Copper: Rectifying AC A Century Ago

April 20, 2022 by Dave Rowntree 32 Comments

[Robert Murray-Smith] presents for us an interesting electronic device from years gone by, before the advent of Silicon semiconductors, the humble metal oxide rectifier. After the electronic dust had settled following the brutal AC/DC current wars of the late 19th century — involving Edison, Tesla and Westinghouse to name a few of the ringleaders — AC was the eventual winner. But there was a problem. It’s straightforward to step down the high voltage AC from the distribution network to a more manageable level with a transformer, and feed that straight into devices which can consume alternating current such as light bulbs and electrical heaters. But other devices really want DC, and to get that, you need a rectifier.

It turns out, that even in those early days, we had semiconductor devices which could perform this operation, based not upon silicon or germanium, but copper. Copper (I) Oxide is a naturally occurring P-type semiconductor, which can be easily constructed by heating a copper sheet in a flame, and scraping off the outer layer of Copper (II) Oxide leaving the active layer below. Simply making contact to a piece of steel is sufficient to complete the device.

Obviously a practical rectifier is a bit harder to make, with a degree of control required, but you get the idea. A CuO metal rectifier can rectify as well as operate as a thermopile, and even as a solar cell, it’s just been forgotten about once we got all excited about silicon.

Other similar metallic rectifiers also saw some action, such as the Selenium rectifier, based on the properties of a Cadmium Selenide – Selenium interface, which forms an NP junction, albeit one that can’t handle as much power as good old copper. One final device, which was a bit of an improvement upon the original CuO rectifiers, was based upon a stack of Copper Sulphide/Magnesium metal plates, but they came along too late. Once we discovered the wonders of germanium and silicon, it was consigned to the history books before it really saw wide adoption.

We’ve covered CuO rectifiers before, but the Copper Sulphide/Magnesium rectifier is new to us. And if you’re interested in yet more ways to steer electrons in one direction, checkout our coverage of the history of the diode.

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What Goes Into A High Voltage Diode?

October 3, 2021 by Jenny List 12 Comments

When we use an electronic component, we have some idea of what goes on inside it. We know that inside a transistor there’s a little piece of semiconductor with a junction made from differently doped regions etched into it, and in a capacitor, there will be metalized plates on the surface of some kind of dielectric. Reverse engineering has given us extensive die photography of integrated circuits, but there remain a few component mysteries to be uncovered. One is laid bare by [WizardTim], as he cross-sections a 20KV high-voltage diode.

A conventional low-voltage silicon diode has a forward voltage drop of about 0.7V and a relatively low maximum reverse voltage, for example with the 1N4001 rectifier it’s 50V. For the higher-spec 1N4007, the reverse voltage rating is 700V. This diode has a 25KV reverse voltage, and a clue to its construction comes in its quoted 45V forward voltage. Sure enough, when mounted in resin and carefully sanded and polished flat it reveals its interior as a stack of diodes in series to increase the reverse voltage at the expense of forward voltage.

Revealing the inner workings of an unusual component is fascinating, and the lapping technique used is definitely worth a look. It’s something we’ve seen before, for example in reducing CPU thickness for increased performance.

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Hackaday Links: August 15, 2021

August 15, 2021 by Dan Maloney 13 Comments

Unless you’re in the market for a new car, household appliance, or game console, or if you’re involved in the manufacture of these things, chances are pretty good that the global semiconductor shortage hasn’t directly impacted you yet. But we hobbyists might be due for a comeuppance as the chip shortage starts to impact our corner of the market. We suppose it’s natural that supplies of the chips needed to build Arduinos and Raspberry Pis would start to dry up, as semiconductor manufacturers realign their resources to service their most lucrative markets. Still, it was all sort of abstract until now, but seeing dire quotes from the likes of Adafruit, Pololu, and Sparkfun about the long lead times they’re being quoted — some chips won’t be seen until 2023! — is disheartening. As are the reports of price gouging and even hoarding; when a $10 part can suddenly command $350, you know something has gone seriously wrong.

But have no fear — we’re certain the global chip shortage will have no impact on the planned 2027 opening of the world’s first space hotel. Voyager Station — once dubbed Von Braun Station but renamed for some reason — looks for all the world like Space Station V in “2001: A Space Odyssey”, or at least half of it. The thing is enormous — witness the Starship docked in the center hub, as well as the several dozen shuttle-like craft — escape pods, perhaps? — attached to the outer rim. The renders are imaginative, to say the least — the station looks very sleek, completely unfettered by such banalities as, say, solar panels. We get that a private outfit needs to attract deep-pocketed investors, and that one doesn’t do that by focusing on the technical details when they can sell a “premium experience”. But really, if you’re going to space, do you want basically the same look and feel as a premium hotel on Earth, just with a better view? Or would you rather feel like you’ve actually traveled to space?

Speaking of space, did you ever wonder what the first programmable calculator in space was? Neither did we, but that doesn’t mean we didn’t find this detailed story about the HP-65 that was sent up on the Apollo-Soyuz Test Project in 1975 pretty fascinating. The ASTP was the last hurrah of Apollo, and an often underappreciated engineering challenge. Linking up the two spacecraft safely was not trivial, and a fair number of burn calculations had to be made in orbit to achieve rendezvous and docking, as well as to maintain orbit. The HP-65, a programmable calculator that went for about $750 at the time (for the non-space-rated version, of course) had several programs loaded onto its removable magnetic cards, and the Apollo crew used it to verify the results calculated by the Apollo Guidance Computer (AGC).

Facebook, a company that exists by providing people with a product they don’t need but now somehow can’t live without, is now dipping a toe into weird, weird waters: reverse-passthrough virtual reality. The idea, we take it, is that as users more widely adopt VR and integrate it into their daily lives, the VR headsets everyone will be wearing will make face-to-face contact more difficult. So what better way to solve that problem than by projecting a live image of the VR user’s eyes onto a screen outside the VR rig, for any and all to see? Pure genius, and not the least bit creepy. They’ve perhaps got a bit of work to go before achieving their goal of “seamless social connection between real and virtual worlds”.

And speaking of eyes, it’s good to know that developers are still hard at work keeping the most vital applications running at peak efficiency on today’s hardware. Yes, the venerable XEyes, a program for the X Window System on Unix-like operating systems that draws a pair of googly eyes on the screen to follow your mouse movements, has finally moved to version 1.2.0. It’s been 11 years since the 1.1.0 upgrade, so it was a long time coming. If you haven’t had the chance to play with XEyes, fear not — just about any Linux machine should be able to show you what you’ve been missing. Or, you know, you could even run it on a camera as the video below the break shows.

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Hackaday Links: July 18, 2021

July 18, 2021 by Dan Maloney 12 Comments

Tell the world that something is in short supply, and you can bet that people will start reacting to that news in the ways that make the most sense to them — remember the toilet paper shortage? It’s the same with the ongoing semiconductor pinch, except that since the item in short supply is (arguably) more valuable than toilet paper, the behavior and the risks people are willing to take around it are even more extreme. Sure, we’ve seen chip hoarding, and a marked rise in counterfeit chips. But we’d imagine that this is the first time we’ve seen chip smuggling quite like this. The smuggler was caught at the Hong Kong-Macao border with 256 Core i7 and i9 processors, valued at about $123,000, strapped to his legs and chest. It reminds us more of “Midnight Express”-style heroin smuggling, although we have to say we love the fact that this guy chose a power of 2 when strapping these babies on.

Speaking of big money, let’s say you’ve pulled off a few chip heists without getting caught, and have retired from the smuggling business. What is one to do with the ill-gotten gains? Apparently, there’s a big boom in artifacts from the early days of console gaming, so you might want to start spreading some money around there. But you’d better prepare to smuggle a lot of chips: last week, an unopened Legend of Zelda cartridge for the NES sold for $870,000 at auction. Not to be outdone, two days later someone actually paid $1.56 million for a Super Mario 64 cartridge, this time apparently still in the tamperproof container that displayed it on a shelf somewhere in 1996. Nostalgia can be an expensive drug.

And it’s not just video games that are commanding high prices these days. If you’ve got a spare quarter million or so, why not bid on this real Apollo Guidance Computer and DSKY? The AGC is a non-flown machine that was installed in LTA-8, the “lunar test article” version of the Landing Module (LM) that was used for vacuum testing. If the photos in the auction listing seem familiar, it’s with good reason: this is the same AGC that was restored to operating condition by Carl Claunch, Mike Stewart, Ken Shiriff, and Marc Verdiell. Sotheby’s estimates the value at $200,000 to $300,000; in a world of billionaire megalomaniacs with dreams of space empires, we wouldn’t be surprised if a working AGC went for much, much more than that.

Meanwhile, current day space exploration is going swimmingly. Just this week NASA got the Hubble Space Telescope back online, which is great news for astronomers. And on Mars, the Ingenuity helicopter just keeps on delivering during its “operations demonstration” mission. Originally just supposed to be a technology demonstration, Ingenuity has proven to be a useful companion to the Perseverance rover, scouting out locations of interest to explore or areas of hazard to avoid. On the helicopter’s recent ninth flight, it scouted a dune field for the team, providing photographs that showed the area would be too dangerous for the rover to cross. The rover’s on-board navigation system isn’t great at seeing sand dunes, so Ingenuity’s images are a real boon to mission planners, not to mention geologists and astrobiologists, who are seeing promising areas of the ancient lakebed to explore.

And finally, most of us know all too well how audio feedback works, and all the occasions to avoid it. But what about video feedback? What happens when you point a camera that a screen displaying the image from the camera? Fractals are what happens, or at least something that looks a lot like fractals. Code Parade has been playing with what he calls “analog fractals”, which are generated just by video feedback and not by computational means. While he’d prefer to do this old school with analog video equipment, it easy enough to replicate on a computer; he even has a web page that lets you arrange a series of virtual monitors on your screen. Point a webcam at the screen, and you’re off on a fractal journey that constantly changes and shifts. Give it a try.

Ask Hackaday: How Is The Chip Shortage Affecting You?

May 24, 2021 by Jenny List 133 Comments

Some friends of mine are designing a new board around the STM32F103 microcontroller, the commodity ARM chip that you’ll find in numerous projects and on plenty of development boards. When the time came to order the parts for the prototype, they were surprised to find that the usual stockholders don’t have any of these chips in stock, and more surprisingly, even the Chinese pin-compatible clones couldn’t be found. The astute among you may by now have guessed that the culprit behind such a commodity part’s curious lack of availability lies in the global semiconductor shortage.

A perfect storm of political unintended consequences, climate-related crises throttling Taiwanese chip foundries and shutting down those in the USA, and faulty pandemic recovery planning, has left the chipmakers unable to keep up with the demand from industries on the rebound from their COVID-induced slump. Particularly mentioned in this context is the automotive industry, which has seen plants closing for lack of chips and even models ditching digital dashboards for their analogue predecessors.

Chips on order everywhere on the Mouser website.

The fall-out from all this drama in the world’s car factories has filtered down through all levels that depend upon semiconductors; as the carmakers bag every scrap of chip fab capacity that they can, so in turn have other chip customers scrambled to keep their own supply lines in place. A quick scan for microcontrollers through distributors like Mouser or Digi-Key finds pages and pages of lines on back-order or out of stock, with those lines still available being largely either for niche applications, unusual package options, or from extremely outdated product lines. The chances of scoring your chosen chip seem remote and most designers would probably baulk at trying to redesign around an ancient 8-bit part from the 1990s, so what’s to be done?

Such things typically involve commercially sensitive information so we understand not all readers will be able to respond, but we’d like to ask the question: how has the semiconductor shortage affected you? We’ve heard tales of unusual choices being made to ship a product with any microcontroller that works, of hugely overpowered chips replacing commodity devices, and even of specialist systems-on-chip being drafted in to fill the gap. In a few years maybe we’ll feature a teardown whose author wonders why a Bluetooth SoC is present without using the radio functions and with a 50R resistor replacing the antenna, and we’ll recognise it as a desperate measure from an engineer caught up in 2021’s chip shortage.

So tell us your tales from the coalface in the comments below. Are you that desperate engineer scouring the distributors’ stock lists for any microcontroller you can find, or has your chosen device remained in production? Whatever your experience we’d like to know what the real state of the semiconductor market is, so over to you!

Hackaday Links: May 16, 2021

May 16, 2021 by Dan Maloney 19 Comments

With the successful arrival of China’s first Mars lander and rover this week, and the relatively recent addition of NASA’s Perseverance rover and its little helicopter sidekick Ingenuity, Mars has collected a lot of new hardware lately. But while the new kids on the block are getting all the attention, spare a thought for the reliable old warhorse which has been plying Gale Crater for the better part of a decade now — Curiosity. NASA has been driving the compact-car-sized rover around Mars for a long time now, long enough to rack up some pretty severe damage to its six highly engineered wheels, thanks to the brutal Martian rocks. But if you think Curiosity will get sidelined as its wheels degrade, think again — the rover’s operators have a plan to continue surface operations that includes ripping off its own wheels if necessary. It’s a complex operation that would require positioning the wheel over a suitable rock and twisting with the steering motor to peel off the outer section of the wheel, leaving a rim to drive around on. JPL has already practiced it, but they predict it won’t be necessary until 2034 or so. Now that’s thinking ahead.

With all the upheaval caused by the ongoing and worsening semiconductor shortage, it might seem natural to expect that manufacturers are responding to market forces by building new fabs to ramp up production. And while there seems to be at least some movement in that direction, we stumbled across an article that seems to give the lie to the thought that we can build our way out of the crisis. It’s a sobering assessment, to say the least; the essence of the argument is that 20 years ago or so, foundries thought that everyone would switch to the new 300-mm wafers, leaving manufacturing based on 200-mm silicon wafers behind. But the opposite happened, and demand for chips coming from the older 200-mm wafers, including a lot of the chips used in cars and trucks, skyrocketed. So more fabs were built for the 200-mm wafers, leaving relatively fewer fabs capable of building the chips that the current generation of phones, IoT appliances, and 5G gear demand. Add to all that the fact that it takes a long time and a lot of money to build new fabs, and you’ve got the makings of a crisis that won’t be solved anytime soon.

From not enough components to too many: the Adafruit blog has a short item about XScomponent, an online marketplace for listing your excess inventory of electronic components for sale. If you perhaps ordered a reel of caps when you only needed a dozen, or if the project you thought was a done deal got canceled after all the parts were ordered, this might be just the thing for you. Most items offered appear to have a large minimum quantity requirement, so it’s probably not going to be a place to pick up a few odd parts to finish a build, but it’s still an interesting look at where the market is heading.

Speaking of learning from the marketplace, if you’re curious about what brands and models of hard drives hold up best in the long run, you could do worse than to look over real-world results from a known torturer of hard drives. Cloud storage concern Backblaze has published their analysis of the reliability of the over 175,000 drives they have installed in their data centers, and there’s a ton of data to pick through. The overall reliability of these drives, which are thrashing about almost endlessly, is pretty impressive: the annualized failure rate of the whole fleet is only 0.85%. They’ve also got an interesting comparison of HDDs and SSDs; Backblaze only uses solid-state disks for boot drives and for logging and such, so they don’t get quite the same level of thrash as drives containing customer data. But the annualized failure rate of boot SDDs is much lower than that of HDDs used in the same role. They slice and dice their data in a lot of fun and revealing ways, including by specific brand and model of drive, so check it out if you’re looking to buy soon.

And finally, you know that throbbing feeling you get in your head when you’re having one of those days? Well, it turns out that whether you can feel it or not, you’re having one of those days every day. Using a new technique called “3D Amplified Magnetic Resonance Imaging”, or 3D aMRI, researchers have made cool new videos that show the brain pulsating in time to the blood flowing through it. The motion is exaggerated by the imaging process, which is good because it sure looks like the brain swells enough with each pulse to crack your skull open, a feeling which every migraine sufferer can relate to. This reminds us a bit of those techniques that use special algorithms to detects a person’s heartbeat from a video by looking for the slight but periodic skin changes that occurs as blood rushes into the capillaries. It’s also interesting that when we spied this item, we were sitting with crossed legs, watching our upper leg bounce slightly in time with our pulse.

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Silicon Carbide Chips Can Go To Hell

May 3, 2021 by Al Williams 75 Comments

IEEE Spectrum had an interesting read about circuits using silicon carbide as a substrate. [Alan Mantooth] and colleagues say that circuits based on this or some other rugged technology will be necessary for missions to Venus, which they liken to hell. That might seem like hyperbole, but at about 460C with an atmosphere full of sulphuric acid, maybe it isn’t such a stretch. When the Soviets sent Venera 13 to Venus, it was able to send data for just over two hours before it was gone. You’d hope 40 years later we could do better.

Silicon carbide is a semiconductor made with an even mix of silicon and carbon. The resulting components can operate for at least a year at 500C. This high-temperature operation has earned them a place in solar energy and other demanding applications. [Alan], with the University of Arkansas along with colleagues from the KTH Royal Insitute of Technology in Stockholm are building test circuits aimed at developing high-temperature radios for use in environments like the one found on Venus.

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