Re: detecting contact closure
- From: Rich Grise <rich@xxxxxxxxxxx>
- Date: Mon, 31 Jul 2006 20:19:36 GMT
On Mon, 31 Jul 2006 00:21:18 -0700, post wrote:
Greets all. I'm an amateur at this, so please disregard any
errors in my techincal description. I have a seemingly simple
task to accomplish and am trying to figure out the best
(most reliable) way to get it done.
I have a mechanical switch located about 300-400 yards
away, on an entrance gate -- the contact closes when
someone opens the gate.
I'd like to detect the closed contact with a TTL circuit. I
already have the TTL logic in place (0V - gate is closed,
5V gate is open).. but am unsure how to "condition" the
mechanical switch so it reliably provides a 5V signal
to my TTL when the gate is open.
For 300-400 yards, TTL will never do. I'm assuming it's hardwired;
what you really should do is use a current loop of some kind, in
the analog domain, then condition that to trigger your response.
Or, if all you want is the equivalent of a doorbell, then just
put the switch in series with a battery or isolated supply and
some kind of indicator.
Good Luck!
Rich
.
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