View single post by ComfortGeek
 Posted: Saturday Oct 6th, 2012 01:39 pm
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Joined: Thursday Jul 12th, 2012
Posts: 66

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Thanks WiredHome

I've measured the resistance in the circuit. It is 2.7k when closed and 7.4k when open - so the circuit resistance seems to be ok, the resistors seem to be ok, the wiring is ok.

So, I think the issue is either a) a faulty PIR opening it's contacts at random, or, b) something else is effecting the resistance of the loop momentarily, causing it to trigger the zone.

What I do have is a normally open zone sharing the same common as this PIR zone - could that be it?

Interestingly, the normally open zone (which is a break glass call point) is on the same wall as a PA zone which also triggers at random (but is normally closed) - so I wonder if there is electromagnetic interference becuase of 230v wires close to the 12v wires - and this is feeding back into the common and effecting the PIR zone....

Could this be it?

I've disconected the normally open zone to try and rule it out....but, is there any reason why a comm terminal cannot support both a normally open and normally closed circuit? i.e. two zones sharing the same comm terminal, but one is normally open circuit, the other is a normally closed circuit - is this probelmatic?

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