Here we go... i've made a sketch of it and here we go.

I only want the alarm to go off when the door is opened. Because i don't think it is possible for even the skinniest person alive to crawl in between a door and a doorframe.

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It doesn\'t matter if the hammer hits the egg or the egg hitsa the hammer. It\'s always bad for the egg!

 

Well i can't seem to get the attachments to work but anyway... The pic ythat John1 has posted is exactly what im looking for.

And for those of you who asked: The alarm has to go off when the door is opened

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It doesn\'t matter if the hammer hits the egg or the egg hitsa the hammer. It\'s always bad for the egg!

 

Hey i was about to buy one of those type of alarms, but i thought it was kinda shabby. Cant you just put a magnet on both of em and open the door without triggering the alarm? If not, i might wanna go ahead and buy it :lol:

 

Hi iwant2drive,

You might think that you could do that,
but these are quite small items, the reed switch
is generally around an inch or less, and they are
sunk into the frame from the inner part of the frame
and there should be no indication of their location
externally. With one magnet the reed switch would be
closed when the door is closed, and the alarm would
operate if the reed switch opened.

In order to maintain a magnetic field to prevent the
reed switch from opening, you would have to provide
one externally, whilst the door was opened.
Such an externally applied field would have to be in
the correct direction, because if it were applied in
opposition, the reed switch would open and trigger
the alarm. You would also need to know pretty closely
where to apply such an external magnetic field,
because even a few centimetres away would mean that
the field would have to be exceptionally strong.

In the arrangement shown earlier in this thread, the
arrangement is reversed. The reed switch is open
with the door closed, because the two magnets are
arranged in opposition, the alarm is triggered when
the reed switch closes in this case.
I would imagine that it would be very difficult to
arrange for a changing magnetic field to ensure the
reed switch remains open whilst the door is opened.

If you applied an external magnetic field to the
second arrangement it would operate the reed switch.

Defeating these kinds of alarm can of course be done,
but it is not as easy as all that, and for the most
part they are easy to set up and to understand.

Best of luck with it, John