Hi!
Does anyone have (Or know of) a proven circuit for a 'Ringing Choke' or 'Resonant Coil Demagnetiser' for use with demagnetising watches?
Thanks.
Len33

 

Instead of building a circuit you could try passing the watch through the energised stator of a shaded pole motor.

 

have you got an old transformer type soldering gun? the wellers have quite a magnetic field. just push the trigger with the watch against the housing, and pull the watch back away before letting go of the trigger.

 

an example of a shaded pole motor with rotor removed.

 

I don't have a ready design but I can tell you that you would need to have a high Q inductor and a good quality high voltage capacitor. The capacitor is charged up then dumped across the inductor, causing a damped sine wave current oscillation through the coil. Getting a high enough Q so you do note leave more residual magnetism than you want while leaving a way for the flux to exit the inductor, go through the object being demagnetized and back into the inductor at the same time can be challenging. A digital or storage scope with a current probe would be a useful tool.

 

I don't know what you mean by "watch demagnetiser", but in the old days, we used to use these for erasing magnetic media.

 

Recent forum thread here