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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Heat Domes: Meet The Quiet And Oppressive Take On The Thunderdome

September 16, 2026 by Maya Posch 38 Comments

One of the nice things about the weather is that even if it’s bad right now, it’ll definitely be changing soon and maybe even for the better. There is one exception to this rule, however, and that comes in the form of heat domes, which are weather systems whereby a region of air becomes isolated from the surrounding systems. This creates effectively a greenhouse, with hot air remaining trapped and moisture unable to get in.

Although until recently not very common, this weather phenomenon poses a major challenge to any flora and fauna that finds itself trapped in a heat dome. With nights being about as hot and stifling as the days with their blue skies unbroken by any cloud cover and no rain for potentially weeks on end, it poses severe hydration, cardiovascular, and other challenges to any affected lifeforms.

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After 6 Years As Road Ornament A Widescreen Sony Trinitron Lives Again

September 15, 2026 by Maya Posch 19 Comments

After previously adopting a big Sony Trinitron CRT TV that had been trying to hitch a ride along the side of a road in Italy for at least six years, [Happychoice] didn’t give up on trying to fix it, with the second part showing the TV being more or less fully fixed up.

In the first part of this mini-series, the TV had been salvaged and had most of the dirt as well as local flora and fauna evicted before an attempt was made to fix it. Unfortunately despite the insides looking remarkably clean and intact considering its use as a road-side ornament, that video ended with the controller refusing to power up due to issues with the power supply.

In this sequel we get to see what six years of weather exposure means in terms of what components to replace in a CRT TV like this. Unsurprisingly this means mostly replacing most of the capacitors, at least on the power supply board, as well as the neck board for the actual CRT. A couple of MOSFETs also tested open, so they were replaced too.

With those fresh new parts the TV fired right up again, and with a Wii console connected it looks pretty spiffy running games like Persona 4. Fortunately modern CRT TVs like these have a built-in service menu that you can access with the remote, so that you can tweak picture alignment and other settings without having to stick a screwdriver into the back of the TV to fiddle with a potentiometer whilst also keeping an eye on the picture.

Although there are undoubtedly more components on the PCBs and of course one grimy speaker to give some TLC, it does show that as long as the tube itself is intact, it’s definitely worth it to give repairing a shot.

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Sampling The Elephant’s Foot And Chornobyl’s Tedious Corium Clean-up

September 15, 2026 by Maya Posch 26 Comments

The site of the Chornobyl Nuclear Power Plant (ChNPP) remains a unique location, as what’s left of the No. 4 reactor is the only place in the world where you can find significant amounts of what is called corium. An amalgamation of nuclear fuel, fuel rod cladding and whatever materials like concrete that the molten mass came into contact with, Soviet scientists initially struggled to make sense of this material, leading them to even have it shot at to get samples.

In this video documentary by [That Chernobyl Guy] these struggles by scientists both in and outside the USSR to comprehend this wholly new material are detailed. Much like trinitite – created by a US nuclear weapons test – these are amalgamations of material combined under extreme conditions. In the case of the ChNPP accident, the botched turbine spin-up test and disabling of all safeties by the operators allowed the bottom core chain reaction to run unconstrained, producing the massive steam explosion that flipped the biosafety lid of the RBMK reactor, while also fully melting the core material that then melted through the concrete below the reactor.

Although this Elephant’s Foot is only a tiny fraction of the total mass of corium inside the No. 4 reactor, it got rather infamous for supposedly being highly radioactive and lethal. In reality it’s one of the least dangerous parts of the exposed corium, and repeated sampling attempts along with internal degradation due to radioactive decay and weathering before the NSC shelter was installed have led to it mostly turning into slightly radioactive, rusty-looking dust at this point.

Also covered in the video is how the corium in the destroyed reactor is likely to be retrieved for final disposal, with robots cutting into the sides of the reactor building rather than trying to navigate destroyed corridors and staircases. This way it might be possible to remove most of the material without the issues that stymied Soviet engineers in the 1980s during their sampling attempts.

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Running Linux 6.11 On The ESP32-S3 With A Few Tweaks

September 15, 2026 by Maya Posch 16 Comments

With the Xtensa Lx7 twin CPU cores in the ESP32-S3 running at a relatively zippy 240 MHz and accompanying PSRAM of up to 16 MB, you might find yourself wondering whether it could run Linux. As [Paulneja] demonstrates with Linux kernel 6.11, the answer is a ‘yes’, though with the usual caveats.

What complicates matters with the ESP32-S3 is that it lacks certain amenities that spoiled OSes like Linux have come to take for granted, such as a Memory Management Unit (MMU). To deal with this, the NOMMU Linux configuration was used, along with a custom fork() implementation. Although the previous 0.7 version sort-of worked, the current 0.8 release is the first that manages to actually boot reliably and has a usable amount of RAM available after boot.

You can see the comparison between the two versions in the header image, with v0.8 having a blistering 3.7 MB available after booting and with overall resource usage and performance having improved massively. Note that only one core is available to Linux, with the other used by the typical FreeRTOS ESP-IDF stack to provide WiFi and Bluetooth.

This was all run on an ESP32-S3 with the N16R8 configuration, meaning 16 MB Flash that’s also used for writable storage and 8 MB of octal PSRAM. As for practical applications, it’s noted by [Paulneja] that this is a research project, though one could imagine this being an embedded Linux project along the lines of a network router running something like BusyBox.

Fixing A Ubiquiti 16-Port PoE Switch With An Extra Hole

September 15, 2026 by Maya Posch 7 Comments

After saving a £300, 16-port Ubiquiti network switch from getting tossed into the trash, [Buy It Fix It] got the honor of trying to repair it. With four ports and their associated PoE function having some major issues it looked like it might take some debugging, but after taking the lid off, the cause seemed rather obvious.

One of the Broadcom BCM5911 controller chips had a rather suspicious chip of the plastic packaging missing, with additional probing of connected components showing that numerous MOSFETs and a diode having had their proverbial guts blown out and were shorted as well. Whatever happened to some connected Ethernet device would appear to have left a serious trail of damage that nearly wrecked the entire switch.

The biggest challenge here was probably to find a replacement for the Broadcom IC, as this isn’t an IC that stores like Digikey or Mouser stock any more. Fortunately it was still available for sale over at AliExpress for £1.84, with the usual caveat that it could be salvage, fake, a factory reject, etc. In this case it appears that it was a legit Broadcom IC, with the four affected ports springing back to life including powering a PoE camera.

With a total cost of about £5 plus the time invested it wasn’t a bad deal to save a pretty nice PoE switch with 16 Ethernet and 2 SFP ports.

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How High-Voltage Current Transformers Monitor The Grid

September 14, 2026 by Maya Posch 7 Comments

Being able to monitor voltages and currents is essential for many applications, with the national electrical grid being no exception. The obvious complication here is that the voltages and currents are massively higher than for those other applications, making safely monitoring these somewhat of an engineering challenge. The used systems for current monitoring are detailed by [Jordan Taylor], also known as [The Electric Brit], in an explainer of grid-level current transformers (CTs) and associated elements that help to provide galvanic isolation for safe current measurements.

Even if the basic principles remain the same, when you’re dealing with currents of 5 kA and more, the associated clearances and penalties for getting a detail wrong increasing correspondingly. The CTs help to implement over-current protection (OCP), over-voltage protection (OVP) as well as differential protection, which is useful to detect leakage and shorts, which could also happen inside the CT if the windings become damaged.

Any such failure condition can trigger a circuit breaker to be tripped, or other corrective measures to be taken. Incidentally this is also how it can be detected when someone is tapping off power in an illicit manner. As with all transformers they’re never perfect due to issues like core saturation, and thus performing accurate measurements and picking the right type of transformer is an art in itself, as explained in the video.

Ultimately CTs and the associated equipment are what makes an AC power grid responsive to any changes and with it into the reliable foundation of modern-day society.

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