2025 One Hertz Challenge: Drop The Beat (But Only At 60 BPM)

July 28, 2025 by Adam Zeloof 1 Comment

Mankind has been using water to mark the passage of time for thousands of years. From dripping stone pots in Ancient Egypt to the more mechanically-complicated Greco-Roman Clepsydrae, the history of timekeeping is a wet one — and it makes sense. As an incompressible fluid, water flows in very predictable patterns. If you fill a leaky pot with water and it takes an hour to drain, it will also take an hour the next time you try. One Hertz Challenge entrant [johnowhitaker] took this idea in a different direction, however, with an electromechanical clock that uses dripping water as an indicator.

This clock uses a solenoid to briefly pop the plunger out of a water-filled syringe. This allows a drop to fall from the tip, into a waiting beaker. In addition to the satisfying audio indication this produces, [johnowhitaker] added a bit of food coloring to the dripping water for visual flair. The entire thing is controlled by a Raspberry Pi Pico and a motor driver board, so if you’ve got some spare parts lying about and would like to build your own be sure to head over to the project page and grab the source code.

While this clock isn’t exactly here for a long time (either the syringe will eventually empty or the beaker will overflow), it’s certainly here for a good time. [John] and commenters on his project even have ideas for the next steps: a 1/60 Hz beaker changer, and a 1/600 Hz spill cleaner. Even so, the first couple of drops hitting the beaker produce a lovely lava lamp-esque cloud that is a joy to watch and has us thinking about other microfluidics projects we’ve seen.

And remember — it’s not too late to enter the 2025 One Hertz Challenge!

Sand Drawing Table Inspired By Sisyphus

June 30, 2025 by Lewin Day 7 Comments

In Greek mythology, Sisyphus was a figure who was doomed to roll a boulder for eternity as a punishment from the gods. Inspired by this, [Aidan], [Jorge], and [Henry] decided to build a sand-drawing table that endlessly traces out beautiful patterns (or at least, for as long as power is applied). You can watch it go in the video below.

The project was undertaken as part of the trio’s work for the ECE4760 class at Cornell. A Raspberry Pi Pico runs the show, using TMC2209 drivers to command a pair of NEMA17 stepper motors to drag a magnet around beneath the sand. The build is based around a polar coordinate system, with one stepper motor rotating an arm under the table, and another panning the magnet back and forth along its length. This setup is well-suited to the round sand pit on top of the table, made with a laser-cut wooden ring affixed to a thick base plate.

The trio does a great job explaining the hardware and software decisions made, as well as showing off how everything works in great detail. If you desire to build a sand table of your own, you would do well to start here. Or, you could explore some of the many other sand table projects we’ve featured over the years.

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Meet Cucumber, The Robot Dog

June 27, 2025 by Lewin Day 6 Comments

Robots can look like all sorts of things, but they’re often more fun if you make them look like some kind of charming animal. That’s precisely what [Ananya], [Laurence] and [Shao] did when they built Cucumber the Robot Dog for their final project in the ECE 4760 class.

Cucumber is controllable over WiFi, which was simple enough to implement by virtue of the fact that it’s based around the Raspberry Pi Pico W. With its custom 3D-printed dog-like body, it’s able to move around on its four wheels driven by DC gear motors, and it can flex its limbs thanks to servos in its various joints. It’s able to follow someone with some autonomy thanks to its ultrasonic sensors, while it can also be driven around manually if so desired. To give it more animal qualities, it can also be posed, or commanded to bark, howl, or growl, with commands issued remotely via a web interface.

The level of sophistication is largely on the level of the robot dogs that were so popular in the early 2000s. One suspects it could be pretty decent at playing soccer, too, with the right hands behind the controls. Video after the break.

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Converting An E-Paper Photo Frame Into Weather Map

June 21, 2025 by John Elliot V 6 Comments

Here’s a great hack sent in to us from [Simon]. He uses an e-paper photo frame as a weather map!

By now you are probably aware of e-paper technology, which is very low power tech for displaying images. E-paper only uses energy when it changes its display, it doesn’t draw power to maintain a picture it has already rendered. The particular e-paper used in this example is fairly large (as e-paper goes) and supports color (not just black and white) which is why it’s expensive. For about US$100 you can get a 5.7″ 7-color EPD display with 600 x 448 pixels.

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Upgrading An Old Espresso Machine

June 14, 2025 by Maya Posch 25 Comments

The Francis! Francis! X1 espresso machine in its assembled state. (Credit: Samuel Leeuwenburg)

Recently, [Samuel Leeuwenburg] got his paws on a Francis! Francis! X1 (yes, that’s the name) espresso machine. This is the espresso machine that is mostly famous for having been in a lot of big TV shows in the 1990s. In the early 2000s, the X1 even became a pretty good espresso machine after the manufacturer did some more tinkering with it, including changing the boiler material, upgrading the pump, etc.

In the case of the second-hand, but rarely used, machine that [Samuel] got, the machine still looked pretty good, but its performance was pretty abysmal. After popping the machine open the boiler turned out to be pretty much full of scale. Rather than just cleaning it, the boiler was upgraded to a brass version for better heat retention and other perks.

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When Wireless MIDI Has Latency, A Hardwired Solution Saves The Day

June 7, 2025 by Lewin Day 14 Comments

[Moby Pixel] wanted to build a fun MIDI controller. In the end, he didn’t build it just once, but twice—with the aim of finding out which microcontroller was most fit for this musical purpose. Pitted against each other? The ESP32 and Raspberry Pi Pico.

The MIDI controller itself is quite fetching. It’s built with a 4 x 4 array of arcade buttons to act as triggers for MIDI notes or events. They’re assembled in a nice wooden case with a lovely graphic wrap on it. The buttons themselves are wired to a microcontroller, which is then responsible for sending MIDI data to other devices.

At this point, the project diverges. Originally, [Moby Pixel] set the device up to work with an ESP32 using wireless MIDI over Bluetooth. However, he soon found a problem. Musical performance is all about timing, and the ESP32 setup was struggling with intermittent latency spikes that would ruin the performance. Enter the Raspberry Pi Pico using MIDI over USB. The hardwired solution eliminated the latency problems and made the controller far more satisfying to use.

There may be solutions to the latency issue with the wireless ESP32 setup, be they in code, hardware configuration, or otherwise. But if you want to play with the most accuracy and the minimum fuss, you’ll probably prefer the hardwired setup.

Latency is a vibe killer in music as we’ve explored previously.

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The five picos on two breadboards and the results of image convolution.

PentaPico: A Pi Pico Cluster For Image Convolution

May 20, 2025 by John Elliot V 22 Comments

Here’s something fun. Our hacker [Willow Cunningham] has sent us a copy of their homework. This is their final project for the “ECE 574: Cluster Computing” course at the University of Maine, Orono.

It was enjoyable going through the process of having a good look at everything in this project. The project is a “cluster” of 5x Raspberry Pi Pico microcontrollers — with one head node as the leader and four compute nodes that work on tasks. The software for both types of node is written in C. The head node is connected to a workstation via USB 1.1 allowing the system to be controlled with a Python script.

The cluster is configured to process an embarrassingly parallel image convolution. The input image is copied into the head node via USB which then divvies it up and distributes it to n compute nodes via I²C, one node at a time. Results are given for n = {1,2,4} compute nodes.

It turns out that the work of distributing the data dwarfs the compute by three orders of magnitude. The result is that the whole system gets slower the more nodes we add. But we’re not going to hold that against anyone. This was a fascinating investigation and we were impressed by [Willow]’s technical chops. This was a complicated project with diverse hardware and software challenges and they’ve done a great job making it all work and in the best scientific tradition.

It was fun reading their journal in which they chronicled their progress and frustrations during the project. Their final report in IEEE format was created using LaTeX and Overleaf, at only six pages it is an easy and interesting read.

For anyone interested in cluster tech be sure to check out the 256-core RISC-V megacluster and a RISC-V supercluster for very low cost.