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Electromagnetic Levitation Force

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physicsod
#1
Dec24-11, 02:01 PM
P: 9
Hello everybody!

For a physics project, I'm trying to create an electromagnet exposed to varying current, determined by a sensor. This sensor will measure the distance between a magnet under the electromagnet and the electromagnet itself, and then we'll need to convert this distance to the current supplied to the elctromagnet, in order to make the magnet levitate under the electromagnet.

Currently, I have barely any knowledge in electromotive forces, magnetomotive forces, and magnetic fields. Can somebody give me a general idea of what wikipedia pages and textbook sections to read about, as well as a general formula (if one exists?)

Any help is appreciated. Thank you all so much!
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Curl
#2
Dec24-11, 06:03 PM
P: 757
It will take you at least a year of studying E&M and electronics to pull this off.
physicsod
#3
Dec24-11, 06:12 PM
P: 9
Thanks for your help (or lack thereof). I'll upload the video onto YouTube once we're done.

Drakkith
#4
Dec24-11, 11:07 PM
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P: 11,878
Electromagnetic Levitation Force

Without a working knowledge of the basics of the Electromagntic force all I can say is go read the articles on "magnet" and "electricity" and just start clicking the links to everything related to those. You're going to need information from alot of them.
kcdodd
#5
Dec26-11, 12:13 PM
P: 192
I think knowledge of feedback control is probably more important than EM theory. One can have all the theory and it still just comes down to a feedback loop. The control circuit/code will probably not use any theory at all. All you have to know is bigger current = bigger force. Then tweak the magnitudes so it works and is stable.
chrisbaird
#6
Dec28-11, 09:51 AM
P: 617
Quote Quote by kcdodd View Post
I think knowledge of feedback control is probably more important than EM theory. One can have all the theory and it still just comes down to a feedback loop. The control circuit/code will probably not use any theory at all. All you have to know is bigger current = bigger force. Then tweak the magnitudes so it works and is stable.
Very true. But I think the OP's purpose is not to just get it to work. It is for a science project, so he is supposed to investigate the science. Pure levitation will require a feedback loop and would be very hard. I would suggest an easier project: supported levitation. Get magnets with holes in the middle and place them on a post, then levitate them up the post using an electromagnet, and measure the distance levitated as a function of current, etc.
Antiphon
#7
Dec28-11, 11:22 AM
P: 1,781
You should be able to make this work in about a week.

Use this sensor positioned under the ball:
http://search.digikey.com/us/en/prod...2498-ND/857232

The data sheet for the sensor has a graph that shows that the output increases as the distance to the ball gets smaller. That's perfect for you; just make that signal be the signal to the coil (but amplified first).

Don't worry about designing a control system, you won't need it. This is because the ball reacts much more slowly than the sensor and amplifier you will hook up.

The amplifier will need to work down to DC. If you need help to get this amplifier part working, post a separate message in the EE subforum. There are many good engineers here who can get you going in no time.
nileshth
#8
Jan27-12, 07:21 AM
P: 2
Hi Physicsod,

I am working on the same thing. I made the levitation with the help of PID controller. But my magnet not levitating more than 5 sec. If you had any progress in your project please help me to implement same thing.


thanks in advance
meldraft
#9
Jan27-12, 08:05 AM
P: 280
These will be useful for your calculations.

http://en.wikipedia.org/wiki/Biot%E2%80%93Savart_law

http://en.wikipedia.org/wiki/Magnetic_force

I do not know if you are comfortable with the mathematics involved in the wikipedia articles however. Your best bet if you want to do it fast would be to find a good undergrad textbook (sorry, don't know of a english one), and start reading backwards. This means, identify the things that you don't understand in the formulas you need, and keep reading up on these sub-sections until you do. The 'proper' way of course, is to start reading from scratch.

Finally, keep in mind that you do not actually need to know what is happening. If you build the thing, you can always make a few experiments and build your own curves on the correlation between current and distance. This would probably be the fastest way, and the least educational one
nileshth
#10
Jan27-12, 08:35 AM
P: 2
HI,

I want to tune my PID controller loop.when i leave the magnet for the levitation that time for first 2-3 sec its stabilize but after that magnet fluttering and falls down this is because the wrong variable of derivative and integral and proportional I used some tuning methods but not able to find out where is the problem so which variable i vary because of that my levitating time is increases.

Thanks in advance


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