Re: moving away from the remote-control paradigm

["Paul Gordon" <paul_gordon@xxxxxxx>]

That's the fundamental flaw with PIR technology - it is so inherently
unsuited to this kind of application that you _have_ to kludge it with
these
timer rules, otherwise you end up with the lights going off when you're in
the middle of reading your evening paper!

But, - suppose, as you say, you don't decrement the the "room
occupancy
counter" until an inactivity delay has expired (say 5 minutes)... now
consider, - do you do the reverse when entering a room? - I would imagine
not, - so in the space of 5 minutes, lets say you go for a piss, answer the
door to the Pizza boy, and go to the kitchen to serve it up.. - Now you
have
set about 4 seperate rooms to occupied, all of which will remain so for 5
minutes - according to your house, there are now 4 people in residence! -
no
mean feat if only two people live there!

If SWMBO is moving around upstairs as well, it's not hard to imagine your
house occupancy count spiraling ever upwards!

So, you say, - you tell the house the max number of occupants that are
permitted... - if there are 2 of you living there, then there can only ever
be a person in two places in the house, so the occupancy count should never
go above 2. - if a 3rd room detects occupancy, then one of the previously
occupied rooms must now be unoccupied, so you look at your detector
histories and find out which of the allegedly occupied rooms has not
triggered for the longest period of time, and mark that as now being
unoccupied... But suppose that the wrong room is chosen? (perhaps because
you might be sitting still reading the paper...) Worse, what happens when
you have friends come over, or the man comes to read the meter? - you then
genuinely do have more people in the house that the house refuses to
acknowledge!


Think about it long enough, and you're brain will explode as well!...

Paul G.




-0000
>
>It should be possible to come up with a reasonably reliable system
using a
>combination of beam breaks and PIRs. For example beam in living room
door
>is
>broken plus activity on PIR in Living room = living room occupied, beam
in
>living room door broken and no activity on PIR = living room empty. If
you
>couple this with counting beam breaks you will have a reasonably
reliable
>system especially if you set the timing so that the system only flags
the
>Living room as empty once there has been no movement for say 10
>mins....personally I can't sit still for 5 mins unless I am asleep ;)
>
>Mick
>
>  Mark McCall <mark@xxxxxxx> said:
>
> > Remember reading way back at the start about this guy that had
two IR
>beams
>in his door frame.  Order they were broken in gave direction of travel
and
>central controller kept a count of people as they went in and out so it
>didn't turn lights out until it knew there was no one left in the room.
> >
> > He couldn't figure out why lights were still on one time and no
one was
>in
>the room.  Then he remembered he'd carried a chair into the room which
was
>slightly in front of him and seen as another person :-)
> >
> > Nothing's perfect in this game.
> >
> > M.
> >
> >   ----- Original Message -----
> >   From: Mark Harrison
> >   To: ukha_d@xxxxxxx
> >   Sent: Wednesday, August 08, 2001 4:39 PM
> >   Subject: RE: [ukha_d] moving away from the remote-control
paradigm
> >
> >
> >   Kieran,
> >
> >   Thanks.
> >
> >   Is there some way of sensing not just that I've been through a
doorway
> >   (broken a beam), but to tell which DIRECTION I was going in.
> >
> >   Given that there are only 2 of us in the house, it wouldn't be
beyond
> >   the wit of man to be able to say that "person enters
room", ROOM IS
>NOW
> >   OCCUPIED, "person enters room", "person
leaves", "person leaves", ROOM
> >   IS NOW EMPTY ... type of thing, but this is contingent on being
able
>to
> >   detect the diffence between "enters" and
"leaves".
> >
> >   Regards,
> >
> >   Mark Harrison
> >   Head of Systems, eKingfisher
> >
> >         Yahoo! Groups Sponsor
> >
> >
> >
> >
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> >   http://www.automatedhome.co.uk
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>
>
>--
>
>
>


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