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From: John Fields
Organization: Austin Instruments,Inc.
X-Mailer: Mozilla 4.01 [en] (Win95; U)
Subject: Re: Reed Switch "dead spot".
NNTP-Posting-Date: Tue, 03 Sep 2002 07:08:59 CDT
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Date: Tue, 03 Sep 2002 12:08:59 GMT
James Meyer wrote:
> How about this? Place the reed switch vertically at the center of the
> square and use a "normal" magnet with the poles oriented up and down in the
That would work, depending on the switch and the magnet. What happens
is that when the magnet is brought near to/touches one of the contacts
it temporarily magnetizes that contact and since the other contact is
also made of magnetic material it's attracted to the magnetized contact
even though it's not itself magnetized. It depends on the switch and
the magnet because for a largish gap or a weak magnet it won't work.
I've got some fairly sensitive signal type switches and some power
switching types, and with a 1" X 1/2" X 1/4" alnico magnet I can get
the signal types to switch but not the power types. However, with the
magnet set up for horizontal actuation
(http://www.ceejay.com/ales01.html) it works quite well for both
switches quite a distance from the switches. Doing rotational actuation
with a couple of switches oriented orthogonally also works very well.
Professional circuit designer
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