Re: PIR Sensor in a Conservatory

[Tim Mitchell]

In article , Jon Weaver writes

My Conservatory is finally finished (Which I am sure you will be glad >to hear means no more questions) > >I am thinking of fitting a PIR sensor off of my house alarm, just to >give me that extra bit of protection. > >Is a PIR a good idea in a construction like this. > >As the temperature will fluctuate, could this trigger the PIR. > >But more imporantly, because its almost entirely glass, can a PIR "see >through" the glass, to anything moving outside?

I haven't tried it, but would have thought that you would get lots of false alarms due to sunlight & temperature changes. PIR's always say "don't point at a window", well you can't really avoid that in a conservatory.

You can get "dual technology" detectors which combine doppler radar & PIR, that might work.

[Toby]

Our shops used to suffer false detection due to large plate glass windows and thermal effects, but we never pointed PIRs at the plate glass they were usually mounted above.

In your case a 'break glass detector' coupled to door contacts may be the way to go. I don't mean the silver tape you see applied to large commercial windows; the BGD is more of an audio device. The combination of an impact & the breakage will trigger it, a single sensor will cover a 16m2 area easily. Sadly alarms didn't seem to bother the ram raiders we were prone to.

Toby.

[BigWallop]

You would have to fit a dual-tech microwave passive infra-red if it's in a situation like that. A dual-tech must have a moving heat source to be activated properly and is designed for such an environment such as conservatories and areas where wide temperature and lighting variation occur. There are many different styles and sizes on the market now, so you can pick one that will suit your surroundings.

Here's an example of just one from Pyronix:

web search for dual-tech PIR will bring up many more.

[Martin]

You can get PIR sensors specifically designed for harsh environments like conservatories, have a look at

[Paul]

I Have had a dual-tec pir sensor in my conservatory for three years now and never had a false alarm.

Paul.