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[david]

I'm having a problem with false alarms in my
system.  Because I'm trying to cover a
detached shop building as well as my house,
and because the back door to the shop is too
far for the wireless signals to travel, I
wired three door/window sensors in series,
using twisted door bell cable.  The location
of the transmitter is close enough for proper
communication.  However, I've been having
problems with false alarms, and they are
always on this circuit.  The magnetic
contacts are spaced no more than about 1/8
inch from each other when the doors are
closed, and I used higher quality magnetic
sensors than come with the standard
door/window sensors.  Could the long wire
runs be somehow picking up false signals?

[Brian H]

Three switches in series should work, but as
you said a real long distance maybe enough
to pick up noise. The switches close a
ground to a logic input to an IC. I don't
know what the pull up resistance in the chip
is so maybe noise.

[Brian H]

If it is noise you maybe able to add a small
bypass capacitor at the point where the two
original wires to the module connect.
Like a radio Shack 272-109 .1uf cap. May do
nothing or may help.

[david]

Thanks, Brian.  I'll give it a try.

[david]

Brian, one question - should the capacitor be
in series or in parallel?

[Brian H]

parallel across the two original wires that
where on the switches contact screws.
This may do nothing but may help.

[RobW]

How many feet is your run?  I have a remote
garage wired in to a window sensor in my
house.  There are 2 sets of magnets in the
garage and the total run is ~70'.  Is your
wire run near any high capacity motors or
anything that could cause this
interference?  What if you bridge one sensor
at a time or run a temorary wire to
eliminate a sesor or wire run?