burgular alarm install advice

[swc]

Hi
I'm looking for some advice on placement of pir.

1)How do most of your cheapo PIR sensors work

2)alot of ppl say to not face them to a window. However what if it's unavoidable due to the room layout?
They say that sunlight can cause false alarms as the sun moves. Are there pirs that are resistent to such issues?

3)Is there a relay unit I can buy to connect up to the bell box input so that when it goes off, it switches on a mains rated relay to turn on security lights?

 

[Richard Burns]

Hi
I'm looking for some advice on placement of pir.

1)How do most of your cheapo PIR sensors work

There is a sensor inside the unit that detects changes in the heat energy received at the sensor (normally for about body heat). humans give off heat and if the heat detected changes because of motion (normally reasonably fast) then the sensor activates.

2)alot of ppl say to not face them to a window. However what if it's unavoidable due to the room layout?
They say that sunlight can cause false alarms as the sun moves. Are there pirs that are resistant to such issues?

You can mask the area of the sensor that points toward the window, if this will not make the sensor ineffective.
Sunlight shining on a sensor from reflections etc. can cause it to activate, they try and design them to be not so sensitive to this but fairly unsuccessfully, if you can mount the sensor high up and there are no reflective surfaces nearby then you may be able to avoid the sunlight. Changing the angle of the senor can help at times.

3)Is there a relay unit I can buy to connect up to the bell box input so that when it goes off, it switches on a mains rated relay to turn on security lights?

Should be an auxiliary contact in the control panel to power things that are not part of the usual set up if you want lights to come on when the alarm is activated, check the loading limits and use a contactor if the load is too high.

My ideas above

 

[swc]

Does the accenta G4 mini have the aux contact you speak of? If not could you recommend me a alarm panel that does? Good idea to know this sort of stuff for furture reference.

Also could you give me an example of the contactor you speak of?

 

[KevinS]

I have pointed PIRs at windows loads of times without problem, the corner near the ceiling never gets direct sunlight

the accenta does not have this on but any 12/240 contactor will work, just wire it into either the bell or strobe output

 

[IzzyS]

You could always fit a dual tech sensor - microwave + PIR detection combined. Ideal for unheated locations like garages or overly hot conservatories...

 

[KFH]

I usually use dual PIRs (MW & IR) to reduce risk of false alarms. Unless you are doing a large installation the difference in price is not large.

Having said that my name is mud in my local village, alarm in village hall went off at 3:00 AM on Sunday morning, police, neighbors the lot were out. I had to fight off the spiders to get to the sensor that had tripped. I have recommended a more frequent cleaning regime.

 

[IzzyS]

I find a bit of blutak to seal the cable entry (or Pirelli R391 sealing compound, if you have money to burn) usually keeps the spiders out.

 

[KFH]

They were not inside the sensor, that was well sealed. They were running around over the outside, lots of them, not quite up to tarantula size but trying hard. It is on double knock now so fingers crossed.