RE: Occupancy detection

["Andrew Richards" <andrew.richards@xxxxxxx>]

Re strain gauges - you might want to check out some pressure sensors
marketed by Steadlands:

http://www.steadlands.com/

These are basically variable resistors, with the 'variability' dependent on
pressure.  I'm looking to use them as touch sensors for light switches,
with
the potential for using them as dimmers in the future - light touch = dim,
heavy touch = brighten.  Obviously needs some circuitry behind it, but
shouldn't be too difficult.


Andrew



-----Original Message-----
From: Keith Doxey [mailto:ukha@xxxxxxx]
Sent: 03 January 2002 19:39
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Occupancy detection


Pressure mats are only simple Open/Closed contact.

What you need is some sort of strain guage (no jokes about toilet functions
please! ) which has a variable output dependant on load. This then needs
some intelligence to convert to a digital signal.

One further idea on the PIR theme....

....how about when the time period is about 1 minute to timeout, a discrete
chime sound comes from a small speaker to indicate the lights are about to
go out, waving an arm etc would retrigger the PIR and a double chime
provides confirmation that the lights will not go out. The
"confirmation"
chime would only occur if the warning had been sounded so that repeated
chiming caused by movement would not be a problem.

Not perfect I know, but relatively cheap and simple. The occasional "1
minute warning" would be much better than being plunged into darkness.
If
the room was empty then the chime would be ignored and the lights would go
out 1 minute later.

Keith

-----Original Message-----
From: Mike Griffiths [mailto:mike@xxxxxxx]
Sent: 03 January 2002 16:36
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Occupancy detection


I've never opened one up but judging by the build quality I would say no
Its design is such that you shove it under a carpet and it you walk on it
the NO goes to NC and NC goes to NO
And that's about it
Mike

-----Original Message-----
From: Mark Harrison [mailto:Mark.Harrison@xxxxxxx]
Sent: 03 January 2002 16:32
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Occupancy detection

Mike,

You are correct. It was an X-10 wireless PIR, bought in the days before
I started wiring with CAT5e.

I am indeed serious. I have an HA-compliant, non-destructive wife, but
she didn't like being cast into darkness :-)

When you say "no tweaks" does that mean you can't adjust the
"base
pressure"?

Mark Harrison
Head of Systems, eKingfisher


-----Original Message-----
From: Mike Griffiths [mailto:mike@xxxxxxx]
Sent: 3 January 2002 16:21
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Occupancy detection


Mark
When you say Mary "took down and hid" the PIR
Are you serious?
I presume it was a wireless PIR??

Well it brought a smile to my face

On a more serious note the normal pressure mats are just that
Over a certain pressure and they change state
No tweaks I'm afraid
The best solution for this is the one I have
The house has such small windows If we are in the house the lights are
on
downstairs and the pressure mats on the stairs turn on and count how
many
people are upstairs


Mike


-----Original Message-----
From: Mark Harrison [mailto:Mark.Harrison@xxxxxxx]
Sent: 03 January 2002 16:13
To: ukha_d@xxxxxxx
Subject: [ukha_d] Occupancy detection

Hmmm... I've been thinking more about this.

At the moment, there's only one room where my "occupancy
detection"
actually works reliably. (Ie both always detects when I come in, and
doesn't give the "false exit".)

This room is my dressing room, and has the key characteristic that, when
I'm in there, I'm moving about. As such, a single PIR, cunningly
positioned, does the trick, together with an HV timeout of about 90
seconds.

This was all sparked from some things that Kieran Broadfoot said at one
of the previous London meets - in fact, the meet in which I uttered the
famous line about an Asian domestic servant :-)

Kieran's ideas have worked out very well, and I'm really finding that
the house WORKS! Remote control is nice, but this is WAY more useful
when it comes to human-house interaction.


In my study, however, I don't move about enough, which got me to
wondering about pressure pads. I have two chairs in the study, both of a
contstant weight.

Is it possible to get a pressure pad with a sort of "trigger
weight"
setting, that could go under the chair. Then EITHER coming into the room
(triggering the PIR) or sitting on the chair would give a "Room is now
occupied" event. But a "Room is now empty" event would only
be triggered
once BOTH a "PIR no longer detects anyone" and a "pressure
pad no longer
reports weight" events had happened.)


In Mary's bathroom it's even worse. After being cast into the dark twice
(once while on the loo, once while in the bath), she has taken down, and
hidden the PIR. With the bath, I can imagine that a pressure-pad
solution would work (ie if the bath is full of water, then the room is
deemed to be occupied, and don't worry about distinguishing between
"full of water" and "full of person".) On the loo, a
"break beam" type
of thing could tell if someone were sitting on it.


Any one got any thoughts about this.


Mark Harrison
Head of Systems, eKingfisher


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