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Magnetic Levitation |
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Levitation
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Designing the Lifting CoilHow do you design a coil for lifting a steel ball? There's no clear design rules, but I can offer tips and suggestions! Do you have suggestions of your own? Please e-mail your ideas to me. I'll update this page with whatever I get. Thanks! Hints for a Lifting CoilYou need to produce a magnetic field which primarily extends downward from the lifting coil. So consider these ideas.
Coil CoreYou can wind a coil on a carriage bolt. (Use one layer of tape first to protect the wire.) The threads can provide adjustability by screwing it in (or out) of your wooden frame.
The bottom of your steel core (coil form) should taper to a point. This gives a point source of flux going downward. I found a flat-bottomed steel core gave too many places for the ball to attach itself to, and allowed too much side-to-side motion. File off any roughness to ensure the bottom of your steel core is pointy and smooth. A Coil That Works
I used 24-ga magnet wire, in 1341 turns on 24 layers wound on a carriage bolt. There is a nylon flatwasher on the bottom (the head end) and a common galvanized steel flatwasher on the top. The coil length is twice the width of Scotch magic transparent tape, which secures the layers of windings. The coil dimensions are:
This coil has 7.0 ohms of resistance. Driven by a 15v source, it carries about 2 amps of current. Unfortunately it tends to get pretty warm, if left full on for ten minutes. However, testing has found it works fine left on overnight holding up a small bolt. But I am still concerned about how hot it may get if left on without an object under it. The coil is energized by a 2N3055 pnp power transistor on a heat sink. The heat sink doesn't seem to be required, but keep an eye on it! Some other people have reported they just put it into the breadboard without any heat sink. But two people said the transistor ran boiling hot, even with a heat sink (but they had a transistor bias problem). |
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Last Update 2008-06-08
©1998-2023 Barry Hansen |