Reed Switches & PIRs

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  • chris_j_hunter
    Automated Home Legend
    • Dec 2007
    • 1713

    Reed Switches & PIRs

    after doing some experimental plaster trials yesterday (hard-work) 'was thinking about how to run the cable for the sensor-switches for our various doors (single & twin-door french-windows) and door-less door-ways (as it were) ... fitting reed-switches for the doors was what I'd intended, linked-back to digital inputs of convenient modules, but got to thinking about putting a PIR sensor immediately above the doorway, perhaps with a short tube over the sensor, to limit its field of view, instead-of or as-well, to better sense comings & goings ... hmmm, would it work (with Cortex) ?

    not sure about reed-switches ... they say nothing about how far open a door is, or what it's doing, whether it's closed-fast & locked, or not ...
    Last edited by chris_j_hunter; 22 March 2008, 01:07 AM. Reason: corrections
    Our self-build - going further with HA...
  • Karam
    Automated Home Legend
    • Mar 2005
    • 863

    #2
    Limited field of view PIRs above doorways sounds like a good idea though these will probably have to be augmented by another/others in the same room to catch movements elsewhere. One common issue is a PIR in one room seeing movement in another which can cause errors in occupancy assessment.

    Door sensors (eg. reed switches) highly recommended for house entry/exit doors in order to allow more accurate assessment of house occupancy and also for alarm arming function. For traditional hinge doors magnets and reeds can be placed at the top of the door frame rather than side so you could potential choose to have a door deemed closed even when slightly ajar (we've seen some cases where people wanted this). Internal door sensing can be useful if you're the type of person who regularly closes doors, or you may choose just to sensorise doors that will be shut as part of your security plan

    Comment

    • Paul_B
      Automated Home Legend
      • Jul 2006
      • 608

      #3
      I have a couple of PIR above doors and they work fine. Although as Karam says positioning is important to ensure they can't "see" into another room. In some cases I would say to get hung about the ideal PIR position as it will always be a compromise. Instead just buy a second PIR.

      I also have a reed switches on my doors and the beauty is they are fast acting so when you open a door they light is already one rather having to wait for a PIR to detect you in the room. One thing I didn't know is that Cortex ignores movement from PIRs when a door is shut. This wasn't configurable before v23 and had a delay of 5 seconds (this is still the default). If I had known this before (i.e. RTFM) then it would have changed my PIR placement.

      As for cable runs, I am lucky in that I had a modern house with plasterboard and hollow walls filled with insulation. Therefore, cable runs are relatively easy, I cut a square for the Idratek unit and then use a long drill to make a hole into the ceiling / loft space. Either that or I use existing lighthing cable runs to pull the Cat 5 cabling. If you have got some already then a set of cable rods are a must have.

      Good luck

      Paul

      Comment

      • toscal
        Moderator
        • Oct 2005
        • 2061

        #4
        For room occupancy you could think about using vibration sensors http://www.sureaction.com/pulsors.htm

        The pdf gives various ideas for home automation.

        Martin at Automated Outlet sells then Ok he is in the US but with the exchange rate they are quite good value. http://automatedoutlet.com/home.php?cat=123
        IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.
        Renovation Spain Blog

        Comment

        • chris_j_hunter
          Automated Home Legend
          • Dec 2007
          • 1713

          #5
          >PIR above doors ...

          I was thinking of having them mounted on the lintel, looking down (with a tube to narrow the view) ... is that how yours are ?

          >reed switches ... fast acting ...

          good point !

          >plasterboard and hollow walls ...

          no board in our case, but not plastered yet, or screeded, so not too bad for us at the moment ...

          going to spend the day developing our plastering technique, so should have time to think some more ... having lots of PIRs could get expensive, so need to think carefully about this ... our place will have a minimum of internal doors, so that's another issue !
          Our self-build - going further with HA...

          Comment

          • Gumby
            Moderator
            • May 2004
            • 437

            #6
            I have used reed switches typically at the same level as the light switch so that it is very easy to connect to the DRB inputs by drilling straight into the wall box position.

            I also had a brief look at proximity sensors when I was considering how to better detect motion at the bottom of my stairs. The difficulty is that ones that use reflected light have a pretty short detection range - it seems better to either plan on mounting a small corresponding reflector or detector/emitter pairs and use beam breaking (which implies a beam across a doorway rather than down from the lintel).

            However, I then decide to exploit a peculiarity of my stairwell construction to mount a restricted view PIR. You will have to wait for the blog post to see well that turned out :-)

            To mount a PIR - such as the high sensitivity ones used by the Idratek modules - in a tube you would need to carefully calculate length and diameter to ensure that sufficient patches in the beam pattern exist to actually detect motion.
            ----------------------
            www.gumbrell.com

            Comment

            • Karam
              Automated Home Legend
              • Mar 2005
              • 863

              #7
              Originally posted by toscal View Post
              For room occupancy you could think about using vibration sensors http://www.sureaction.com/pulsors.htm

              The pdf gives various ideas for home automation.

              Martin at Automated Outlet sells then Ok he is in the US but with the exchange rate they are quite good value. http://automatedoutlet.com/home.php?cat=123
              Interesting idea. It looks to me like strain gauge technology (or similar) for measuring beam bending. The way new houses are built I think I'd just need to stick a strain gauge on the ground floor ceilings to get a good indication of upstairs occupancy :-). Come to think of it, the way the house creaks when the heating comes on makes me wonder what sort of joist stresses the sensor would pick up just from heating ..

              Comment

              • Paul_B
                Automated Home Legend
                • Jul 2006
                • 608

                #8
                Chris,

                I have placed the PIRs above the door header so I guess you could say the lintel. I haven't angled them or anything so they just face into the room.

                One room that doesn't quite work is the ensuite. It is a small room with the presence set to register just 1 second after the door closes it can fail to pickup movement before the light time-out period.

                Comment

                • chris_j_hunter
                  Automated Home Legend
                  • Dec 2007
                  • 1713

                  #9
                  >seeing movement in another which can cause errors in occupancy assessment ...

                  >PIR ... high sensitivity ones ... carefully calculate length & diameter to ensure that sufficient patches in the beam pattern exist to actually detect motion ...

                  >above the door header ... haven't angled them or anything so they just face into the room ...

                  interesting ... maybe we'll try them looking-down, but with a flat or curved screen rather than a tube, and experiment with size & location ... will have to contrive a neat way of doing it, though, to keep SWMBO happy ...
                  Last edited by chris_j_hunter; 23 March 2008, 10:54 AM. Reason: add curved
                  Our self-build - going further with HA...

                  Comment

                  • chris_j_hunter
                    Automated Home Legend
                    • Dec 2007
                    • 1713

                    #10
                    >vibration sensor ...

                    interesting ... 'though, reading the .pdf, the sensor seems not to respond to vibration, but to movement (people walking about, so long as they weigh enough) ... maybe movement could be called very-low frequency vibration, but ... (!) ... it's not clear how smart the processor is (one per four or twelve sensors, according to which) or how it would be interfaced to Idratek ...

                    could be a useful device, maybe, with Cortex adding the smartness, 'though in our case our floors are bonded concrete beam & block, so the beams will move very little & really not very individually ... perhaps they could be used on built-in furniture, if that would be useful (?) ...
                    Last edited by chris_j_hunter; 24 March 2008, 09:29 AM. Reason: typos
                    Our self-build - going further with HA...

                    Comment

                    • Kevin
                      Moderator
                      • Jan 2004
                      • 558

                      #11
                      Another great topic :-)

                      I'm one of the 'rarely close internal doors' types so the doorway sensors are going to be important to me. Most of my doorways are deep fortunately as my walls are very thick. A while back I bought some of the Maxbotix tiny ultrasonic sensors and Gerrys PCB to control them. Like so many of my intents - they're still in the box though.

                      My idea was to mount them pointing across or above the doorways, and use the reported distance to limit any 'into room' operation. . Above the door appealed because I wondered if I might be able to get any height indication of people - so some 'who' detection. Then I had the idea that if I mounted them at the side of the door pointing diagonally into or out of a room I could also get an indication of whether someone was entering or leaving the room based on the distance indication - short to long or long to short. My deep doorways will help - at one stage Gerry was considering adding this interpretation into the controller - just a binary IN|OUT indicator - again with range limiting for the into room sensing removal. This is the route I still intend to take as it would be helpful in getting more accurate, and faster room occupancy sensing and counting . Having a direction indication input within Cortex would be useful too - feature request ;-).

                      I do use some of those Pulsor strain gauge sensors around the house - they can be very sensitive and how and where you mount them is key to successful operation. Unfortunately due to the epoxy mounting system getting it wrong usually means you sacrifice the sensor. I was trying to use them around the sofas to detect when people sat down /dozed - but I still haven't got that working usefully. The sensors obviously only report change and not constant weight. On the lookout just for some weight sensors that might be useable like castor cups here. I tried some Pulsors in the doorway entrances and on the stairs and even on the terrace flagstones outside.

                      Although I have trawled the internet I haven't found any really tiny IR break beam sensors - I was hoping to find something about the size of the keyring type IR pointer devices - ie pencil widths - that could be sunk inconspicuosly into door surrounds - separate TX and Rx units probably as reflection might not be dependable - but no luck so far which is surprising as I'm sure they must exist. If anyone know of any do let me know.. They would need to be light immune - with modulated/coded beam to allow for two beams without interference.

                      Cheers K
                      Last edited by Kevin; 24 March 2008, 11:26 AM.

                      Comment

                      • Viv
                        Automated Home Ninja
                        • Dec 2004
                        • 284

                        #12
                        PIR as Proximity sensor

                        Originally posted by chris_j_hunter View Post
                        but got to thinking about putting a PIR sensor immediately above the doorway, perhaps with a short tube over the sensor, to limit its field of view, instead-of or as-well, to better sense comings & goings ... hmmm, would it work (with Cortex) ?...
                        You could use such a designed PIR as a proximity sensor in the doorway. You would configure a digital input as a proximity object. It is then connected to the door object it is monitoring.

                        As someone was detected walking through the door it would clear the presence in both rooms. You would expect a conventionally placed PIR to then locate which room the person is in.

                        The advantage of having such a sensor is that presence can be registered in both rooms either side of the door when the door is open i.e. the logic does not move the presence between the rooms. This is because the proximity sensor in effect creates a barrier (a bit like the door is closed).

                        Comment

                        • chris_j_hunter
                          Automated Home Legend
                          • Dec 2007
                          • 1713

                          #13
                          >PIR as a proximity-sensor ...

                          yep, only the PIR would not be a simple switch, so might add complications ... how easily could the logic / Cortex cope ?

                          >the logic does not move the presence between the rooms ... because the proximity sensor in-effect creates a barrier ...

                          not sure I follow ! Again, though, the PIR behaviour may be complicated - eg: how locally will it be sensing ?

                          BTW ... was looking at our uPVC french-windows today, to see how to add reed-switches ... and wondering about how to put them in the jam, inconspicuously / reliably, and whether it would be possible to sense the locking-mechanism ... hmmm !
                          Last edited by chris_j_hunter; 31 March 2008, 05:18 AM. Reason: clarity
                          Our self-build - going further with HA...

                          Comment

                          • Viv
                            Automated Home Ninja
                            • Dec 2004
                            • 284

                            #14
                            Originally posted by chris_j_hunter View Post
                            >PIR as a proximity-sensor ...

                            yep, only the PIR would not be a simple switch, so might add complications ... how easily could the logic / Cortex cope ?
                            The proximity object receives a true state when someone passes its sensor. A PIR looking down at the floor from above the door will generate a pulse as someone passes through. Provided it does not generate a false trigger from someone simply in the room it should work fine.

                            Originally posted by chris_j_hunter View Post
                            >PIR as a proximity-sensor ...
                            not sure I follow ! Again, though, the PIR behaviour may be complicated - eg: how locally will it be sensing ?
                            Consider two adjacent rooms A and B have an open door. A PIR detection in room A will register presence in room A. A PIR detection in room B will then register presence in room B and remove presence from room A. PIR detection in room A will register presence in room A and remove it from room B and so on (unless the go off in other rooms). If the door was closed then presence would be registered in room A and room B if both PIR's triggered.

                            The use of a proximity sensor in the doorway allows both rooms to have simultaneous presence registered (if valid) with the door open.

                            Comment

                            • chris_j_hunter
                              Automated Home Legend
                              • Dec 2007
                              • 1713

                              #15
                              thanks ...

                              looking at our doorways (& doorless doorways) today, it might be more convenient / aesthetically better to put the PIRs on the side, rather than on the top - the back-box (and even teh face-plate) could buried, rather than surface-mounted ... the tops having reinforced concrete lintels !
                              Our self-build - going further with HA...

                              Comment

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