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Feb16-12, 07:49 PM
berkeman's Avatar
P: 41,347
Quote Quote by Harvey Sherma View Post
My question pertains to model trains. I use a magnet under my last car to activate computer commands via a reed switch. One locomotive has a speaker placed near the bottom and the magnet of the speaker activates the reed switch - which I don't want it to do. One thought to correct this is to place a thin substance under the locomotive, between the speaker and the reed, this substance would block/distort/weaken the magnetic strength. It would need to be thin. Is there such a material. I tried aluminum paper but that did not work.


It needs to be ferrous (like iron) in order to deflect/route the magnetic field.

Try bending a flat piece of iron so that it forms a 4-sided box around your speaker. Drill holes in the diaphram side of the iron strip before you bend it around the speaker. This will divert the external magnetic field lines closer to the speaker, instead of letting them spray out farther where they can affect your reed switch. Try to use the thickest iron strip you can, to avoid having it saturate from the magnetic field so close to the speaker magnet.