Worst Clock Ever Teaches You QR Codes

September 18, 2025 by Elliot Williams 9 Comments

[WhiskeyTangoHotel] wrote in with his newest clock build — and he did warn us that it was minimalist and maybe less than useful. Indeed, it is nothing more than a super-cheap ESP32-C3 breakout board with an OLED screen and some code. Worse, you can’t even tell the time on it without pointing your cell phone at the QR code it generates. Plot twist: you skip the QR code and check the time on your phone.

But then we got to thinking, and there is actually a lot to learn from here on the software side. This thing pulls the time down from an NTP server, formats it into a nice human-readable string using strftime, throws that string into a QR code that’s generated on the fly, and then pushes the bits out to the screen. All in a handful of lines of code.

As always, the secret is in the libraries and how you use them, and we wanted to check out the QR code generator, but we couldn’t find an exact match for QRCodeGenerator.h. Probably the most popular library is the Arduino QRCode library by [ricmoo]. It’s bundled with Arduino, but labelled version 0.0.1, which we find a little bit modest given how widely it’s used. It also hasn’t been updated in eight years: proof that it just works?

That library drew from [nayuki]’s fantastically documented multi-language QR-Code-generator library, which should have you covered on any platform you can imagine, with additional third-party ports to languages you haven’t even heard of. That’s where we’d go for a non-Arduino project.

What library did [WTH] use? We hope to find out soon, but at least we found a couple good candidates, and it appears to be a version of one or the other.

We’ve seen a lot of projects where the hacker generates a QR code using some online tool, packs the bits into a C header array, and displays that. That’s fine when you only need a single static QR code, but absolutely limiting when you want to make something dynamic. You know, like an unreadable clock.

You will not be surprised to know that this isn’t the first unreadable QR-code clock we’ve featured here. But it’s definitely the smallest and most instructive.

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PCBs The Prehistoric Way

September 18, 2025 by Elliot Williams 46 Comments

When we see an extremely DIY project, you always get someone who jokes “well, you didn’t collect sand and grow your own silicon”. [Patrícia J. Reis] and [Stefanie Wuschitz] did the next best thing: they collected local soil, sieved it down, and fired their own clay PCB substrates over a campfire. They even built up a portable lab-in-a-backpack so they could go from dirt to blinky in the woods with just what they carried on their back.

This project is half art, half extreme DIY practice, and half environmental consciousness. (There’s overlap.) And the clay PCB is just part of the equation. In an effort to approach zero-impact electronics, they pulled ATmega328s out of broken Arduino boards, and otherwise “urban mined” everything else they could: desoldering components from the junk bin along the way.

The traces themselves turned out to be the tricky bit. They are embossed with a 3D print into the clay and then filled with silver before firing. The pair experimented with a variety of the obvious metals, and silver was the only candidate that was both conductive and could be soldered to after firing. Where did they get the silver dust? They bought silver paint from a local supplier who makes it out of waste dust from a jewelry factory. We suppose they could have sat around the campfire with some old silver spoons and a file, but you have to draw the line somewhere. These are clay PCBs, people!

Is this practical? Nope! It’s an experiment to see how far they can take the idea of the pre-industrial, or maybe post-apocalyptic, Arduino. [Patrícia] mentions that the firing is particularly unreliable, and variations in thickness and firing temperature lead to many cracks. It’s an art that takes experience to master.

We actually got to see the working demos in the flesh, and can confirm that they did indeed blink! Plus, they look super cool. The video from their talk is heavy on theory, but we love the practice.

DIY clay PCBs make our own toner transfer techniques look like something out of the Jetsons.

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Old Projects? Memorialize Them Into Functional Art

September 1, 2025 by Donald Papp 3 Comments

What does one do with old circuit boards and projects? Throwing them out doesn’t feel right, but storage space is at a premium for most of us. [Gregory Charvat] suggests doing what he did: combining them all into a wall-mountable panel in order to memorialize them, creating a functional digital clock in the process. As a side benefit, it frees up storage space!

Everything contributes. If it had lights, they light up. If it had a motor, it moves.

Memorializing and honoring his old hardware is a journey that involved more than just gluing components to a panel and hanging it on the wall. [Gregory] went through his old projects one by one, doing repairs where necessary and modifying as required to ensure that each unit could power up, and did something once it did. Composition-wise, earlier projects (some from childhood) are mounted near the bottom. The higher up on the panel, the more recent the project.

As mentioned, the whole panel is more than just a collage of vintage hardware — it functions as a digital clock, complete with seven-segment LED displays and a sheet metal panel festooned with salvaged controls. Behind it all, an Arduino MEGA takes care of running the show.

Creating it was clearly a nostalgic journey for [Gregory], resulting in a piece that celebrates and showcases his hardware work into something functional that seems to have a life of its own. You can get a closer look in the video embedded below the page break.

This really seems like a rewarding way to memorialize one’s old projects, and maybe even help let go of unfinished ones.

And of course, we’re also a fan of the way it frees up space. After all, many of us do not thrive in clutter and our own [Gerrit Coetzee] has some guidance and advice on controlling it.

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NFC Hidden In Floppy Disk For Retro-Themed PC

August 29, 2025 by Bryan Cockfield 13 Comments

As we all look across a sea of lifeless, nearly identically-styled consumer goods, a few of us have become nostalgic for a time when products like stereo equipment, phones, appliances, homes, cars, and furniture didn’t all look indistinguishable. Computers suffered a similar fate, with nearly everything designed to be flat and minimalist with very little character. To be sure there are plenty of retro computing projects to recapture nostalgia, but to get useful modern hardware in a fun retro-themed case check out this desktop build from [Mar] that hides a few unique extras.

The PC itself is a modern build with an up-to-date operating system, but hidden in a 386-era case with early-90s styling. The real gem of this build though is the floppy disk drive, which looks unaltered on the surface. But its core functionality has been removed and in its place an Arduino sits, looking for NFC devices. The floppy disks similarly had NFC tags installed so that when they interact with the Arduino, it can send a command to the computer to launch a corresponding game. To the user it looks as though the game loads from a floppy disk, much like it would have in the 90s albeit with much more speed and much less noise.

Modern industrial design is something that we’ve generally bemoaned as of late, and it’s great to see some of us rebelling by building unique machines like this, not to mention repurposing hardware like floppy drives for fun new uses (which [Mar] has also open-sourced on a GitHub page). It’s not the first build to toss modern hardware in a cool PC case from days of yore, either. This Hot Wheels desktop is one of our favorites.

2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4

August 9, 2025 by Lewin Day 10 Comments

Humanity pretty much has Pi figured out at this point. We’ve calculated it many times over and are confident about what it is down to many, many decimal places. However, if you fancy estimating it with some electronic assistance, you might find this project from [Roni Bandini] interesting.

[Roni] programmed an Arduino Nano R4 to estimate Pi using the Monte Carlo method. For this specific case, it involves drawing a circle inscribed inside a square. Points are then randomly scattered inside the square, and checked to see if they lie inside or outside the circle based on their position and distance of the circle’s outline from the center point of the square. By taking the ratio of the points inside the circle to the total number of points, you get an approximation of the ratio of the square and circle’s areas, which is equal to Pi/4. Thus, multiply the ratio by 4, and you’ve got your approximation of Pi.

[Roni] coded a program to run the Monte Carlo simulation on the Arduino Nano R4, taking advantage of the mathematical benefits of its onboard Floating Point Unit. It generates 100 new samples for the Monte Carlo approximation every second, improving the estimation of pi as it goes. It then displays the result on a 7-segment display, and beeps as it goes. [Roni] readily admits the project is a little too close in appearance to a classic Hollywood bomb.

We’ve seen some other neat Pi-calculating projects before, too.

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A Repeater For WWVB

August 7, 2025 by Bryan Cockfield 12 Comments

For those living in the continental US who, for whatever reason, don’t have access to an NTP server or a GPS device, the next best way to make sure the correct time is known is with the WWVB radio signal. Transmitting out of Colorado, the 60-bit 1 Hz signal reaches all 48 states in the low-frequency band and is a great way to get a clock within a few hundred nanoseconds of the official time. But in high noise situations, particularly on the coasts or in populated areas these radio-based clocks might miss some of the updates. To keep that from happening [Mike] built a repeater for this radio signal.

The repeater works by offloading most of the radio components to an Arduino. The microcontroller listens to the WWVB signal and re-transmits it at a lower power to the immediate area, in this case no further than a few inches away or enough to synchronize a few wristwatches. But it has a much better antenna for listening to WWVB so this eliminates the (admittedly uncommon) problem of [Mike]’s watches not synchronizing at least once per day. WWVB broadcasts a PWM signal which is easy for an Arduino to duplicate, but this one needed help from a DRV8833 amplifier to generate a meaningfully strong radio signal.

Although there have been other similar projects oriented around the WWVB signal, [Mike]’s goal for this was to improve the range of these projects so it could sync more than a single timekeeping device at a time as well as using parts which are more readily available and which have a higher ease of use. We’d say he’s done a pretty good job here, and his build instructions cover almost everything even the most beginner breadboarders would need to know to duplicate it on their own.

Experience Other Planets With The Gravity Simulator

July 27, 2025 by Bryan Cockfield 8 Comments

As Earthlings, most of us don’t spend a lot of extra time thinking about the gravity on our home planet. Instead, we go about our days only occasionally dropping things or tripping over furniture but largely attending to other matters of more consequence. When humans visit other worlds, though, there’s a lot more consideration of the gravity and its effects on how humans live and many different ways of training for going to places like the Moon or Mars. This gravity simulator, for example, lets anyone experience what it would be like to balance an object anywhere with different gravity from Earth’s.

The simulator itself largely consists of a row of about 60 NeoPixels, spread out in a line along a length of lightweight PVC pipe. They’re controlled by an Arduino Nano which has a built-in inertial measurement unit, allowing it to sense the angle the pipe is being held at as well as making determinations about its movement. A set of LEDs on the NeoPixel strip is illuminated, which simulates a ball being balanced on this pipe, and motion one way or the other will allow the ball to travel back and forth along its length. With the Earth gravity setting this is fairly intuitive but when the gravity simulation is turned up for heavier planets or turned down for lighter ones the experience changes dramatically. Most of the video explains the math behind determining the effects of a rolling ball in each of these environments, which is worth taking a look at on its own.

While the device obviously can’t change the mass or the force of gravity by pressing a button, it’s a unique way to experience and feel what a small part of existence on another world might be like. With enough budget available there are certainly other ways of providing training for other amounts of gravity like parabolic flights or buoyancy tanks, although one of the other more affordable ways of doing this for laypeople is this low-gravity acrobatic device.

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