Magnet connected to a Wellerman wst188, magnet gets stuck

sebastiannielsen

I have a door magnet connected to a Wellerman wst188 (breaks supply to the wst188).

Problem is that the magnet gets stuck randomly, so the wellerman wst188 is permanently activated. To get it to release, I have to whack the magnetic contact with a screwdriver lightly.

My first tought was that the back-EMF from the relay sabotaged the magnet, but what I can see in the schematic there is a supression diode over the relay. So what can be the problem?

Here is schematic of timer module:

The timer circuit is there to add a delay before magnet is "activated" when door is closed, to ensure a PIR on the inside releases its relay before door is registred as closed.

Reason is, that the PIR and magnet is on a toilet, and I have configured the alarm panel to register toilet as occupied (and not allow arming) if the PIR opens while the door is closed, and then not allow PIR to reset until door is opened again.

Problem is that if someone exits toilet and closes the door too quickly (before the PIR closes its relay again, it has a "pulse time" of like 3.5 sec) the toilet will still be "occuped" and alarm cannot arm. So by having a time delay on the magnet, I can ensure the door gets a "close delay of 3 seconds" thus after door is closed, alarm system waits 3 seconds before considering the door as closed.

Thus, toilet will never be occuped if there isn't somebody there.