Tech In Plain Sight: Microwave Ovens

Our homes are full of technological marvels, and, as a Hackaday reader, we are betting you know the basic ideas behind a microwave oven even if you haven’t torn one apart for transformers and magnetrons. So we aren’t going to explain how the magnetron rotates water molecules to produce uniform dielectric heating. However, when we see our microwave, we think about two things: 1) this thing is one of the most dangerous things in our house and 2) what makes that little turntable flip a different direction every time you run the thing?

First, a Little History

Westinghouse Powercaster which could, among other things, toast bread in six seconds

People think that Raytheon engineer Percy Spenser, the chief of their power tube division, noticed that while working with a magnetron he found his candy bar had melted. This is, apparently, true, but Spenser wasn’t the first to notice. He was, however, the first to investigate it and legend holds that he popped popcorn and blew up an egg on a colleague’s face (this sounds like an urban legend about “egg on your face” to us). The Raytheon patent goes back to 1945.

However, cooking with radio energy was not a new idea. In 1933, Westinghouse demonstrated cooking foods with a 10 kW 60 MHz transmitter (jump to page 394). According to reports, the device could toast bread in six seconds.  The same equipment could beam power and — reportedly — exposing yourself to the field caused “artificial fever” and an experience like having a cocktail, including a hangover on overindulgence. In fact, doctors would develop radiothermy to heat parts of the body locally, but we don’t suggest spending an hour in the device.

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A Pulse Of Annoyance About Oscillators, Followed By A Flyback Of A Rant

Everyone likes to play with high voltages, right?. Even though the danger of death goes up with every volt, it’s likely that a few readers will have at some time or other made fancy long sparks. You’re reading this so you lived to tell the tale, and we’d only ever counsel only doing so safely, but the point of this piece lies not in the volts themselves but in a touch of frustration at the voltage generators. There’s a circuit I see so often which annoys me every single time, so here if you don’t mind I’m going to deliver both a little rant and a look into flyback converters.

It’s Got Coils, so It’s A Transformer

A power supply with the lid removed, visible is a large transformer
Linear power supplies with a mains transformer are a surprisingly rare sight now. Dilshan Jayakody, CC BY-SA 2.0.

How does a transformer work? An alternating current in a primary winding induces an opposite current in its secondary winding. The voltage out is equal to the turns ratio times the voltage in. Thus if you want to make a high voltage, it’s simply a case of finding a transformer with the right turns ratio, and applying the right AC to the input.

A handy choice for a high voltage transformer has been for years a TV line output transformer, also sometimes known as a flyback transformer. You could find these in CRT displays and TVs, and they consist of a square ferrite core with a big chunky high voltage overwinding for the CRT anode circuit and a load of lower voltage windings. TV designers were always out to save on parts costs, so they often had windings for all the voltage rails inside the set as well as the anode voltage, using the timebase as a crude switching power supply. Continue reading “A Pulse Of Annoyance About Oscillators, Followed By A Flyback Of A Rant”

A software-defined radio system in a 3D-printed case with a 7" display and an array of knobs and switches

Hackaday Prize 2023: A Software-Defined Radio With Real Knobs And Switches

When cheap digital TV dongles enabled radio enthusiasts to set up software defined radio (SDR) systems at almost zero cost, it caused a revolution in the amateur radio world: now anyone could tune in to any frequency, with any modulation type, by just pointing and clicking in a computer program. While this undoubtably made exploring the radio waves much more accessible, we can imagine that some people miss the feeling of manipulating physical buttons on a radio while hunting for that one faint signal in a sea of noise. If you’re one of those people, you’re in luck: [Kaushlesh C.] has built a portable, self-contained SDR system with real knobs and switches, called SDR Dock 1.0. Continue reading “Hackaday Prize 2023: A Software-Defined Radio With Real Knobs And Switches”

Inverse Vaccines Could Help Treat Autoimmune Conditions

Autoimmune diseases occur when the immune system starts attacking the body’s own cells. They can cause a wide range of deleterious symptoms that greatly reduce a patient’s quality of life. Treatments often involve globally suppressing the immune system, which can lead to a host of undesirable side effects.

However, researchers at the University of Chicago might have found a workaround by tapping into the body’s own control mechanisms. It may be possible to hack the immune system and change its targeting without disabling it entirely. The new technique of creating “inverse vaccines” could revolutionize the treatment of autoimmune conditions.

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Hackaday Links: September 24, 2023

Modern video games are almost always written on the backs of a game engine platform, and the two most popular are definitely Unreal Engine and Unity. Some bean counter at Unity decided they essentially wanted a bigger piece of the pie and rolled out new terms of use that would have game development houses paying per Unity install. This was a horrible blow to small indie game development houses, where the fees would end up eating up something like 15% of revenue in an industry that’s already squeezed between the Apple Store and Steam. It caused an absolutely gigantic uproar in the game dev community, and now Unity is walking it back.

We noticed the change first because tons of “migrate from Unity to Godot” tutorials popped up in our YouTube stream. Godot is a free and open-source game engine, and while we’re no game devs, it looks to be at about the level of Blender five years ago – not quite as easy to use or polished as its closed-source equivalents, but just about poised to make the transition to full usability. While we’re sure Unreal Engine is happy enough to see Unity kick some more business their way, we’re crossing our fingers for the open-source underdog.

Amazon’s Kindle Direct Publishing allows independent authors to self-publish. And it’s apparently been awash in prose written by large language models. While it was fun for a while to look through self-published books for the shibboleth phrase “As an AI language model,” Amazon caught on pretty quickly. Of course, that only gets the lowest-hanging fruit. Books like the AI-written guidebook to mushrooms that recommends eating the Death Cap still manage to sneak through, as we mentioned two weeks ago.

Amazon’s solution? Limiting self-published books to three per day. I wrote a book once, and it took me the better part of a year, and Amazon is letting through three per day. If this limit is going to help limit the size of the problem, then we vastly underestimate the problem.

And it’s good news, bad news from space. The good news is that NASA’s OSIRIS-REx mission to return a sample from the asteroid Bennu successfully landed just a few hours ago. As we write this, they’ve sent a team driving around the Utah desert to pick up the capsule. The effort reminds us of retrieving high-altitude balloon capsules after a flight: you know roughly where it is, but you still have to get out there to fetch it.  Only NASA has a helicopter to go out looking for the capsule and a lot more science to do before they can throw it in the back of their car.

On the bad news side, India’s Vikram and Pragyan lunar lander/rover pair wasn’t really expected to make it through the long lunar night and had successfully executed all of its planned mission goals before going into deep sleep mode two weeks ago. But you’ve got to try to wake it up anyway, right? Well, the sun came up on Vikram on Friday, and the Indian space agency tweeted a stoic, “Efforts have been made to establish communication with the Vikram lander and Pragyan rover to ascertain their wake-up condition. As of now, no signals have been received from them. Efforts to establish contact will continue.” We’ve still got our fingers crossed, but at this point it would just be extra icing on the cake.

This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina

Last week we covered the latest 0-day from NSO group, BLASTPASS. There’s more details about exactly how that works, and a bit of a worrying revelation for Android users. One of the vulnerabilities used was CVE-2023-41064, a buffer overflow in the ImageIO library. The details have not been confirmed, but the timing suggests that this is the same bug as CVE-2023-4863, a Webp 0-day flaw in Chrome that is known to be exploited in the wild.

The problem seems to be an Out Of Bounds write in the BuildHuffmanTable() function of libwebp. And to understand that, we have to understand libwebp does, and what a Huffman Table has to do with it. The first is easy. Webp is Google’s pet image format, potentially replacing JPEG, PNG, and GIF. It supports lossy and lossless compression, and the compression format for lossless images uses Huffman coding among other techniques. And hence, we have a Huffman table, a building block in the image compression and decompression.

What’s particularly fun about this compression technique is that the image includes not just Huffman compressed data, but also a table of statistical data needed for decompression. The table is rather large, so it gets Huffman compressed too. It turns out, there can be multiple layers of this compression format, which makes the vulnerability particularly challenging to reverse-engineer. The vulnerability is when the pre-allocated buffer isn’t big enough to hold one of these decompressed Huffman tables, and it turns out that the way to do that is to make maximum-size tables for the outer layers, and then malform the last one. In this configuration, it can write out of bounds before the final consistency check.

An interesting note is that as one of Google’s C libraries, this is an extensively fuzzed codebase. While fuzzing and code coverage are both great, neither is guaranteed to find vulnerabilities, particularly well hidden ones like this one. And on that note, this vulnerability is present in Android, and the fix is likely going to wait til the October security update. And who knows where else this bug is lurking. Continue reading “This Week In Security: WebP, Cavium, Gitlab, And Asahi Lina”

Toy Bulldozer Becomes Epic Terrifying Lawnmower

Regular lawnmowers are a perfectly fine way to mow your lawn, but they can be a bit boring. They’re also not always the best at tackling thick brush and bushes. [rctestflight] has a solution to both of those problems, in the form of a plant-munching bulldozer.

The concept is simple — it starts with a hefty miniature RC bulldozer. Weighing in at 27 kilograms (60 pounds), the beast has actual functioning hydraulics to control the blade and plow. It struggles somewhat with traction, particularly in muddier conditions, and can’t really dig much, but it nonetheless looks the business.

As cool as it was, [rctestflight] decided to employ it for some real yard work by outfitting it with a mowing rig. The ‘dozer was outfitted with a pair of sawblades, run by twin brushless motors for plenty of grunt. That gave the bulldozer the ability to mow through not just lawn, but even thick blackberry bushes and two-foot high weeds.

It’s not great at steering, but it’s able to destroy thick brush with reckless abandon. Fundamentally, it looks like a very fun way to mow an overgrown yard.

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