Re: Occupancy detection

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

<ben.parees@xxxxxxxxx> wrote in message
news:1186161221.507446.92080@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> I'm glad to see this getting attention, because motion activation of
> lights is definitely on the top of my list of things i'm not happy w/
> about my automation installation.

It's definitely at the top of my list after I ended up at the bottom of my
stairs!

> However, reliability doesn't seem to be the issue for me, what is
> an issue is the latency.

My fall was caused by precisely by the latency problem.  I came home and
heard the sounds of a dog yelping piteously in the basement.  The stair
light latency was fast enough for normal speed but not for full military
thrust.  I recall as I hit mid-stairs (about where the light from the
kitchen peters out) thinking "Hmm - the light wasn't coming on and that I
couldn't see where I was going and that I was going there very quickly!"

I missed the last step and sailed into a shelving unit that brought an old
PC crashing down on me.  I cracked a rib and a front tooth.  Turns out the
dog had gotten her jaw stuck in the crate wire wall trying to reach a
Nylabone that had fallen out.   I've known people who died in stairway
falls, so when I finally came to a rest *without* a broken neck I considered
myself one lucky dude, even with all the injuries and damage.  A little
bending of the crate "bars" unhooked her lower jaw and I went off the ER.
That's when I decided to return to manual switching for the basement stairs
until I could do something better.

> Generally I have to carefully position the sensors so that just walking by
the
> room (but not into it) doesn't trigger the light to come on, but this
> means that you have to take a step or two into the room before you are
> detected.

I mount mine about two feet inboard of the doorway pointed across the door
opening.  They're blind to pass-by traffic but react quickly when someone
passes through the doorway.

> Add to that the delay of the detector picking you up once
> you are in range, sending the signal, the tranceiver relaying the
> signal to the powerline, my PC picking up the signal, and my PC
> broadcasting a "hey turn on the kitchen lights" signal back down, and
> it takes at least 1-2 seconds before anything happens.

To me that's just too long.  It's barely acceptable in non-emergency
situations but not if you're really moving.  Since I know now that's a
possibility, I've got to either implement a faster and more reliable system
(no PC involved, I'm afraid) or go back to manual switches.  A system that's
capable of making a crisis situation worse won't do it for me, not after the
fall.

> (I relay through the PC so i can do more macro control such as only
turning on
> lights when it's after dark).

Sounds very familiar.  The X-10 Hawkeyes were a fine start in selling me on
the idea of automating lights based on motion detection.  But now the time
has come for more than simple "on/off based on motion" control.  Large
stores have triple-redundant opening and closing mechanisms because they've
been sued so many times they need the additional reliability.  If that's
where the "state of the art" is, then using just PIR via RF via PC via PLC
is way far behind.  The light control, at least for dangerous areas like
stairwells, needs to be as close to instantaneous as possible.  I believe
that presents just too great a hurdle for X-10 to reliably pass, even with
the tremendous boost in reliability that Jeff's XTBs have given my system.

The problem, as I see it, is that I still want that light under X-10
control.  The reality might just be that in order to do what I want, the
emergency lighting might well have to be "off the grid" as far as X-10 is
concerned.  Since a broadcast storm can knock out critical X-10 lightning,
I'm thinking more and more stairway and other critical lights have to have
an
independent control mechanism that's completely immune to any known X-10
problems.

> Often this means walking into a dark room.  I've actually
> subconsciously trained myself to walk into the room more slowly to
> ensure the lights have a chance to come on before i get too far and
> walk into something i can't see.  I started on HA to make my house
> adapt to me, not to adapt myself to my house.

I didn't think about it until you mentioned it, but I, too, had conditioned
myself to walk more slowly when I knew I was in the view of the PIR sensor.
That's an OK solution until there's a problem and you're rushing to respond
quickly.  Ironic, isn't it, that we've both adapted to the limitations of
the hardware instead of the other way around!    I think that's because the
first step has been made very easy by X-10.  It takes only 10 minutes to set
up a fairly sophisticated motion/light control system.  It's the next step -
improving latency and reliability - that will take a lot of customized work.

> One thing i've considered to help the situation is a product I saw a
> while ago (sorry no link handy right now) which acts as a whole-house
> radio reciever and connects to your PC directly.  This would eliminate
> the "sensors->transceiver->PC" leg of the trip and probably cut the
> response time in half.  You still have the latency of being noticed by
> the sensor and the PLC lag time though.  Incidentally this product has
> a "real" antenna and claims to boost reception ranges significantly.
> I'm sure Dave Houston knows what i'm talking about and knows whether
> those claims are valid.

I think that's the WGL "whole house" transceiver, and indeed I acquired two
products very much like it, but both were unsuccessful.  I live in a wire
and lathe plaster wall house with lots of steel shelving and other
impediments to RF.  There was no single place to locate an all-housecode
transceiver that could "hear" all the transmitters.  That situation bred a
whole load of other problems.  Collisions from competing transceivers was
the biggest problem.  Sometimes the light wouldn't trigger, other times the
wrong light would.  The worst instance caused a light to flash on and then
off when you entered a controlled room.

While it may be working well for you, the bottom line for my situation is
that PIR via RF just isn't reliable or fast enough.  That's why I was
looking at "beam break" units.  I can't imagine going through a doorway so
fast that a detector wouldn't "see" the break in the light beam
transmission.  For that reason alone, IR beams seem to me the most reliable
of the detection options within a hobbyist's price range.

> I've considered going the route of individual hardwired motion sensor
> lightswitches like lutron makes which would no doubt operate faster
> than my x10 mechanism, but I really like having a central "brain" to
> my house and having the ability to set rules or be able to remotely
> control those lights independently if i need/want to.

I agree.  What I want is a system that senses motion and occupancy,
processes that information quickly and reliably, stores the information for
future analysis, and exercises some "common sense" when turning lights on or
off.   Turning a light OFF when the system "knows" that there's still a
person on the stairs lit by that light should be close to impossible. That's
why I've become interested in floor mat sensors, IR "beam break"
sensors, PIR's, microwave, ultrasonic and anything else that can help solve
the problems associated with X-10 PIR controlled lighting.  As I see it, the
system should be heavily biased toward NOT turning out stairway lights until
there's a preponderance of evidence indicating that there's no one on or
even near the stairs.

X-10 and the Hawkeyes were a good start, and I learned an awful lot about
the "real world" problems of occupancy and motion detection for very little
money.  But the time has come for a better, more reliable, faster and
smarter solution.  Or a return to manual light switches!

--
Bobby G.