Re: Occupancy detection

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
news:46b30155.2031329000@xxxxxxxxxxxxxxxx
> Just a couple of points...
>
> 1. There's no reason to think the various motion detectors are saturating
> the RF environment. They only transmit for a very brief period (5 bursts
> that last about 65mS each) when triggered by motion so unless someone in
the
> household is now constantly wandering about aimlessly (or purposefully,
for
> that matter), RF activity attributable to the motion sensors should remain
> more or less the same over time. The decrease in range could be caused by
> any number of things - weaker batteries, higher humidity, temperature,
etc.

The RF range has decreased over time, and I did not mean to imply it's from
the RF detectors "saturating" the environment.  There are times in the
morning now where the X-10 RF flat out doesn't work unless you put a Palmpad
or keychain remote within a few feet of the transceiver.   Whether these
blackouts are caused by sunspots, military transmissions or whatever, I
can't say.  Without an RF meter it's just guesswork.

However, one doesn't need to know the cause to see the effects.  They are
pretty hard to ignore.  When it happens, all the wireless thermometer
displays either go blank or fail to update.  That sort of unreliable
environment makes occupancy and motion detection using the X-10 RF frequency
unworkable, at least IMHO.  The lax enforcement by the FCC tells me things
will get worse and not better as more and more wireless gizmos make their
way to market.

More importantly, the apparent lack of collision detection of the RF
component of the "chain of command" means that if there's more than one
person and one detector in the house, problems are bound to occur.  I've
tried all sorts of combinations of transceivers.  The protocol's just not
robust enough to support the task, at least in a house where there's fast
motion of more than one occupant.  When I lived alone, I recall being
skeptical about all the problems people reported with multiple occupants and
motion detectors.  Not anymore!

> 2. The IR used in the types of sensors you are considering is usually of a
> different wavelength and does not modulate a 38-40kHz carrier and IR is
also
> line-of-sight so it's unlikely to affect the Powermids.

That's good news.  I was worried because I didn't think either the sun,
CFL's or plasma TV's modulated a carrier or worked on the Powermid
wavelengths but managed to trash IR distribution just the same.  Like
mercury in CFLs, I hate solving one problem by inducing others!  I guess
I'll plunk down some bucks and buy a few of the kits:

http://www.apogeekits.com/ir_light_barrier_mk120.htm

and see what's what.  They're not very expensive.  Thanks for the input,
Dave.

--
Bobby G.