Ask Hackaday: Why Is TTL 5 Volts?

October 8, 2025 by Dan Maloney 63 Comments

The familiar five volts standard from back in the TTL days always struck me as odd. Back when I was just a poor kid trying to cobble together my first circuits from the Forrest Mims Engineer’s Notebook, TTL was always a problem. That narrow 4.75 V to 5.25 V spec for Vcc was hard to hit, thanks to being too poor to buy or build a dedicated 5 V power supply. Yes, I could have wired up four 1.5 V dry cells and used a series diode to drop it down into range, but that was awkward and went through batteries pretty fast once you got past more than a few chips.

As a hobbyist, the five volt TTL standard always seemed a little capricious, but I strongly suspected there had to be a solid reason behind it. To get some insights into the engineering rationale, I did what anyone living in the future would do: I asked ChatGPT. My question was simple: “How did five volts become the standard voltage for TTL logic chips?” And while overall the answers were plausible, like every other time I use the chatbot, they left me wanting more.

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Two Decades Of Hackaday In Words

September 29, 2025 by Jenny List 23 Comments

I think most of us who make or build things have a thing we are known for making. Where it’s football robots, radios, guitars, cameras, or inflatable textile sculptures, we all have the thing we do. For me that’s over the years been various things but has recently been camera hacking, however there’s another thing I do that’s not so obvious. For the last twenty years, I’ve been interested in computational language analysis. There’s so much that a large body of text can reveal without a single piece of AI being involved, and in pursuing that I’ve created for myself a succession of corpus analysis engines. This month I’ve finally been allowed to try one of them with a corpus of Hackaday articles, and while it’s been a significant amount of work getting everything shipshape, I can now analyse our world over the last couple of decades.

The Burning Question You All Want Answered

A graph of "arduino" versis "raspberry", comparing Arduino and Raspberry Pi coverage over time. — Battle of the Boards, over the decades.

A corpus engine is not clever in its own right, instead it will simply give you straightforward statistics in return for the queries you give it. But the thing that keeps me coming back for more is that those answers can sometimes surprise you. In short, it’s a machine for telling you things you didn’t know. To start off, it’s time to settle a Hackaday trope of many years’ standing. Do we write too much about Arduino projects? Into the engine goes “arduino”, and for comparison also “raspberry”, for the Raspberry Pi.

What comes out is a potted history of experimenter’s development boards, with the graph showing the launch date and subsequent popularity of each. We’re guessing that the Hackaday Arduino trope has its origins in 2011 when the Italian board peaked, while we see a succession of peaks following the launch of the Pi in 2012. I think we are seeing renewals of interest after the launch of the Pi 3 and Pi 4, respectively. Perhaps the most interesting part of the graph comes on the right as we see both boards tail off after 2020, and if I had to hazard a guess as to why I would cite the rise of the many cheap dev boards from China.

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Thanks, Tamiya-san

August 2, 2025 by Elliot Williams 18 Comments

We’re saddened to report the passing of Shunsaku Tamiya, the man behind the Tamiya line of models. What was surprising about this, though, is how many of our readers and writers alike felt touched by the Tamiya model company. I mean, they made great models, and they’re definitely a quality outfit, but the outpouring of fond memories across a broad spectrum was striking.

For example, we originally ran the story as breaking news, but our art director Joe Kim spent a good part of his childhood putting together Tamiya kits, and felt like he absolutely had to do a portrait of Mr. Tamiya to pay his respects. I presume Joe is more on the painting-the-models end of the spectrum of Tamiya customers, given his artistic bent. Jenny’s writeup is absolutely touching, and her fond remembrances of the kits shines through her writing.

Myself, I’m on the making-small-robots end of the spectrum, and was equally well served. Back in the early ’90s, the “twin motor gearbox” was a moderately challenging and tremendously rewarding build for me, but it was also the only variable-ratio small motor gearbox that we had easy access to for making small bots to run around the living room.

Indeed, the Tamiya line included a whole series of educational models and components that were just perfect for the budding robot builder. I’m sure I have a set of their tank treads or a slip clutch in a box somewhere, even today.

It’s nice to think of how many people’s lives were touched by their kits, and to get even a small glimpse of that, you just need to read our comment section. We hope the company holds on to Mr. Tamiya’s love for quality kits that inspire future generations, whether they end up becoming artists, engineers, or simply hackers.

The DEW Line Remembered

July 16, 2025 by Al Williams 20 Comments

The DEW line was one of three radar early warning systems of the time.

If you grew up in the middle of the Cold War, you probably remember hearing about the Distant Early Warning line between duck-and-cover drills. The United States and Canada built the DEW line radar stations throughout the Arctic to detect potential attacks from the other side of the globe.

MIT’s Lincoln Lab proposed the DEW Line in 1952, and the plan was ambitious. In order to spot bombers crossing over the Arctic circle in time, it required radar twice as powerful as the best radar of the day. It also needed communications systems that were 99 percent reliable, even in the face of terrestrial and solar weather.

In the end, there were 33 stations built from Alaska to Greenland in an astonishing 32 months. Keep in mind that these stations were located in a very inhospitable environment, where temperatures reached down to -60 °F (-51 °C). Operators kept the stations running 24/7 for 36 years, from 1957 to 1993.

System of Systems

The DEW line wasn’t the only radar early-warning system that the US and Canada had in place, only the most ambitious. The Pinetree Line was first activated in 1951. However, its simple radar was prone to jamming and couldn’t pick up things close to the ground. It was also too close to main cities along the border to offer them much protection. Even so, the 33 major stations, along with six smaller stations, did better than expected. Continue reading “The DEW Line Remembered” →

Simulating Empires With Procedurally Generated History

June 25, 2025 by Tyler August 11 Comments

Procedural generation is a big part of game design these days. Usually you generate your map, and [Fractal Philosophy] has decided to go one step further: using a procedurally-generated world from an older video, he is procedurally generating history by simulating the rise and fall of empires on that map in a video embedded below.

Now, lacking a proper theory of Psychohistory, [Fractal Philosophy] has chosen to go with what he admits is the simplest model he could find, one centered on the concept of “solidarity” and based on the work of [Peter Turchin], a Russian-American thinker. “Solidarity” in the population holds the Empire together; external pressures increase it, and internal pressures decrease it. This leads to an obvious cellular automation type system (like Conway’s Game of Life), where cells are evaluated based on their nearest neighbors: the number of nearest neighbors in the empire goes into a function that gives the probability of increasing or decreasing the solidarity score each “turn”. (Probability, in order to preserve some randomness.) The “strength” of the Empire is given by the sum of the solidarity scores in every cell. Continue reading “Simulating Empires With Procedurally Generated History” →

High-Stakes Fox Hunting: The FCC’s Radio Intelligence Division In World War II

June 4, 2025 by Dan Maloney 32 Comments

With few exceptions, amateur radio is a notably sedentary pursuit. Yes, some hams will set up in a national or state park for a “Parks on the Air” activation, and particularly energetic operators may climb a mountain for “Summits on the Air,” but most hams spend a lot of time firmly planted in a comfortable chair, spinning the dials in search of distant signals or familiar callsigns to add to their logbook.

There’s another exception to the band-surfing tendencies of hams: fox hunting. Generally undertaken at a field day event, fox hunts pit hams against each other in a search for a small hidden transmitter, using directional antennas and portable receivers to zero in on often faint signals. It’s all in good fun, but fox hunts serve a more serious purpose: they train hams in the finer points of radio direction finding, a skill that can be used to track down everything from manmade noise sources to unlicensed operators. Or, as was done in the 1940s, to ferret out foreign agents using shortwave radio to transmit intelligence overseas.

That was the primary mission of the Radio Intelligence Division, a rapidly assembled organization tasked with protecting the United States by monitoring the airwaves and searching for spies. The RID proved to be remarkably effective during the war years, in part because it drew heavily from the amateur radio community to populate its many field stations, but also because it brought an engineering mindset to the problem of finding needles in a radio haystack.

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How Shrinking Feature Size Made Modern Wireless Work

April 5, 2025 by Elliot Williams 4 Comments

If you’re living your life right, you probably know what as MOSFET is. But do you know the MESFET? They are like the faster, uninsulated, Schottky version of a MOSFET, and they used to rule the roost in radio-frequency (RF) silicon. But if you’re like us, and you have never heard of a MESFET, then give this phenomenal video by [Asianometry] a watch. In it, among other things, he explains how the shrinking feature size in CMOS made RF chips cheap, which brought you the modern cellphone as we know it.

MESFET

MOSFET

The basic overview is that in the 1960s, most high-frequency stuff had to be done with discrete parts because the bipolar-junction semiconductors of the time were just too slow. At this time, MOSFETs were just becoming manufacturable, but were even slower still. The MESFET, without its insulating oxide layer between the metal and the silicon, had less capacitance, and switched faster. When silicon feature sizes got small enough that you could do gigahertz work with them, the MESFET was the tech of choice.

As late as the 1980s, you’d find MESFETs in radio devices. At this time, the feature size of the gates and the thickness of the oxide layer in MOSFETs kept them out of the game. But as CPU manufacturers pushed CMOS features smaller, not only did we get chips like the 8086 and 80386, two of Intel’s earliest CMOS designs, but the tech started getting fast enough for RF. And the world never looked back.

If you’re interested in the history of the modern monolithic RF ICs, definitely give the 18-minute video a watch. (You can skip the first three or so if you’re already a radio head.) If you just want to build some radio circuits, this fantastic talk from [Michael Ossmann] at the first-ever Supercon will make you an RF design hero. His secrets? Among them, making the most of exactly these modern everything-in-one-chip RF ICs so that you don’t have to think about that side of things too hard.

Thanks [Stephen] for the tip!

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