Off-the-shelf stock parts are the blocks from which we build mechanical projects. And while plenty of parts have dedicated uses, I enjoy reusing them in ways that challenge what they were originally meant for while respecting the constraints of their construction. Building off of my piece from last time, I’d like to add to your mechanical hacking palette with four more ways we can re-use some familiar off-the-shelf parts. Continue reading “The BSides: More Curious Uses Of Off-the-shelf Parts”
Water cooler talk at the office usually centers around movies, sports, or life events. Not at Hackaday. We have the oddest conversations and, this week, we are asking for your help. It is no secret that we have a special badge each year for Supercon. Have you ever wondered where those badges come from? Sometimes we do too. We can’t tell you what the badge is going to be for Supercon 2023, but here’s a chance for you to contribute to its design.
What I can tell you is that at least part of the badge is analog. Part, too, is digital. So we were discussing a seemingly simple question: How do we best generate a bipolar power source for the op amps on a badge? Like all design requests, this one is unreasonable. We want:
Continue reading “Ask Hackaday: Split Rail Op Amp Power Supply”
We’ve always been a little sad that supercapacitors aren’t marked with a big red S on a yellow background. Nevertheless, [DiodeGoneWild] picked up some large-value supercapacitors and used his interesting homemade oscilloscope to examine how they worked. You can watch what he is up to in his workshop in the video below.
Supercapacitors use special techniques to achieve very high capacitance values. For example, the first unit in the video is a 500 F capacitor. That’s not a typo — not microfarads or even millifarads — a full 500 Farads. With reasonable resistance, it can take a long time to charge 500F, so it is easier to see the behavior, especially with the homemade scope, which probably won’t pick up very fast signals.
For example, A 350 mA charging current takes about an hour to bring the capacitor up to 2.6 V, just under its maximum rating of 2.7 V. Supercapacitors usually have low voltage tolerance. Their high capacity makes them ideal for low-current backup applications where you might not want a rechargeable battery because of weight, heat, or problems with long-term capacity loss.
The real star of the video, though, is the cast of homemade test equipment, including the oscilloscope, a power supply, and a battery analyzer. To be fair, he also has some store-bought test gear, too, and the results seem to match well.
Supercapacitors are one of those things that you don’t need until you do. If you haven’t had a chance to play with them, check out the video or at least watch it to enjoy the homebrew gear. We usually look to [Andreas Spiess] for ESP32 advice, but he knows about supercaps, too. If you really like making as much as you can, you can make your own supercapacitors.
Continue reading “Homemade Scope Does Supercapacitor Experiments”
The 16×2 LCD display is a classic in the microcontroller world, and for good reason. Add a couple of wires, download a library, mash out a few lines of code, and your project has a user interface. A utilitarian and somewhat boring UI, though, and one that can be hard to read at a distance. So why not spice it up with these large-type custom fonts?
As [upir] explains, the trick to getting large fonts on a display that’s normally limited to two rows of 16 characters each lies in the eight custom characters the display allows to be added to its preprogrammed character set. These can store carefully crafted patterns that can then be assembled to make reasonable facsimiles of the ten numerals. Each custom pattern forms one-quarter of the finished numeral, which spans what would normally be a two-by-two character matrix on the display. Yes, there’s a one-pixel wide blank space running horizontally and vertically through each big character, but it’s not that distracting.
Composing the custom patterns, and making sure they’re usable across multiple characters, is the real hack here, and [upir] put a lot of work into that. He started out in Illustrator, but quickly switched to a spreadsheet because it allowed him to easily generate the correct binary numbers to pass to the display for each pattern. It seems to have really let his creative juices flow, too — he came up with 24 different fonts! Our favorite is the one he calls “Tron,” which looks a bit like the magnetic character recognition font on the bottom of bank checks. Everyone remembers checks, right?
Hats off to [upir] for a creative and fun way to spice up the humble 16×2 display. We’d love to see someone pick this up and try a complete alphanumeric character set, although that might be a tall order with only eight custom characters to work with. Then again, if Bad Apple on a 16×2 is possible…
Continue reading “Spice Up The Humble 16×2 LCD With Big Digits”
For most of us, vacuum tubes haven’t appeared in any of our schematics or BOMs in — well, ever. Once mass-manufacturing made reliable transistors cheap enough for hobbyists, vacuum tubes became pretty passe, and it wasn’t long before the once mighty US tube industry was decimated, leaving the few remaining tube enthusiasts to ferret out caches of old stock, or even seek new tubes from overseas manufacturers.
However, all that may change if [Charles Whitener] succeeds in reshoring at least part of the US vacuum tube manufacturing base. He seems to have made a good start, having purchased the Western Electric brand from AT&T and some of its remaining vacuum tube manufacturing equipment back in 1995. Since then, he has been on a talent hunt, locating as many people as possible who have experience in the tube business to help him gear back up. Continue reading “Reshoring Vacuum Tube Manufacturing, One Tube At A Time”
Anyone who works with older electronic equipment will before long learn to spot Rifa capacitors, a distinctive yellow-translucent component often used in mains filters, that is notorious for failures. It’s commonly thought to be due to their absorbing water, but based upon [Jerry Walker]’s long experience, he’s not so sure about that. Thus he’s taken a large stock of the parts and subjected them to tests in order to get to the bottom of the Rifa question once and for all.
What he was able to gather both from the parts he removed from older equipment and by applying AC and DC voltages to test capacitors, was that those which had been used in DC applications had a much lower likelihood of exhibiting precursors to failure, and also a much longer time before failure when connected to AC mains.
Indeed, it’s only at the end of the video that he reveals one of the parts in front of him is an ex-DC part that’s been hooked up to the mains all the time without blowing up. It’s likely then that these capacitors didn’t perform tot heir spec only when used in AC applications. He still recommends replacing them wherever they are found and we’d completely agree with him, but it’s fascinating to have some light shed on these notorious parts.
If you’ve done any amount of electronic design work, you’ll be familiar with the need for decoupling capacitors. Sometimes a chip’s datasheet will tell you exactly what kind of caps to place where, but quite often you’ll have to rely on experience and rules of thumb. For example, you might have heard that you should put 100 µF across the power supply pins and 100 nF close to each chip. But how close is “close”? And can that bigger cap really sit anywhere? [James Wilson] has been doing research to get some firm answers to those questions, and wrote down his findings in a fascinating blog post.
[James] designed a set of circuit boards that enabled him to place different types of capacitors at various distances along a set of PCB traces. By measuring the impedance of such a power distribution network (PDN) across frequency, he could then calculate its performance under different circumstances.
The ideal tool for those measurements would have been a vector network analyzer (VNA), but because [James] didn’t have such an instrument, he made a slightly simpler setup using a spectrum analyzer with a tracking generator. This can only measure the impedance’s magnitude, without any phase information, but that should be good enough for basic PDN characterization.
The results of [James]’s tests are pretty interesting, if not too surprising. For example, those 100 nF capacitors really ought to be placed within 10 mm of your chip if it’s operating at 100 MHz, but you can get away with even 10 cm if no signals go much above 1 MHz. A bulk 100 µF cap can be placed at 10 cm without much penalty in either case. Combining several capacitors of increasing size to get a low impedance across frequency is a good idea in principle, but you need to design the network carefully to avoid resonances between the various components. This is where a not-too-low equivalent series resistance (ESR) is actually a good thing, because it helps to dampen those resonances.
Overall, [James]’s blog post is a good primer on the topic, and gives a bit of much-needed context to those rules of thumb. If you want to dive deeper into the details of PDN design or the inductance of PCB traces, our own [Bil Herd] has made some excellent videos on those topics.
