F
-Ferdinand-
- Jan 1, 1970
- 0
Can anyone here help me out with some suggestions? I have a deluxe
FreezeAlarm (FA-D) installed at our cottage. In addition to its
primary function of monitoring the cottage temperature and electricity
power supply status, both of which work very well, the unit also has
an auxiliary alarm port. Any circuit which closes the two terminals of
this auxiliary alarm port triggers an alarm call-out.
To take advantage of this function I installed a normally-OPEN
magnetic reed switch on the cottage door and wired this to the
auxiliary alarm terminals of the FreezeAlarm using twisted pair
wiring. When the door is opened the contacts on the reed switch close,
thereby completing the circuit between the alarm terminals.
So as not to trip the alarm myself whenever I open the door, an X-10
Universal Relay Module (PUM01) is installed in the circuit so I can
remotely disable/enable the door alarm. The X-10 relay and the reed
switch BOTH have to be closed at the same time to complete the
circuit.
This simple door alarm has worked reliably except for an annoying
tendency of triggering a false alarm whenever we experience a thunder
storm within the area.
I don't believe it has anything to do with the magnetic reed switch
itself because it is in the normally-OPEN position when the door is
closed. Can lightning somehow cause the reed switch to momentarily
bounce closed? To test this possibility I left the X-10 relay module
in the open position, so there is no way for the reed switch alone to
complete the cicuit. Still the alarm was triggered by the next thunder
storm.
My current theory is that the two lengths of wire (~15 feet) joining
the door switch to the FreezeAlarm are acting like an antenna. It was
my understanding that the alarm could only be tripped by a dry contact
between the two terminals of the auxiliary alarm port. But I now think
that lightning is inducing a voltage difference in the door alarm
wires, and this voltage difference experienced at the alarm terminals
is sufficient to trip the alarm.
Am I on the right track here? How would I shield the wiring run from
the effects of lightning? Should I be using coaxial cable instead of
the twisted pair wires? Is there some sort of filter
(resistor/capacitor combination) I could hang between the auxiliary
alarm terminals on the FreezeAlarm?
I've searched through old posts in this newsgroup and seen that others
have had problems with reed switch contacts being welded stuck by
lightning strikes. I suspect those stories do not relate to my issue
because in my case the reed switch is in the normally-open position.
We're unlikely to experience any more thunder storms until next
spring, but I sure would like to have this figured out by then, or at
least have an understanding of why this happening.
What am I doing wrong? I'm hoping someone here can point me to a
simple solution that I've been too stupid to think of by myself.
thanks.
FreezeAlarm (FA-D) installed at our cottage. In addition to its
primary function of monitoring the cottage temperature and electricity
power supply status, both of which work very well, the unit also has
an auxiliary alarm port. Any circuit which closes the two terminals of
this auxiliary alarm port triggers an alarm call-out.
To take advantage of this function I installed a normally-OPEN
magnetic reed switch on the cottage door and wired this to the
auxiliary alarm terminals of the FreezeAlarm using twisted pair
wiring. When the door is opened the contacts on the reed switch close,
thereby completing the circuit between the alarm terminals.
So as not to trip the alarm myself whenever I open the door, an X-10
Universal Relay Module (PUM01) is installed in the circuit so I can
remotely disable/enable the door alarm. The X-10 relay and the reed
switch BOTH have to be closed at the same time to complete the
circuit.
This simple door alarm has worked reliably except for an annoying
tendency of triggering a false alarm whenever we experience a thunder
storm within the area.
I don't believe it has anything to do with the magnetic reed switch
itself because it is in the normally-OPEN position when the door is
closed. Can lightning somehow cause the reed switch to momentarily
bounce closed? To test this possibility I left the X-10 relay module
in the open position, so there is no way for the reed switch alone to
complete the cicuit. Still the alarm was triggered by the next thunder
storm.
My current theory is that the two lengths of wire (~15 feet) joining
the door switch to the FreezeAlarm are acting like an antenna. It was
my understanding that the alarm could only be tripped by a dry contact
between the two terminals of the auxiliary alarm port. But I now think
that lightning is inducing a voltage difference in the door alarm
wires, and this voltage difference experienced at the alarm terminals
is sufficient to trip the alarm.
Am I on the right track here? How would I shield the wiring run from
the effects of lightning? Should I be using coaxial cable instead of
the twisted pair wires? Is there some sort of filter
(resistor/capacitor combination) I could hang between the auxiliary
alarm terminals on the FreezeAlarm?
I've searched through old posts in this newsgroup and seen that others
have had problems with reed switch contacts being welded stuck by
lightning strikes. I suspect those stories do not relate to my issue
because in my case the reed switch is in the normally-open position.
We're unlikely to experience any more thunder storms until next
spring, but I sure would like to have this figured out by then, or at
least have an understanding of why this happening.
What am I doing wrong? I'm hoping someone here can point me to a
simple solution that I've been too stupid to think of by myself.
thanks.