static presence sensor..HELP

Discussion in 'General Electronics Chat' started by aditya.rajgaria, Mar 5, 2010.

  1. aditya.rajgaria

    Thread Starter New Member

    Feb 10, 2010
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    i wanted to know that is there any sensor available for presence detection in the following condition :

    i want this sensor to be ON when any human presence is detected but thing is that how to still give a high output,say,when the person sleeps in a room...???

    i considered PIR but i think the problem arises when a person enters and sleeps then the control cant detect him....actually my presence detection part works as a Master controller for other parts..!!

    any viable option or suggestion..:confused:
     
  2. Mike33

    AAC Fanatic!

    Feb 4, 2005
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    Are you thinking of something like when a person goes in a public bathroom, the light comes on, and then it automatically goes out once they leave?
     
  3. aditya.rajgaria

    Thread Starter New Member

    Feb 10, 2010
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    ummm....ya but u can think that like a person enters is bedroom light and fans goes ON...but he sleeps and still they are ON.
    As soon as he leaves the room everything switches off...!!
    :confused:
     
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    That sounds like a typical 'Home Automation' problem.

    My solution is to have all PIRs in the house also linked through the automation system.

    If you detect movement in a room, a person is there.
    If movements stops, but movement is NOT detected in the hallway (outside the room), then the room is still 'active'.
     
  5. aditya.rajgaria

    Thread Starter New Member

    Feb 10, 2010
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    umm....that wont work for me i guess....as i m planning more as a automatic classroom lighting...so if a student goes in a class room and sleeps then also there can be many students roaming in the corridor outside..so its a problem....

    Is there any other solution to this PIR problem and is there any other sensor to do my job....??
     
  6. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    With multiple people, it is a very difficult problem.

    Possibly a PIR just inside the door to detect people entering & leaving while ignoring movement outside, but that would not work if someone was asleep when the rest of the class left, there would have to be movement away from the door to confirm people still present.

    You could fit PIRs to servo motors and mechanically scan them over an area of the room; any (stationary) people would still be moving in relation to the PIRs field of view, so it would trigger.

    But, that would only work if the ambient temperature is well below body heat and there are no hotspots in the room due to heating or sunlight..

    Beyond that, the only thing I can think of is something along the lines of a computer vision system.
     
  7. aditya.rajgaria

    Thread Starter New Member

    Feb 10, 2010
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    thank you very much for ur ideas...!!!:)

    but i dont think i can go in computer vision direction..u see it is our final year project i am doing...i guess i have to somehow ignore that part....

    well i thought of one idea that adding a timer with RC circuit so that if within that time period also the person is asleep then the pir goes off...this is the maximum possible thing we can do to avoid sleeping in classrooms...:D;)

    but still it doesn't solve the problem for household bedroom with a joint family of more than 3-4 people..!!!
    :(:rolleyes:
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Use the PIR to count how many people enter and exit the door. If the numbers equal shut the light off.

    For instance In the door way could be 2 light beams that would tell what direction the person was going, in or out.. Every time someone walks in the (Pin for PeopleIN) counter would count up one. (Pout for PeopleOUT) if the two numbers dont match, there is still someone in the room, so the light stays on.

    Room Empty, light off
    If Pin = Pout Light OFF
    If Pin <> Pout Light ON

    someone walks in
    People in (Pin) =1 (Pout) = 0
    some one else walks in
    Pin =2 Pout = 0
    5 people walk in
    Pin= 7 Pout = 0
    4 people leave
    Pin= 7 Pout = 4
    Two more people leave (And one falls asleep)
    Pin=7 Pout = 6

    Last guy wakes up an hour later and leaves
    Pin = 7 Pout = 7

    Pin=Pout so Light OFF
     
  9. aditya.rajgaria

    Thread Starter New Member

    Feb 10, 2010
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    thank you you very much...thats also one of the way to do it....!!
    :)
     
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