Garage - PIR false alarm (car alarm related?)

[Gadget]

Hi,

I have searched the net high and low and can't seem to find anyone who might be experiencing a similar problem...

Around 5 weeks ago I added a PIR in my garage to protect a new car. Since I got the car I have had 2 or 3 false alarms on this sensor. I believe the sensor is OK but there are a few things that I am concerned about that could be causing the false alarms.

Is it possible that the IR produced by the cars own alarm could be detected by the house PIR? I understand that most IR produced by PIR sensors can't penetrate glass? Wouldn't that mean that there's little to no chance that the garage PIR is detecting IR from the Car Alarm? Although it is a convertable and it's rear window is plastic, and no doubt there won't be a perfect snug fit with the roof against the windows, is it possible that IR is leaking out?

The garage is quite drafty, is it possible that wind / light changes could be causing problems?

The false alarms seem to be appearing around the same approximate time, around 03:00 am in the UK atm

Any advice related to garage alarm setup would be appreciated.

[Jim]

I think IR can go through most glass. It does with my IR cameras. The problem is usually reflection when you're using an IR camera with a built-in light source. When placed to look through glass you get the same effect as trying to take flash photography through a window. You just get a bright reflection. My general belief is that the IR will easily pass through the glass unless it is filtered specifically to prevent it. Whether that will trigger your alarm I can't say but the output should be constant I would think not intermittent at the same time of day.

Is there a possibility that the "false" alarms can be triggered by a cat or similar creature? In this instance it wouldn't be false as much as it would be undesirable sensitivity.

Also, is there some overiding phenomena that would bleed over into your system around 3 AM? The reason I'm asking is that we had a neighbour who was a taxi driver. He got in about midnight every night. When he got home, he keyed his radio to report off work and it drove our PC speakers mad even when the PC was off, plus it triggered my wife's mobile phone to make strange noises.

[securityman]

In my experience as a Security Fitter we never Fit PIR in Garages as once we did and someone kept going off and we found out they had MICE so maybe checking for any Dropping as maybe you got Rats or Mice or something there and if that Not working Try getting maybe a local Sparky or someone who Installs Security Systems