solenoid wound pickup coil next to a selection of bolts and a steel rod

The Barkhausen Effect: Hearing Magnets Being Born

The Barkhausen effect — named after German Physicist Heinrich Barkhausen — is the term given to the noise output produced by a ferromagnetic material due to the change in size and orientation of its discrete magnetic domains under the influence of an external magnetic field. The domains are small: smaller than the microcrystalline grains that form the magnetic material, but larger than the atomic scale. Barkausen discovered that as a magnetic field was brought close to a ferrous material, the local magnetic field would flip around randomly, as the magnetic domains rearranged themselves into a minimum energy configuration and that this magnetic field noise could be sensed with an appropriately arranged pickup coil and an amplifier. In the short demonstration video below, this Barkhausen noise can be fed into an audio amplifier, producing a very illustrative example of the effect.

One example of practical use for this effect is with non-destructive testing and qualification of magnetic structures which may be subject to damage in use, such as in the nuclear industry. Crystalline discontinuities or impurities within a part under examination result in increased localized mechanical stresses, which could result in unexpected failure. The Barkhausen noise effect can be easily leveraged to detect such discontinuities and give the evaluator a sense of the condition of the part in question. All in all, a useful technique to know about!

If you were thinking that the Barkhausen is a familiar name, you may well be thinking about the Barkhausen stability criterion, which is fundamental to describing some of the conditions necessary for a linear feedback circuit to oscillate. We’ve covered such circuits before, such as this dive into bridge oscillators.

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Raspberry Pi Simulates The Real Analog TV Experience

If you’ve laid hands on a retro analog TV, have the restoration bug, and you plan to make the final project at least somewhat period-correct, you face a bit of a conundrum: what are you going to watch? Sure, you can serve up just about any content digitally these days, but some programs just don’t feel right on an old TV. And even if you do get suitably retro programming, streaming isn’t quite the same as the experience of tuning your way through the somewhat meager selections as we did back in the analog days.

But don’t worry — this Raspberry Pi TV simulator can make your streaming experience just like the analog TV experience of yore. It comes to us from [Rodrigo], who found a slightly abused 5″ black-and-white portable TV that was just right for the modification. The battery compartment underneath the set made the perfect place to mount a Pi, which takes care of streaming a variety of old movies and shorts. The position of the original tuning potentiometer is read by an Arduino, which tells the Pi which “channel” you’re currently tuned to.

Composite video is fed from the Pi’s output right into the TV’s video input, and the image quality is just about what you’d expect. But for our money, the thing that really sells this is the use of a relay to switch the TV’s tuner back into the circuit for a short bit between channel changes. This gives a realistic burst of static and snow, just like we endured in the old days. Hats off to [Rodrigo] for capturing everything that was awful about TV back in the day — Mesa of Lost Women, indeed! — but still managing to make it look good.

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Nanovolt Meter Requires Careful Design For Accuracy’s Sake

Measuring voltages is fairly straightforward most of the time. Simply grab any old cheap multimeter, hook up the probes, and read off the answer. If, however, you need to measure very tiny voltages, the problem gets more complex. [Jaromir-Sukuba] designed a nanovoltmeter specifically to deal with this difficult case.

The nanovoltmeter is exactly what it sounds like: a voltmeter that is sensitive and stable enough to measure and report voltages on the scale of nanovolts. Having a tool that can do this reliably can be very useful when it comes to measuring very small resistances or working with ever-so-slight differential voltages. Continue reading “Nanovolt Meter Requires Careful Design For Accuracy’s Sake”

EMC Tutorial Puts You In The Loop

A student once asked his lab instructor why his amplifier was oscillating. After looking at it and noting the wild construction, the instructor remarked, “A better question would be why shouldn’t it oscillate?” The truth of it is, our circuits generate noise and especially if they are oscillating anyway. Distortion and nonlinearities generate harmonics and other component imperfections also contribute.

[FesZ Electronics] has a great video series about noise in switching power supplies and the latest talks about the hot loop. If you want to improve the noise performance of your next design, these videos are well worth watching. You can see the hot loop video below.

We really liked the homebrew noise probes. In addition to real-world probing. The video also observes circuit operation under simulation. Even if you don’t care about noise performance, there’s a lot of good information about basic switching power supply design here.

You can see the difference in a PCB that has a small hot loop versus a very small hot loop. Something to think about next time you are laying out a power supply board.

If you want to dive deeper into noise simulation, we have a good read on that for you. Or ditch simulation, and make your own cheap probe with an SDR dongle.

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Hackaday Links: July 11, 2021

Well, at least the acronym will stay the same. It looks like black is the new blue for Windows 11, as the BSOD screen gets its first makeover in years. It’s an admittedly minor change, since the on-screen text is virtually identical to the BSOD from recent versions of Windows 10, and the new death-knell even sports the same frowny-face emoji and QR code. Really, the white-on-black color scheme is the only major difference we can see — even the acronym will stay the same. It’s not really that newsworthy, we suppose, although it does make us miss the extremely busy BSODs from back in the Windows NT days.

As the semiconductor shortage continues, manufacturers are getting desperate to procure the parts they need to make their products. And if there’s one thing as certain as death and taxes, it’s that desperation provides opportunity to criminals. A thread over on EEVBlog details an encounter one company had with an alleged scammer, who sent an unsolicited offer to them for a large number of ordinarily hard-to-find microprocessors at a good price. Wisely, the company explored the offer in some depth and found that “Brian” (the representative who contacted them) is actually named Nick Martin and, according to an article on the Electronic Resellers Association International (ERAI) website, is apparently associated with a number of fraudulent operations. Their list of allegedly fraudulent deals made by Mr. Martin stretches back to 2018 and totals over $300,000 of ill-gotten gain.

Last year, friend-of-Hackaday and laser artist Seb Lee-Delisle spent a lot of time and effort getting together an amazing interactive laser light show for the night skies of cities in the UK. Laser Light City, with powerful lasers mounted on the tops of tall buildings, was a smashing success that brought a little cheer into what was an otherwise dreadful time. But we have to admit that the videos and other materials covering Laser Light City left us wanting more — something like that, with a far-flung installation on rooftops and the ability for audience members to control it all from their phone, really needs a deeper “how it works” treatment. Thankfully, Seb has released a video that dives into the nuts and bolts of the show, including a look at ludicrously powerful lasers with beams that can still be seen in broad daylight.

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Bricking Your 3D Printer, In A Good Way

In our vernacular, bricking something is almost never good. It implies that something has gone very wrong indeed, and that your once-useful and likely expensive widget is now about as useful as a brick. Given their importance to civilization, that seems somewhat unfair to bricks, but it gets the point across.

It turns out, though, that bricks can play an important role in 3D-printing in terms of both noise control and print quality. As [Stefan] points out in the video below, living with a 3D printer whirring away on a long print can be disturbing, especially when the vibrations of the stepper motors are transmitted into and amplified by a solid surface, like a benchtop. He found that isolating the printer from the resonant surface was the key. While the stock felt pad feet on his Original Prusa i3 Mk 3S helped, the best results were achieved by building a platform of closed-cell packing foam and a concrete paver block. The combination of the springy foam and the dampening mass of the paver brought the sound level down almost 8 dBA.

[Stefan] also thoughtfully tested his setups on print quality. Machine tools generally perform better with more mass to damp unwanted vibration, so it stands to reason that perching a printer on top of a heavy concrete slab would improve performance. Even though the difference in quality wasn’t huge, it was noticeable, and coupled with the noise reduction, it makes the inclusion of a paver and some scraps of foam into your printing setup a no-brainer.

Not content to spend just a couple of bucks on a paver for vibration damping? Then cast a composite epoxy base for your machine — either with aluminum or with granite.

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Understanding A Bit About Noise Can Help You Go A Long Way

There are many ways in which one’s youth can be misspent, most of which people wish they’d done when they get older and look back on their own relatively boring formative years. I misspent my youth pulling TV sets out of dumpsters and fixing them or using their parts in my projects. I recognise with hindsight that there might have been a few things I could have done with more street cred, but for me, it was broken TVs. Continue reading “Understanding A Bit About Noise Can Help You Go A Long Way”