Rŏ̽ta: Counting, With Style

Rǒta counts things. That’s it, really — what a cheap little mechanical counter does with a thumb press, or what you can do by counting on your fingers and toes, that’s pretty much all that Rǒta does. But it does it with style.

OK, that’s being a bit unfair to [Kevin Santo Cappuccio] — Rǒta has a few more tricks up its sleeve than simple counting. But really, those functions are just icing on the cake of how this little gadget looks. Rǒta was built around the unbeatable combination of a rotary telephone dial mechanism and a trio of Nixie tubes. The dial looks like it might have come from an old pay phone, all shiny and chrome and super robust looking. The Nixies sit atop the dial on a custom PCB, and everything, including the high-voltage supply for the tubes, is enclosed in a 3D printed case with a little bit of a Fallout vibe.

But what does this thing do? Actually, quite a lot. It’ll count up and down, using whatever number you dial into it. You can either increment from zero, or enter any three-digit number as the starting count. It keeps track of the score of your golf game, if that’s your thing, and it’s also got a stopwatch function. You can even dial up a display of the current battery voltage. It takes some ingenuity to use just the dial for all these functions, but that’s as easy as dialing the operator used to be — dialing 0 puts it in menu mode, allowing you to access any of the functions printed on the card in the center of the dial. It’s pretty clever — check out the video below.

Is it particularly useful? Perhaps not. But when has that ever been a measure of the worth of a project? Something like this rotary cellphone might be more useful, but sometimes looking great is good enough.

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LCD Monitor Plays The Hits

In the old days, it wasn’t uncommon to put an AM radio near a computer or a monitor and deliberately cause interference to have a crude form of sound generation. Did you miss out on that? No! Thanks to [luambfb] you can now do the same trick with a common LCD monitor. You’ll need the horizontal refresh rate of the monitor in question.

Of course, doing it is somewhat less interesting than learning how it works. The effect relies on the fact that the LCDs emit signals as it refreshes a row. A black row emits relatively low energy while a white row emits more. Grayscale… well, you get the idea. Continue reading “LCD Monitor Plays The Hits”

Conference badge with the custom chip soldered-on on top left, the custom chip itself in a SOIC-16 package on the top right, two close-up die shots on the bottom

Student Competition Badge Bears Custom Silicon

[Daniel Valuch] shared a fun and record-setting conference badge story (Slovak, translated) with us. He was one of the organizers for the “ZENIT in electronics” event, which is an annual Slovak national competition for students. During the competition, students are assigned a letter+number code for the purpose of result submission anonymity, and organizers are always on the lookout for a fun way to assign these codes – this time, they did it with custom silicon!

It just so happened that [Peter], one of [Daniel]’s colleagues, was at the time working for onsemi who were doing a tapeout and had some free space on their test chips. Of course, they didn’t have to think twice. When it was a student’s turn to draw their identification number, instead of a slip of paper, they received a SOIC-16 package with custom silicon bonded to it. Then, they had to solder it to their competition badge – which was, of course, a PCB. Each chip was individually laser-trimmed to contain the student’s number, and that number could then be decoded using a multimeter – or a reasonably sharp eye.

There’s way more to this competition story than just the badge, but the custom silicon part of it sure caught our eyes. Who knows, maybe next year stars will align again and we’ll see custom silicon on one of the hacker conference badges. After all, things have been advancing rapidly on that front – for instance, since Skywater PDK project’s inception in 2020, there’s been several successful runs already, and if you’d like to learn more, you could check the HackChat we’ve had this year, and this Remoticon 2020 workshop!

The SDWire board plugged into some SoM's breakout board's MicroSD socket

Automated MicroSD Card Swapping Helps In Embedded Shenanigans

[Saulius Lukse] has been working on some single board computer, seemingly, running Linux. Naturally, that boots from a microSD card – and as development goes on, that card has to be reimaged all the time. Sick of constantly plugging and unplugging the microSD card between the SBC and an SD card reader, [Saulius] started looking for a more automated solution – and it wasn’t long before he found out about the SDWire project, a hardware tool that lets you swap a card between a DUT (Device Under Test) and your personal computer with no moving parts involved.

SDWire is an offshoot from the Tizen project, evidently, designed to be of help in device development, be it single-board computers or smartphones. The idea is simple – you plug your MicroSD card into the SDWire board, plug the SDWire into a MicroSD slot of your embedded device, and then connect a USB cable from the SDWire to your development computer. This way, if you need to reflash the firmware on the SBC you’re tinkering with, you only need to issue a command to the SDWire board over the USB cable, and the MicroSD card appears as a storage drive on your computer. SDWire is a fully open source project, both in hardware and in software, and you can also buy preassembled boards online.

Such shortening of development time helps in things like automated testing, but it also speeds your development up quite a bit, saving you time between iterations, freeing you from all the tiny SD card fiddling, and letting you have more fun as you hack. There’s a clear need for a project like SDWire, as we’ve already seen a hacker assemble such a device using breakouts.

Homemade CAT Scan Shouldn’t Scan Cats

[Pyrotechnical] thought about buying a CAT scanner and found out they cost millions of dollars. So he decided to build one for about $200 using a salvage X-ray tube and some other miscellaneous parts. A scintillating detector provides the image for pick up with a camera phone. The control? An Arduino, what else? You can watch the video below, but due to plenty of NSFW language, you might want to put your headphones on if you don’t want to shock anyone.

Of course, you need to be careful when working with energetic X-rays. To keep away from the X-ray source, [Pyrotechnical] used a Roku remote and an IR sensor to control the device from afar. The electronics is pretty easy. You just have to rotate a turntable and trigger the camera while lighting up the X-ray tube.

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This Stainless Steel Knife Build Starts With Raw Iron Ore

Making knives at home has become a popular hobby, thanks partly to reality TV and the free time and idle hands afforded by lockdowns. Depending on how far you get into the hobby, builds can range from assembling and finishing a kit with pre-forged parts, to actual blacksmithing with a hammer and anvil. But pretty much every build includes steel from a commercial supplier.

Not this one. Rather than buy his metal from the usual sources, [Thoisoi]’s first stop was an iron mine in the Italian Alps, where he picked up a chunk of iron ore — magnetite, to be precise. Smelting one’s own iron from raw ore and alloying it into steel is generally not a backyard project thanks to the high temperatures needed, a problem [Thoisoi] solved with the magic of thermite. The iron oxide and aluminum in the thermite mix react in an exceptionally exothermic manner to generate elemental iron, which under controlled conditions can be captured as a more or less pure ingot, ready for forging.

After a test with commercially obtained iron oxide, [Thoisoi] tried his pulverized magnetite. And thanks to the addition of goodies like graphite, manganese, nickel, silicon, and chromium, he was eventually able to create a sizable lump of 402 stainless steel. He turned the metal over to an actual blacksmith for rough forging; it sure seemed to act like steel on the anvil. The finished knife looks good and performs well, and the blade has the characteristic look of stainless. Not a bad result, and all at the cost of a couple of clay flowerpots.

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BPS.Space Succesfully Lands A Model Rocket

If you’ve been following [Joe Barnard]’s rocketry projects for the past few years, you’ll know that one of his primary goals has been to propulsively land a model rocket like SpaceX. Now, 7 years into the rollercoaster journey, he has finally achieved that goal with the latest version of his Scout rocket.

Rocket touching down
We have touchdown!

Many things need to come together to launch AND land a rocket on standard hobby-grade solid fuel rocket motors. A core component is stabilization of the rocket during the entire flight, which achieved using a thrust-vectoring control (TVC) mount for the rocket motors and a custom flight computer loaded with carefully tuned guidance software. Until recently, the TVC mounts were 3D printed, but [Joe] upgraded it to machined aluminum to eliminate as much flex and play as possible.

Since solid-fuel rockets can’t technically be throttled, [Joe] originally tried to time the ignition time of the descent motor in such a manner that it would burn out as the rocket touches down. The ignition time and exact thrust numbers simply weren’t repeatable enough, so in his 2020 landing attempts, he achieved some throttling effect by oscillating the TVC side to side, reducing the vertical thrust component. This eventually gave way to the final solution, a pair of ceramic pincers which block the thrust of the motors as required.

Another interesting component is the landing legs. Made from light carbon fiber rods, they are released by melting a rubber band with nichrome wire and fold into place under spring tension. They also had to be carefully refined to absorb as much impact as possible without bouncing, which killed a few previous landing attempts.

Scrolling back through [Joe]’s videos and seeing the progress in his engineering is absolutely inspiring, and we look forward to his future plans. These include a functional scale model of the belly-flopping starship, a mysterious “meat rocket”, and the big one, a space shot to exceed 100 km altitude.

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