> 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
> ...
>
>

> 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

> > 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" <@spam@Seth889KILLspamSTARTREKMAIL.COM>
> > To: <KILLspamPICLISTKILLspamMITVMA.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

> > > "IR" detector that do not triggers with pets like cats ...
> > >
> > > Thanks
> > >
> > > ----- Original Message -----
> > > From: "Justin Fielding" <RemoveMEj.fieldingTakeThisOuTBTINTERNET.COM>
> > > To: <spamBeGonePICLISTspamBeGoneMITVMA.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" <TakeThisOuTSeth889EraseMEspam_OUTSTARTREKMAIL.COM>
> > > > To: <RemoveMEPICLISTTakeThisOuTMITVMA.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

> > is
> > > > the trick ?  Is it less sensitive ? Does it require a minimum of
> > movement
> > > > ...
> > > >
> > > > Thanks
> > > > ---
> > > > Simon Ethier
> > > > sethierEraseME.....justine.umontreal.ca
> > > > ICQ 66019153
> > > >
> > > > --
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> > > > (like ads or off topics) for you. See http://www.piclist.com/#topics
> > > >
> > > >
> > >
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> > >
> > >
> > >
> >
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> EraseMEjimjpes.com
>
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>

>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 |
>|        |          <shb7@CORNELL|
>|        |          .EDU>        |
>|        |                       |
>|        |          02/27/01     |
>|        |          03:07 PM     |
>|        |          Please       |
>|        |          respond to   |
>|        |          pic          |
>|        |          microcontroll|
>|        |          er discussion|
>|        |          list         |
>|        |                       |
>|--------+----------------------->
>

>
>
>
>
>
>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.
> >
> >

>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 |
>|        |          <shb7@CORNELL|
>|        |          .EDU>        |
>|        |                       |
>|        |          02/27/01     |
>|        |          03:07 PM     |
>|        |          Please       |
>|        |          respond to   |
>|        |          pic          |
>|        |          microcontroll|
>|        |          er discussion|
>|        |          list         |
>|        |                       |
>|--------+----------------------->
>

>----------------------------------------------------------------------------|
>
>
>
>
>
>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.
> >
> >

> About 4 years ago one of my students managed to get a sensor
> donated (cosmetic defect) that I believe was a very large area
> brown colored chip. Chip was about 1/2 inch square mounted in a
> round package about 3/4 inch round with a top that was optically
> clear. This thing had just two wires. I designed a simple
> op-amp circuit that would respond only to changes in output.
> I used a current to voltage coverter at the front end to get
> maximum sensitivity. This thing was quite amazing. It was
> extremely sensitive to the radiation emitted by humans. What
> I found interesting was that it had no trouble at all detecting
> a human through several layers of clothing, including heavy
> winter coats. It did not seem to be "infra-red" detecting in the
> sense that we normally use that word. It was sort of
> tuned to the specific heat signature of the human body. It
> could even detect this heat signature when the detector was
> covered with a sheet of aluminum foil. In fact, one of our
> major problems was preventing it from picking up signals
> that were coming in from the sides (and even the BACK!).
>
> But it ignored squirrels. (Never tried it on a cat).
> I don't think it was the fur that prevented detection,
> because we had one person acting as our target who
> had TWO very thick coats on, gloves, and two hats facing
> with their back to the sensor, and they were easily
> detected.
>
> Unfortunately I can't seem to find the project report in any
> of my filing cabinets at the moment, but I vividly
> remember how it could detect humans with great ease.
>
> It could be that the detector being touted by this company
> actually responds to the specific human body signature,
> just like the sensor in our project.
>
> Fr. Tom McGahee
>
>
> ----- Original Message -----
> From: Sean H. Breheny <spamBeGoneshb7STOPspamEraseMECORNELL.EDU>
> To: <KILLspamPICLISTspamBeGoneMITVMA.MIT.EDU>
> Sent: Tuesday, February 27, 2001 3:40 PM
> Subject: Re: [EE]: Infrared Detector vs Pet
>
>
> > 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

> > if there is an optically feasible means to reject small objects :-)
> >
>
> --
> 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
>
>
>
>

> > 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,
>
>As an aside, black objects are better thermal radiation (black body)
>emitters than white objects.  This is a common misconception because black
>objects are also better thermal radiation absorbers.
>
>
>*****************************************************************
>Olin Lathrop, embedded systems consultant in Devens Massachusetts
>(978) 772-3129, @spam@olin@spam@spam_OUTembedinc.com, http://www.embedinc.com
>
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>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

>
> Hi Olin,
>
> Yes, that's what I was saying, the black object (at the same temperature)
> would probably emit better than the white object. I say probably because I
> don't know if all objects which are black at visible wavelengths are also
> black bodies at IR.
>
> It's a basic consequence of thermodynamics. If an object were a better
> emitter than it is an absorber, it would spontaneously cool below the
> ambient temperature. The other way around and it would spontaneously  get
> warmer.
>
> Sean
>
> At 06:13 PM 2/27/01 -0500, you wrote:
> > > 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,
> >
> >As an aside, black objects are better thermal radiation (black body)
> >emitters than white objects.  This is a common misconception because black
> >objects are also better thermal radiation absorbers.
> >
> >
> >*****************************************************************
> >Olin Lathrop, embedded systems consultant in Devens Massachusetts
> >(978) 772-3129, .....olinRemoveMEembedinc.com, http://www.embedinc.com
> >
> >--
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>"Alan B. Pearce" wrote:
> >
> > >I have a friend that works with IR laser diodes. He says that it is very
> > >hard to guess the reflectivity of IR by looking at something. Things
> > >that LOOK black do not always absorb IR.
> >
> > >Also, he says that one of the best black surfaces (for IR) he has found
> > >is black conductive foam.
> >
> > A colleague I used to work with was into motorbikes, especially painted
> black.
> > He had some theory that black paint was actually transparent at either
> IR or UV,
> > to get the black colour by diffraction. He reckoned you tell which end
> of the
> > spectrum it was transparent at by looking at a reflective sheen from
> sunlight.
> > If it had a blue hue to it then it was transparent at UV, if a red hue then
> > transparent at IR.
> >
> > How true this might be I do not know, but at the time it seemed to make
> sense.
> >
>
>I don't know about that but here is another bit of insight.
>
>I worked on a project that needed molded parts for prototyping. A master
>part was machined and polished out of aluminum. Then a silicon rubber
>mold was made using the master. The mold was then used to make a black
>epoxy part. This part was a shiny black color. When it was decided that
>the molded part was too shiny, the master was painted flat black.
>Another mold was made and a new part was cast. The new part was now FLAT
>BLACK. I seems that the characteristic of black is not only the color
>but the texture as well. Also note that the silicon rubber mold was able
>to transfer the "flat" texture to the molded part. That implies to me
>that a huge amount of detail is posible using silicon rubber molds.
>
>-- Rich
>