Hackaday Prize Entry: Measuring 3D Magnetic Fields

Sometimes you have to start out with big goals. Ninth-graders [Finja Schneider] and [Myrijam Stoetzer] are aiming to make a magnetic field scanner that would be helpful in finding large underground metallic objects, like unexploded WWII bombs that pose a real threat whenever a new parking garage is excavated in Germany. But even big goals have to start out somewhere, so they’re gaining experience with the sensors and the math necessary to recreate 3D magnetic flux vector fields on household objects like sawblades and magnetized screwdrivers.

Magnetized screwdriver in the "valley"
Magnetized screwdriver in the “valley”

For their science-fair project, [Finja] and [Myrijam] took a mid-80s fischertechnik “toy” 2D scanner kit, mounted a 3D magnetic sensor to it, and wrote some firmware to scan around and pass the data back to a computer where they reconstructed the field lines and made some nice visualizations. Along the way, they tried a number of designs, from a DIY chassis on carbon-fiber rails to sensors with ferrofluid. They document their successes and failures equally nicely in their lab report (PDF, German). You can get a lot of the gist, however, from [Myrijam]’s blog and their Hackaday.io entry.

You might also recognize [Myrijam] from her work with [Paul Foltin] on their eye-controlled wheelchair interface. These are some really cool projects! We’re excited to see how they develop, and are stoked that the future of hacking is in such capable hands.

28 thoughts on “Hackaday Prize Entry: Measuring 3D Magnetic Fields

    1. ops he mistaked

      I’ve wanted to make a RC truck-based low resolution metal detector.
      This project looks really good, especially if it can reliably detect objects underground.

  1. “unexploded WWII bombs that pose a real threat whenever a new parking garage is excavated in German”

    Not the best example:
    It´s literally NOTHING compared to the two millions of metric tons of bombs that were spread on Laos between 1964 and 1973 …
    Only 1/3 of those 270 millions of bombs exploded at the time, but the after-effects are still going on: only 1% of the land surface has been cleared of buried bombs, today 40% of victims are children.

    And today the US budget allowed to cleaning that mess is around 83 Mio USD.
    Compare it to the budget of the terrible F-35 …

    1. Sure, nevertheless in some german (and austrian) cities it is almost common to read about bomb disarming on building sites. The horrible lesson for humankind is that these relics of war stay on ground for a long term. See for example http://www.dailymail.co.uk/news/article-3125088/Inside-toxic-grave-longest-battle-history-French-forest-300-000-died-300-days-Battle-Verdun-littered-bodies-arsenic-unexploded-shells-grows-100-years.html I bet you would find something comparable on battlefields from earlier wars. It’s only a few years that the convention on cluster bombs got into place (not signed by many nations including the US), so we’ll have a long way to get used to contaminated soil.

      1. I wanted to point out that HaD in it immense gentleness toward US military-industrial complex, I always keen to choose the examples that glorify US, but not so much on those which give a not-so-good image of this country.
        Yes every war leaves bombs scars for a long time. But what has been done to Laos is beyond imagination, and very little known from US citizens.

      2. It’s not common to hear about it in other countries, usually the poorest ones, because fuck those guys, they’re not white, we don’t identify or empathise with them. Even though they suffer much more from mines, than the occasional 70 year old bomb turning up in Germany, which has the money and the organisation necessary to make the effort of removing them.

        Land mines are a great example of modern war, as far as the rich spending so much on scattering them, money’s no object, then the poorest being killed and mutilated for years afterward. Because we don’t have the money to help them.

        Geek-wise, there’s technologies available, and developing, that might help mines become safer after a war, where they can be located, or remotely disarmed, electronically.

        1. But it would be enough if the rich countries stop manufacturing these weapons.

          There are many companies specializing in disarming, but mines are intrinsically built to be not detectable (for example plastic body), so often the brute force way is used.

          And Yes, it’s a shame that in most cases the innocent people get hurt. Even worse if there is no sufficient help afterwards, no question.

          That would be a project for a HaD-price…

      1. Or a challenge!

        Doesn’t matter. You can always follow-up if you really need to fix your error. Most of the time nobody cares about typos or a bit of a mistake or whatever, we all know there’s no editing, we’re used to it.

        It could be implemented, but perhaps not easily, particularly with the no-registration system HAD uses, which I, and I think many others, like a lot. Of course we can’t have people editing other people’s posts.

        We could have editing, but could we keep all the advantages and features we have now? Feel free to take that as an intellectual challenge.

  2. I built something similar to this as a college project about a decade ago: http://www.chrisfenton.com/magnetube/ – the idea at the time was to make a linear array that you could have cars drive under and see if their trunks were full of iron (i.e. old artillery shells). It did actually use 3D sensors, but it just computed the absolute magnitude of the magnetic field at each point to simplify things.

    It was quite neat to play with – the sensors were sensitive enough that if you held it over a stack of iron plates you could kick them and see the magnitude of the field jump slightly as the magnetic domains re-aligned with the earth’s field.

    1. Hi CF, I looked at the project and your presentation, very interesting. We thought about taking the heads of used hard discs as well as they must be able to puck up extremely fast very small changes in magnetic fields…

  3. Amazing work that will no doubt open a few doors for them.

    GPR is a mature field with lawnmower sized units already common in industry, though in dense obstacles you get artificial hits and ringing in the signal. As for shallow UXO, African pouched rats are great at smelling out degrading explosives & indicating to their handlers. To get this to market it’ll need to be competitive with these methods.

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