Burglar Alarm - Front Door Sensor

Discussion in 'Electricians' Talk' started by Alan Sausse, Aug 11, 2017.

  1. Alan Sausse

    Alan Sausse New Member

    Hello forum,

    I'm doing some renovations on my flat in London. One of the jobs I want to do is to fix some problems with the old burglar alarm system.

    I have a sensor on the front door. This seems not to be working because I have constant warning messages on the control panel telling me that there is a fault here.

    On closer inspection...(see 3 attached photos) it looks like there might be something missing. There is what appears to be a small sensor set into the door frame, covered in a small metal plate. A couple of small wires poke out of the side which used to connect up to the control box (I've temporarily disconnected them because I need access to replace skirting boards).

    On the door itself, at the exact same height, is a round indentation in the wood (painted blue) with what looks like a couple of old screw holes. This makes me think that maybe there used to be some kind of magnet or something like that fixed to the door...? Whatever it was, it doesn't seem to be there any more, which is presumably why the warning messages are flashing up on the control panel - the alarm system must think that the front door is never closed.

    Is my reasoning correct? Does anyone know what the missing bit is, and where I can get one? Not sure how best to proceed here and various google searches, looking on eBay for replacement sensors, etc. didn't really help much - I worry that I may be barking up the wrong tree.

    Grateful for any advice. The local alarm company (which fitted the system in about 2001) would happily come & fix the problem but their call-out charges and hourly rates are eye-watering, so I'm hoping to do it myself if I can.

    Many thanks,
    Alan.
     

    Attached Files:

  2. Alan Sausse

    Alan Sausse New Member

    This forum site seems to have rotated all the photos anticlockwise by 90 degrees for some reason, so as you look at them, left is up and right is down.
     
  3. Dr Bodgit

    Dr Bodgit Well-Known Member

  4. Alan Sausse

    Alan Sausse New Member

    Thank you. I had a little magnet to test with but it didn't seem to do anything to the sensor - my assumption was that the magnetic field would cause a circuit to close but this didn't happen. Rather than waste too much time scratching my head, I dug the old sensor out with a screwdriver! See photo below. Now my job, I guess, is to find a replacement one (with the magnet to go with of course)...
     

    Attached Files:

  5. Pollowick

    Pollowick Well-Known Member

    Under the small plate is a magnetic reed switch in a housing. There could be four wires to it - one pair to the actual reed and another to an unused terminal which form a tamper loop. The reed will be normally closed and when a magnet is placed closeby it will open up.

    You will need to pull out the small plastic housing and see what wires are connected where. The two by the side do not inspire confidence either.

    A reed switch as linked to by Bodgit will do if you want to do some woodwork, or you can get round ones to match.

    Once you can see what is behind, then it could be easier to do something.


    What alarm panel is it?
     
  6. Alan Sausse

    Alan Sausse New Member

    See attached photo - Bates Alarms is just the local alarm company. I think it's actually a "Castle Care-Tech Euro Meridian" or something like that (from previous enquiries) - if that makes sense...
     

    Attached Files:

  7. Alan Sausse

    Alan Sausse New Member

    Plenty of reed switches of various shapes & sizes on eBay for very little money (or yes, could pop to Maplin). Are they all essentially the same - normally closed, couple of wires out of the back, with a magnet to fit into the door? If so, just need to pick shape & size to fit the door & frame and hopefully problem solved?
     
  8. Dr Bodgit

    Dr Bodgit Well-Known Member

    Reed switches are pretty standard, however yours looks as thought its got a wee chip attached it to which provides the main unit with an identification tag for the sensor (its the plastic thing with 3 wires coming from it). I don't know if that's standard or not, but guess is that it isn't.
     
  9. Alan Sausse

    Alan Sausse New Member

    ohhhhhhhhhhhhhh :-(
     
  10. Pollowick

    Pollowick Well-Known Member

    That is not a standard reed switch - there is an ID biscuit (Google them) which transmits information back to the control panel. You will need to source a reed switch with an internal ID biscuit or a type that works with your panel.
     
    Dr Bodgit likes this.
  11. Dr Bodgit

    Dr Bodgit Well-Known Member

    ID biscuit - that's the thing!!!
     
  12. Dr Bodgit

    Dr Bodgit Well-Known Member

    I had these things on an alarm outfit I bought around 1999 but never got round to installing it.
     
  13. Alan Sausse

    Alan Sausse New Member

    Yes, you're right - I googled and this is exactly what it is.

    If the two reed switches are still working then I guess I'd be best advised to leave well alone ie remount the existing switch and just find a new magnet to set into the door - correct?

    I'm not sure they are working though - I couldn't get anything much to happen (ie my multimeter didn't show any switch from open to closed circuit in the presence of a magnet) but maybe the magnet I was using (one of those whiteboard magnets, which is all I have in right now) wasn't strong enough.
     
  14. Alan Sausse

    Alan Sausse New Member

    Ohhhhh the magnet is still in place inside the door! :D

    Faulty reed switches then?
     

    Attached Files:

    Last edited: Aug 11, 2017
  15. Alan Sausse

    Alan Sausse New Member

    Managed to retrieve the magnet. Will fill in the hole and relocate a bit higher up the door. New skirting boards are taller than the old ones so I need to shift the sensor up so that the wires can still sit on top of the skirting.

    Now to see if I can work out what's wrong with the reed switches (which still don't seem to do anything with this magnet either).
     

    Attached Files:

  16. Pollowick

    Pollowick Well-Known Member

    What were the wires connected to? The first picture shows them to be disconnected, so is there a hidden wire somewhere in the frame?
     
  17. Alan Sausse

    Alan Sausse New Member

    They were connected to a long cable which ran up & along the wall/ceiling/skirting board etc. and eventually to the main "box" of the alarm system itself. I had to cut the wires temporarily though because of redoing the skirting boards, floors, etc. - but the problem was present already when I did that.
     
  18. Alan Sausse

    Alan Sausse New Member

    Even when I've got everything back wired up properly & fixed, I'm expecting to still have to get the alarm company to do an engineer reset for me, but I think that's something they can do over the phone if you ask them nicely, hopefully at a very low cost.
     
  19. Rulland

    Rulland Well-Known Member

    Connecting up ID biscuits to a zone and checking isn't really diy, get a company in I reckon, I can show you how it should be wired, also it will have a number (the ID biscuit, from 1-30), they are like rocking horse poo, especially low numbers 1-10).
     
  20. Alan Sausse

    Alan Sausse New Member

    Not sure I follow...this is a reed switch which was installed complete with the ID biscuit in about 2001. I suspect the switch isn't working but I've no reason to think that the biscuit has failed - in which case if I can fix the reed switch I should just be able to reconnect the blue and yellow wires up to the cable that comes from the main alarm box and the wiring will be exactly as it always was. Or am I missing something?
     

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