Magnetic sphere is N38, diameter 1" (26 mm).
Coil is a basic vortex coil, 120 notches; stepping 41, aready energized with 180° phase-shifted square wave signals @ ca. 13 Hz at start of video. Powered by a 12 V car battery, with a 21 W car light bulb as load in each circuit.
Signal generation by sqare wave generator, 50% duty cycle.
I use a DDS20 digital square wave generator which I bought from www.elv.de www.elv.de/output/controller.aspx
Signal B is produced by a NOR-gate, so that it should be exactly in phase opposition to signal A, that is to say while A is ON, B is OFF and vice versa. With my signal generator I can only change the frequency. No alteration of duty cycle, phase shifting or other fancy stuff.
The sphere spins with good torque, i.e. there is a lot of friction between the sphere and the white stone slab, which lies under the coil.