Re: Dual Tech motion detectors with dual relay outputs ?

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, 24 Aug 2007 14:54:42 -0700, Jim <alarminex@xxxxxxx> wrote in
message  <1187992482.176450.182980@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>I didn't read all the replies in this thread so you may have been
>already advised of the following.
>
>Sentrol makes dual tech motion detectors that you can shut off the PIR
>or the Microwave detection. If you had to and you set one with PIR
>detection and one with Microwave detection, would that solve your
>problem?
>
>Also .... I don't know how much you know about the difference between
>PIR detectors and Microwave detectors.
>
>You're project sounds as if timing is an important factor but I don't
>know how exact you're planing on needing.
>
>Just in case, ..... I think that where you mount the detectors, in the
>path of movement will be a most significant factor, as PIR detectors
>are most sensitive with cross motion, while microwave detectors are
>most sensitive to toward and away motion. Also, the moving object that
>you want to detect will have some impact on the sensitivity of the
>detectors. Lots of metal or RF reflective items will cause a microwave
>device to detect quicker than soft plyable material. Heat sources or
>material that is highly reflective of infrared light will cause a PIR
>to detect quicker than will cooler  or IR absorbent material. Also ...
>with PIR's, the ambient temperature and lighting can either enhance or
>inhibit the sensitivity also.
>
>You may find that the inherent variables of the detectors is too wide
>a spectrum.
>
Thanks Jim. That was very helpful.

In short, what I want, in the least obtrusive package and 'reasonably'
priced is:

1) Occupancy detection optimized for speed such that lights are quickly
turned on as a person walks into and through an area (false reports are a
secondary issue) and

2) Intrusion Detection that avoids falses. Most detectors and descriptions
literature address this application.

My assumption was that PIR were typically faster.

Your point about  direction of travel is especially useful and important.
Robert pointed out the very unobtrusive Visonic Spy series,  one of which
can be used to make a narrow vertical or horizontal detection 'wall'. So in
the bedroom, for example, I would have  a sensor near the exit to the hall,
and one near the exit to the bathroom. These would operating in the manner
of a beam-break-- not the same technology or physics, but similar
geometries.

The interior and exterior walls of our home are solid brick, so
wall-mounting involves lots of chiseling, dust and replastering. In some
places, ceiling mounting is simple and conventional (complete with
fiberglass, coal dust, nails through the roof boards everywhere, jumping
across rafters to avoid putting foot through ceiling  and so on -- but
still better than pounding through brick ;-)

So in many places, a down-facing detector with narrow detection area and
the PIR set to a low count  would seem to be preferable for the lighting
path function. As I think about it, in mind's eye, I was thinking mostly
high corner mounting which is not optimal for PIR detection (person tends
to walking toward these, not crosswise in my particular geometry/layout.

So I'm rethinking each of the locations with geometry in mind, rather than
focusing on a one-size-fits-all detector  solution.

I will probably end up with a high corner dual tech in most places for
intrusion  supplemented with ceiling mounted narrow volume/width PIRs in
critically chosen locations for the lighting path function.

Thanks all. You've been helpful ... Marc

Marc_F_Hult
www.ECOntrol.org