Hi Scott, Perhaps you are right, maybe the outer layer of fur is cool and obscures the inner layer. Also, I realized that my idea is a little messed up (you don't want a dead zone), and I don't have time at the moment to figure out if there is an optically feasible means to reject small objects :-) Sean At 03:22 PM 2/27/01 -0500, you wrote: >My limited experience with furry critters seemed to indicate the >opposite. Was >trying to detect squirrels with a PIR system for remote camera >activation. The >PIR had a heck of a time seeing them. I thought that the fur may be at the >ambient temp, and not at the squirrel body temp. Seemed as if there was no >discernible moving heat signature for the PIR to see. > > >|--------+-----------------------> >| | Sean Breheny | >| | | | .EDU> | >| | | >| | 02/27/01 | >| | 03:07 PM | >| | Please | >| | respond to | >| | pic | >| | microcontroll| >| | er discussion| >| | list | >| | | >|--------+-----------------------> > > >----------------------------------------------------------------------------| > | > | > | To: PICLIST@MITVMA.MIT.EDU > | > | cc: (bcc: Scott > Touchton/US/UNIPHASE) | > | Subject: Re: [EE]: Infrared Detector vs > Pet | > > >----------------------------------------------------------------------------| > > > > > >Doesn't clothing effect the emissivity of a person? I would think that a >moderately sized pet (medium size dog) with black fur might emit more IR >than a person clothed in white, so differentiating between people and >animals based on amount of heat might not work reliably. Then again, >perhaps a person has so much more surface area that it more than makes up >for the lower emissivity, I don't know. > >What about using a metal-covered plastic parabolic reflector with the PIR >at its focus? You could place a small disk in front of the PIR to make >the instrument's FOV have a dead zone in the center. This would require >an IR emitting object to be larger than a certain size in order to be >detected. There may be a way to do this with a specially molded or >modified plastic lens (like they have on most PIR modules). > >One problem is that an object very close to the sensor would appear >larger than one farther away, which would mean that a sensor like this >could only cover a limited area (i.e., a person who is too far away would >appear as small as a dog and not be detected). > >Sean > > >On Tue, 27 Feb 2001, Justin Fielding wrote: > > > Im not sure that is how they work, I read about them in the mobile robotics > > book. the more heat an object emits the larger the output pulse so you > > could set the sensitivity by ignoring all pulses below a certain > level. You > > can also tell which direction an object is travelling in by analysing the > > output. I cant remember much about them, just a few bits from that book so > > I may be wrong. > > > > > > ----- Original Message ----- > > From: "James Paul" > > To: > > Sent: Tuesday, February 27, 2001 6:33 PM > > Subject: Re: [EE]: Infrared Detector vs Pet > > > > > > > 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" > > > > To: > > > > 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" > > > > > To: > > > > > 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" > > > > > > To: > > > > > > 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 > > > > > > > > > > > > -- > > > > > > http://www.piclist.com hint: The list server can filter out > > subtopics > > > > > > (like ads or off topics) for you. See > http://www.piclist.com/#topics > > > > > > > > > > > > -- > > > > > > http://www.piclist.com hint: The list server can filter out > > subtopics > > > > > > (like ads or off topics) for you. See > http://www.piclist.com/#topics > > > > > > > > > > > > > > > > > > > > > > -- > > > > > http://www.piclist.com hint: The list server can filter out subtopics > > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > http://www.piclist.com hint: The list server can filter out subtopics > > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > jim@jpes.com > > > > > > -- > > > http://www.piclist.com hint: The list server can filter out subtopics > > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > > > > > > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > > >-- >http://www.piclist.com hint: The list server can filter out subtopics >(like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics