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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.

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You know how it goes — some gadgets stick around in your toolbox far longer than reason dictates, because maybe one day you’ll need it. How many of us held onto ISA diagnostic cards long past the death of the interface?

But unlike ISA, USB isn’t going away anytime soon. Which is exactly why this USB and more tester by [Iron Fuse] deserves a spot in your toolbox. This post is not meant to directly lure you into buying something, but seen how compact it is, it would be sad to challenge anyone to reinvent this ‘wheel’, instead of just ordering it.

So, to get into the details. This is far from the first USB tester to appear on these pages, but it is one of the most versatile ones we’ve seen so far. On the surface, it looks simple: a hand-soldered 14×17 cm PCB with twelve different connectors, all broken out to labelled test points. Hook up a dodgy cable or device, connect a known-good counterpart, and the board makes it painless to probe continuity, resistance, or those pesky shorts where D+ suddenly thinks it’s a ground line.

You’ll still need your multimeter (automation is promised for a future revision), but the convenience of not juggling probes into microscopic USB-C cavities is hard to overstate. Also, if finding out whether you have a power-only or a data cable is your goal, this might be the tool for you instead.

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We often think that if a piece of software had the level of documentation you usually see for hardware, you wouldn’t think much of it. Sure, there are exceptions. Some hardware is beautifully documented, and poorly documented software is everywhere. [Graham Sutherland’s] been reviewing schematics and put together some notes on what makes a clean schematic.

Like coding standards, some of these are a bit subjective, but we thought it was all good advice. Of course, we’ve also violated some of them when we are in a hurry to get to a simulation.

Most of the rules are common sense: use enough space, add labels, and avoid using quirky angles. [Flannery O’Connor] once said, “You can do anything you can get away with, but nobody has ever gotten away with much.” She was talking about writing, but the same could be said about schematics.

[Graham] says as much, pointing out that these are more guidelines. He even points out places where you might deliberately break the rules. For example, in general, wires should always go horizontally or vertically. However, if you are crossing two parallel wires, you probably should take advantage of the diagonals.

So what are your schematic rules? Software has standards like MISRA, CERT, and various NASA standards. Oddly enough, one of our favorite quick schematic editors is truly terrible but obeys most of these rules. But you can surely do better than that.

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Few toys are more iconic than the Etch A Sketch, which has been popular for 65 years now. In that time, more than 100 million units have been sold worldwide. And every single one of them has had the same problem: the lack of an “undo” button. If you mess up your masterpiece, your only choice is to give the Etch A Sketch a good shake and start over. That’s an unavoidable result of the Etch A Sketch’s drawing mechanism, which Tekavou overcame by building a digital “Teka-Sketch.”

An Etch A Sketch is a two-dimensional manually operated cable-driven plotter with a stylus that scrapes a whitish aluminum powder off the screen, leaving a transparent line that looks dark because the interior of the enclosure is unlit. When you shake the whole thing, the aluminum powder sticks back onto the screen and “erases” the entire drawing. That mechanism doesn’t leave room for a simple solution for erasing portions of lines, which is why complex drawings induce so much anxiety.

The Teka-Sketch is a digital device and it can arbitrarily draw or erase lines in whatever manner its programming dictates. In this case, Tekavou kept it simple and mimicked most of the functionality of an Etch A Sketch. There are still two knobs to control movement of the virtual stylus in the X and Y axes, and it still draws straight darkish lines on a whitish background. The big change is the introduction of an “undo” button (clicking the left knob), which erases the most recent few centimeters of the line.

The key component in the Teka-Sketch is an Inkplate 6 from a brand called Soldered Electronics. The basic unit combines a high-quality 6” e-paper display with an ESP32 microcontroller, and there are also packages available with an enclosure and battery. Tekavou simply added a couple of rotary encoders and packed everything into a custom 3D-printed enclosure. Everything else was coding, which Tekavou first started learning as a kid after discovering NIBBLES.BAS —a Snake variant programmed in QBasic.

As an homage to that formative experience, Tekavou created a Nibbles game that runs on the Teka-Sketch. It even has a two-player mode, with two onscreen snakes (one controlled by the left knob and one controlled by the right knob). E-paper screens are notorious for poor refresh rates, which is why they aren’t more common, but the Inkplate 6’s screen has partial refresh rates fast enough to make the game perfectly playable.

Now Tekavou’s own kids can share some of the experiences he had as a child, but in a way that has been improved with technology.

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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.

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Normally when you think solar projects, you think of big photovoltaic cells. But a photodiode is just an inefficient, and usually much smaller, PV cell. Since [Pocket Concepts]’s Solar_nRF has such a low power budget, it can get away with using BPW34 photodiodes in place of batteries. (Video, embedded below.)

The BPW34 silicon PIN photodiode feeds a small voltage into a BQ25504 ultra-low-power boost converter energy harvester which stores power in a capacitor. When the capacitor is fully charged the battery-good pin is toggled which drives a MOSFET that powers everything downstream.

When it’s powered on, the Nordic nRF initializes, reads the current temperature from an attached I2C thermometer, and then sends out a Bluetooth Low Energy (BLE) advertising packet containing the temperature data. When the capacitor runs out of energy, the battery-good pin is turned off and downstream electronics become unpowered and the cycle begins again.

[Pocket Concepts] uses a Nordic Semiconductors Power Profiler Kit II to help determine charge requirements. He calculates that 37 uF would be enough power for a single cycle, then uses 100 uF to get between one and three transmissions done using a single charge.

[Pocket Concepts] finishes his video with a request for project ideas. Is this a soil moisture meter? Earrings that monitor your biometrics? Something else? If you have some ideas of your own please sound off in the comments!

[Pocket Concepts] said he was inspired by Ultra low power energy harvester from BPW34 over on Hackaday.io, be sure to check that out for some interesting low-power project ideas. If you’re interested in other applications for Nordic nRF chips check out ESP32 Turned Handy SWD Flasher For NRF52 Chips and Ground Off Part Number Leads To Chip Detective Work for some examples.

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Engineezy, formerly known as JBV Creative or Jay BV, builds really impressive machines. But most of them are large and portability isn’t a feature he usually cares about. That was a problem when Engineezy decided to attend Open Sauce 2025, which has become the biggest maker event of the year. He wanted something to show off while he perused the various booths and nothing he had previously built fit the bill. So, he reimagined his marble pixel art machine as a wearable fashion piece for strutting around Open Sauce.

We covered Engineezy’s original marble pixel art machine last year and it was really impressive. On demand, it could arrange colored marbles in several columns to form a grid of “pixels” that create an image. Each image had a resolution of 32×32, which required a total of 1024 marbles. In practice, the machine needed many, many more marbles than that in order to accommodate the colors of different images. The resulting machine was pretty massive and the best way for Engineezy to make it more portable was to reduce the image resolution to 11×11 (yes, there is a reason for the odd numbers) and the color palette to two.

Engineezy came up with a clever way to get the marbles into the desired columns: binary gates. They work a bit like transistors, creating a path like tree roots that the marbles can follow. Through the power of doubling at each stage, one input eventually leads to 12 outputs — only two of the four legs on the second stage were doubled. That 12th output is there so the machine can recirculate marbles that are the wrong color.

Unlike the original machine, this one only produces black-and-white images. So, if it needs a white marble and both of the hoppers have a black marble next in line, it will simply send a black marble back down into the hopper and hope a white marble comes up next (repeating if it has especially bad luck).

The gates are actuated by servo motors and marbles feed from the hopper back to the top with a double auger mechanism. A final stop mechanism holds all of the marbles in place in the columns until it is time to reset the image, at which point a servo moves to release them back into the hoppers.

Finally, Engineezy mounted the machine onto laser-cut plates attached to the back of a jacket, so he could walk the floors of Open Sauce while everyone admired his handywork.

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Guitar Hero was all the rage for a few years, before the entire world apparently got sick of it overnight. Some diehards still remember the charms of rhythm games, though. Among them you might count [Joseph Valenti] and [Daniel Rodriguez], who built a Keyboard Hero game for their ECE 4760 class at Cornell.

Keyboard Hero differs quite fundamentally from Guitar Hero in one major way. Rather than having the player tackle a preset series of “notes,” the buttons to press are instead procedurally generated by the game based on incoming audio input. It only works with simple single-instrument piano music, but it does indeed work. A Raspberry Pi Pico is charged with analyzing incoming audio and assigning the proper notes. Another Pi Pico generates the VGA video output with the game graphics, which is kept in sync with the audio pumped out from the first Pico so the user can play the notes in time with the music. Rather than a guitar controller, Keyboard Hero instead relies on five plastic buttons assembled on a piece of wood. It works.

It’s obviously not as refined as the game that inspired it, but the procedural generation of “notes” reminds us of old-school rhythm game Audiosurf. Video after the break.

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Coin cell battery power: how to hold it?

As hackers, we often consider the fun parts of a design first, then think about how to power it later. Maybe it’s natural to leave the boring, known-ish stuff until later, but if you don’t get this fundamental part settled, you don’t have a project.

For really low-power applications, a coin cell (CR2032 or CR2016) battery can be a great choice, but holding them means another component on your BOM, more soldering, and an additional point of failure. Or does it? As I’ll outline in this post, a properly formed PCB footprint can actually act as the holder itself, eliminating a component and its assembly. Whether or not this reduced the chance of failure is still an open question, since PCBs can break or simply bend over time.

Coin cell battery cutout options

So as not to bury the lede – or lead– below are links to several of my PCB coin cell holder designs:

• LED-No-Solder – an early experiment with PCB coin cell holding
• Transistor-Nightlight – light-sensitive LED illumination
• Jeremy Cook business card – PCB card illuminates when pressed

Nominally, such designs use a 0.8mm thick PCB, though other thicknesses can also work. If you prefer to buy an example of this battery holding “tech,” several of my designs are available on Tindie.

The above files give you plenty to experiment with, but read on for a few more important points that can cut down on your development time. According to the LED-No-Solder GitHub page, I’ve been working on this “simplified” battery holder for at least two years.

Inspiration and early experiments

I’m not the first to try using deformed PCBs as coin cell holders, though I’m probably close to the top for number of attempts. This 2017 post by Brian McEvoy uses an (even thinner) 0.6mm PCB for a blinky business card battery holder, as does this somewhat more complicated LED matrix card by Dennis Kaandorp. Not to be left out, I eventually made my own light-up business card as linked above.

My first try at this no-components design came – as detailed here – in the form of the “creatively” named LED-No-Solder below. Its footprint lets you attach both an LED and a coin cell battery to the 0.8mm PCB without solder, making what amounts to a glorified throwie.

Contact problems = button and vibration sensor?

The middle “fork” in the LED-No-Solder contacts the negative CRxx pad, and its conductive surface extends around 6mm from the tip. This design ensures that this conductor can’t touch the vertical portion of the positive battery terminal. However, what often happens is that it touches the protruding negative edge where there is no conductive pad on the PCB. The middle of the fork is therefore angled so that there is a slight gap at the end and no connection is made – and it wouldn’t have touched the positive terminal anyway.

The upside to this situation is that the middle fork can be used as either a hair-trigger momentary button, or even as a vibration sensor. I took advantage of this property to make the LightStrum light-up pick below. While it looks very cool, its relatively large size makes it somewhat difficult to use.

If you want solid contact instead of a button/sensor, the middle fork simply needs to be extended to the outer diameter of the coin cell, as shown below. My paranoia about potentially connecting to the positive side appears to be unwarranted. With an elongated middle contact, my work-in-progress Transistor Night Light design produces a solid connection.

Although most quick-turn board houses will get you thinner 0.8mm PCBs without much of a hassle, they’re not as common as 1.6mm boards. This means that while the price might be the same, there’s a very good chance you’ll need to wait longer for the skinny version of your design.

Based on recent preliminary testing, my Transistor Night Light design in 1.6mm thickness can hold a CR2032 battery. The issue (and possible benefit) is that it is very hard to get the battery in place, and correspondingly difficult to get it out. This can keep things secure, but if you’re selling a product involving this attachment method, I say make sure the buyer is aware of the required force-in process!

Of course, if you really don’t want the battery getting loose, you can also add a zip-tie to keep it in place. Below is the latest version of my Transistor Night Light with zip-tie cutouts.

Technical aside: CR2032, CR2016 name and dimensions

The first two digits in CR2032 and CR2016 indicate the diameter in mm (20mm). The last two are the thickness in tenths of a mm (32 = 3.2mm, 16 = 1.6mm). Naturally, the -32 cell typically has (a lot) more capacity than its -16 counterpart.

The C in CR supposedly means that the battery uses a Lithium battery chemistry, while the R indicates it is round. I’ve also seen it stated that CR stands for “coin cell,” which… only sort of makes sense.

Is this the future of coin cell holding? [Maybe… not]

As noted above by Mike Szczys on Bsky, this technique is both appealing to hacking-minded people.. and a bit of an abuse of PCB designs. In my limited testing, FR4 tends to conform to the battery shape over time, and while it still makes contact, I’m not sure how well it will hold onto its captured battery in years to come.

Also, there’s the concern about kids eating these batteries (which – and this is just my uninformed guess – I suspect has been unfairly lumped in with smaller hearing aid batteries). This might make a larger entity hesitant to try something new. So no, I don’t see more serious firms subbing out purpose-built battery holders for the PCB equivalent any time soon.

At the same time, hackers eventually grow into business leaders… or at least design influencers. As this concept gets proven out over time, people might come to trust it. Early testing shows the 1.6mm thick PCB design holds a CR2032 battery REALLY tightly. So who knows?

So if you need a way to sneak a coin cell battery into your design without bothering with a new component and its assembly, why not give this PCB-only solution a shot? After quite a bit of testing and iteration, I’m a fan of this technique!

Thanks for reading!

Thanks for reading the first of my biweekly PCB Friday columns on Hackster. I’m looking forward to sharing more PCB-related knowledge and insight here, and I hope you’ll follow along. You can find my more semi-technical musings at TechAdjacent.io, or email me at hi@jeremyscook.com if you have any suggestions!

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