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Coil Design for Uniform Magnetic Field?

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Jun27-12, 12:28 AM
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Dear Forum,

I am attempting to make a treatment mattress or pad for PEMF treatment of osteoporosis. I have osteo, and there are commercial units available, but they cost ~$3K+! I have a capacitor discharge circuit, but need a coil design for the pad. I created a gauss probe with a linear hall effect, and can measure the desired levels on my PC Scope. I wound a flat circular coil, and see that the desired levels are present. The coil is wound all the way to the center. Over the center the field is quite strong, and tapers off as the probe is passed from the center to the outside edges.

Would a flat ring coil design, with a large open center work better? Or one with a certain size open center? I wish there was a free fea program that was easy to use available, but I cannot find one. Any guidance would be greatly appreciated!

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Simon Bridge
Jun27-12, 11:54 PM
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Welcome to PF.

There have been a lot of claims about PEMF for all kinds of things, and some encouraging scientific papers published as well. Unfortunately most of the claims about these beds are overstated. I found an accessible discussion covering positive and negative sides here.

The commercial beds don't seem to be bothered with having a uniform field over the body ... to do that I'd suggest either sleeping in the middle of a huge long solenoid or using an array of small solenoids above and below the bed (for a vertical field).

A spiral solenoid won't be ideal - you want to wrap the bed in the coil and leave the inside empty (or, use an iron core?) but I think the array above and below would have a steampunk aesthetic that could be quite fetching: forget mirrors on the ceiling...

However - although the method has good results for things like bone fusing, the mats are quite quacky and long terms exposure to some pulsed fields could be dangerous. As a sufferer you will be aware that there are a lot of quack "treatments" making claims about oesteoporosis so you are right not to shell out thousands for this stuff.

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