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Inside the top (rotating
part) are eight permanent
magnets, evenly spaced. The poles of the magnets
all face the same direction.
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Inside the base are an
electromagnet, a magnetic reed switch and a battery. The
pole of the electromagnet is the same as the poles of the
permanent magnets in the top, so that when it is on it will
oppose those magnets and push them away. |
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The active component
is the magnetic reed switch, invented at Bell Telephone
Laboratories in 1936 by W. B. Ellwood.
The reed switch is normally open but closes in the
presence of a magnetic field. Two types are shown here. |
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The position of the reed
switch is critical. It controls
the timing, the way an old fashioned distributer in
a car controlled the spark to the spark plugs. There
is a capacitor across the switch. More on that later. |
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In operation... |
As a magnet in the top
cheese box approaches the reed switch in the bottom box, the
magnetic flux closes the reed switch, activating the
electromagnet. The electromagnet kicks the permanent magnet
away and the reed switch opens. The next magnet swings by and the process is
repeated. This happens over and over, causing the top cheese box to spin.
The reed switch closes eight times for every time the cheese box spins
once. |
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NEXT, how it was made and
tips for making your own. |
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