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Highly Configurable 3D Printed Helmholtz Coil

Design for 3D printed Helmholtz Coil that can be configured for any wire size, number of wraps and magnetic strength

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Helmholtz Coils contain a region of uniform magnetic field which is commonly used to measure the strength of magnets, measure electrical charges at the atomic level, and measure or null Earth's magnetic field. The magnetic field calculation for the coil is done for you as part of configuring the coil size for 3D Printing.

This project uses OpenScad which is a 3D Solid modeler for 3D printing. OpenScad has the advantage that it's a programming language too, which lends itself to heavy customization. You can customize everything, and if you don't like it or need something else, then change it.

Helmholtz Coil Configuration Statistics:Output in the OpenScad console details the coil configuration, wire length, field strength per Amp / mA and the maximum capacity of the coil:

    AWG: 30
    Coil Diameter: 21cm
    Coil Turns: 3
        25649.22370 nT / 0.25649 Gauss per amp
        25.649224 nT per mA
        Wire length per coil: 1.98m
        Combined resistance of both coils: 0.001342Ohms
        Voltage required to drive coil: 0.00026979Volts @ 0.201Amps
        Maximum magnetic coil capacity: 5155.49396nT for
        the provded gauge
        Usable Volume (Cylinder): 105Length(mm) x 70Diameter(mm)

The inner cylinder of the coils (the space that is 1/3 the diameter of coil), denotes the area of uniform magnetic field.

The platform for magnetic experiments is replaceable, so you can switch platforms for different applications.

This device was designed for testing magnetometer coils in the Aurora Observatory project.

It's easy to build multiple coils, e.g. I require one strong enough to null Earth's field, but also require one that is sensitive enough for measuring 1nT changes in the Earth's field.

Here is a slideshow I've put together on how to measure the Earth's magnetic field using this Helmholtz Coil design:

Measuring Earth's Magnetic Field Slideshow (pdf)

  • Built, tested and surprisingly accurate

    jetty08/25/2015 at 17:12 0 comments

    Finished the build, time to test...

    Needed to check all the math is correct and the coil is performing correctly against a known magnetic field strength. Earth's magnetic field for my location is a good reference data point to check against. So dug out a regular hiking type compass to test, essentially making the Helmholtz Coil into a well behaved Tangent Galvanometer.

    First issue was locating a magnetically clean environment in the building, bench doesn't cut it due to the pull out keyboard draw underneath with steel sliders, and I suspect the ESD mat contains some ferrous impurities due to the needle movement observed with the compass. These abnormalities were causing my initial bench top calculation of the earths field to be off by 3000nT (about 25%), so location location location. It's also possible I've been magnetizing these items with the Helmholtz coil and / or the magnets I've been testing the Aurora Observatory coils with.

    Pretty much everything turns out to affect the compass, but I did find one clean spot, and yes the bench top PSU needs to be far away from the coil too due to the transformers inside :-) . On the plus side, the copper in the coil shows no residual magnetism (as it shouldn't), and the banana jacks also are good, so the coil is well behaved.

    So the results...

    Horizontal magnetic component for my location (i.e. magnetic north, also known as H; Bh; Horizontal Component) is:

    16090nT

    Calculating the current to deflect the needle 45 degrees and -45 degrees, I get 599 and 651mA. Averaging = 625mA. 625mA x by the nT per mA for my coil from the openscad output for my coil geometry, I get:

    16030nT

    This is an error of 0.37% (60nT), I can live with that when it's considered a mid strength aurora equates to a 100nT difference, and the Quiet Day Curve typically varies by around 30-60nT.

    Method and Calcs to follow shortly in a YouTube video.

  • Everything Uploaded

    jetty08/24/2015 at 16:07 0 comments

    Everything is now online for the project, completing the build of a 3 Turns x 30AWG 21cm coils and onto testing.

View all 2 project logs

  • 1
    Step 1
    • Download Helmholtz.scad from https://github.com/jetty840/HelmholtzCoil
    • Change desired settings in the file, and save the resulting .stl's
    • 3D Print the parts
    • If splitting coils for printing, glue halves flat and let dry
    • Wrap 2 coils in the SAME direction, by entering in one hole at the bottom and exiting the other, leave enough wire to connect the 2 coils together and connect to the banana plugs
    • Attach banana plugs
    • Orientate the coils so the windings go in the same direction and mount on the base, the inner 2 wires connect together and the outer 2 go to each of the negative/positive banana plugs
    • Verify dimensions of the coils and distance. 3D printed plastic can shrink when cooled, and printer accuracy varies. If there's any substantial difference, plug the new dimensions into Helmholtz.scad
    • Print the coil data from the OpenScad console, and attach to the coil base

View all instructions

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Discussions

Simon Michael Laube wrote 06/02/2017 at 06:17 point

It is indeed possible to use a pair of coils for each axis. I saw a construction like this in an exercise in one of my university books. I'm currently looking into it to build one, but at the moment I'm not sure how to determine the accuracy of the setup after the build. As you mentioned the power supply / constant current will also be a little challenge.

  Are you sure? yes | no

coiling wrote 08/16/2016 at 16:39 point

Really cool setup! Which powersupply did you use and is it possible to create a triaxial setup based on this?

  Are you sure? yes | no

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