Infra-red door sensor issue

Discussion in 'Electronics & Electrics' started by loupseul, Jan 15, 2015.

  1. loupseul

    loupseul Member

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    I've a door sensor that keeps playing up. Some days it'll be good and works properly, some days it'll decide it'll trigger and let the door stay open all day, and some days it'll stay closed and not work.
    I've uploaded pictures of the model, and I'm wondering if anyone out there has a manual or can tell me how to I adjust the settings on the device?

    I've tried playing with the two white screws in the blue boxes to see if that influences the way it acts. I can't yet determine what influences what. Pic below.

    Click to view full size!


    I've also tried loosening/tightening the copper and silver screw on the top part and sometimes it works, sometimes it doesn't.

    Click to view full size!



    Click to view full size!


    I've also noticed that the width of the sensor has decreased, so definitely I've triggered the settings somewhere.
    I think it's an infra red sensor as there's a black cover that completely covers the front of the device.

    Many thanks in advance!
     
  2. RobRoySyd

    RobRoySyd Member

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    I think it's an old microwave doppler motion detector.
    The copper screw tunes the cavity, probably not a good idea fiddling with that :(

    It might just be time for a new one.
     
  3. OP
    OP
    loupseul

    loupseul Member

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    Noooo. It was just installed for a few hundred a few months ago. Not really happy to have another callout fee for a few hundred.

    I gave it a good clean with contact cleaner and it seems to be working perfectly fine right now. May have been dirty to start with.
    I just need to figure out what the two blue boxes adjust.
     
  4. RobRoySyd

    RobRoySyd Member

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    Well some more digging around and I think I'm right.
    It's a Gunn Diode Doppler Radar Module in that unit.

    http://www.eevblog.com/forum/projects/gunn-oscillator-doppler-radar-transceiver/

    Sorry mate but I think you've been had, that's long obsolete tech for that application. Explains why I couldn't find anything that remotely looked like it, the current microwave motion detectors use different tech.

    If it's any help those little blue boxes are potentiometers, I *think* one adjusts range; how far away, and the other sensitivity; how fast the object has to move to trip the unit. You can also adjust the coverage by tilting the unit.

    Hopefully paulvk will chime in, my memory of these modules dates back to an old Electronics Australia project that used one.
     
  5. OP
    OP
    loupseul

    loupseul Member

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    It used to work quite reliably. I think dust and stuff get in the way.


    Yeah I realised I've been had from those Dogma door guys. They installed one, water damaged happened, reinstalled but thought they'd fix the area around the water leakage. Waterlogged again in 2 weeks and bam another couple hundred down the drain.
     
  6. RobRoySyd

    RobRoySyd Member

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    Don't feel too bad, mention "those door guys" to my local chemist and he loses it. A couple of hundred doesn't sound much but it's a lot of coin for many running their own shop.
     
  7. wingnut

    wingnut Member

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    Yeah that's a bwn/dorma microwave motion detector.
    From memory one pot is for sensitivity and one is for pulse length
    they are a fairly reliable unit often giving 10 years service
    I am one of those door guys, but for another company, every time I replace one of their doors we throw those old sensors.
    If you keep having probs pm me and I will try and dig you up another unit
     

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