perpetual motion using magnets

I want to make a toy swing appear to move back and forth without any help, but the magnet on it is repeatedly attracted and repelled by a hidden electromagnet, pulsed about every 2 seconds. Has anyone got a simple circuit idea (555 ?)

You need to sense when the swinging magnet is in the correct position to pulse the electromagnet.
You need to determine which direction the magnet is swinging to determine which polarity of current is in the electromagnet.

Please don't call it perpetual motion because the battery is providing its power.

I have seen these in stores as "executive toys", where a small moving object is moved by a hidden electromagnetic circuit, and assumed there was a simple permanent magnet being moved by a hidden coil, which is alternatively switched on and off. I realise it is not "perpetual motion". If the coil was energised, say, every two seconds - just on and off, wouldn't this set up an oscillation in the swing, causing it to fall into step and rock back and forth, without any additional sensing circuit?

If the frequency of the electronic oscillator driving the electromagnet matched the natural oscillation of the swing then a pulse of one polarity will push the swinging magnet in the correct direction at the correct time.

That's exactly the thing I need. Do you know of a simple schematic for it anywhere?
Thanks.

Jules said:

That's exactly the thing I need. Do you know of a simple schematic for it anywhere?

Click to expand...

It is just a 555 oscillator driving a power transistor to match the current of the electromagnet. The schematic for a 555 oscillator is all over the web and in its datasheet.

Some of the really simple ones in chinatown dont even have a curcuit...they simply have a reed switch that closes when it senses the pendulum is in its furthest swing away from the electromagnet, and opens when the pendulum moves closest to the electromagnet. There isnt even a magnet involoved.
The schematic would simply be that the reed switch is in series with the coil, after the battery.