On 19/02/2021 20:38, Brian Gaff (Sofa) wrote:
I don't see how you can have a pir that works that does not detect pets. It
is after all just detecting changes in the heat radiation as something moves
across domains on the sensore one assumes. This would need some smarts to
ignore certain profiles.

Pet friendly PIRs have been available for many years. We have an indoor
one, in the living-room, that I fitted about 20 years ago. We keep the
doors shut so that our cats cannot get to the rest of the house when the
alarm is on.

The manufacturer's specs list what size of pet they will ignore. Cats
are well within the ignore range, unless they get up high, while dogs
are okay, up to a certain size.

The basic versions work by having a cut-off low down, but others combine
that with a second sensor (possibly with a mid-level layer cut-off and
only trigger if both are activated (an upright person being in both
zones at once). Others (like the one we have) combine PIR and microwave
sensors - we can see the LED change from green to yellow as one is
triggered and then red if the second is triggered).

In this case, as it is for a light rather than an alarm, false
triggering is not a major problem - we just want to cut down on the
number of times a night the curtains/blinds suddenly brighten.