RE: Re: Occupancy Sensors and No Light Switches

[nick.broughton@xxxxxxx]

I understand that the 'Gates residence' controls room functions (Music,
pictures etc) by knowing not only that the room is occupied, but who is
in there?

Anybody know how this works and (more to the point) if us mortals can
afford it?

Nick

> -----Original Message-----
> From: paul.gordon [mailto:paul_gordon@xxxxxxx]
> Sent: 23 June 2000 12:34
> To: ukha.d
> Cc: paul.gordon
> Subject: Re: [ukha_d] Occupancy Sensors and No Light Switches
>
>
> I don't think this can really be done properly with only one
> form of input
> (IE PIR's) - at least not economically!
>
> I think you need a minimum of two types of sensor - PIR for movement
> detection within the room, AND perimeter sensing to detect
> actual entry/exit
> into the room.
>
> Perimeter detection could be by pressure pads by the doors -
> you'd need a
> minimum of two of them - one outside the door, one inside, to
> be sure of
> correctly deducing the direction of travel. This still would
> need care to
> ensure you could guarantee detecting someone using the door -
> IE the pads
> would need to be big enough to ensure that they would not be
> stepped over by
> accident... Also, some logic would be required to ensure that
> it didn't get
> confused when only ONE pad is activated (someone walking
> around one one side
> of the door, without actually passing through it...)
>
> Alternatively, a break-beam type detector in the door frame,
> positioned on
> the "outside" of the door - IE the opposite side to which it
> opens - so that
> the door itself never breaks the beam regardless of whether
> its open or
> closed...  This could be high enough of the ground to avoid
> pets, but still
> always "see" people passing through.
>
> A combination of both of these types of detector would
> probably be most
> reliable - allied with some reasonably simple "state"
> tracking - IE start
> off knowing the room is empty, then using the detectors
> combined inputs,
> it's possible to keep a counter of exactly how many occupants
> are in each
> room at any time.
>
> Entry or exit is determined by the order in which the zones
> are tripped, and
> the delay between each zone. - Of course, it's ALWAYS going
> to be possible
> to fool any of these systems, but only if you're in the habit of
> long-jumping through the doors in your house!!
>
> A front door is a far more tricky proposition - what about
> when someone
> comes to the door, and you have a conversation with them -
> both the inside
> and outside pressure pads would be tripped concurrently (although not
> simultaneously), and a break-beam would not be tripped at
> all! - anyone care
> to think about how you'd program for this scenario??
>
> No doubt about it though - this is going to need a lot of zones!! - a
> minimum of two per door, for every door in a room!...
>
> Why can't it be as easy as it is on Star Trek?? - Any of
> those i-button
> gizmo's have anything to offer for occupancy detection?? - How about
> proximity detection within a room, by wearing a special badge?
>
> Regards.
>
> Paul G.
>
>
> >This may be another daft suggestion by me but here goes
> anyway.... why not
> >mount the PIRs on the ceiling facing down just in front of
> the door, as you
> >oper the door the sensor would trigger before you got into
> the room (unless
> >you were running!). You'd probably need another sensor
> 'further in the
> >room'
> >for once-you-were-in-there detection. This assumes that you
> close doors
> >behind you though...
> >
> >Andy
> >
> >
> >
> >
> >
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