Nothing to do with cars question

[Deleted account DD]

Hopefully therell be someone on the forum who knows this one

PIR sensors on burglar alarms, are they normally open circuit and close on activation or are they normally closed circuit and open on activation :doh:doh:doh

I need to rplace a couple in our house, its that long since I've had to buy any I cant remember which way round and I know you can get both :augie:doh

 

[zippy656]

PIR thats waht i need....

turn the lights off the kids keep leaving ON!!



um could be either... depends on use

 

[Deleted account DD]

Helpful answer mate




Keep watching a decent one may appear :thumb2

 

[Deleted account DD]

Just been looking via google and my monies on normally closed because most systems tell you to wire multiple pirs in series

 

[(RIP) PLANK]

cant you take one of your old ones down and test it?

I beleive thay are normaly closed, as in this case cutting the wires would cause an open circuit and would set the alarm off, so it makes sense.

Though it has been a long time since i have messed with alarm systems!

 

[rayf3262]

The majority of the ALARM pir's are normally closed (the idea being if you cut the wires it creates an alarm condition) some units have a small reed relay that has changeover contacts offering both NC and NO options.
Ray

 

[Deleted account DD]

Thanks folks :thumb2