Mobile toy

you already answered your own question... the base contains a battery, read this as 'source of energy', the 'kick' on each swing that makes up for losses due to mechanical friction and hysterisis heating or induced current heating of the metal parts.

Perhaps you should investigate the role of the battery and coil? Or do a search for plans for these gadgets. I think that you will soon discover how it works :)

Regards Brad

It's not a static magnetic field in the base. If it were, the toy wouldn't need a battery.

It's all in the timing. There's probably one or two pickup coils in the base that will sense the swinging magnet's position.

--
"Very well, he replied, I allow you cow's dung in place of human 
excrement; bake your bread on that." -- Ezekiel 4:15

Are you sure there isn't also a package of electronic circuitry in the system somewhere? Obviously the battery isn't merely running current constantly through the solenoid. Otherwise, as you note, there'd be no important difference between it & a pendulum swinging in the gravity field. Also, the battery would be drained awfully quickly.

But there's a permanent magnet in the pendulum bob. When it swings it induces current in the coil. On one swing, the current runs one way, on the the backswing, the current runs the other way. In fact, it's a continuously alternating current, graphed by a sine wave. A circuit could be made to recognise when the bob is at some phase in its swing, and it'd then tell the battery to let a burst of stored energy into the coil, which then pumps the pendulum with just enough energy to suppliment its losses.

-Mark Martin

I suspect all the base needs to do is apply a repulsive magnetic pulse at regular intervals (remember how pendulums work). No need to sync it to the swing of the pendulum - get the frequency and pulse width right and that will probably happen all on it's own.

There is probably a transister involved as well. There is probably a lead from a sensor coil on the driver coil core that is connected to the base or gate of the transistor. There are thus probably three leads off the coil core: a ground lead, a sensor tap, and the main driver lead. The pendulum has a magnet in it. As it approaches the coil the flux change dB/dt in the coil core generates a voltage in the sensor coil that causes the transistor to on the driver coil. The driver coil is arranged so as to increase the flux in the coil core. This creates a positive feedback that sustains the driver coil current until the magnet starts to depart the vicinity of the core. At this time dB/dt reverses polarity and negative feedback shuts off the driver coil current, leaving the pendulum free to contiue on with the momentum it gained when attracted to the coil core as it approached. If there is no change in local magnetic field, i.e. no swinging pendulum, then the device is automatically in off mode.

Regards, Horace Heffner

1) Parametric amplifier. 2) A kid "pumping" on a swing. 3) Remove the battery. Damp the pendulum to hang absolutely still. Replace the battery without disturbing the system -->

nothing. Now, give the pendulum a little horizontal tap. 4) Cheap compass: the field is pulsed and synchronized.

--
Uncle Al
http://www.mazepath.com/uncleal/
 (Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

Yes the pendulum contains a magnet "N" side down (as per a compass ). The base actually shows a little "S" magnetism. I can see a large iron core electromagnet there. Up to a ~7º deflection the pendulum oscillates and damps down. Larger than that and it will "pump up" to full deflection. You can actually see the speed up when the bob approaches the base. I got this these for my kids. They won't let me take it apart.

Richard

In the name of all that's empirical, buy another one and tear its gutz out man!!!

-Mark Martin

OK they're asleep now. I'm getting better at cracking stuff like this open. Two gentle taps with my rubber hammer.... OK there are just three basic parts to this thing.

1. 9V battery
2. 1 transistor? marked "LC845P" with the Motorola "M" logo on it. Anyone know this type? I only get a reference to it being obsolete.
3. A large COAXIAL (inner and outer) coil. Tiny wire, measures .08mm The coil itself is 20.87mm Dia. X 23.97mm Long. The inner coil (different color) is about 10.65mm Dia. Connections are: B- inner coil Reading Xsistor L-R camfer up base up L other end of inner coil 1 lead of outer coil C B+ R other end of outer coil

That's it! I think Gregory had it right with the sense coil and one drive coil.

Richard

Now I get to use that Plastix (Locktite) glue which BTW works really well. Maybe solvent just in case.

Parametric amplifier. It slightly pumps the pendulum against air resistance losses. LC845P may be a small IC rather than a transistor.

--
Uncle Al
http://www.mazepath.com/uncleal/
 (Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

No need. Look here:

I built one, and it works just fine.

Isaac

Probably just a transistor being used as a switch with current gain. Not enough components for a PID (parametric) amp. Though that would be the fancy way to go.

jk