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Thread: Perimeter detection

  1. #1
    Automated Home Ninja Andrew Millne's Avatar
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    Default Perimeter detection

    We are currently being plagued by people trespassing, have had a few attempted burglarys and one actual burglary. I am now looking at ways of securing the perimeter. I had thought of stringing a small wire under tension along the tops of walls and fences, which would perhaps pull a closed contact connected to the idratek kit at one end. Does anybody have any ideas of what to use or have any better ideas?

    Thanks

  2. #2
    Automated Home Legend chris_j_hunter's Avatar
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    how about gravel around the house (makes a noise) ... and small bright LEDs by each window (to warn of sensing being about, with proper LV power source to ensure low power consumption) ... CCTV cameras, of course ... and Cortex switching lights, to say you are home ... plus, the Police in some areas, offer to come-round & offer advice ...

  3. #3
    Moderator toscal's Avatar
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    How about a few of these things http://www.maplin.co.uk/module.aspx?...22506&doy=30m6
    The only problem is if you have a hose pipe ban in the UK.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.
    www.casatech.eu Renovation Spain Blog

  4. #4
    Automated Home Sr Member n07tv's Avatar
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    Toscal, I am in the North East like Andrew and we have Kielder which means we never have a hosepipe ban. We never get any sun either I suppose

    IR beams are ideal, but expensive and trigger when leaves blow through them etc. We used to have a laser perimiter around our factory but again, this used to nuisance trigger all the time.

    A wire may work quite well Andrew, attached to something a Rope E-Switch such as

    "http://uk.farnell.com/9939725/industrial-controls-automation/product.us0?sku=imo-fd983"

    but having fitted these in factories some do need quite a tug force and also tug travel. You may be able to find one with a lower actuating force, but then your wire would need supporting in multiple locations at a regular pitch otherwise it sags and you can't get it tight due to the switch actuating.

    Would the obvious external PIR light be good enough, maybe you could get an external IDRATEK light sensor to trigger on it's delta change, i.e. a rapid turn on off light would cause it to fire a reflex.? Maybe someone could try this.

    Regards,
    N.

  5. #5
    Automated Home Legend TimH's Avatar
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    Andrew,

    I was going to suggest the optical, line-of-sight detectors but see someone else mentioned those (we had them at a previous office and they needed a good separation from hedges etc. to avoid false detections.

    A quick google for "perimeter sensor" brought up these guys:
    http://www.opticsens.com/Perimeter_Security.htm

    I'm not entirely sure how it works (!) and whether it requires the optical cable to be cut/broken or just disturbed... As they say it detects climbing, I guess the cable just has to be disturbed.

    Good luck,

    Tim.

  6. #6
    Automated Home Legend chris_j_hunter's Avatar
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    ... ISTR hearing of something called DNA water ... water encoded with a unique DNA marker ... and that every Police station in the country was supposed to have a reader (!!) ... spraying a bit of water on someone should be harmless, and Idratek ought to be up to the job of doing it smartly / appropriately ... !

  7. #7
    Automated Home Legend chris_j_hunter's Avatar
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  8. #8
    Automated Home Guru JonS's Avatar
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    [QUOTE=TimH;7976]

    A quick google for "perimeter sensor" brought up these guys:
    http://www.opticsens.com/Perimeter_Security.htm

    I'm not entirely sure how it works (!) and whether it requires the optical cable to be cut/broken or just disturbed... As they say it detects climbing, I guess the cable just has to be disturbed.
    QUOTE]

    My guess is that the transmitter is a carefully regulated one and the reciever is calibrated so that changes in the loss (caused by a change in losses at bends etc) allow inference that something has touched it I note that the detection range is a few Kms so shorter than state of art fibre so probably a non optimal fibre/frequency combo to get "good" attenuation. I guess by modulating the signal (maybe wavelength modulatoion too) they could work out where the intrusion is. Not a domestic scale solution unless you have a long boundary + v deep pockets.

    The water spray seems like a good option if a few video cameras are out of budget. A further option you could consider is to add a capilary tube to a 5L container of cider vinegar (bit like the way car wash / miracle grow is added to water spray). You get something smellier than water that at such dilution is fairly harmless, but potentially annoying/ easy to detect.

    2p
    Jon

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