> From:   Brendan Moran[SMTP:annirack@SHAW.CA]
> Sent:         Thursday, October 16, 2003 2:04 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: Active maglev with permanent magnets & solenoids

> At 10:51 AM 16/10/2003 -0600, you wrote:
>> Sounds like a pretty good plan, but if you plan to use permanent magnets to
>> augment the coils, you'll have to abandon the control system that he
>> proposed, or your "train" will only be able to move in one direction. The
>> magnetic fields have to be able to reverse direction freely in order to
>> repel the train in either direction. I'd say, forget the perm. mags, and
>> just buy yourself a 24V, 5 Amp wall wart. :O)
>>
>>- Robert

> Sorry, I intended to say that the thing I wanted to levitate should be
> static.  I don't want it to move.

> --Brendan

There is a construction article in the September 2003 issue of "Nuts &
Volts" magazine (page 58) describing how to do exactly what you
want to do. From the article: "The design problem has to do with
overcoming Earnshaw's Theorem ..."

The idea is to mount a permanent magnet on the top of the object to
levitate, and put a Hall effect sensor on the bottom of the electromagnet
which is pulling the object up. The output of the sensor controls a PWM
output to the magnet, keeping the object at a fixed distance from the
electromagnet.

John Power

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