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Thread: Presence-Sensing & Particular People

  1. #11
    Moderator Gumby's Avatar
    Join Date
    May 2004


    Makes you wonder if it would be a good security feature. After all, it wouldn't be the first time a criminal got done because of their mobile...

  2. #12
    Moderator Kevin's Avatar
    Join Date
    Jan 2004
    West Yorkshire


    Now that is a most interesting thought ..... although the phone/service provider likely couldn't identify the user easily via the BT ID... but if they were a suspect it would be helpful...

    Last edited by Kevin; 8th September 2008 at 01:00 AM.

  3. #13
    Automated Home Jr Member KirasHome's Avatar
    Join Date
    Oct 2006


    I have to admit I keep looking at this every 6 months or so, there are so many ways you could make use of the info in HA terms if you knew exactly where specific people were in the house.
    Example: You have an alarm system that is permanently active, if a sensor gets triggered, first thing it does is check if an authorised person is nearby, if so it resets the sensor for say 5 secs. If there isn't an authorised person nearby it triggers the alarm. Great if your in a house on your own, or if you have pets. Put a tag on the pet's collar and leave the alarm on all night.
    Example: You want to direct notification to a specific person (eg "Your tea is ready") :-)
    Example: You want to avoid room occupancy issues where you have an open plan house.
    Example: you want to be warned if your dog has gone into the larder :-)
    Example: you want to have your music/tv follow you round the house.
    Example: the house unlocks the front door as you approach.
    Etc, etc.

    I figure the easiest way to do this would be to have people carry something like an RFID tag. You could have it as a watch (, have it as a charm on a neck chain etc, a tag clipped to a pet's collar - you may notice a theme here :-).

    How to detect the location of the tag gets a bit more interesting. Most RFID reader are quite short range, so you'd need multiple readers to cover a room. The longer range ones have the problem that you might not be able to tell exactly which room your currently in if your next to the wall.

    A more elegant solution would be to have say 4 omni-directional readers mounted at the corners of the house and then triangulate the location of the tag in much the same way that GPS system does it. In theory you should be able to be quite accurate with that. Combine it with a 3d plan of the house and you know where the tag is. You could also use it to cover gardens as well.

    Security: RFID tags are quite easy to read and fake, so I would be relucant to use it for unlocking the house. The flip side of that is virtually no one uses RFID to lock their house so the chances of a criminal type have a scanner and realising he needs to clone an RFID tag to unlock the house are small.

    Bad news: Cost and trying to find a system that can actually do this.

    Bluetooth phones: Good point: they are becoming univerisal. Bad point: People often put them down when they get into the house. We periodically have to ring SWMBO's phone to find it.

    Apologies - a bit of a brain dump :-)


  4. #14
    Automated Home Sr Member n07tv's Avatar
    Join Date
    May 2004


    I used to work in access control. Always looking to improve on short range RFID tags (hiprox, mifare, hid etc) as they worked a treat for convenience of being contactless but they were still prone to skimming.

    Best method is, and i think always will be, something which is wired or connected. We ended up using iButtons a lot ... yes you can emulate them, but the sheer number of bits in the IDs would take a while to crack even using brute force :-). Can't see a burglar standing their with a serial number generator lpugged into a port for hours.

    I have a stainless iButton port in the door frame wired to a small PIC based module running some custom firmware. It toggles a relay when a valid iButton is inserted.

    When I leave, I lock the doors and the Cortex automatically arms, when i return, press the ibutton to the reader, hallway light flashes 'disarmed' and I unlock the door.

    I got the idea from watching Weatherspoons barstaff logging on to their cash tills with iButtons.


  5. #15
    Automated Home Jr Member jcmiguel's Avatar
    Join Date
    Apr 2008
    Ayrshire, Scotland

    Default Bluetooth

    I was looking at this and remembered about this thread. Why not a presence detector for the security system in which cortex identify your presence and DFP2 politely ask for the password to disable the alarm system? Of course you will have to remember turning on mobile BT before entering the property.

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