Justin,

 Typically I believe the way these things discriminate between man
 and beast is that they aim the devices so that the bottom of the
 cone of coverage is about 2-3 feet off the floor.   That way, most
 house pets won't set off the alarm because it is not within the
 transmitted beam.   However, humans, being substantially taller
 than most house pets, is within the beam, and does set off the
 alarm.

                                          Regards,

                                            Jim








On Tue, 27 February 2001, Justin Fielding wrote:

>
> Lookup pyrometers, they may be a good way to do this as you could adjust the
> sensitivity.  They actually work by detecting movement of body heat ( I
> think).  With an IR beam it is all or nothing,
>
>
> ----- Original Message -----
> From: "Simon Ethier" <Seth889@STARTREKMAIL.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Tuesday, February 27, 2001 5:21 PM
> Subject: Re: [EE]: Infrared Detector vs Pet
>
>
> > I don't really know ... All I'd like to do is build a cheap but effective
> > "IR" detector that do not triggers with pets like cats ...
> >
> > Thanks
> >
> > ----- Original Message -----
> > From: "Justin Fielding" <j.fielding@BTINTERNET.COM>
> > To: <PICLIST@MITVMA.MIT.EDU>
> > Sent: Tuesday, February 27, 2001 11:59 AM
> > Subject: Re: [EE]: Infrared Detector vs Pet
> >
> >
> > > I assume that you are talking about IRbeams (which must be broken to
> > trigger
> > > alarm) rather than a PIR detector (using a pyrometer).
> > >
> > >
> > > ----- Original Message -----
> > > From: "Simon Ethier" <Seth889@STARTREKMAIL.COM>
> > > To: <PICLIST@MITVMA.MIT.EDU>
> > > Sent: Tuesday, February 27, 2001 4:07 PM
> > > Subject: [EE]: Infrared Detector vs Pet
> > >
> > >
> > > Hi, I'm wondering.. I heard in a publicity of an alarm company that they
> > > have an infrared detecter which can make the difference between pet and
> > > human (how, I don't know ... ok it don't really "make" the difference,
> but
> > > the IR won't react to a cat for exemple, but will react to a human) I
> > found
> > > this very cool, especially if you have pet at your house...
> > >
> > > I'd like to build something like that ... Do any of you guys know what
> is
> > > the trick ?  Is it less sensitive ? Does it require a minimum of
> movement
> > > ...
> > >
> > > Thanks
> > > ---
> > > Simon Ethier
> > > sethier@justine.umontreal.ca
> > > ICQ 66019153
> > >
> > > --
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jim@jpes.com

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