Door contacts or PIR's

[Guest Chewie]

Thats a bit to cryptic for mr eng

Can you elaborate

I have also edited my previous post

[Guest]

Thats a bit to cryptic for mr eng 

Can you elaborate 

I have also edited my previous post

38588[/snapback]

if you have a pir facing the door,you have to watch out for the postie posting the letters at 100 mph into the hallway which can cause false alarms....

[ian.cant]

Thats a bit to cryptic for mr eng 

Can you elaborate 

I have also edited my previous post

38588[/snapback]

It is possible that when Postman Pat chucks his wad through the box it can trigger the PIR so dont point it at the door. Point it back into the hallway.

[Guest Chewie]

OK thanks, but dont they look for a heat signature as well as movement.

[Guest]

OK thanks, but dont they look for a heat signature as well as movement.

38594[/snapback]

that depends if its recorded mail..

[Guest Chewie]

[ian.cant]

OK thanks, but dont they look for a heat signature as well as movement.

38594[/snapback]

Nice one Gaz!

How a PIR works isnt the way your thinking. It see's IR energy and uses that as a reference, then if anything changes rapidly using its processors it decides if its big enough a change of reference and acts accordingly.

So Imagine your nice warm floor and suddenly theres a big wet cold envelope on it. Depending on the quality of your PIR and the sensetivety set up will depend on wether you get false alarms or not. Plus a bit of luck and the weather and ............

[Guest Chewie]

OK thanks so it can trigger from a rapid reduction in temperature as well as an increase, learn something every day.

[ian.cant]

OK thanks so it can trigger from a rapid reduction in temperature as well as an increase, learn something every day.

38606[/snapback]

Which is why when on a cloudy but sunny day, when the sun pops from behind a clound and creates a hot spot on a floor it can trigger a PIR. Also if a spider walks across the sensor it will trigger because it see's a major change in its reference picture.

[Guest Chewie]

Thanks for all your help Ian (and everyone else) I really appreciate it. I am looking at PIR's from TLC. Wonder if you could make some reccomendations.

360 deg ceiling PIR for the garage. Either of these any good. We do have a Chincilla in the garage in a cage, could this possibly cause false alarms with these PIR's.

http://www.tlc-direct.co.uk/Main_Index/Ala...cial/index.html

Then I need one for the hallway, one for the kitchen and one each for the Living room, Dining room and study. Not really sure what I should be looking for out of these ones.

Kitchen ?

http://www.tlc-direct.co.uk/Main_Index/Ala...arsh/index.html

Should I be looking at standard or dual tech for the rest ?

http://www.tlc-direct.co.uk/Main_Index/Ala...larm/index.html

http://www.tlc-direct.co.uk/Main_Index/Ala...Tech/index.html