PSN-L Email List Message

Subject: Re: How to arrange the magnets?
From: "Geoff" gmvoeth@...........
Date: Sun, 23 Dec 2007 15:21:53 -0700

You Need to think of making the
lines of flux around the magnet visible
then arrange things so that the lines of flux
cut the wires at 90 deg ( normal )
whenever there is relative motion.
Also one side should compliment the other
in pushing the current about a closed loop.
You can greatly increase the lines of force
by using an iron core like a solinoid coil
but you most probably will not get any
kind linear relationship between velocity
and motion or so iut seems to me.

I have tried it in the past using a flat
speaker magnet hoovering atop the coil
as well as a rod magnet in the center of the coil
as well as the solinoid idea the solinoid idea
was most sensitive but was never sure about free
period since there is a magnetic attraction to the
core of the solinoid.

I never finished this idea since I went to
a manufactured geophone because a
pendulum seemed just too big
and troublesome to bury in the ground.

If you can use copper plate and magnet damping
seperate from the sensor you can realize the max
sensitivity of the pickup coil or so it seems.


----- Original Message ----- 
To: "psn" 
Sent: Sunday, December 23, 2007 9:34 AM
Subject: How to arrange the magnets?

Hi Folks,   I want to make a simple Pendulum with  magnets on the end, which swings like a plumb bob over a ring shaped coil  (dough 
nut shaped).

I think if the magnet was the same shape and size as the coil, it would neutralize the voltage as it moved.  As it would be North 
side down and South side up, so of the same North pole would stimulate two parts of the coil at the same time. In this case it 
should be One North and one South.

I think if I used two square magnets, one N pole down and one S pole down, that would work for swinging, say East and West, but 
would not create much if it swung North and South.
Perhaps I could use four magnets, N, S, N, S?

I could make the coil square or round.

In this experiment, I need all the magnets to float above the coil.   How might I arrange the magnets?

Thanks, Ted


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