"whisky-dave" wrote in message
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On Tuesday, 3 December 2019 15:27:06 UTC, Rod Speed wrote:
"whisky-dave" wrote in message
...
On Monday, 2 December 2019 16:30:17 UTC, Rod Speed wrote:
whisky-dave wrote
Rod Speed wrote
T i m wrote
Martin Brown
wrote

A wildlife PIR triggered camera might be more useful for your
application - that way you have some video of the scrotes.

I was going to investigate a(n invisible?) break-beam
sort of device that could be set higher than most ground
dwelling creatures and below the typical flight line of a bird.

Wouldn't work here, lots of birds zoom thru my trees at well
below human head height. Amazing how well they manage
to avoid crashing into anything at the speed they zoom thru.

As I found with my cat came many critters can cross
such beams I had quite a few months, perhaps attracted
by the dull red glow of the IR LEDs.

But it is possible to get hybrid radar/PIRs that can
distinguish between cats and people by body mass.

Not they don't they just use the amount of IR
refected and where the reflection comes from.

Thats just one way of doing it.
https://en.wikipedia.org/wiki/Motion...sor_technology

yes that is the way PIR works the clues in the name.

Pity about the hybrids. And thats what
the best of the pet immune ones are.

I dont currently have any outside the house,

why not ?

Too easy to steal.

So you have an alarm system that is to easy to steal,

Nope, I use surveillance cameras inside the house looking
out the patio doors which are much harder to steal.