On 28/09/2017 20:01, Andrew Gabriel wrote:
In article ,
Martin Brown writes:
On 27/09/2017 22:06, Andy Burns wrote:
Andrew Gabriel wrote:

Bats tend to fly up into corners of rooms (looking for something
they can grab hold of), and that's exactly where PIR's are often
mounted.

Maybe there's circuitry within the sensor (assuming it's not actually a
combined PIR/ultrasonic one) which happens to oscillate in the bat's
hearing range that they find "interesting" ...

I think it is more that the bat explores all the available space in the
room looking for a way out. If they ever end up on the floor then they
can find it impossible to climb up again on painted skirting boards.

In the wild they would climb the nearest rough piece of wood.

Many years ago in a previous house, I woke up in the middle of
the night. Not sure what woke me, but there was enough residual
light in the room for me to make out several things dive-bombing
me in bed. Turned the light on, and they were bats, repeatedly
swooping down in the middle of the room as they flew between
opposite corners of the room, trying but failing to find
something they could grab hold of in the corners near ceiling
level. I was thinking if I sit up, I'm going to get hit, but
then I thought they have good echo location for that, and sure
enough they went around me.

I have been known to give up when I am on my own and sleep with a bat
wizzing round the room. My wife insists I evict them. They eventually
settle on curtains, but the young ones are a bit dim and can get trapped
on the floor against skirting boards. Bat conservation taught me how to
handle them properly since they got fed up with call outs in peak
season. Ours is a summer roost near open fields.

Wasn't much I could do to catch them, but they eventaully ran
out of energy and dropped to the floor. Hadn't occured to me
they can't take off from the floor, but I lifted the outside
at that point and put them in a tree.

They had come in where some large holes were left in the ceiling
through to the loft the previous day. I fixed up the holes
next day. I was often in that loft and it was all nice and clean
with new insulation, and I never saw any sign of them in the
loft, but presumably they were there somewhere.

Doesn't nee much of a hole they can get through cracks in mortar fairly
easily. I have a bunch or old roasting tins under their roost in the
loft to catch their dry droppings which makes good fertiliser.

There will be a small pile somewhere in your loft but nothing to worry
about. I favour live and let live - they eat mosquitoes after all.

--
Regards,
Martin Brown

In article ,
Bill Wright wrote:
On 29/09/2017 00:05, Dave Plowman (News) wrote:
In article ,
Bill Wright wrote:
Personally I'd forget window contacts. They do false alarm if there's
a gust of wind or a bird hits one.

Eh? If you're talking reed switches you'd need a pretty terrible
fitting window before wind would break the circuit. And if things like
that are flapping around in the wind, a PIR might well trigger too.

Course I'm not talking about simple reed switches. I'm talking about
break glass detectors.

Ah - I'd not call that a window contact.

--
*Shin: a device for finding furniture in the dark *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
wrote:
I was thinking of using sealed reed switches (which is what I used in
the previous house) - how do they get affected by damp?

They don't. Except perhaps the terminals if kept soaking wet. The switches
themselves are hermetically sealed.

I hate seeing such things.

So here, with sash windows, I drilled a hole in the sill to take the
switch part and a corresponding one in the window rail for the magnet.
Cable chased into the wall as and when the rooms were re-decorated. Same
sort of trick worked for the modern sliding PVC patio doors in the kitchen.

But this house has suspended wood floors and internal stud walls so
relatively easy to hide cables. A modern house with solid everything would
be a different matter.

Didn't bother with the top sash as I doubt many burglars would want to
crawl over the bottom one to get in.

--
*Your kid may be an honours student, but you're still an idiot.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Bill Wright writes:
On 29/09/2017 00:05, Dave Plowman (News) wrote:
In article ,
Bill Wright wrote:
Personally I'd forget window contacts. They do false alarm if there's a
gust of wind or a bird hits one.

Eh? If you're talking reed switches you'd need a pretty terrible fitting
window before wind would break the circuit. And if things like that are
flapping around in the wind, a PIR might well trigger too.

Course I'm not talking about simple reed switches. I'm talking about
break glass detectors.

Only ever had one false alarm from those in 20 years.
When I came home, there was a perfect imprint of a pigeon
with wings outstretched in white dust on the outside of
the glass, although it hadn't broken the glass.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
writes:
Personally I'd want to treat one detection event as a minor warning, and 2 =
as a person present rather than 1.

That's called double-knock.
Some systems are configured so the second event must come from a
different sensor, but that's only viable if you have enough sensors
separately connected to the panel that any intruder is pretty much
guaranteed to trip more than one. It can also delay the alarm so
that instead of sounding before the intruder gains entry, the alarm
is only raised after gaining entry, and that's not necessarily good,
although it significantly reduces false alarms.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]