PVC Magnetometer To Measure Magnetic Storms

In the hopes of getting a heads up on when the aurora borealis will be visible from his back yard, [Alex] built a magnetometer to measure disruptions in Earth’s magnetic field. The build is extremely simple, too. It’s amazing what you can build with a few components and a trip to the dollar store.

The design or [Alex]’s project is called a torsion magnetometers. In this setup, two mirrors are affixed to a permanent magnet connected to a string. A laser is shone onto the mirror and is reflected back to an array of sensors. In [Alex]’s case he used a simple laser pointer and a pair of photoresistors encased in a PVC tube.

[Alex] has been running his magnetometer in his back yard for over a month now and has the data to prove it. Luckily for [Alex], those graphs he has been generating may get a little more interesting. A coronal mass ejection is coming our way and is expected to hit today around 22:30 UTC. We’ll go outside to look for an aurora, but we’re sure [Alex] will be glued to his laptop tonight.

Check out the CGI visualization of [Alex]’s magnetometer after the break


26 thoughts on “PVC Magnetometer To Measure Magnetic Storms

      1. This design is only useful to measure changes over time in a static location. You couldn’t (easily…) move it in and around the field near power lines, as just the motion will cause the mirror to rotate, fouling the measurement.

        As well, moving the thing around that field will cause motion just because of the interaction with the electric field.

        So, unless you can get the power company to toggle the lines off while you place the sensor and allow it to steady, this won’t be very useful.

  1. Very interesting work. Looking forward to tonight’s results.

    One suggestion regarding the electronics: I wonder if he considered arranging the LDRs in a Wheatstone bridge so the remote amplifier gets a differential signal? That ought to cut down on any electrical noise he might be seeing in his results. Obviously it would require one extra wire to be laid, and it would be good practice to twist the differential signal pair together, as well as the power rails.

  2. It’s a nifty idea however it’s really a lot of work for an inferior quality sensor. It’s entirely vulnerable to seismic and physical vibrations, sound, …etc Also, the resolution of the two photosensors is questionable.

    You can just easily go out and buy one of the several solid-state sensors at http://www.sparkfun.com/search/results?term=magnetometer&what=products for less than the price of the PVC and be done with it.

    Neat project and design though, but not very practical is all.

    1. When I checked my web counter statistics today they were off the chart! In the logs I found that my magnetometer project made it to hackaday.com. Wow, thanks!

      Regarding the data – I’m waiting for today’s magnetic storm, but so far it’s not here. I’m also checking spaceweather.com and the ACE spacecraft plots that will give us an hour or so warning for an approaching storm – nothing so far. I hope it will come. If it does, it will appear on the site automatically.

      Regarding using the magnetometer modules from sparkfun – those are not going to work, because their sensitivity is way too low. If I’m not mistaken, the _most_ sensitive I found has is 0.015uT resolution. In the latitudes where I live (central California) the _whole_ _range_ of the daily fluctuation will fit in those 0.015uT. The mirror magnetometer is currently running at [very] approximately 300 times higher resolution than the most sensitive of those modules and increasing the resolution further is not a problem at all (but the fluctuations will get out of range then, so there’s no point).

      Finally, regarding the 3D software – I used Blender.

  3. As one having used basically the same sensor, only reflecting the laser beam onto a wall 4 meters away, i can attest that this works most excellently indeed in the form i utilize it, eyeballing the drift. The only fiddly thing with this kind of sensor is in cancelling the NS magnetic vector. In its most sensitive form, the mirror rotates 180 degrees in about 12 hours, thus tracking either the moon or the sun, havent really bothered to figure out which one (id wager the moon, since there is tidal forces acting on the terrestial seas) Naturally, a car driving past my house on a road 50 meters away will flip the mirror around instantaneously in that sensitivity state. As a rule of thumb, if the mirrored laser dot moves 20 cm when a magnetic tip philips screw driver is pointed first to west then to east sufficient sensitivity to magnetic variations is reached. Any less, and you will miss the more etheral northern lights, any more sensitivity will knock the mirror around when you vacuum or got more more than one car on your runway. Agree with the previous poster that only two photosensors wont be adequate. The basic operating principle is very sound, especially when reflecting the beam further away.

  4. Could you look to see if there is a small black hole in orbit around the earth? Theretically its got the same gavity as the moon, a similar distance away, but much smaller than the moon! You should look in the opposite direction to the moon. It should have a massive impact on the magnetosphere. This is why there are two tides a day not one. The Russians sent a probe there in 1972, but their results are top secret.
    NSA and the Cold War “Space Race”

    1. Light bouncing off the moon makes it to us here on earth. Radio waves bounced off the moon by radio amateurs make it back to earth.

      It therefore follows that the moon’s gravity is not strong enough to prevent electromagnetic radiation escaping from its pull.

      Accordingly, any ‘black’ hole with the same gravitational pull as the moon would be visible, and not invisible/black.


  5. BTW, the much anticipated magnetic storm turned out to not be a strong one, especially at the latitudes where I live. You can see the first magnetic shock as the sharp bump around 6:15
    here. The big waves toward the end of the 6 hour interval are the main event – still weaker than expected.

    1. I tried something similar. I have a pair of
      these RF modules.

      They work fine, when it comes to the data. I was getting the signal reliably from over 50 meters. The only problem was that they introduced a lot of noise in the analog part of the circuit. I tried even with a separate power supply for the module, but still noise was creeping in.

      I’m pretty sure there is a way to shield the amplifier, but at the end it was easier to just use a long cable. Anyway, I needed a cable for the power, so it wasn’t much of a tradeoff.

  6. interesting project. however i’m surprised you haven’t calibrated the instrument (no units in your graphs), characterised its frequency response, and measured the noise performance (in nT/sqrt(Hz) ).

    1. I haven’t calibrated it, yes. The problem is that I don’t have anything to calibrate it with. The closest magnetometer is the one at Fresno, and while this gives me a rough idea about the range, it is not the same.

  7. I will have to hack one of the string-magnet things up. Would a high flux mag in disc form work? This has held my interest since the 60’s UFO era and how to build a detector for them. My friend suggests ghosts as a target?

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