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A photo of a fully assembled PVCSub.

PVCSub: A Submarine From The Plumbing Aisle

July 18, 2025 by 11 Comments

Today in the submersibles department our hacker [Rupin Chheda] wrote in to tell us about their submarine project.

This sub is made from a few lengths of PVC piping of various diameters. There is an inflation system comprised of a solenoid and a pump, and a deflation system, also comprised of a solenoid and a pump. The inflation and deflation systems are used to flood or evacuate the ballast which controls depth. There are three pumps for propulsion and steering, one central pump for propulsion and two side pumps for directional control, allowing for steering through differential thrust. Power and control is external and provided via CAT6 cable.

Continue reading “PVCSub: A Submarine From The Plumbing Aisle” →

A photo of a Stirling Engine attached to a bike

Building A Stirling Engine Bike

July 17, 2025 by 27 Comments

Over on his YouTube channel [Tom Stanton] shows us how to build a Stirling Engine for a bike.

A Stirling Engine is a heat engine, powered by the expansion and contraction of a working fluid (such as air) which is heated and cooled in a cycle. In the video [Tom] begins by demonstrating the Stirling Engine with some model engines and explains the role of the displacer piston. His target power output for his bike engine is 150 watts (about 0.2 horsepower) which is enough power to cycle at about 15 mph (about 24 km/h). After considering a CPU heatsink as the cooling system he decided on water cooling instead.

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USB VSense

USB-C Rainbow Ranger: Sensing Volts With Style

July 15, 2025 by 1 Comment

USB-C has enabled a lot of great things, most notably removing the no less than three attempts to plug in the cable correctly, but gone are the days of just 5V over those lines. [Meticulous Technologies] sent in their project to help easily identify what voltage your USB-C line is running at, the USB VSense.

The USB VSense is an inline board that has USB-C connectors on either end, and supporting up to 240W you don’t have to worry about it throttling your device. One of the coolest design aspects of this board is that it uses stacked PCB construction as the enclosure, the display, and the PCB doing all the sensing and displaying. And for sensing this small device has a good number of cool tricks, it will sense all the eight common USB-C voltages, but it will also measure and alert you to variations of the voltage outside the normal range by blinking the various colored LEDs in specific patterns. For instance should you have it plugged into a line that’s sitting over 48V the VSense white 48V LED will be rapidly blinking, warning you that something in your setup has gone horribly wrong.

Having dedicated uniquely colored LEDs for each common level allows you to at a glance know what the voltage is at without the need to read anything. With a max current draw of less than 6mA you won’t feel bad about using it on a USB battery pack for many applications.

The USB VSense has completed a small production run and has stated their intention to open source their design as soon as possible after their Crowd Supply campaign. We’ve featured other USB-C PD projects and no doubt we’ll be seeing more as this standard continues to gain traction with more and more devices relying on it for their DC power.

Quasi-Quantifying Qubits For 100 Quid

July 14, 2025 by 3 Comments

As part of his multi-year project to build a quantum computer, hacakday.io poster [skywo1f] has shared with us his most recent accomplishment — a Nuclear Magnetic Resonance Spectrometer, which he built for less than $100.

The NMR spectrometer is designed to disturb protons, which naturally line up according to the Earth’s magnetic field, using an electric coil. Once disturbed, the protons nutate (a fancy physics word for wobble), and flip quantum spin states. [skywo1f]’s NMR device can detect these spin state changes, as he demonstrates with a series of control experiments designed to eliminate sources of false positives (which can be annoyingly prevalent in experimental physics). His newest experimental device includes a number of improvements over previous iterations, including proper shielding, quieter power topology, and better coil winding in the core of the device. Everything was assembled with cost in mind, while remaining sensitive enough to conduct experiments — the whole thing is even driven by a Raspberry Pi Pico.

Here at Hackaday, we love to see experiments that should be happening in million-dollar laboratories chugging along on kitchen tables, like this magnetohydrodynamic drive system or some good old-fashioned PCB etching. [skywo1f] doesn’t seem to be running any quantum calculations yet, but the NMR device is an important building block in one flavor of quantum computer, so we’re excited to see where he takes his work next.

Two views of a motor are shown. On the left, a ring of copper-wire-wound stator arms is visible inside a ring of magnets. Inside this, a planetary gearbox is visible, with three mid-sized gears surrounding a small central gear. On the right, the same motor is shown, but with the internal components mostly covered by a black faceplate with brass inserts.

A Budget Quasi-Direct-Drive Motor Inspired By MIT’s Mini Cheetah

July 14, 2025 by 27 Comments

It’s an unfortunate fact that when a scientist at MIT describes an exciting new piece of hardware as “low-cost,” it might not mean the same thing as if a hobbyist had said it. [Caden Kraft] encountered this disparity when he was building a SCARA arm and needed good actuators. An actuator like those on MIT’s Mini Cheetah would have been ideal, but they cost about $300. Instead, [Caden] designed his own actuator, much cheaper but still with excellent performance.

The actuator [Caden] built is a quasi-direct-drive actuator, which combines a brushless DC motor with an integrated gearbox in a small, efficient package. [Caden] wanted all of the custom parts in the motor to be 3D printed, so a backing iron for the permanent magnets was out of the question. Instead, he arranged the magnets to form a Halbach array; according to his simulations, this gave almost identical performance to a motor with a backing iron. As a side benefit, this reduced the inertia of the rotor and let it reverse more easily.

To increase torque, [Caden] used a planetary gearbox with cycloidal gear profiles, which may be the stars of the show here. These reduced backlash, decreased stress concentration on the teeth, and were easier to 3D print. He found a Python program to generate planetary gearbox designs, but ended up creating a fork with the ability to export 3D files. The motor’s stator was commercially-bought and hand-wound, and the finished drive integrates a cheap embedded motor controller. Continue reading “A Budget Quasi-Direct-Drive Motor Inspired By MIT’s Mini Cheetah” →

Picture of front and back of thumb drive enclosure

Jcorp Nomad: ESP32-S3 Offline Media Server In A Thumbdrive

July 13, 2025 by 27 Comments

[Jackson Studner] wrote in to let us know about his ESP32-based media server: Jcorp Nomad.

This project uses a ESP32-S3 to create a WiFi hotspot you can connect to from your devices. The hotspot is a captive portal which directs the user to a web-interface comprised of static HTML assets which are in situ with the various media on an attached SD card formatted with a FAT32 file system. The static HTML assets are generated by the media.py Python 3 script when the ESP32 boots.

This project exists because the typical Raspberry Pi media server costs more than an ESP32 does. The ESP32 is smaller too, and demands less power.

According to [Jackson] this ESP32-based solution can support at least four concurrent viewers. The captive portal is implemented with DNS and HTTP services from the ESP32. The firmware is an Arduino project that integrates a bunch of libraries to provide the necessary services. The Jcorp Nomad media template supports Books (in pdf files), Music (in mp3 files), and Movies and Shows (in mp4 files). Also there is a convention for including JPEG files which can represent media in the user-interface.

And the icing on the cake? The project files include STL files so you can 3D print an enclosure. All in all, a very nice hack.

Playing Snake With Digital Microfluidics

July 12, 2025 by 2 Comments

Display technology has come a long way since the advent of the CRT in the late 1800s (yes, really!). Since then, we’ve enjoyed the Nixie tubes, flip dots, gas plasma, LCD, LED, ePaper, the list goes on. Now, there’s a new kid on the block — water.

[Steve Mould] recently got his hands on an OpenDrop — an open-source digital microfluidics platform for biology research. It’s essentially a grid of electrodes coated in a dielectric. Water sits atop this insulating layer, and due to its polarized nature, droplets can be moved around the grid by voltages applied to the electrodes. The original intent was to automate experiments (see 8:19 in the video below for some wild examples), but [Steve] had far more important uses in mind.

When [Steve]’s €1,000 device shipped from Switzerland, it was destined for greatness. It was turned into a game console for classics such as Pac-Man, Frogger, and of course, Snake. With help from the OpenDrop’s inventor (and Copilot), he built paired-down versions of the games that could run on the 8×14 “pixel” grid. Pac-Man in particular proved difficult, because due to the conservation of mass, whenever Pac-Man ate a ghost, he grew and eventually became unwieldy. Fortunately, Snake is one of the few videogames that actually respects the laws of classical mechanics, as the snake grows by one unit each time it consumes food.

[Steve] has also issued a challenge — if you code up another game, he’ll run it on his OpenDrop. He’s even offering a prize for the first working Tetris implementation, so be sure to check out his source code linked in the video description as a starting point. We’ve seen Tetris on oscilloscopes and 3D LED matrices before, so it’s about time we get a watery implementation.

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