Magnetics design & reed switches - lost article

Rodwell · 2013-05-15T12:17:36+00:00

Ages ago I had a great .pdf app note type document that covered the practical implementation of reed switches. It had stuff on biasing with other magnets & a whole pile of drawings & notes on how sheet metal & other fabricated parts could be used to control the operation of the reed. Needless to say I cant find it & google has not been helpful. Does it ring a bell for anyone? I've got a feeling it was a pretty old article, it would be great to find it again. I've got a situation where I need a reed to only operate when the magnet is directly in front of it & to release when the magnet moves slightly to either side. The mechanical arrangement is similar to a pendulum except that the pendulum is stable at both A and B. It moves from A to B (or B to A) when an external force is applied. We want the reed to operate as the pendulum mounted magnet passes the centre, but only right at the centre +/- 5mm or so. AB |REED| ------OFF------------|-ON-|-------OFF--------- DESIRED OP. ------OFF-----|--------ON--------|----OFF----- ACTUAL OP. Our problem is that the mechanical parts bounces a bit resulting in multiple actuations of the reed rather just a single operation. The reed clears the magnet by ~5mm & the switching "dwell" is quite sensitive to the gap. We're thinking some simple sheet metal may be useful to shield the reed either side of centre. Practical?

May 15, 2013 24 Replies

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Syd Rumpo 13 years ago

Sorry, James, that's not even worth arguing with. You don't understand magnets.

Cheers

Syd

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josephkk 13 years ago

with

old

magnet

slightly

centre

Can't you

effect?

Why is there so much wanting to fix really bad (legacy) designs, but do not want the changes that a real fix would entail?

?-)

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Bill Sloman 13 years ago

It's a lot less work to document a band-aid fix than "real" fix. Sensible people do both - the band-aid fix keeps the production line running until you can find the effort to document the real fix.

Bill Sloman, Sydney

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Robert Macy 13 years ago

net

Can't you

ffect?

Because, we march 'backwards' into the future.

Or, because the user base is too large to ignore.

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Tom Hoehler 13 years ago

How about a shielded reed switch triggering a 555? :) Tom

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