Op-Amp Challenge: Interactive Analog LED Wave Array

May 12, 2023 by Dave Rowntree 20 Comments

A while back, [Chris Lu] was studying how analog circuits, specifically op-amps can be used to perform mathematical operations and wondered if they could be persuaded to solve differential equations, such as the wave equation. After sitting on the idea for a few years, it was time to make it a reality, and the result is an entry into the Op-Amp Challenge.

Unlike many similar interactive LED matrix displays that are digital in nature (because it’s a lot easier), this design is pure analog, using many, many op-amps. A custom PCB houses a 4×4 array of compute units, each with a blue and white LED indicating the sign and magnitude of the local signal.

The local input signal is provided by an IR photodiode, AC coupled to only respond to change, with every other circuit sharing a sensor to keep it simple. Each circuit is connected to its immediate neighbors on the PCB, and off the PCB via board-to-board connectors. This simple scheme makes this easily scalable if desired in the future.

[Chris] does a great job of breaking down the math involved, which makes this project a neat illustration of how op-amp circuits can implement complex mathematical problems in an easy-to-understand process. Even more op-amps are pressed into service for generating the split-rail voltage reference and for amplifying the weak photodiode signals, but the computation circuit is the star of the show.

We like analog computing a fair bit around these parts. Here’s a little something we were previously drooling over.

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Making Music By Probing Magnetite Crystals

May 9, 2023 by Dave Rowntree 2 Comments

Well, noises anyway. [Dmitry Morozov] and [Alexandra Gavrilova] present an interesting electronics-based art installation, which probes a large chunk of crystalline magnetite, using a pair of servo-mounted probes, ‘measuring’ the surface conductivity and generating some sound and visuals.

It appears to have only one degree of freedom per probe, so we’re not so sure all that much of the surface gets probed per run, but however it works it produces some interesting, almost random results. The premise is that the point-to-point surface resistivity is unpredictable due to the chaotically formed crystals all jumbled up, but somehow uses these measured data to generate some waveshapes vaguely reminiscent of the resistivity profile of the sample, the output of which is then fed into a sound synthesis application and pumped out of a speaker. It certainly looks fun.

From a constructional perspective, hardware is based around a LattePanda fed samples by an ADS1115 ADC, which presumably is also responsible for driving the LCD monitor and the sound system. An Arduino is also wedged in there perhaps for servo-driving duty, maybe also as part of the signal chain from the probes, but that is just a guess on our part. The software uses the VVVV (Visual Live-programming suite) and the Pure Data environment.

We haven’t seen magnetite used for this type of application before, we tend to see it as a source of Iron for DIY knifemaking, as a medium to help separate DNA or just to make nanoparticles, for erm, reasons.

Barcodes Enter The Matrix In 2027

May 3, 2023 by Kristina Panos 80 Comments

Beep. We’ve come a long way since June 26, 1974 when the first bar code was scanned at a grocery store in Troy, Ohio. That legendary pack of Juicy Fruit proved that even the smallest of items could now carry numbers associated with inventory and price.

By now, we’re all too familiar with this sound as self-checkouts have become the norm. Whereas you yourself could at one time literally check out during the transaction, you must now be on your toes and play find the bar code on every item.

What does the consumer gain from the bar code today? Practically nothing, except the chance to purchase, and potentially return, the item without too much hassle. Well, the non-profit outfit that runs the bar code world — GS1 US — wants to change all that. By 2027, they are confident that all 1D bar codes will be replaced with 2D bar codes similar to QR codes. Why?

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Building A WiFi Picture Frame With An EInk Display

April 29, 2023 by Lewin Day 7 Comments

LCD photo frames never really caught on — by emitting light, they didn’t seamlessly blend in with a home’s decor in the way printed photos do. [Sprite_tm] decided to see if a color e-Ink screen could do any better, and whipped up a WiFi-enabled photo frame using a Waveshare display.

The part in question is a 5.65-inch display with 640 x 448 resolution, and is capable of displaying seven colors. It’s not designed to display photorealistic images, so much as display simple graphics with block colors. However, with some dithering, [Sprite_tm] suspected it might do an okay job. An algorithm that uses Floyd-Steinberg diffusion and the CIEDE2000 color space takes regular RGB images and breaks them down into dithered images that are displayed using the screen’s 7 available colors.

The build relies on an ESP32-C3, which drives the display and fetches new images daily over WiFi. Thanks to the e-Ink screen, which uses zero power when not updating, the whole setup runs off two AA batteries and a Natlinear LN2266 boost converter.

There are some limitations; the screen’s color space is altogether quite limited, and images don’t look very high-fidelity in such low resolution. However, it does an able job of displaying photos for a device that was never designed to do so. It looks rather handsome all wrapped up as a 3D printed picture frame, and [Sprite_tm]’s monkey test photos are very cute.

Files are on GitHub for those that wish to roll their own. We’ve seen similar works before, like this e-Ink wall-hanging newspaper display that keeps up with the times. If you’ve got your own neat e-ink build, hit us up on the tipsline!

Sound Sculpture Uses Daisy Seed To Generate Audio

April 2, 2023 by Lewin Day No comments

Here at Hackaday, we love a good art piece, whether that involves light or sound. Combining both is a sure-fire way to get our attention, and [Eirik Brandal] did just that with his Void Extrusion piece.

The project is built around the Daisy Seed from Electrosmith. It’s an embedded platform designed for musical purposes, which made it perfect for [Eirik]’s project. Based on an STM32 chip, it’s very capable when it comes to DSP tasks. In this role, it’s charged with algorithmic music composition, providing the captivating soundtrack that emanates from the sculpture.

The sculpture itself looks almost like a fancy mid-century home from the Hollywood Hills, but it’s fundamentally a little more abstract than that. [Eirik] built it as an opportunity to experiment with using 3D printed forms in his work. To that end, it features a beautiful diffused LED wall and a speaker enclosure as an integral part of the build. The LEDs are run from an Arduino Nano Every.

[Eirik’s] work shows us that “generative” music can be intoxicating and compelling with a real sense of feeling and mood. The sculpture is a visually-capable pairing that works with the soundscape. It recalls us of some other great artworks we’ve featured from [Eirik] before, too.

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Make Anything Clockwork With This Ridiculous Stick-On Device

March 30, 2023 by Lewin Day 38 Comments

Clockwork devices were popular right up until motors and electronics proved far more capable in just about every way. However, there’s something charming about a device you can wind up to make it do its thing. To recreate this feeling on modern technology, [Kousuke Saito] created a clockwork winder that you can fit to a wide variety of modern appliances.

The design is simple. It consists of a motor which is run from a battery. The two components are installed in a 3D printed housing with a magnet on the bottom. When the device is attached to a metal surface, a switch is activated which turns the motor on. The motor is attached to a large printed “winding key” that would be familiar to anyone who has used a clockwork toy or timepiece before. If the magnetic manner of activation is familiar, you might recall it from [Kousuke Saito’s] chirping cicada project.

It’s a silly build, to be sure. Regardless, when placed on certain appliances, like a simple fan, the motion really does imply that the clockwork winder is connected to the mechanism inside. It’s a falsehood, of course, but a joyous one.

We’ve featured some real clockwork hardware before, too, like these amazing time locks.

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CNC Intaglio-Esque Engraving

March 24, 2023 by Dave Rowntree 3 Comments

Intaglio is an ancient carving technique for adding details to a workpiece, by manually removing material from a surface with only basic hand tools. If enough material depth is removed, the resulting piece can be used as a stamp, as was the case with rings, used to stamp the wax seals of verified letters. [Nicolas Tranchant] works in the jewelry industry, and wondered if he could press a CNC engraving machine into service to engrave gemstones in a more time-efficient manner than the manual carving methods of old.

Engraving and machining generally work only if the tool you are using is mechanically harder than the material the workpiece is made from. In this case, this property is measured on the Mohs scale, which is a qualitative measurement of the ability of one (harder) material to scratch another. Diamond is the hardest known material on the Mohs scale and has a Mohs hardness of 10, so it can produce a scratch on the surface of say, Corundum — Mohs value 9 — but not the other way around.

[Nicolas] shows the results of using a diamond tip equipped CNC engraver on various gemstones typical of Intaglio work, such as Black Onyx, Malachite, and Amethyst with some details of the number of engraving passes needed and visual comparison to the same material treated to traditional carving.

Let’s be clear here, the traditional intaglio process produces deep grooves on the surface of the workpiece and the results are different from this simple multi-pass engraving method — but limiting the CNC machine to purely metal engraving duties seemed a tad wasteful. Now if they can only get a suitable machine for deeper engraving, then custom digitally engraved intaglio style seal rings could be seeing a comeback!

Intaglio isn’t just about jewelry of course, the technique has been used in the typesetting industry for centuries. But to bring this back into ours, here’s a little something about making a simple printing press.