Reed Switches & PIRs

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  • Karam
    Automated Home Legend
    • Mar 2005
    • 863

    #46
    Well I suppose one the more interesting facets of an integrated system is the ability to fuse together various sources of information, so more sources can perhaps improve accuracy, though how this information is managed is of course the tricky bit ...

    Anyhow, regarding the speed of reaction of PIR only based detection - it depends how you place the PIRs. If a PIR is mounted close to a doorway and facing away from the door (or perhaps even above the door), then when the door is opened it can cause the PIR to trigger due to the sudden fluctuation of air temperatures in the vicinity of the sensor or perhaps even moving IR reflections/occlusions by the door body. Even if this doesn't happen, then with a PIR close to the door the person will trigger the PIR pretty soon after their body crosses the threshold. So reaction can be improved by PIR positioning. Of course one can also have multiple PIRs in a room.

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    • Paul_B
      Automated Home Legend
      • Jul 2006
      • 608

      #47
      Totally agree Karam. My most difficult room is a small ensuite. Without getting too base I've realised I probably need another PIR. For a male, movement is in one direction, whilst a female it is in the opposite direction (think about it guys ;o) My HA is aimed at saving me energy so my thresholds are aggresive, 10 seconds is the default lights after presence removal. Bearing in mind the PIR grace period of 5 seconds, I have potentially 5 seconds for the PIR to detect movement.

      A PIR above the door still requires someone to enter the room before the light comes on, whereas opening a closed door with a reed switch the light is already on before entering. This may seem a minor point but to me it makes a huge difference to the experience of HA

      Paul

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      • Karam
        Automated Home Legend
        • Mar 2005
        • 863

        #48
        No I think you're right Paul - what may seem like minor lags on paper of a few tenths of seconds can make quite a difference to the experience. Its a bit like you don't realise quite how sensitive we are to even sub degree temperature variations until you start monitoring and correlating with the data.

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