Science

1375 Articles

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

The Barkhausen Effect: Hearing Magnets Being Born

November 19, 2022 by 21 Comments

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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Logic Via DNA

November 17, 2022 by 8 Comments

We often say you can make logic gates out of nearly anything. [Steve Mould] would agree as he just finished playing naughts and crosses (tic tac toe if you are an American) with a tray full of DNA. You can see the resulting game and how it works in the video below.

The use of DNA isn’t really significant as it simply implements a logic equation for each of the nine cells. So, for example, each cell is taken by an X (the DNA) only when certain other squares have been taken by O or not taken by O. So you essentially create an AND/OR gate using the state of each cell and its inverse.

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A two picture montage with the left montage showing a pair of hands holding an assembled and closed turbidity sensor and the right picture showing A pair of hands holding the screw on cap for the turbidity sensor and a prototype board against a backdrop of green leave

Rapid Prototyping To Measure Turbidity In Rapids

November 15, 2022 by 6 Comments

[RiverTechJess] is in the process of getting a PhD in environmental engineering and has devoted a chapter to creating a turbidity sensor for river network monitoring. Environmental sensing benefits from being able to measure accurately and frequently, so providing low cost devices helps get more data and excuse the occasional device loss that’s bound to happen when deploying electronics out in the wild. Towards this end, [RiverTechJess] has created a low cost turbidity sensor that rivals the more expensive alternatives in cost and accuracy.

The turbidity sensor is designed to be at least partially submerged allowing for the LED and light sensors to be be able to take measurements. [RiverTechJess] has made a 3D printed prototype to test the design, allowing for rapid experimentation and deployment of the sensors to work out issues. The 3D printed enclosure prototype uses rubber o-rings and “vacuum grease” to provide a watertight seal. An ESP32 microcontroller is used to store logged data on an SD card and drive the TSHG6200 850nm infrared LED and the two TSL237S-LF sensors.

The resulting paper on the turbidity sensor, in addition to the blogs of the process, provide a wealth of data that show what goes into developing and calibrating a device that is meant to be used for environmental monitoring. All source code is available on GitHub and development continues on a newer revision of the turbidity sensor with updated electronics and hardware.

We’re no strangers to water sensors and we’ve seen devices from internet connected water pollution monitors to small handheld potable water detectors.

Video after the break!

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The Blood Factory: New Research May Open The Door To Artificial Blood

November 15, 2022 by 37 Comments

There were news stories afoot this week with somewhat breathless headlines that suggested a medical breakthrough was at hand: “In a 1st, two people receive transfusions of lab-grown blood cells.” A headline like that certainly catches the eye, especially as the holidays approach and the inevitable calls for increased blood donations that always seem to happen this time of year as the supply gets pinched. Does a headline like that mean that someone is working on completely artificial blood?

As always with this sort of thing, the answer is a mixed bag. Yes, a team in the UK has transfused two patients with a small amount of lab-grown red blood cells, and it’s the first time that particular procedure has been performed. But while the headline is technically correct, the amount transfused was very small, so the day when lab-grown whole blood transfusions replace donated blood isn’t exactly here yet. But the details of what was done and why it was attempted are the really interesting part here, and it’s worth a deep dive because it does potentially point the way to a future where totally synthetic blood may be a real thing.

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Three Norths Align, And It’s Not Even Up North

November 8, 2022 by 7 Comments

Sometimes here at Hackaday we bring you stories from slightly outside our world of tech, because they have an interesting angle. Maybe they relate to science or astronomy, or in the case of the UK’s Ordnance Survey explaining how Britain’s three Norths will align, geography.

Some of you may know that the British monarch has two birthdays, but three Norths, what on earth is going on? You’ll guess that two of them are true North, pointing to the North Pole, and magnetic North, pointing to the Earth’s north magnetic field, but how about the third? It’s grid North — the north of the country’s mapping grid system in which the curved surface is projected onto a flat sheet.

It aligns with true North at 2 degrees West of Greenwich, and the news is that for the first time ever due to movement of the magnetic North Pole, the three different Norths will align at a point in the south of England. Magnetic North has been on the move at some pace over the last few decades, from a position somewhere in the Canadian Arctic islands northwards, and it so happens that for Brits its direction is briefly aligned with our view of the Pole. The Ordnance Survey story is of some interest, but for a wealth of information it’s worth consulting NASA. Take a look at the video below the break.

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Dosimetry: Measuring Radiation

November 7, 2022 by 21 Comments

Thanks to stints as an X-ray technician in my early 20s followed by work in various biology labs into my early 40s, I’ve been classified as an “occupationally exposed worker” with regard to ionizing radiation for a lot of my life. And while the jobs I’ve done under that umbrella have been vastly different, they’ve all had some common ground. One is the required annual radiation safety training classes. Since the physics never changed and the regulations rarely did, these sessions would inevitably bore everyone to tears, which was a pity because it always felt like something I should be paying very close attention to, like the safety briefings flight attendants give but everyone ignores.

The other thing in common was the need to keep track of how much radiation my colleagues and I were exposed to. Aside from the obvious health and safety implications for us personally, there were legal and regulatory considerations for the various institutions involved, which explained the ritual of finding your name on a printout and signing off on the dose measured by your dosimeter for the month.

Dosimetry has come a long way since I was actively considered occupationally exposed, and even further from the times when very little was known about the effects of radiation on living tissue. What the early pioneers of radiochemistry learned about the dangers of exposure was hard-won indeed, but gave us the insights needed to develop dosimetric methods and tools that make working with radiation far safer than it ever was.

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Conducting Plastic Can Replace Metal

November 6, 2022 by 45 Comments

The University of Chicago has announced they have created a material that behaves like plastic but conducts like metal. They also say they don’t fully understand why it works yet. Usually, good conductors like metals have very orderly atomic structures, something that plastics tend not to have.

The material is based on nickel, carbon, and sulfur. The resulting material was conductive and stable. However, the atomic structure isn’t orderly like a traditional conductor.

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