible, and why I try my best to open-source all the PCBs I design.

Let’s get into it! The board’s on GitHub as linked, already containing the latest changes.

Git’ting Better

I found the very first review item when downloading the repo onto my computer. It took a surprising amount of time, which led me to believe the repo contains a fair bit of binary files – something quite counterproductive to keep in Git. My first guess was that the repo had no .gitignore for KiCad, and indeed – it had the backups/ directory with a heap of hefty .zips, as well as a fair bit of stuff like gerbers and footprint/symbol cache files. I checked in with [LtBrain] that these won’t be an issue to delete, and then added a .gitignore from the Blepis project.

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Continuous-Path 3D Printed Case Is Clearly Superior

[porchlogic] had a problem. The desire was to print a crystal-like case for an ESP32 project, reminiscent of so many glorious game consoles and other transparent hardware of the 1990s. However, with 3D printing the only realistic option on offer, it seemed difficult to achieve a nice visual result. The solution? Custom G-code to produce as nice a print as possible, by having the hot end trace a single continuous path.

The first job was to pick a filament. Transparent PLA didn’t look great, and was easily dented—something [porchlogic] didn’t like given the device was intended to be pocketable. PETG promised better results, but stringing was common and tended to reduce the visual appeal. The solution to avoid stringing would be to stop the hot end lifting away from the print and moving to different areas of the part. Thus, [porchlogic] had to find a way to make the hot end move in a single continuous path—something that isn’t exactly a regular feature of common 3D printing slicer utilities.

The enclosure itself was designed from the ground up to enable this method of printing. Rhino and Grasshopper were used to create the enclosure and generate the custom G-code for an all-continuous print. Or, almost—there is a single hop across the USB port opening, which creates a small blob of plastic that is easy to remove once the print is done, along with strings coming off the start and end points of the print.

Designing an enclosure in this way isn’t easy, per se, but it did net [porchLogic] the results desired. We’ve seen some other neat hacks in this vein before, too, like using innovative non-planar infill techniques to improve the strength of prints.

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Remembering James Lovell: The Man Who Cheated Death In Space

Many people have looked Death in the eye sockets and survived to tell others about it, but few situations speak as much to the imagination as situations where there’s absolutely zero prospect of rescuers swooping in. Top among these is the harrowing tale of the Apollo 13 moon mission and its crew – commanded by James “Jim” Lovell – as they found themselves stranded in space far away from Earth in a crippled spacecraft, facing near-certain doom.

Lovell and his crew came away from that experience in one piece, with millions tuning into the live broadcast on April 17 of 1970 as the capsule managed to land safely back on Earth, defying all odds. Like so many NASA astronauts, Lovell was a test pilot. He graduated from the US Naval Academy in Maryland, serving in the US Navy as a mechanical engineer, flight instructor and more, before being selected as NASA astronaut.

On August 7, 2025, Lovell died at the age of 97 at his home in Illinois, after a dizzying career that saw a Moon walk swapped for an in-space rescue mission like never seen before.

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The WHY 2025 Badge And Its 18650s

The largest European hacker camp this year was in the Netherlands —  What Hackers Yearn (WHY) 2025 is the latest in the long-running series of four-yearly events from that country, and 2025 saw a move from the Flevoland site used by SHA2017 and MCH2021, back to just north of Alkmaar in Noord-Holland, where the OHM2013 event took place. WHY has found itself making the news in the Dutch technical media for all the wrong reasons over the last few days, after serious concerns were raised about the fire safety of its badge.

The cell supplied with a WHY 2025 badge, with very clear fire safety warning
This is the cell supplied with the WHY badge, complete with manufacturer’s warning.

The concerns were raised from the RevSpace hackerspace in Leidschendam, and centre around the design of the battery power traces on the PCB between the battery holders and the power supply circuitry. Because the 18650 cells supplied with that badge lack any protection circuitry, bridging the power traces could be a fire risk.

In short: their report names the cell holders as having tags too large for their pads on the PCB, a too-tight gap between positive and negative battery traces, protected only by soldermask, and the inadequacy of the badge’s short circuit protection. In the event that metal shorted these battery tags, or wore through the soldermask, the batteries would be effectively shorted, and traces or components could get dangerously hot.

The WHY organizers have responded with a printed disclaimer leaflet warning against misuse of the cells, and added a last-minute epoxy coating to the boards to offer additional protection. Some people are 3D-printing cases, which should also help reduce the risk of short-circuiting due to foreign metal objects. Using an external powerbank with short-circuit protection instead of the cells would solve the problem as well. Meanwhile a group of hackers collecting aid for Ukraine are accepting the batteries as donations.

It’s understood that sometimes bugs find their way into any project, and in that an event badge is no exception. In this particular case, the original Dutch badge team resigned en masse at the start of the year following a disagreement with the  WHY2025 organizers, so this badge has been a particularly hurried production. Either way, we are fortunate that the issue was spotted, and conference organizers took action before any regrettable incidents occurred.