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Hackaday Links: September 12, 2021

The last thing an astronaut or cosmonaut on the International Space Stations wants to hear from one of their crewmates is, “Do you smell plastic burning?” But that’s apparently what happened this week aboard the increasingly problematic spacecraft, as the burning smell and visible smoke spread from the Russian Zvezda module to the American side of town. The reports say it occurred while charging the station’s batteries, and we all know how dicey that can get. But apparently, the situation resolved itself somehow, as normal operations continued soon after the event. Between reports of cracks, air leaks, problems with attitude control, and even accusations of sabotage, the ISS is really starting to show its age.

Speaking of burning and batteries, normally a story about burning Tesla batteries wouldn’t raise our eyebrows much. But this story out of California introduces a potential failure mode for Tesla batteries that we hadn’t considered before. It seems a semi-truck with a load of Tesla batteries lost its brakes on Interstate 80 in the Sierra Nevada mountains and ended up flipping across the highway. Video from the scene shows the cargo, which looks like replacement batteries or perhaps batteries salvaged from wrecked cars, scattered across the highway on their shipping pallets. A fire was reported, but it’s not clear whether it was one of the batteries which had gotten compromised in the crash, or if it was something other than the batteries. Still, we hadn’t considered the potential for disaster while shipping batteries like that.

Attention all GNURadio fans — GRCon21 is rapidly approaching. Unlike most of the conferences over the last year and half, GRCon21 will actually be both live and online. We always love the post-conference dump of talks, which cover such a wide range of topics and really dive deeply into so many cool areas. We’re especially looking forward to the SETI talks, and we’re pleased to see our friend Hash, who was on the Hack Chat a while back, scheduled to talk about his smart-meter hacking efforts. The conference starts on September 20 and is being held in Charlotte, North Carolina, and virtually of course. If you attend, make sure to drop tips to your favorite talks in the tips line so we can share them with everyone.

We got a tip this week on a video about how 1/4-wave tuning stubs work. It’s a simple demonstration using a length of coax, a signal generator, and an oscilloscope to show how an unterminated feedline can reflect RF back to the transmitter, and how that can be used to build super-simple notch filters and impedance transformers. We love demos that make the mysteries of RF a little simpler — W2AEW’s videos come to mind, like this one on standing waves.

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Make Some Noise Or Simulate It, At Least

Noise is a fact of life, especially in electronic circuits. But on our paper schematics and just as often our simulations, there is no noise. If you are blinking an LED on a breadboard, you probably don’t care. But if you are working on something meatier, handling electrical noise gracefully is important and simulation can help you. [Ignacio de Mendizábal] has a great piece on simulating EMC filters using LTSpice that can get you started.

There are many ways of classifying noise and [Ignacio] starts with common-mode versus differential noise, where common-mode is noise with current flowing in the same direction without regard to the circuit’s normal operation, and differential noise having currents that flow in the opposite direction of normal current flow.

Continue reading “Make Some Noise Or Simulate It, At Least”

Camera Sees Electromagnetic Interference Using An SDR And Machine Vision

It’s one thing to know that your device is leaking electromagnetic interference (EMI), but if you really want to solve the problem, it might be helpful to know where the emissions are coming from. This heat-mapping EMI probe will answer that question, with style. It uses a webcam to record an EMI probe and the overlay a heat map of the interference on the image itself.

Regular readers will note that the hardware end of [Charles Grassin]’s EMI mapper bears a strong resemblance to the EMC probe made from semi-rigid coax we featured recently. Built as a cheap DIY substitute for an expensive off-the-shelf probe set for electromagnetic testing, the probe was super simple: just a semi-rigid coax jumper with one SMA plug lopped off and the raw end looped back and soldered. Connected to an SDR dongle, the probe proved useful for tracking down noisy circuits.

[Charles]’ project takes that a step further by adding a camera that looks down upon the device under test. OpenCV is used to track the probe, which is moved over the DUT manually with the help of an augmented reality display that helps track coverage, with a Python script recording its position and the RF power measurements. The video below shows the capture process and what the data looks like when reassembled as an overlay on top of the device.

Even if EMC testing isn’t your thing, this one seems like a lot of fun for the curious. [Charles] has kindly made the sources available on GitHub, so this is a great project to just knock out quickly and start mapping.

Continue reading “Camera Sees Electromagnetic Interference Using An SDR And Machine Vision”

A DIY EMC Probe From Semi-Rigid Coax And An SDR

Do you have an EMC probe in your toolkit? Probably not, unless you’re in the business of electromagnetic compatibility testing or getting a product ready for the regulatory compliance process. Usually such probes are used in anechoic chambers and connected to sophisticated gear like spectrum analyzers – expensive stuff. But there are ways to probe the electromagnetic mysteries of your projects on the cheap, as this DIY EMC testing setup proves.

As with many projects, [dimtass]’ build was inspired by a video over on EEVblog, where [Dave] made a simple EMC probe from a length of semi-rigid coax cable. At $10, it’s a cheap solution, but lacking a spectrum analyzer like the one that [Dave] plugged his cheap probe into, [dimtass] went a different way. With the homemade probe plugged into an RTL-SDR dongle and SDR# running on a PC, [dimtass] was able to get a decent approximation of a spectrum analyzer, at least when tested against a 10-MHz oven-controlled crystal oscillator. It’s not the same thing as a dedicated spectrum analyzer – limited bandwidth, higher noise, and not calibrated – but it works well enough, and as [dimtass] points out, infinitely hackable through the SDR# API. The probe even works decently when plugged right into a DSO with the FFT function running.

Again, neither of these setups is a substitute for proper EMC testing, but it’ll probably do for the home gamer. If you want to check out the lengths the pros go through to make sure their products don’t spew signals, check out [Jenny]’s overview of the EMC testing process.

[via RTL-SDR.com]

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Hackaday Links: February 11, 2018

Are you a student? Are you part of a hackerspace? We have a contest going on right now where you can win a fancy new Prusa i3 MK3. The Repairs You Can Print contest is a challenge to do something useful with that machine that spits out tugboats. We’re looking for functional repairs of items around your house, office, or garage. Did you repair something with a 3D printer? Then you too can get in on the action! Enter now! Check out the entries!

You may know Flite Test as the group who do everything surrounding remote control flight (mostly fixed wings, a nice counter to the quadification of the hobby over the last few years). Flite Test designs and sells airplanes made out of Dollar Tree foam board, they have yearly, bi-coastal meetups, and they’re all-around awesome dudes. Now, they want to build the Disneyland of RC flight. [Josh Bixler], the face of Flite Test and a guy who has a plane named after him, wants to buy a golf course and turn it into the world’s best RC flying park, with a ~2000 foot grass strip for general aviation. We’re looking at their crowdfunding campaign, and it looks promising it might be funded by the time this goes live.

A while ago, [Peter Jansen], the guy who built a tricorder and a laser-cut CT scanner, made a magnetic camera. This Hall Effect camera is a camera for magnetism instead of light. Now, this camera has been fully built and vastly improved. He’s capturing ‘frames’ of magnetism in a spinning fan at 2000 Hz (or FPS, terminology kind of breaks down here), and it’s beautiful.

Oh thank God we can finally buy GPUs again. Try buying them with Bitcoin.

In the last few years, CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, has expanded. Originally, this was one of the treaties that banned the import or export of rhino horn, but recently this expanded to the export of rosewood thanks to increased demand in China for rosewood furniture. The laws of unintended consequences kicked into effect, and importing anything made out of rosewood is now a mess of permits and inspections at the border, including musical instruments. Travelling orchestras, for example, are at risk of having their string section confiscated because of rosewood tuning pegs. Cooler minds may now be prevailing, and there’s some hope the regulations may be changed during the next meeting of the CITES convention next year.

As noted a few months ago, there was a possibility of Broadcom buying Qualcomm for one… hundred… Billion dollarsThis offer was rejected, with Qualcomm saying the offer wasn’t high enough. Broadcom fired back with an offer of $82 per share, or $121B. This offer was rejected this week.

Need some EMC testing? [Zach]’s got your back. He’s reserved some time in a 10m EMC chamber for testing NeuroBytes this week. If you have an Open Source project that needs a pre-test scan for unintentional radiator, you can get in on the action. This is just a pre-test, you’re not getting certification, and you’re not going to test anything with radios, and you need to ship [Zach] your stuff. But still, free test time. Woo.

One Man’s Tale Of EMC Compliance Testing

If you turn over almost any electronic device, you should find all those compliance logos: CE, FCC, UL, TÜV, and friends. They mean that the device meets required standards set by a particular region or testing organisation, and is safe for you, the consumer.

Among those standards are those concerning EMC, or ElectroMagnetic Compatibility. These ensure that the device neither emits RF radiation such that it might interfere with anything in its surroundings, nor is it unusually susceptible to radiation from those surroundings. Achieving a pass in those tests is something of a black art, and it’s one that [Pero] has detailed his exposure to in the process of seeing a large 3-phase power supply through them. It’s a lengthy, and fascinating post.

He takes us through a basic though slightly redacted look at the device itself, before describing the testing process, and the EMC lab. These are fascinating places with expert staff who can really help, though they are extremely expensive to book time in. Since the test involves a mains power supply he describes the Line Impedance Stabilisation Network, or LISN, whose job is to safely filter away the RF component on the mains cable, and present a uniform impedance to the device.

In the end his device failed its test, and he was only able to achieve a pass with a bit of that black magic involving the RF compliance engineer’s secret weapons: copper tape and ferrite rings. [Pero] and his colleagues are going to have to redesign their shielding.

We’ve covered our visits to the EMC test lab here before.

RF Noise Floor Concerns From Both Sides Of The Atlantic

Our feed is full of stories about the RF noise floor today, and with good reason. The ARRL reports on the International Amateur Radio Union Region 1 president, [Don Beattie, G3BJ] warning that in densely populated parts of Europe there is a danger that parts of the RF spectrum have become so swamped with noise as to be rendered unusable, while on the other side of the Atlantic we have RadioWorld reporting on similar problems facing AM broadcasting in the USA.

At issue are the usual suspects, interference from poorly shielded or suppressed domestic electronic devices, VDSL broadband, power-over-Ethernet, solar and wind power systems, and a host of other RF-spewing electronics. The combined emissions from all these sources have raised the noise level at some frequencies to the point at which it conceals all but the strongest signals. Any radio amateur will tell you that a station in a rural location will be electrically much quieter than one in a city, it seems that this effect has now reached a crescendo.

In the RadioWorld article, the author [Tom F. King] and his collaborator [Jack Sellmeyer] detail a series of tests they performed on a selection of lighting products from a quality brand, bought at a local Home Depot store. They were gathering data for a submission to the FCC enquiry on the noise floor issue we reported on last year. What they found was unsurprising, significant emissions from all the products they tested. They make some stiff recommendations to the FCC and other bodies concerned with radio spectrum to get tough with offending devices, to stay on top of future developments, and for operators of AM stations to pursue sources of interference.

It could be that there is so much equipment contributing to the noise floor that this battle is lost, but it doesn’t have to be this way. Anyone who has had to prepare a product to pass a properly carried out EMC test will tell you that the requirements are stringent, and it is thus obvious that many manufacturers are shipping products unworthy of the certification they display. It is to be hoped that the authorities will begin to take it seriously before it becomes an order of magnitude worse.

Compliance label image, Moppet65535 [CC BY-SA 3.0].