RE: Occupancy Sensors and No Light Switches

[REB.Barnett@xxxxxxx]

I tried this sort of idea when I first had Comfort. These are the main
problems I had...

Light sensor - you've already thought of this. In our house one sensor
isn't
enough to accurately spot when it is light or dark. IMHO, you need at least
an East and West sensor, and some intelligence to work out which rooms are
dark and when. I found I was quite fussy too, and that the lights would
come
on too early one day, and too late the next - it depends on ambient light
levels, whether you've just come in from outside etc. etc. A discreet
button
somewhere to say "It is now dark" and "It is now light"
is perhaps a good
idea.

Occupancy sensors - I couldn't get this to work. Switching lights on is
easy
so long as your sensors are positioned intelligently, and are sensitive
enough. I found that standard alarm sensors tend not to be - they are
usually positioned to be most sensitive to intruders coming through windows
etc, not people walking through internal doors. Knowing when to switch off
lights is much harder. A person sitting still is invisible to most sensors
I
could think of. I now have one room set such that it switches off after a
period of inactivity, with inactivity being determined by no movement in
that room or the adjacent hallway. The rest rely on a manual X10 off
switch.

X10 control - I found that alarm sensors have a time lag when activating,
Comfort has a small processing lag when movement is detected, and X10 can
also take a while. In all the lags add up to about 1-2s which is annoying
at
first, but you get to live with it. You sometimes end up wondering if you
would have been better pressing a switch when you walk into the room...
Another problem is that X10 isn't a reliable transmission protocol. Signals
sometimes go missing, which is also annoying 'cos the lights don't come on.

Overnight guests - final thing to remember. We occasionaly have guests stay
overnight in rooms with automatic light controls. You need to provide a
mechanism to prevent the lights switching on everytime they roll over ;-0 I
tried using either a flag in Comfort, or unplugging the light. In the end I
used one too many flags in Comfort resulting in nightmarish code to debug,
so I now resort to simply unplugging devices...

Hope this doesn't put you off. The real key to it IMHO is the occupancy
sensor. If you can get this to work you're sorted (and let me know how too
please!). I'm now edging more to installing a number of those natty X10 RF
switches around the place - the photos on Mark's site make them look quite
discreet and high tech, so could be a good solution to switching the lights
off.

Ray Barnett.






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