A DIY Geomagnetic Observatory

Magnetometer observatory

[Dr. Fortin] teaches physics at a French High School, and to get his students interested in the natural world around them, he built a geomagnetic observatory, able to tell his students if they have a chance at seeing an aurora, or if a large truck just drove by.

We’ve seen this sort of device before, and the basic construction is extremely similar – a laser shines on a mirror attached to magnets. When a change occurs in the local magnetic field, the mirror rotates slightly and the laser beam is deflected. Older versions have used photoresistors, but [the doctor] is shining his laser on a piece of paper and logging everything with a webcam and a bit of OpenCV.

The design is a huge improvement over earlier DIY attempts at measuring the local magnetic field, if only because the baseline between the webcam and mirror are so long. When set up in his house, the magnetometer can detect cars parked in front of his building, but the data he’s collecting (French, but it’s just a bunch of graphs) is comparable to the official Russian magnetic field data.

High Voltage Hacks: shrinking coins

The anthem for the Great Recession might be something along the lines of, “That we’re gonna do it anyway, even if doesn’t pay.” Some men just want to watch the world burn, so Hackerbot Labs posted a great walkthrough about shrinking coins and in the process making our pocket change worth just a little bit more.

Their build pushes 15,000 Joules (from a 10kV 300μF cap) through a coil of wire wrapped around a coin. This creates a magnetic field in the coil and the coin. These two fields repel each other, and there’s only one way that it can end: the coin shrinks and the coil of wire explodes. The team at Hackerbot Labs linked to a great theory of operations that does a great job explaining the physics has some awesome pictures.

During our research, we saw a few questions about the legality of altering currency. According to the U.S. Code, shrinking coins only illegal if it’s done fraudulently, like shrinking a penny down to the size of a dime to fool a pay phone or vending machine. Check out a video of the Hackerbot Labs setup putting as much energy as 100 heart defibrillators into a coin after the break.

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