We’re all familiar with getting feedback from a rotating shaft, for which we usually employ a potentiometer or encoder. But there’s another device that, while less well-known, has some advantages that just might make it worth figuring out how to include it in hobbyist projects: the synchro.
If you’ve never heard of a synchro, don’t feel bad; as [Glen Akins] explains, it’s an expensive bit of kit most commonly found in avionics gear. It’s in effect a set of coaxial transformers with a three-phase stator coil and a single-phase rotor. When excited by an AC reference voltage, the voltage induced on the rotor coil is proportional to the cosine of the angle between the rotor and stator. It seems simple enough, but the reality is that synchros present some interfacing challenges.
[Glen] chose a surplus altitude alert indicator for his experiments, a formidable-looking piece of avionics. Also formidable was the bench full of electronics needed to drive and decode the synchro inside it — a 26-volt 400-Hz AC reference voltage generator, an industrial data acquisition module to digitize the synchro output, and an ESP32 dev board with a little OLED display to show the results. And those are impressive; as seen in the video below, the whole setup is capable of detecting tenth-of-a-degree differences in rotation.
The blog post has a wealth of detail on using synchros, as does this Retrotechtacular piece from our own [Al Williams]. Are they practical for general hobbyist use? Probably not, but it’s still cool to see them put to use.
Anyone who’s done an electronics project knows the most important part of any good design is making sure to keep the magic smoke inside of all of the components. There are a lot of ways to make sure the smoke stays in there, but one of the most important is making sure that the power supply is isolated. If you’re using a USB port on a computer as your power source, though, it can be a little more complicated to isolate it from the computer.
The power supply is based around a small transformer with a set of diodes to act as a rectifier. Of course, while a transformer is great at isolating power supplies, it isn’t much good at DC. That’s what the ATtiny microcontroller is for. It handles the high-speed switching of the MOSFETs, which drive the transformer and handle some power regulation. There are two different power supplies created as part of this project as well — the first generates +5V much like a normal USB plug would have, and the other creates both +5V and -5V. It will be important not to mix these two up, or that tricky blue smoke may escape.
The project page goes into extensive details on the operation of the device, so if electrical theory is of interest, this will definitely be worth a read. Isolating a valuable computer from a prototype circuit is certainly important, but if you’re looking for a way to isolate a complete USB connection, look at this build which includes isolation for a USB to FTDI adapter.
Russia’s loose cannon of a space boss is sending mixed messages about the future of the International Space Station. Among the conflicting statements from Director-General Dmitry Rogozin, the Roscosmos version of Eric Cartman, is that “the decision has been made” to pull out of the ISS over international sanctions on Russia thanks to its war on Ukraine. But exactly when would this happen? Good question. Rogozin said the agency would honor its commitment to give a year’s notice before pulling out, which based on the current 2024 end-of-mission projections, means we might hear something definitive sometime next year. Then again, Rogozin also said last week that Roscosmos would be testing a one-orbit rendezvous technique with the ISS in 2023 or 2024; it currently takes a Soyuz about four orbits to catch up to the ISS. So which is it? Your guess is as good as anyones at this point.
At what point does falsifying test data on your products stop being a “pattern of malfeasance” and become just the company culture? Apparently, something other than the 40 years that Mitsubishi Electric has allegedly been doctoring test results on some of their transformers. The company has confessed to the testing issue, and also to “improper design” of the transformers, going back to the 1980s and covering about 40% of the roughly 8,400 transformers it made and shipped worldwide. The tests that were falsified were to see if the transformers could hold up thermally and withstand overvoltage conditions. The good news is, unless you’re a power systems engineer, these aren’t transformers you’d use in any of your designs — they’re multi-ton, multi-story beasts that run the grid. The bad news is, they’re the kind of transformers used to run the grid, so nobody’s stuff will work if one of these fails. There’s no indication whether any of the sketchy units have failed, but the company is “considering” contacting owners and making any repairs that are necessary.
For your viewing pleasure, you might want to catch the upcoming documentary series called “A League of Extraordinary Makers.” The five-part series seeks to explain the maker movement to the world, and features quite a few of the luminaries of our culture, including Anouk Wipprecht, Bunnie Huang, Jimmy DiResta, and the gang at Makers Asylum in Mumbai, which we assume would include Anool Mahidharia. It looks like the series will focus on the real-world impact of hacking, like the oxygen concentrators hacked up by Makers Asylum for COVID-19 response, and the influence the movement has had on the wider culture. Judging by the trailer below, it looks pretty interesting. Seems like it’ll be released on YouTube as well as other channels this weekend, so check it out.
But, if you’re looking for something to watch that doesn’t require as much commitment, you might want to check out this look at the crawler-transporter that NASA uses to move rockets to the launch pad. We’ve all probably seen these massive beasts before, moving at a snail’s pace along a gravel path with a couple of billion dollars worth of rocket stacked up and teetering precariously on top. What’s really cool is that these things are about as old as the Space Race itself, and still going strong. We suppose it’s easier to make a vehicle last almost 60 years when you only ever drive it at half a normal walking speed.
And finally, if you’re wondering what your outdoor cat gets up to when you’re not around — actually, strike that; it’s usually pretty obvious what they’ve been up to by the “presents” they bring home to you. But if you’re curious about the impact your murder floof is having on the local ecosystem, this Norwegian study of the “catscape” should be right up your alley. They GPS-tagged 92 outdoor cats — which they dryly but hilariously describe as “non-feral and food-subsidized” — and created maps of both the ranges of individual animals, plus a “population-level utilization distribution,” which we think is a euphemism for “kill zone.” Surprisingly, the population studied spent almost 80% of their time within 50 meters of home, which makes sense — after all, they know where those food subsidies are coming from.
Not too many people build their own microphones, and those who do usually build them out of materials like plastic and metal. [Frank Olson] not only loves to make microphones, but he’s also got a thing about making them from wood, with some pretty stunning results.
[Frank]’s latest build is a sorta-kinda replica of the RCA BK-5, a classic of mid-century design. Both the original and [Frank]’s homage are ribbon microphones, in which a thin strip of corrugated metal suspended between the poles of magnets acts as a transducer. But the similarities end there, as [Frank] uses stacked layers of walnut veneer as the frame of his ribbon motor. The wood pieces are cut with a vinyl cutter, stacked up, and glued into a monolithic structure using lots of cyanoacrylate glue. The video below makes it seem easy, but we can imagine getting everything stacked neatly and lined up correctly is a chore, especially when dealing with neodymium magnets. Cutting and corrugating the aluminum foil ribbon is no mean feat either, nor is properly tensioning it and making a solid electrical contact.
The ribbon motor is suspended in a case made of yet more wood, all of which contributes to a warm, rich sound. The voice-over for the whole video below was recorded on a pair of these mics, and we think it sounds just as good as [Frank]’s earlier wooden Model 44 build. He says he has more designs in the works, and we’re looking forward to hearing them, too. Continue reading “A New Wrinkle On Wooden Ribbon Microphones”→
Grounding of electrical systems is an often forgotten yet important design consideration. Issues with proper grounding can be complicated, confusing, and downright frustrating to solve. So much so that engineers can spend their entire careers specializing in grounding and bonding. [Bsilvereagle] was running into just this sort of frustrating problem while attempting to send audio from a Nintendo Switch into a PC, and documented some of the ways he attempted to fix a common problem known as a ground loop.
Ground loops occur when there are multiple paths to ground, especially in wires carrying signals. The low impedance path creates oscillations and ringing which is especially problematic for audio. When sending the Switch audio into a computer a loop like this formed. [Bsilvereagle] set about solving the issue using an isolating transformer. It took a few revisions, but eventually they settled on a circuit which improved sound quality tremendously. With that out of the way, the task of mixing the Switch audio with sources from other devices could finally proceed unimpeded.
As an investigation into a nuisance problem, this project goes into quite a bit of depth about ground loops and carrying signals over various transforming devices. It’s a great read if you’ve ever been stumped by a mysterious noise in a project. If you’ve never heard of a ground loop before, take a look at this guide to we featured a few years ago.
How far would you go for your cup of tea? [samsungite]’s missus doesn’t like clutter on her countertops, so away the one-cup kettle would go back into the cupboard for next time while the tea steeped. As long as there’s room for it in there, why not install it there permanently? That’s the idea behind RoboTray, which would only be cooler if it could be plumbed somehow.
RoboTray went through a few iterations, most importantly the switch from 6mm MDF to 4 mm aluminum plate. A transformer acts as a current sensor, and when the kettle is powered on, the tray first advances forward 7 cm using a 12 VDC motor and an Arduino. Then it pivots 90° on a lazy Susan driven by another 12 VDC motor. The kettle is smart enough to turn itself off when finished, and the Arduino senses this and reverses all the steps after a ten-second warning period. Check it out in action after the break.
If [samsungite] has any more Arduinos lying around, he might appreciate this tea inventory tracker.
Like many hackers, [Matthias Wandel] has a penchant for measuring the world around him, and quantifying the goings-on in his home is a bit of a hobby. And so when it came time to sense the current flowing in the wires of his house, he did what any of us would do: he built his own current sensing system.
What’s that you say? Any sane hacker would buy something like a Kill-a-Watt meter, or even perhaps use commercially available current transformers? Perhaps, but then one wouldn’t exactly be hacking, would one? [Matthias] opted to roll his own sensors for quite practical reasons: commercial meters don’t quite have the response time to catch the start-up spikes he was interested in seeing, and clamp-on current transformers require splitting the jacket on the nonmetallic cabling used in most residential wiring — doing so tends to run afoul of building codes. So his sensors were simply coils of wire shaped to fit the outside of the NM cable, with a bit of filtering to provide a cleaner signal in the high-noise environment of a lot of switch-mode power supplies.
Fed through an ADC board into a Raspberry Pi, [Matthias]’ sensor system did a surprisingly good job of catching the start-up surge of some tools around the shop. That led to the entertaining “Circuit Breaker Challenge” part of the video below, wherein we learn just what it really takes to pop the breaker on a 15-Amp branch circuit. Spoiler alert: it’s a lot.
