Alt-BEAM Archive
Message #04292
To: Bram.A.A.vanZoelen@is.shell.com
From: Jesse Meers jmeers@desconnect.com
Date: Sat, 5 Jun 1999 15:52:47 -0400
Subject: Maglev info:ALT: BEAM forcefield....
> Here is some information I came up with through the last 4 months of
> experimenting to make a magnetic weapon. A picture of my "hall effect
> device" is attatched.
>
> The device operates like this: when each Hall switch is on, one polarity
> of voltage is applied to the coil, a current appears, and the tip of the
> core becomes a north pole. The Hall switch is oriented so that this
> polarity of magnetic field turns the switch off before the magnetic field
> has a chance to grow very strong. When the switch is off, the direction of
> current reverses, the tip of the core becomes a south pole, and the Hall
> switch turns back on. This reverses the current again, etc. As a result,
> the device acts like a buzzer, the Hall switch turns on and off very
> rapidly, and the magnetic field wiggles north and south a little, but the
> average field is zero. When a magnet pole approaches, the Hall sensor
> starts turning the coil on north longer than south (or vice versa) in
> order to keep the field in the sensor averaging at just about zero. It's a
> feedback system which creates zero magnetic field dynamically.
>
> What good is this? A device that creates zero magnetic field? Very useful,
> actually. Superconductive plates also create zero field inside themselves
> and thereby repel either pole of a permanent magnet. This is how
> superconductive levitation works. Therefore the above coil-assemblies will
> repel a bar magnet regardless of whether it is an N or an S pole. When an
> N pole approaches the hall sensor, the circuit will send a current through
> the coil more in one direction than the other, which makes the coil's pole
> become "N" rather than zero, and it repels the magnet. And the two
> oppositely-pointing magnetic fields cancel to zero right between the
> magnet and the coil, right where the Hall sensor sits. It's a negative
> feedback system based on naturally occuring oscillator and
> Pulse-Width-Modulation. Cool, eh?
>
> Before undertaking a huge maglev railroad project, build a single
> "repulsor" coil to get a feel for operation and to demonstrate the
> interesting repulsion effect. If you build large numbers of coil circuits
> and they turn out not to work, you'll have to debug ALL of them. Better to
> get the bugs out of a single one first.
>
> Other ideas:(I actually did this, thats how I can tell you!!!!) build one
> coil into a hollow silver plastic rod, run it from batteries in the rod,
> then and show your physics teacher that one end of your "metal rod" repels
> BOTH ends of any bar magnet. He/she will freak, because only a
> room-temperature superconductor can do this. Room-temp superconductors
> don't exist. Yet.
>
> A pair of rows of these devices acts as a maglev railroad track. A bar
> magnet will fly along above them if it is gently thrown between the rows.
>
> One serious problem with the device: Tiny movements in the suspended bar
> magnet trigger the compensating magnetic field after a small time delay.
> This will trigger slightly larger movements, which triggers even larger
> movements, and after a few seconds the magnet will be wiggling so
> violently that it will be thrown out of the device. The device has
> slightly negative stability. If you can get the magnet to stop moving
> initially, the oscillations will build up very slowly or not at all.
>
> A simple solution: place a thick copper bar right below the bar magnet.
> The electrical resistance of the bar will offer some mechanical damping to
> changing fields, this will dampen the magnet motion, and the quivering
> will die away. Another solution: Replace each circuit with an ANALOG Hall
> sensor and a DC power amp (needs big heat sinks,) route the analog hall
> sensor signal through the amp and to the coil, and add a bit of
> differentiated hall signal into the signal going to the power amp. This
> will create some programmable damping via analog computation, and will
> cancel out the effects of the loop-delay which causes the oscillation in
> the first place. And if you succeed in all this, you will be an expert in
> linear control theory and dynamic positioning systems!
>
> I hope you guys appreciate me providing this info, It takes a lot for me
> to write all this off the top of my head!
>
> Jesse Meers
> http://www.geocities.com/ResearchTriangle/Node/3375/
>
>
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