Magnetic Pendulum circuit help

Thread Starter

Joined Aug 24, 2007
Yes, that's what I want to make. I swinging magnet. But, I want to build it on wooden platform and set it on my desk at work.

Thanks for you help.


Joined Jul 17, 2007
Take a look at Hall-effect devices. Some detect the relative signal strength of a magnetic field. Some simply output the presence or absense of a magnetic field. You would want the latter type.

There are Hall-effect devices available that have three connections; power, ground, and output, type UGN130 if I remember correctly - or something similar. [edit - it's UGN3130; it's stocked under the Philmore brand by #86-1030; package is similar to yet MUCH smaller than TO-92]

You could use such a device to trigger a very brief one-shot pulse (say, from a 555 timer wired in a monostable configuration) to a coil centered under the path of the swinging magnet. The magnet would need to be oriented so the poles are vertical; N on top and S on the bottom, or the other way around. If the coil is hooked up backwards, it will quickly stop the magnet from swinging. The one-shot pulse needs to be VERY brief not only to conserve battery power, but to ensure the magnet is pulled towards the coil rather than being held in place or braked by it.

You will need a diode across the coil to absorb the "spike" when the timer cuts off; otherwiise the spike will kill your 555 timer.