How Shrinking Feature Size Made Modern Wireless Work

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.

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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Lockdown Remote Control Project Is Free And Open

If you flew or drove anything remote controlled until the last few years, chances are very good that you’d be using some faceless corporation’s equipment and radio protocols. But recently, open-source options have taken over the market, at least among the enthusiast core who are into squeezing every last bit of performance out of their gear. So why not take it one step further and roll your own complete system?

Apparently, that’s what [Malcolm Messiter] was thinking when, during the COVID lockdowns, he started his own RC project that he’s calling LockDownRadioControl. The result covers the entire stack, from the protocol to the transmitter and receiver hardware, even to the software that runs it all. The 3D-printed remote sports a Teensy 4.1 and off-the-shelf radio modules on the inside, and premium FrSky hardware on the outside. He’s even got an extensive folder of sound effects that the controller can play to alert you. It’s very complete. Heck, the transmitter even has a game of Pong implemented so that you can keep yourself amused when it’s too rainy to go flying.

Of course, as we alluded to in the beginning, there is a healthy commercial infrastructure and community around other open-source RC projects, namely ExpressLRS and OpenTX, and you can buy gear that runs those software straight out of the box, but it never hurts to have alternatives. And nothing is easier to customize and start hacking on than something you built yourself, so maybe [Malcolm]’s full-stack RC solution is right for you? Either way, it’s certainly impressive for a lockdown project, and evidence of time well spent.

Thanks [Malcolm] for sending that one in!

First PCB With The Smallest MCU?

[Morten] works very fast. He has already designed, fabbed, populated, and tested a breakout board for the new tiniest microcontroller on the market, and he’s even made a video about it, embedded below.

You might have heard about this new TI ARM Cortex MO micro on these very pages, where we asked you what you’d do with this grain-of-rice-sized chunk of thinking sand. (The number one answer was “sneeze and lose it in the carpet”.)

From the video, it looks like [Morten] would design a breakout board using Kicad 8, populate it, get it blinking, and then use its I2C lines to make a simple digital thermometer demo. In the video, he shows how he worked with the part, from making a custom footprint to spending quite a while nudging it into place before soldering it carefully down.

But he nailed it on the first try, and honestly it doesn’t look nearly as intimidating as we’d feared, mostly because of the two-row layout of the balls. It actually looks easy enough to fan out. Because you can’t inspect the soldering work underneath the chip, he broke out all of the lines to a header to make it quick to check for shorts between those tiny little balls. Smart.

We love to see people trying out the newest hotness. Let us know down in the comments what new parts you’re trying out.

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Vintage Computer Festival East This Weekend

If you’re on the US East Coast, you should head on over to Wall, NJ and check out the Vintage Computer Festival East. After all, [Brian Kernighan] is going to be there. Yes, that [Brian Kernighan].

Events are actually well underway, and you’ve already missed the first few TRS-80 Color Computer programming workshops, but rest assured that they’re going on all weekend. If you’re from the other side of the retrocomputing fence, namely the C64 side, you’ve also got a lot to look forward to, because the theme this year is “The Sounds of Retro” which means that your favorite chiptune chips will be getting a workout.

[Tom Nardi] went to VCF East last year, so if you’re on the fence, just have a look at his writeup and you’ll probably hop in your car, or like us, wish you could. If when you do end up going, let us know how it was in the comments!

70 DIY Synths On One Webpage

If you want to dip your toes into the deep, deep water of synth DIY but don’t know where to start, [Atarity] has just the resource for you. He’s compiled a list of 70 wonderful DIY synth and noise-making projects and put them all in one place. And as connoisseurs of the bleepy-bloopy ourselves, we can vouch for his choices here.

The collection runs the gamut from [Ray Wilson]’s “Music From Outer Space” analog oddities, through faithful recreations like Adafruit’s XOXBOX, and on to more modern synths powered by simple microcontrollers or even entire embedded Linux devices. Alongside the links to the original projects, there is also an estimate of the difficulty level, and a handy demo video for every example we tried out.

Our only self-serving complaint is that it’s a little bit light on the Logic Noise / CMOS-abuse side of synth hacking, but there are tons of other non-traditional noisemakers, sound manglers, and a good dose of musically useful devices here. Pick one, and get to work!

Contagious Ideas

We ran a story about a wall-mounted plotter bot this week, Mural. It’s a simple, but very well implemented, take on a theme that we’ve seen over and over again in various forms. Two lines, or in this case timing belts, hang the bot on a wall, and two motors drive it around. Maybe a servo pulls the pen in and out, but that’s about it. The rest is motor driving and code.

We were thinking about the first such bot we’ve ever seen, and couldn’t come up with anything earlier than Hektor, a spray-painting version of this idea by [Juerg Lehni]. And since then, it’s reappeared in numerous variations.

Some implementations mount the motors on the wall, some on the bot. There are various geometries and refinements to try to make the system behave more like a simple Cartesian one, but in the end, you always have to deal with a little bit of geometry, or just relish the not-quite-straight lines. (We have yet to see an implementation that maps out the nonlinearities using a webcam, for instance, but that would be cool.) If you’re feeling particularly reductionist, you can even do away with the pen-lifter entirely and simply draw everything as a connected line, Etch-a-Sketch style. Maslow CNC swaps out the pen for a router, and cuts wood.

What I love about this family of wall-plotter bots is that none of them are identical, but they all clearly share the same fundamental idea. You certainly wouldn’t call any one of them a “copy” of another, but they’re all related, like riffing off of the same piece of music, or painting the same haystack in different lighting conditions: robot jazz, or a study in various mechanical implementations of the same core concept. The collection of all wall bots is more than the sum of its parts, and you can learn something from each one. Have you made yours yet?

(Fantastic plotter-bot art by [Sarah Petkus] from her write-up ten years ago!)

Your Badminton Racket Needs Restringing? There’s A DIY Machine For That

We don’t often get our badminton rackets restrung, but if we did, [kuokuo702]’s PicoBETH project would be where we’d turn. This is a neat machine build for a very niche application, but it’s also a nicely elaborated project with motors, load cells, and even a sweet knobby-patterned faceplate that is certainly worth a look even if you’re not doing your own restringing.

We’ll admit that everything we know about restringing rackets we learned by watching [kuokuo]’s demo video, but the basic procedure goes like this: you zigzag the string through the holes in the racket, controlling the tension at each stage along the way. A professional racket frame and clamp hold the tension constant while you fiddle the string through the next hole, but getting the tension just right in the first place is the job of [kuokuo]’s machine. It does this with a load cell, stepper motor, and ball screw, all under microcontroller control. Pull the string through, let the machine tension it, clamp it down, and then move on to the next row.

Automating the tension head allows [kuokuo] to do some fancy tricks, like pre-stretching the strings and even logging the tension in the string at each step along the way. The firmware has an extensive self-calibration procedure, and in all seems to be very professional. But it’s not simply functional; it also has a fun LEGO-compatible collection of bumps integrated into the 3D-printed dust cover. That way, your minifigs can watch you at work? Why not!

Automating random chores is a great excuse to build fun little machines, and in that vein, we salute [kuokuo]’s endeavor. Once you start, you’ll find stepper motors sprouting all around like crocuses in a spring field. And speaking of spring, Easter is just around the corner. So if you don’t play badminton, maybe it’s time to build yourself an eggbot.

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