When Hackaday runs a contest, we see all manner of clever projects. But inevitably there are some we don’t see, because their builders didn’t manage to get them finished in time. [Park Frazer]’s phase-locked loop is one of them. The circuit is an all-discrete PLL that derives a 440kHz output from a 1Hz input, and it arrived just too late for our 1Hz contest.

If you aren’t familiar with a phase-locked loop, in this context you can think of them as a programmable frequency multiplier. A voltage-controlled oscillator is locked to an input frequency by comparing the two with a phase detector. Multiplication can be achieved by putting a frequency divider between the oscillator and the phase detector. It’s at the same time a complex and easy to understand circuit. In this case, when broken down into a set of multivibrators, it makes sense. The charge pump phase detector is a little different from the XOR gate we were expecting, but as he explains, it’s better.

If PLLs are a mystery, have a look at this video from a [Jeri Ellsworth] and [Bil Herd].

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[David] is building a project with an OLED, a keyboard, and an RP2040. He’s perfected a scanning routine in C to work with the keyboard, but he still had some places he wanted to use even lower-level instructions. That was as good an excuse as any to experiment with inline assembly language inside the C program.

The goal was to grab the keyboard’s input and stick it into a memory address register so the data at that address could be shown on the display. However, there was a complication because memory access of this type has to be word-aligned.

Sure, you could mask the low bits of the address, do the read, and then set an index to pick the specific byte, but assembly is easy, and it is good to know how to put it in your code, anyway.

[David] only needed one instruction that is meant for byte access, so as assembly embeddings go, this was quite simple. We’ve done similar things for Linux, although, of course, the Arm assembly language here is different than what we used.

You probably don’t need assembly for every project. But it is nice to know how to do it when you need it. Many people think you don’t need to learn assembly these days, but we mostly disagree.

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“Emergency Law Enforcement Officer Hologram program activated. Please state the nature of your criminal or civil emergency.” Taking a cue from Star Trek: Voyager, the Seoul Metropolitan Police Agency is testing a holographic police officer, with surprisingly — dare we say, suspiciously? — positive results. The virtual officer makes an appearance every two minutes in the evening hours in a public park, presumably one with a history of criminal activity. The projection is accompanied by a stern warning that the area is being monitored with cameras, and that should anything untoward transpire, meat-based officers, presumably wearing something other than the dapper but impractical full-dress uniform the hologram sports, will be dispatched to deal with the issue.

The projected police officer is the product of the South Korean firm Hologramica, which seems to be focused on bringing obsolete or metabolically challenged pop and sports stars back to life. The company uses one of two techniques for its 3D projection: the tried and true “Pepper’s Ghost” trick or a proprietary method they call “3D Holonet.” Given the conditions, we’d guess the police projection is using the latter, which uses a transparent screen with metallic silver embedded into it. Aside from the cool factor, we’re not sure how this is better than something as simple as a cardboard cutout with a cop printed on it, or even just some signs telling people to watch their step. Then again, maybe Starbucks will consider employing the holo-cops in their South Korean stores to deal with their cagonjok problem.

“The first rule of Robo Fight Club is: you don’t talk about Robo Fight Club.” Unfortunately, that rule won’t work when you’re trying to create the world’s premier cyber blood sport, as a fellow named Cix Liv — that’s “109 54” in Roman numerals for those of you keeping score at home — aims to do. His outfit is called REK, which he claims will be “the next UFC,” referring to the wildly popular mixed martial arts organization. To meet that improbable goal, he stages fights between humanoid robots controlled by VR-wearing pilots. There’s a video clip of the action in the article; perhaps as humanoid bots get better, so will the fights, but for now, the action is a little tame for our tastes. But what would really jazz things up is human versus robot fights. We’d pay to see someone mix it up with Atlas. Maybe not the original electro-hydraulic version, though — that would probably get out of hand pretty fast.

We stumbled across a really interesting article on Arthur A. Collins, someone whose name will likely only ring a bell among aficionados of old amateur radio gear. The Collins Radio Company produced legendary ham radio equipment from the 1930s all the way into the 1970s. Their bulky, vacuum tube “boat anchor” radios are still highly prized among collectors, long after the company was absorbed into a series of corporations with less and less interest in radio communications. The article details the genesis of Collins Radio, including the shortwave exploits of a 15-year-old Arthur Collins, who in 1925 used his homebrew 1,000-watt transmitter to contact the National Geographic Society’s expedition to Greenland. It’s a fascinating story and aptly illustrates how a passion for electronics can lead to pretty important breakthroughs, even if you’re just a teenager in your parents’ attic.

How do you cut your onions? It’s not an unimportant question, at least if you care enough about your cooking that your onions are diced evenly to ensure proper cooking. However you’re doing it, though, you’re probably wrong, at least according to this wonderfully but needlessly in-depth look at the mathematics of onion dicing. The analysis looks at an optimized cross-section of an onion and determines the best way to cut it to achieve maximum uniformity in the resulting dices. The diagrams are interactive, allowing you to adjust the number of vertical or radial cuts and categorize the results based on the standard deviation in the area of the pieces. It’s an impressive bit of work, with the obvious limitation of simplifying the onion to two dimensions. But with that awesome onion font, we can forgive a lot.

And finally, when you think of instruments played with a bow, you probably think of violins, cellos, and the like. What doesn’t spring to mind is bow-played open-reel tape decks, but it turns out that they’re a thing, and they’re pretty cool. The Open Reel Ensemble has three classic open-reel decks, which look like Pioneer RT-1011Ls, each of which has a length of tape fed through the heads and around one reel. The ends of the tape are attached to either end of a bamboo pole, which the artist holds taut and moves back and forth through the heads. Whatever signals are on the tape — we assume it’s just simple tones — gets played back and piped into a keyboard synth, which the artist plays with his other hand. One of the decks also has a mic attached near the heads, which seems to pick up the sound of the artist thumping on the bow, delivering a nice rhythm section. It’s a unique and surprisingly funky sound. Enjoy!

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Bus Pirate is nearly a household name in the hardware hacking world. The first version came out way back in 2008, and there have been several revisions since then. You can buy pre-built Bus Pirate devices, but there’s also the option now to build our own. The ESP32 Bus Pirate project has everything you need to turn an ESP32 device into a protocol sniffing/decoding powerhouse—all on a board you may have sitting around from another project.

There are a ton of solutions when it comes to talking to different buses —I2C, UART, JTAG, you name it, there’s a purpose-built device for it. Over a decade ago, Dangerous Prototypes released the Bus Pirate, offering a Swiss Army knife of a tool to interface with this ever-expanding list of communications standards. The ESP32 Bus Pirate project is open-source firmware for ESP32s that gives them the ability to be the multi-tool that lets us communicate with a long list of protocols.

It supports a wide variety of devices, from the straightforward ESP32 S3 Dev Kit available from a long list of suppliers to the more specialized M5 Cardputer equipped with its own keyboard. The original Bus Pirate required plugging the board into a PC to use it; with this being ESP32-based, that’s no longer a limitation. So long as you can supply power to the ESP32, you can connect and control it via WiFi and a web browser. In addition to the Bus Pirate protocols, the project allows us to directly control the pins on the ESP32 board, should you want to do more with it besides interfacing with one of the supported protocols. Be sure to check out some of our other articles about Bus Pirate, as it’s been a fantastic tool for the hacker community over the years.

hackaday.com/2025/08/24/esp32-…

Fax machines had a moment in the sun, but they are actually much older than you might expect. Before the consumer-grade fax machines arrived, there was a thriving market for “wire photos” used by, for example, news organizations and the weather service. In the United States, the WEFax from Western Electric was fairly common and shows up on the surplus market. [Thomas] has an English unit, a Muirhead K-570B, that is very clearly not a consumer-oriented machine. His unit dates back to 1983, but it reminds us of many older designs. Check out his teardown in the video below.

The phone line connection on this device is a pair of banana jacks! There are even jacks for an external meter. Inside, the device is about what you’d expect for a 1983 build. PCBs with bare tinned conductors and lots of through-hole parts.

While not a universally well-known name, Muirhead was a pioneering Scottish inventor. He recorded the first human electrocardiogram and collaborated with Sir Oliver Lodge on wireless telegraph patents. While another Scotsman, Alexander Bain, worked out how to chemically print on paper and Arthur Korn built the first machines that optically scanned the page, it was Murihead, in 1947, that worked out using a drum as the scanner, just as this machine does.

Think this is among the oldest fax machines ever? No way. Remember, though, in 1983, the consumer fax machines were just about to appear. Ask FedEx, we are sure they remember.

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