Cluster Deck Packs Four Pis Into One Portable Package

October 22, 2020 by 8 Comments

Parallel computing is a fair complex subject, and something many of us only have limited hands-on experience with. But breaking up tasks into smaller chunks and shuffling them around between different processors, or even entirely different computers, is arguably the future of software development. Looking to get ahead of the game, many people put together their own affordable home clusters to help them learn the ropes.

As part of his work with decentralized cryptocurrency, [Jay Doscher] recently found himself in need of a small research cluster. He determined that the Raspberry Pi 4 would give him the best bang for his buck, so he started work on a small self-contained cluster that could handle four of the single board computers. As we’ve come to expect given his existing body of work, the final result is compact, elegant, and well documented for anyone wishing to follow in his footsteps.

The core unit would make a great desktop cluster.

Outwardly the cluster looks quite a bit like the Mil-Plastic that he developed a few months back, complete with the same ten inch Pimoroni IPS LCD. But the internal design of the 3D printed case has been adjusted to fit four Pis with a unique staggered mounting arrangement that makes a unit considerably more compact than others we’ve seen in the past. In fact, even if you didn’t want to build the whole Cluster Deck as [Jay] calls it, just printing out the “core” itself would be a great way to put together a tidy Pi cluster for your own experimentation.

Thanks to the Power over Ethernet HAT, [Jay] only needed to run a short Ethernet cable between each Pi and the TP-Link five port switch. This largely eliminates the tangle of wires we usually associate with these little Pi clusters, which not only looks a lot cleaner, but makes it easier for the dual Noctua 80 mm to get cool air circulated inside the enclosure. Ultimately, the final product doesn’t really look like a cluster of Raspberry Pis at all. But then, we imagine that was sort of the point.

Of course, a couple of Pis and a network switch is all you really need to play around with parallel computing on everyone’s favorite Linux board. How far you take the concept after that is entirely up to you.

Affordable Ground-Penetrating Radar

October 22, 2020 by 31 Comments

While you might think of radar pointing toward the skies, applications for radar have found their way underground as well. Ground-penetrating radar (GPR) is a tool that sends signals into the earth and measures their return to make determinations about what’s buried underground in much the same way that distant aircraft can be located or identified by looking for radar reflections. This technology can also be built with a few common items now for a relatively small cost.

This is a project from [Mirel] who built the system around a Arduino Mega 2560 and antipodal Vivaldi antennas, a type of directional antenna. Everything is mounted into a small cart that can be rolled along the ground. A switch attached to the wheels triggers the radar at regular intervals as it rolls, and the radar emits a signal and listens to reflections at each point. It operates at a frequency range from 323 MHz to 910 MHz, and a small graph of what it “sees” is displayed on an LCD screen that is paired to the Arduino.

Using this tool allows you to see different densities of materials located underground, as well as their depths. This can be very handy when starting a large excavation project, detecting rock layers or underground utilities before digging. [Mirel] made all of the hardware and software open-source for this project, and if you’d like to see another take on GPR then head over to this project which involves a lot of technical discussion on how it works.

Do Your Part To Stop The Robot Uprising

October 21, 2020 by 11 Comments

One of the pleasures of consuming old science fiction movies and novels is that they capture the mood of the time in which they are written. Captain Kirk was a 1960s guy and Picard was a 1990s guy, after all. Cold war science fiction often dealt with invasion. In the 1960s and 70s, you were afraid of losing your job to a computer, so science fiction often had morality tales of robots running amok, reminding us what a bad idea it was to give robots too much power. As it turns out, robots might be dangerous, but not for the reasons we thought. The robots won’t turn on us by themselves. But they could be hacked. To that end, there’s a growing interest in robot cybersecurity and Alias Robotics is releasing Alurity, a toolbox for robot cybersecurity.

Currently, the toolbox is available for Linux and MacOS with some support for Windows. It targets 25 base robots including the usual suspects. There’s a white paper from when the product entered testing available if you want more technical details.

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Correlated Electron Memory… Coming Soon?

October 21, 2020 by 26 Comments

We often see press releases and announcements about the next big technology in batteries, memory, displays, capacitors, or any of a number of other things. Usually we are suspicious since we typically don’t see any of this new technology in the marketplace over any reasonable timescale. So when we read about correlated-electron memory Cerfe Labs, we had to wonder if it would be more of the same. IOur suspicions may be justified of course, but it is telling that the company is a spin-off from ARM, so that gives them some real-world credibility.

Correlated-electron RAM or CeRAM is the usual press release material. Nonvolatile, smaller than SRAM, and fast. It sounds as though it could replace the SRAM in PC caches, for example, and take up less die space on the CPU chip. The principle is a bit odd. When electrons are forced together in certain materials, the properties of the material can change. This Mott transition (named after the inventor [Neville Mott]) can take carbon-doped nickel oxide and switch it from its natural electrical insulating state to a conducting state and back again.

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Exoskeleton Muscles Powered By Hydrogen

October 21, 2020 by 19 Comments

The idea of building a suit that increases the wearer’s strength is a compelling one, often featured in science fiction. There are a handful of real world examples, and [Alex] can now add his to the list. The build comes with a twist however, relying on hydrogen to do the work.

At its heart, the build is not dissimilar to other artificial muscle projects. The muscles in [Alex’s] build consist of a rubber tube inside a nylon braid. When the rubber tube is inflated, it expands, causing the nylon braid to shorten as it grows wider. Commonly, such builds rely on compressed air to power the muscles, however [Alex] took a different path. Instead, water is electrolysed in a chamber designed to look like Iron Man’s arc reactor, with the resulting gases produced being used to drive the muscles. With five muscles ganged up to pull together, the wearable arm support is capable of generating up to 15 kg of pull force.

It’s a design that has a few benefits; the electrolyser has no moving parts, and is much simpler and quieter than a typical air compressor. Obviously, there is a risk of fire thanks to the flammable gases used, but [Alex] explains the precautions taken to minimise this risk in the video.

Exosuits may not be mainstream just yet, but that doesn’t mean people aren’t working to make them a reality. We’ve featured a few before, like this open-source design. Video after the break.

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Small Spotify Remote Broadens Musical Horizons

October 21, 2020 by 9 Comments

When was the last time you tried listening to a new genre of music, or even explored a sub-genre of something you already like? That’s what we thought. It’s good to listen to other stuff once in a while and remind ourselves that there’s a whole lot of music out there, and our tastes are probably not all that diverse. As a reminder, [sorghum] made a spiffy little Spotify remote that can cruise through the musical taxonomy that is Every Noise at Once and control any Spotify-enabled device.

There’s a lot to like about this little remote, which is based upon a LilyGo TTGO ESP32 board with on-board display. The circuitry is basically that and a rotary encoder plus a tiny LiPo battery. Can we talk about the finish on those prints? Yes, those are both printed enclosures. Getting that buttery smooth finish took two grits of wet/dry sandpaper plus nine grits of polishing cloths.

As you can see in the brief demo after the break, there are several ways to discover new music. [sorghum] can surf through all kinds of Japanese music for example, or surf by the genre’s ending word and listen to metalcore, deathcore, and grindcore from all over the globe. For extra fun, there’s a genre-ending randomizer so you can discover just how many forms of *core there are.

Want everyone in the room to know what you’re listening to? Behold the Spotify split-flap display.

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How An Engineer Designs A DIY Energy Recovery Ventilator

October 21, 2020 by 81 Comments

We have no idea whether [Nick Goodey] is a trained engineer or not. But given the detailed design of this DIY energy recovery ventilator for his home HVAC system, we’re going to go out on a limb and say he probably knows what he’s doing.

For those not in the know, an energy recovery ventilator (ERV) is an increasingly common piece of equipment in modern residential and commercial construction. As buildings have become progressively “tighter” to decrease heating and cooling energy losses to the environment, the air inside them has gotten increasingly stale. ERVs solve the problem by bringing fresh, unconditioned air in from the outside while venting stale but conditioned air to the outside. The two streams pass each other in a heat exchanger so that much of the energy put into the conditioned air is transferred to the incoming unconditioned air.

While ERV systems are readily available commercially, [Nick] decided to roll his own after a few experiments with Coroplast and some extensive calculations convinced him it would be a viable idea. One may scoff at the idea of corrugated plastic for the heat exchanger, but the smooth channels through the material make it a great choice. He built up a block of Coroplast squares with the channels in alternate layers oriented orthogonally, letting stale inside air pass very close to fresh outside air to exchange heat without ever mixing directly. The entire system, including fans, an Arduino for control, sensors galore, and the Hubitat home automation hub, is powered by DC, so no electrician was needed. [Nick] has a ton of detail in his build log, including all the tools and calculators he used to design the system.

Given the expense of ERV systems, we’re surprised we haven’t seen more stories about DIY versions. We have talked about HVAC systems a lot, though — after all, HVAC techs are hackers who make housecalls.