an EIKI machine playing back a card

Finding Lo-fi In All The Strange Places

If you haven’t heard any lo-fi music yet, it stands for low-fidelity music. Lofi music today is characterized by audio imperfections such as cable noise or tape hiss. To get a pleasantly warm imperfect sound, many artists turn to vintage equipment. [HAINBACH] found an excellent instrument, the obsolete classroom tool known as magnetic card audio recorders.

The basic mechanism of the device is that it reads and writes to the two tracks on the quarter-inch tape fed through it. One track is meant for the teacher and one track is meant for the student. Originally designed to assist language learners, we can see why it would be an ideal source of good lo-fi samples. The microphone and speaker need to be high quality to hear the nuances of the example sentence. [HAINBACH] also admires the general tone and timbre of the device as opposed to just using a cassette recorder.

The tape in question is glued to little plastic cards. With some modification, you can run the card backward, create a loop, or stitch sections together. With multiple machines, you can run the card from one machine directly into another. They were made by several companies and can be found relatively cheap on online auction houses. While we can’t credit [HAINBACH] for coming up with the idea as it was featured in the movie Baby Driver, it’s still an example of an awesome hack.

Magnetic tape has long been a fascination of musical instruments. This Crudman, which is a modern-day interpretation of the much older Mellotron from 1963, is a great example of that.

Video after the break.

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Pixelating Text Not A Good Idea

People have gotten much savvier about computer security in the last decade or so. Most people know that sending a document with sensitive information in it is a no-no, so many people try to redact documents with varying levels of success. A common strategy is to replace text with a black box, but you sometimes see sophisticated users pixelate part of an image or document they want to keep private. If you do this for text, be careful. It is possible to unredact pixelated images through software.

It appears that the algorithm is pretty straightforward. It simply guesses letters, pixelates them, and matches the result. You do have to estimate the size of the pixelation, but that’s usually not very hard to do. The code is built using TypeScript and while the process does require a little manual preparation, there’s nothing that seems very difficult or that couldn’t be automated if you were sufficiently motivated.

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Bend It Like (Sonar) Beacon With A Phased Array

Ultrasonic transducers are incredible, with them you can detect distances, as well as levitate and peer through objects. They can emit and receive ultrasonic soundwaves (typically above 18khz) and just like all waves, they can be steered via a phased array. [Bitluni] was trying to accurately measure distances but found the large field of view of the sensor was just too imprecise, so he made a phased array of transducers.

The inspiration came from a Hackaday Supercon talk from 2019 about phased arrays. [Bitluni] walks through an excellent explanation of how the array works with a bucket of water and his finger, as well as a separate simulation. By changing the phase offset of the different array members, the beam can effectively be steered as interference muffs the undesired waves. Using a set of solenoids, he created a test bench to validate his idea in a medium he could see; water. The solenoids fire a single pulse into the water creating a wave. You can see the wave move in the correct direction in the water, which validates the concept. A simple PCB sent off to a fab house with a stencil offers a surface to solder the transducers and drivers onto. An ESP32 drives the 8 PWM signals that go to the transmitters and reads in the single receiver via a small amplifier. Still not content to let the idea be unproven, he sets up the receiver on his CNC gantry and plots the signal strength at different points, yielding beautiful “heat maps.”
bitluni's heatmap for his sonar array

It sweeps a 60-degree field in front of it at around 1-3 frames per second. As you might imagine, turning sound wave reflections into distance fields is a somewhat noisy affair. He projects the sonar display on top of what we can see in the camera and it is fun to see the blobs line up in the correct spot.

We noticed he built quite a few boards, perhaps in the future, he will scale it up like this 100 transducer array? Video after the break.

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Pulling Off A CRT Transplant Doesn’t Have To Be Tricky!

Whether it’s an engine swap in an old car or pulling a hard drive out of an old computer, we often find ourselves transplanting bits from one piece of hardware to another. [Emily Velasco] recently attempted this with a pair of CRTs, and came away with great success.

The donor was an old 1980s fishing sounder, which came complete with a rather fetching monochrome amber CRT display. [Emily]’s goal was to transplant this into the body of a early 2000s portable television. The displays were of a similar size and shape, though the Toshiba CRT from the 80s used a lot more glass in its construction.

The tube socket in the TV used to hook up the display matched the old CRT perfectly, so there were no hassles there. A bit of soldering was all that was needed to hook up the yoke, and [Emily] was ready to test. Amazingly, it powered up cleanly, displaying rolling amber static as you’d expect, given that analog television stations have been off the air for some time now.

After some perseverance, a VCR playing Mystic Pizza on VHS was able to deliver a video signal to the TV, proving that everything was working well. The next stage of the project is to get the television electronics to fit inside the 1980s fishing sounder housing, as it’s the more attractive of the two. Things were just built differently back in those days!

We’ve seen some other great vintage display swaps before, too. Video after the break.

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Coin Cell Eliminator Does More Than Save Batteries

Coin cells are useful things that allow us to run small electronic devices off a tiny power source. However, they don’t have a lot of capacity, and they can run out pretty quickly if you’re hitting them hard when developing a project. Thankfully, [bobricius] has just the tool to help.

The device is simple – it’s a PCB sized just so to fit into a slot for a CR2016 or CR2032 coin cell. The standard board fits a CR2016 slot thanks to the thickness of the PCB, and a shim PCB can be used to allow the device to be used in a CR2032-sized slot instead.

It’s powered via a Micro USB connector, and has a small regulator on board to step down the 5 V supply to the requisite 3 V expected from a typical coin cell. [bobricius] also gave the device a neat additional feature – a pair of pads for easy attachment of multimeter current probes. Simply open the jumper on the board, hook up a pair of leads, and it’s easy to measure the current being drawn from the ersatz coin cell.

If you’re regularly developing low-power devices that use coin cells, this tool is one that could save a lot of mucking about in the lab. [bobricius] has them available on Tindie for those eager to get their hands on one. We’ve seen similar designs before too, albeit pursued in a different way!

Inputs Of Interest: Canadian MCM/70 Was Kinda Like The First Cyberdeck

Not to start a debate in the comments or anything, but what would you say was the first microcomputer, or personal computer? We suppose the answer depends on your definition. Some would argue that the PC was born at Xerox PARC with a curious portrait-mode display and a three-button mouse, while others would say it all began in a garage in either Los Altos, California or Albuquerque, New Mexico.

If you take the term ‘computer’ to mean that which can crunch big numbers fairly quickly, then the Canadian-made MCM/70 is arguably the first personal computer in that it is portable, has an alphanumeric keyboard, a display, and supports cassette storage, which could be used to extend the 8K of memory. It was an all-in-one computing solution, and it could have an optional telephone modem built in. This was a forward-thinking machine for 1974.

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Pressure Gauge Built In A Vacuum

Necessity might be the mother of all invention, but we often find that inventions around here are just as often driven by expensive off-the-shelf parts and a lack of willingness to spend top dollar for them. More often than not, we find people building their own tools or parts as if these high prices are a challenge instead of simply shrugging and ordering them from a supplier. The latest in those accepting the challenge of building their own parts is [Advanced Tinkering] who needed a specialty pressure gauge for a vacuum chamber.

In this specific case, the sensor itself is not too highly priced but the controller for it was the deal-breaker, so with a trusty Arduino in hand a custom gauge was fashioned once the sensor was acquired. This one uses an external analog-to-digital converter to interface with the sensor with 16-bit resolution, along with some circuitry to bring the ~8 V output of the sensor down to the 5 V required by the microcontroller. [Advanced Tinkering] wanted a custom live readout as well, so a 3D printed enclosure was built that includes both an LCD readout of the pressure and a screen with a graph of the pressure over time.

For anyone else making sensitive pressure measurements in a vacuum chamber, [Advanced Tinkering] made the project code available on a GitHub page. It’s a great solution to an otherwise overpriced part provided you have the time to build something custom. If you’re looking for something a little less delicate, though, take a look at this no-battery pressure sensor meant to ride along on a bicycle wheel.

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