Make a Magnetic Field Detector to Find Earth's Dip Angle

[arydberg]

I made a magnetic field detector. I used a small U shaped magnet transformer core and wound a coil on the bottom length. This was then mounted on a piece of one inch PVC plastic pipe. One red LED and one green led were then attached to the core. A opamp was used to amplify the signal from the core and drive the LEDs. Two 9 volt batteries were mounted in the pipe and the pipe was mounted in a 2 inch piece of PVC so it could be rotated with a electric motor.

The result was a spinning pipe that pointed north and south. As it can be used at any angle I found that it indicated a null and the LEDs went out when the pipe was parallel to the dip angle of the Earth's magnetic field.

I'm not sure what to do with it. Any ideas?

 

[Charles Link]

If I understand the device correctly, the magnetic field from the Earth causes a change in the magnetism of the transformer core, which doesn't stay constant because you are rotating the transformer core. (The magnetic field of the Earth acts on the iron and the iron enhances the magnetic field of the earth, perhaps by a factor of 100 or more.) The result is a Faraday EMF in the loop(s) around the transformer that feeds an op-amp circuit which drives the LED's. It's difficult to follow every detail without detailed schematics, and it is possible you could do something similar with a straight cylindrical type transformer core. It sounds quite clever. I would have to believe that similar devices are likely to have been previously patented.

 

[arydberg]

If I understand the device correctly, the magnetic field from the Earth causes a change in the magnetism of the transformer core, which doesn't stay constant because you are rotating the transformer core. (The magnetic field of the Earth acts on the iron and the iron enhances the magnetic field of the earth, perhaps by a factor of 100 or more.) The result is a Faraday EMF in the loop(s) around the transformer that feeds an op-amp circuit which drives the LED's. It's difficult to follow every detail without detailed schematics, and it is possible you could do something similar with a straight cylindrical type transformer core. It sounds quite clever. I would have to believe that similar devices are likely to have been previously patented.

Here is a schematic.

 

[Charles Link]

That makes sense. (The electronics.) It's clever to use the induced voltage that occurs in the iron as it is moved around in different directions, in that it responds to the Earth's magnetic field. To use something like this to measure magnetic field direction and/or amplitude would take some additional effort. (That's part of what I was referring to in my first reply mentioning diagrams). You might find certain directions in spinning your apparatus generate increased or decreased response, but I would need more detailed drawings (and if you did want to consider marketing this, you might not necessarily want it for public viewing), to try to analyze and optimize the device to give the most info as possible about the magnetic field from the voltage signals of the circuit.