Introducing The Periodic Table Of US Electrical Receptacles

September 16, 2026 by Maya Posch 57 Comments

Although things may seem simple on the North American grid as an end-user if you limit yourself to just 120 VAC and NEMA 1-15 and 5-15 connectors, there is a veritable zoo of different voltages and receptacles out there in the NEMA connector catalogue. Recently [Practical Engineering] decided to not only take a look at how many of these defined standards are actually used, but also put them in a nice periodic table style graphic.

Responsible for these standards is the National Electrical Manufacturers Association (NEMA), which as the name says is a collection of manufacturers. Founded in 1926, this US trade association also affects outlet standards in countries like Canada, Mexico, Japan and so on. The caveat here is that compatibility between e.g. a similar looking Japanese 1-15-style plug and a US 1-15 outlet is not guaranteed, even if you ignore voltage and grid frequency differences.

In an ideal world everyone would agree on a set of reasonable connector designs and we could move on, but we live in a world where even today designing your own national connector instead of picking something like the ubiquitous Type F is considered to be reasonable. At least it’s not susceptible to the ‘penny challenge‘ flaw that the NEMA 5-15 connector suffers from, but that’s small comfort.

NEMA connectors are also unique in that they are often polarized, while Type E/F and others rarely are, putting the onus of dealing with AC polarity on the device. This already shows why the NEMA connector diversity exists, as this trade association wanted to have specific connectors for different polarities, different current limits and also the nearly half a dozen of different voltages commonly used throughout the US.

This ‘one connector for a specific combination’ approach means that quite a few of them are not really used in real life, though from a European perspective where you deal with Type C (‘euro plug’) and Type E/F (‘Schuko’) on ~240 VAC and triple-phase 440 VAC connectors if you run a heavy machine shop or want to fast-charge an EV at home, it’s still a bewildering number of active combinations.

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Can AI Now Design PCBs That Just Work?

September 5, 2026 by Maya Posch 65 Comments

With the recent release of its GPT-6 Astra model, OpenAI explicitly pushed the claim that it is capable of designing complete circuit boards in KiCad, starting from a provided schematic and outputting a fully routed PCB that theoretically could be sent off to be manufactured. This of course raises the question whether this is just a nifty party trick that works under strictly controlled conditions like most auto-routing tools, or whether there’s more to it. In a recent [EEBench] blog post, OpenAI’s claims are put to the test.

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Crowdsourcing An Investigation Into Coil Whine

September 1, 2026 by Zoe Skyforest 32 Comments

If you’ve heard the high-pitched whine or buzz from an electronic device when a current-carrying inductor is vibrating, you’ll know how unpleasant it can be. It’s common in all kinds of equipment, but it’s become a particular annoyance of late in hardware like PC power supplies, GPUs, and cooling pumps. There is plenty of hearsay on the web about which parts whine and which don’t, and [Lowell Wood] wants to get to the bottom of it.

To track the issue, [Lowell] has put together the Coil Whine Database. It accepts user reports on hardware, regarding the level at which coil whine is present. A score of 0 is given to a part that is inaudible in a quiet room, with higher scores representing higher sound levels. A part scored at 2 is audible working at a desk with the computer under load; a part scored at 4 is audible even when the machine or device is at idle.

For now, the database is largely empty—[Lowell] has just opened submissions, adding a report on their own ROG Astral RTX 5080 card for good measure. If you want to submit a report on a unit, either silent or noisy, that’s simple enough—just fill in the coil whine report form. Over time, submissions will hopefully grow, and it will be easier to get a good idea of what equipment whines and what is likely to operate silently out of the box.

The database aims to present a guide to what parts whine, and how much, noting that any given population of devices tends to vary. To that end, any given device won’t be reported on publicly until it receives at least 5 reports. To counter bias, reports of silent parts will be weighted higher, since it’s unlikely that people happy with their quiet hardware will be rushing to research this issue or report it to a database. Relevant files to the project are available on GitHub for the curious.

This database could be a great boon to the brigade of PC builders out there who like their machines to be as silent as possible. If that sort of thing appeals to you, it’s probably time you started researching passive cooling as well…

New Controller Makes Heavy Machinery Intuitive

August 26, 2026 by Bryan Cockfield 33 Comments

As children, many of us looked wistfully into the cockpits of heavy machinery, wondering just how the series of knobs and levers would do something like operate a bulldozer, crane, or excavator. The nature of these myriad of hydraulic and electronic controls for equipment like this is often inscrutable to adults as well; it takes a considerable amount of training to be able to competently operate most of these machines. But this new controller from MIT may help shorten that training time.

The controller is specifically meant for excavators. In a standard excavator, a pair of joysticks is typically used, with one controlling the swing and the boom and the other controlling the stick and the bucket. Getting used to this combination can take practice, so instead the group of researchers replaced them with a model excavator arm that the operator controls directly with their own arm. The new controller is more intuitive to use as it translates the movements of the model to that of either a real excavator or a training simulation.

The researchers plan to include haptic feedback in future versions, which will hopefully further increase the ease of which new operators can get a feel for using these machines. For those not working towards a new career or an ambitious weekend with rental equipment, there are some other ways of learning how to operate excavators and other pieces of heavy machinery.

A man's hand is shown holding brass-colored tweezers. In the tweezers are held the inner race and the ball cage of a ball bearing, with half of the outer race lying below them on a table.

Splitting A Ball Bearing To Cut Out Backlash

August 11, 2026 by Aaron Beckendorf 9 Comments

Gears are usually the biggest contributors to backlash in a mechanical system, but they’re far from the only culprits. Ball bearings are a less obvious source of imprecision, since any gaps between the balls and the races can lead to axial wobble. Precision mechanisms can eliminate this by pairing two ball bearings, holding the outer races fixed, and applying a preload force to the inner traces. [Chronova Engineering], however, has a different solution, for which he split a ball bearing in half.

Besides taking up more room, thermal expansion also means that it’s difficult to apply a consistent preload force between two ball bearings. Instead, to make a self-contained preloaded bearing, [Chronova Engineering] first disassembled a single ball bearing. The most difficult part of this is taking apart the ball cage; the two parts of this are normally riveted together, but he managed to find a crimped cage and pry it apart. After taking the bearing completely apart, he cut the outer trace in half along the circumference, then reassembled the bearing. The split outer trace makes it possible to press the two halves together, preloading it and removing slop.

To see how well this worked, [Chronova Engineering] replaced the the ball bearing supporting one end of the feed screw for a milling machine with this new bearing. Before the replacement, it had a backlash of 0.1 to 0.2 millimeters; after the modification, it dropped to 30 to 40 microns. This kind of bearing is already known in the machining world – four-point-contact bearings use a very similar principle – but they don’t seem to be well known.

For more about these common yet remarkable rotary mechanisms, check out our article on bearings. If, on the other hard, precision isn’t a priority, you can always 3D print ball bearings.

Behold The Most Beautifully Ambitious Starship Simulator Yet

July 29, 2026 by Donald Papp 24 Comments

[Kevin Kelm] created something wondrous: Halcyon Dawn, an utterly unique and desperately challenging game that is equal parts intricate starship simulator, imposing hardware console, video game, and love letter to John Scalzi’s Old Man’s War book series. Grab a beverage for this one, because it’s chock-full of detail.

First, how is it played? The simulator represents the ship Halcyon Dawn, a stolen and renamed vessel, and the player representing its sole crew member. The ship’s new mission is to establish a home for its payload of genetically-engineered unfortunates, escaping a cruel sort of indentured military servitude. The former masters of course have a very different view of the whole situation, throwing around terms like “treason” and “theft” and in general preferring the version of the desperate protagonist they had the most control over.

Aluminum extrusion, laser-cut panels, and custom PCBs for interfacing physical controls and displays make up the bulk of the build.

As the player is meant to be operating the ship on their own, the cockpit is imposing. All 152 controls and six screens are meaningful and will be needed to pilot the Halcyon Dawn, survive hostile actions, repel boarding attempts, mine and refine vast amounts of raw materials, and in general keep the ship running and intact until an autofactory can be deployed in orbit of a suitable planet to create a new home.

All easier said than done. It’s one thing to pilot and tweak a temperamental ship, but doing so while also performing damage control and thwarting a boarding attempt by manipulating life support is quite another. Want more details? Gameplay is documented here and the physical controls have their own library.

The product of a year of focused work, [Kevin] – now retired – pointed his decades of hardware and software experience at Halcyon Dawn after realizing one night that everything he needed to create it already existed. How this whole project came to be is also a tribute to the amazing tools and equipment that hobbyists and hackers of all kinds now have to turn an idea into something that actually exists in the world. Even so, it was a load of work he is not keen to repeat. Don’t miss the technical deep-dive and photo gallery of the build.

While the game itself — being a fan-made derivative of Scalzi’s work (and useless without the custom-made hardware console) — isn’t being released, [Kevin] has shared the underlying hardware framework it is built on. Enigma is an ESP32-based set of input and output PCBs made for integrating switches, knobs, displays, relays, and more with a Python library to make them easy to work with.

Starship simulators are a wonderful subset of projects, and every one is different from the last. Something about physical builds really works for them, and while we’ve seen a camper trailer converted to starship simulator [Kevin]’s project focuses the whole experience beautifully into the single-person console you see here. Watch a video of Halcyon Dawn running in an arcade-like “attract” mode embedded just below.

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Scanwheel: A Pocket-Sized POV TV

July 26, 2026 by Matt Varian 21 Comments

When you hear the word TV, you probably think of a big LED screen, maybe even the old CRT TVs, but in either case it’s something large and fairly complicated. However, thanks to the persistence of vision, it doesn’t have to be. In this handheld-sized project from [Ancient], the Scanwheel is born, a miniature mechanical TV that uses a spinning disk and some LEDs to produce an image.

The electronics of the Scanwheel are pretty straightforward. The smarts come from a Raspberry Pi Pico, an A4988 motor driver, a couple of LEDs, and a small 21-02485 stepper motor. The Raspberry Pi Pico is used to command the motor speed as well as coordinate the LEDs to turn on at the right time. The case is 3D printed; the base includes space for the various support electronics as well as some small light baffles to ensure the LEDs don’t bleed over outside their intended area. The top of the case is a disk that includes 20 small holes spaced evenly around the perimeter at varying heights, allowing light to only leave the disk when one of these holes is in front of the LEDs.

When you put all these pieces together, spin the motor up to roughly 900 RPM, and turn the LEDs on in a precise order, you end up with a really cool result: a miniature TV. And due to the five different LEDs in this build, you actually have a color 20×20 pixel display in the center and, on either side of that, two more 20×20 black-and-white displays capable of showing different images. Thanks [Ancient] for sharing this awesome build that takes advantage of the persistence of vision effect to create a unique display. Be sure to check out the video below as well as the instructions on how to build your own. And if you enjoy this sort of thing, check out some of our other persistence-of-vision projects as well.

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