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Thread: Looking for discrete door & window switches ...

  1. #1
    Automated Home Legend chris_j_hunter's Avatar
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    Default Looking for discrete door & window switches ...

    Reed switches might not work for us - our door & window frames are either foiled uPVC or aluminium - only some of the doors, the unglazed ones, are actually wood, and they are hollow (& pivoted rather than hinged) - ie: can't easily drill or chisel holes or slots, and working with a stand-off & through aluminium (albeit just a few mm) would probably not work, plus SWMBO won't allow a (very) visible surface-mount.

    One solution, for the internal ones, might be to put the magnet out of sight either on or in the lower edge of the doors, with the reed switch in the floor, in the threshold, perhaps using one of these :

    http://www.maplin.co.uk/Module.aspx?ModuleNo=4767

    http://www.maplin.co.uk/Module.aspx?ModuleNo=3076

    http://www.rapidonline.com/Electroni...y-switch/34325

    http://www.rapidonline.com/Electroni...y-switch/65354

    http://www.rapidonline.com/Electroni...y-switch/62088

    but (obviously) the depth into the floor might be tricky to arrange ... and clearances might also be a problem, putting the magnet too-far away to work properly - 'though maybe this might help :

    http://www.rapidonline.com/Electroni...ssemtech/33897

    An alternative might be to use one of these :

    http://www.rapidonline.com/Electroni...y-sensor/35950

    A more novel approach might be to use a shock sensor - eg:

    http://www.rapidonline.com/Electroni...n-switch/30183

    various options, 2g to 15g to operate, not sure how effective or which level to choose, for this application !

    And a more conventional option might be this :

    http://www.tlc-direct.co.uk/Products/FM143.html

    which would probably have to be surface-mount, perhaps at floor-level - but reliability again seems uncertain, for this application !

    Hmm, any other ideas - maybe I'm not being imaginative enough ! ?

    I did think of optical sensors, and of having something in the catch, but both-ways failed to find anything suitable ...

    And how did shop-bells used to be triggered - some sort of dangling contact arrangement that the door brushed against as it moved past it - couldn't find anything like that, either ...
    Last edited by chris_j_hunter; 7th April 2010 at 06:23 PM. Reason: extra thought

  2. #2
    Automated Home Lurker
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    May 2010
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    Default Hall effect sensors

    Chris

    I'm experimenting with Hall effect sensors at the moment. Early days, but I too want to keep things hidden. I'm using the following sensor (this is linear, so you need to do your own voltage comparisons, but there are others that act as switches):

    http://uk.farnell.com/jsp/search/pro...sp?sku=1225624

    and looking for the right magnets from (amongst others):

    http://e-magnetsuk.com/magnets/measu...t_magnets.aspx

    If you get a strong enough magnet then it should work across a cm or two.

    rgds, Andrew

  3. #3
    Automated Home Legend Karam's Avatar
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    Mar 2005
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    Default

    Might you get away with a retroflective IR sensor in the ceiling? Some examples can be found here:
    http://uk.farnell.com/jsp/search/bro...atchallpartial

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