As far as I know, perpetual motion orbital desktops like below use an electromagnet in the base.
Why aren't permanent magnets used on both ends instead?
Does anyone know where I could find a teardown of the base of a generic one?
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They use batteries and electromagnets. They are NOT perpetual motion devices. They just run a very long (too damn long) time on a battery.
The lower end of the pendulum may have a permanent magnet. The base MUST use an electromagnet because it has to be turned on and off in time to the pendulum motion to keep it running.
The electromagnet is turned on for a short period the either pull the pendulum closer or to push it away.
This action makes up for energy lost in the friction of the bearings and with the air.
Without the energy supplied by the battery, it would stop moving.
Take the battery out and try it. No battery, slows down and stops - blessed peace and quiet for those of us who can't stand the irritating junk piles.
Yes, many of them probably use electromagnets.
In order to keep a "perpetual motion" machine going, you need to keep adding energy to the system.
A battery powered electromagnet with an oscillator can convert chemical energy from the battery to kinetic energy in the machine. A stationary permanent magnet can't do that.