A person holds a glass jar in their left hand and a spark plug in their right atop a white cylindrical canister. The jar and canister are sitting on top of a green cutting mat.

Spark Plug Becomes Glass Cutter

Sometimes a hack doesn’t need to be rocket science to be useful. Take for instance [MofigoDIY] using an old spark plug to build a glass cutter.

Sure, going to grab a glass cutter at the hardware store might be easy, but there’s something satisfying about going the DIY route. [MofigoDIY]’s version of this classic hack is a bit more refined than the quick and dirty route of smashing the spark plug alumina and hot gluing it into a tube.

After using a rotary tool to cut off the threads and expose the narrow part of the ceramic, [MofigoDIY] grinds it down to a fine point. This lets the spark plug itself become the handle, so you don’t need any additional parts to make the cutter. Toward the end of the video, a heated wire is used to break a glass jar apart after it was scored which might be of interest even if you already have a glass cutter. Once you’re finished making your glass cutter, make sure you dispose of any chips left over, since ceramic spark plug fragments are considered burglary tools in some areas.

Would you rather just build the glass up additively? How about using a laser cutter to sinter glass or 3D printing fused silica using a polymerized composite precursor?

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Auto Harp Typewriter

An extremely large split keyboard with giant knobs, and pedals underneath the desk.
Image by [crazymittens-r] via reddit
Where do I even begin with this one? Let’s start with the reasoning behind this giant beast’s existence, and that is medical necessity. [crazymittens-r] needed something that would let them keep working, and after many hours and many versions, this is the current iteration of their ArcBoard, which looks like it could control a spaceship.

You can read all about this version on GitHub, but here’s the gist — you’re looking at a split keyboard with dual macro pads, rotary encoders, and a built-in trackball. And oh yeah, there are pedals, too. Those are a whole other thing.

In this revision, [crazymittens-4] said no to hand-wiring and instead went with custom flexible PCBs. The encoders now have push-button LED screens, and overall, there are “more LEDs than QMK can handle”. There’s even a secret keyboard within the keyboard! I can’t express how much I want to put my hands on this thing.

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Rotary Phone Lives On As Arduino Kitchen Timer

It’s safe to say that few people still use rotary phones on a daily basis. Hell, most of us don’t even use landline telephones anymore. But just because these classic phones are no longer being used for their original purpose doesn’t necessarily mean they’re doomed to become e-waste.

[Scott-28] recently sent in a particularly well-documented project that turned an antique rotary phone into a digital kitchen timer using an internal Arduino. While we’re not sure practical is a word most folks would use to describe the resulting device, it’s certainly a conversation starter, and the details on how it was all implemented make for an interesting read.

As explained in the README, [Scott-28] first used an oscilloscope to figure out the pulses generated by the phone’s dial. From there, it was relatively easy to connect the dial to one of the pins on an Arduino Uno to determine which numbers the user had entered. The trickier part was getting the original bells to work — in North America, it takes up to 90 VAC to get a phone’s ringer going, which is quite a bit more than the lowly Arduino can handle.

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The Tragic Story Of The Ill-Fated Supergun

In the annals of ambitious engineering projects, few have captured the imagination and courted controversy quite like Gerald Bull’s Supergun. Bull, a Canadian artillery expert, envisioned a gun that could shoot payloads directly into orbit. In time, his ambition led him down a path that ended in both tragedy and unfinished business.

Depending on who you talk to, the Supergun was either a new and innovative space technology, or a weapon of war so dangerous, it couldn’t be allowed to exist. Ultimately, the powers that be intervened to ensure we would never find out either way.

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Feast Your Eyes On These AI-Generated Sounds

The radio hackers in the audience will be familiar with a spectrogram display, but for the uninitiated, it’s basically a visual representation of how a range of frequencies are changing with time. Usually such a display is used to identify a clear transmission in a sea of noise, but with the right software, it’s possible to generate a signal that shows up as text or an image when viewed as a spectrogram. Musicians even occasionally use the technique to hide images in their songs. Unfortunately, the audio side of such a trick generally sounds like gibberish to human ears.

Or at least, it used to. Students from the University of Michigan have found a way to use diffusion models to not only create a spectrogram image for a given prompt, but to do it with audio that actually makes sense given what the image shows. So for example if you asked for a spectrogram of a race car, you might get an audio track that sounds like a revving engine.

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Adafruit Badges Turned Electronic Invitations

Despite what you might have heard, even the most devout Hackaday readers may eventually find themselves getting married. Should you ever find yourself in a situation where you need to send out invitations for your big day, or any other major celebration for that matter, you could do worse than follow the example [Mokas] and their partner set with these memorable electronic wedding invitations.

Inspired by the electronic badges distributed at hacker cons, [Mokas] decided to use Adafruit’ EdgeBadge and PyBadge devices to create a similar interactive keepsake that would be a bit more exciting than a piece of paper. While it would have been enough to have the wedding information pop up on the screen when they were turned on, the final invites actually boot into a retro-style game where you walk around talking to characters to uncover information about the event and the venue.

The game was created in Microsoft MakeCode Arcade, with a sprinkling of original and commissioned sprites. Early versions of the game ended up being a bit much for the Adafruit badge’s to handle, but after doing a bit of research on creating games for computationally-constrained platforms, [Mokas] was able to optimize the performance. For those that didn’t get a physical invite (no doubt ours was simply lost in the mail), you can play the whole thing right in your browser.

It’s a very clever idea, and while using custom hardware would have allowed for a more bespoke package, we can’t blame [Mokas] for wanting to keep this one simple. Getting everything ready for your wedding is already enough stress — it’s hardly the time to spin up a new board.

For a similar reasons, another Adafruit offering was selected to power the couple’s e-ink baby development display.

An Improved Spectrometer, No Lasers Required

Here at Hackaday, we love it when someone picks up the ball from a previous project and runs with it. That’s what we’re all about, really — putting out cool projects that just might stimulate someone else to extend and enhance it, or even head off in an entirely new direction. That’s how the state of the art keeps moving.

This DIY spectrometer project is a fantastic example of that ethos. It comes to us from [Michael Prasthofer], who was inspired by [Les Wright]’s PySpectrometer, a simple device cobbled together from a pocket spectroscope and a PiCam. As we noted at the time, [Les] put a lot of the complexity of his instrument in the software, but that doesn’t mean there wasn’t room for improvement.

[Michael]’s goals were to make his spectrometer a little easier to build, and to improve the calibration process and overall accuracy. To help with the former, he went with software correction of the color filter array on his Fuji X-T2. This has the advantage of not requiring a high-power laser and precision micropositioner to ablate the CFA, and avoids potentially destroying an expensive camera. For the latter, [Michael] delved deep into the theory behind spectroscopy and camera optics to develop a process for correlating the intensity of light along the spectrum with the specific wavelength at that location. He also worked a little machine learning into the process, training a network to optimize the response functions.

The result is pretty accurate spectra with no lasers required for calibration. The video below goes into a lot of detail and ends up being a good introduction to some of the basics of spectroscopy, along with the not-so-basics.

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