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Reed Switch and Lightning

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.
 
P

petem

Jan 1, 1970
0
have you considered that maybe you have a ground on the wiring,that could
makethe system go a bit crazy ina case of a thunder storm

if not grounded maybe you could had a small capacitor in paralel of the
input of the board,maybe it could filter the spike created by the thunder
storm

another thing to do could be to use a toroid ferite on the wiring,turn a few
loop of the wiring in the ferite close to the board..

and at last be sure the power supply from the board is all filtered
properly..

surge from the strike could make the board go crazy
 
B

BIG NIGE

Jan 1, 1970
0
instead of using twisted pair use a screened alarm cable and earth the
screen at the panel end.
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
BIG said:
instead of using twisted pair use a screened alarm cable and earth the
screen at the panel end.

This sounds really good. Screened alarm cable. That sounds just
like what I'm looking for. Yes, I like this idea. Except, what
exactly is a "screened alarm cable" and where do I find something
like that?

Sorry, I'm a complete newbie at this game.

I'm picturing this stuff to look something like the coaxial cable
that hooks up to my TV, right? But TV coax has just a single copper
core wire contained within a mesh shielding. I'm assuming the alarm
cable would need to have TWO conductors within the grounded mesh
shielding? I've never seen anything like that. Can I find stuff
like this at Home Depot?

Also just so I'm clear on this, when you say "earth the screen",
would I just hook that to the grounded connecter at my electrical
outlet?

cheers,

-Ferdinand-
 
F

Frank Olson

Jan 1, 1970
0
-Ferdinand- said:
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.


Here's a better solution... Disconnect the contact wiring completely from
the system and see whether or not the next thunderstorm trips the circuit.
I've never heard of a reed switch "bouncing" like that, but then most of the
switches utilized in the security profession are "normally closed" and open
when the door or window does. Once you've eliminated your panel as the
possible source of the false alarms, then you can start to "track in" on the
other issues you (and a few other posters) have mentioned.
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
Robert said:
You can buy 22-gauge, 2-conductor, shielded cable at Home Depot...
Get the stuff that has a 100% foil shield and a tinned drain wire if you can
find it. That's a bit easier to work with than the braided shield cable.

Excellent! I'll stop by Home Depot tonight to have a look.

Side note: While switching to shielded cable *may* do the trick, it's not
100% certain that this will eliminate the problem. Many X10 devices behave
erratically during lightning. If this is what is happening, it won't make
any difference what kind of cable is connected between the X10 device and
the sensor.

I've noticed that too. I have a couple of X-10 Motion Detector
FloodLights that generally work fine, coming on only after dark if
they detect motion then going off automatically after a set time
period, or coming on and staying on whenever requested by the proper
X-10 signal. But sometimes when we arrive I find the damn lights
have somehow turned themselves on and stayed on full time during
daylight hours.

However, the X-10 Universal relay I'm using in the door alarm
cabling cannot be tripping the alarm no matter how erratically it
might be behaving during lightning. That's because the alarm
circuit is using a normally-OPEN reed switch on the door, and the
X-10 relay is between the reed switch and the alarm box.

With the X-10 relay open the alarm circuit is disabled, so even if
the reed switch is closed the alarm shouldn't trip.

With the X-10 relay closed the alarm circuit is merely armed,
waiting for the reed switch at the door to close and trigger the
alarm.

So if the X-10 relay is somehow being toggled by lightning, the
worst that should happen is that the alarm gets cycled between being
armed or disarmed. The X-10 relay itself should not be capable of
triggering the alarm (unless the reed switch is simultaneously
closed).

-Ferdinand-
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
Frank said:
Here's a better solution... Disconnect the contact wiring completely from
the system and see whether or not the next thunderstorm trips the circuit.
... Once you've eliminated your panel as the possible source of the false
alarms, then you can start to "track in" on the other issues you (and a
few other posters) have mentioned.

I bought the FreezeAlarm for our cottage primarily to give us
adequate warning of power failures and temperature extremes. It has
worked perfectly in this regard for most of a year with no false
alarm callouts whatsoever. That makes me think that the alarm box
itself is pretty much immune to interference from thunderstorms.

The FreezeAlarm will identify and dial a callout alarm under several
different conditions:

- temperature probe detects a temp hi/low outside a preset range
- power failure (either momentary, or gone for more than an hour)
- 9v backup battery low on power
- auxiliary alarm port triggered

I had tested the various functions and all worked well. The
problems only began after I decided to make use of the auxiliary
alarm port terminals on the FreezeAlarm to monitor a normally-OPEN
magnetic reed switch mounted on the door. Anything closing the
contacts of the auxiliary alarm port triggers an alarm callout.

I had stapled the wires in place. At first I though maybe one of
the metal staples had cut through the wire insulation somewhere and
was shorting out the circuit. So I tore it all out, ran fresh
wires, and fastened them with plastic clips.

Still the false alarm callouts occurred. It took a little while to
figure out the correlation between false alarms and the presence of
thunderstorms in the area.
I've never heard of a reed switch "bouncing" like that, ...

I'm pretty sceptical of that theory too, because the alarm still
gets triggered by lightning even when I leave the X-10 relay switch
open to disable the door alarm circuit.

Hence my suspicion that the false alarms are being triggered by the
door alarm wires somehow acting as an antenna and picking up a
charge whenever there is lightning nearby.

I'm itching to try out this "shielded cable" that the others are
recommending. That sounds like it should do the trick, but I'll
probably have to wait until spring for the next thunderstorm now
that winter is setting in.

-Ferdinand-
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
Frank said:
... most of the switches utilized in the security profession are
"normally closed" and open when the door or window does.

That's another issue I'm curious about. I'd actually much rather be
using a normally-CLOSED reed switch, but the auxiliary alarm port on
the FreezeAlarm is triggered whenever the alarm terminal contacts
are closed. Hence my requirement for using a normally-OPEN reed
switch on the door.

I'm thinking my problems might even be a direct result of using this
normally-OPEN switch. If the two wires connecting the alarm
terminals to either side of the open reed switch aren't exactly the
same length, then the antenna effect on the long wires subjected to
an electromagnetic pulse from lightning is probably generating a
measurable voltage difference between the two wires at the alarm
terminals. Maybe that voltage difference is sufficient to trigger a
false alarm. Hopefully I can cure that by using shielded cable.

A normally-CLOSED switch effectively creates a single long loop of
wire, rather than the two individual and separate lengths of wire
with a normally-OPEN switch. So, even if the voltage is still
momentarily elevated everwhere within the loop, a lightning pulse
shouldn't be able to create a voltage difference BETWEEN the alarm
terminals, right? I don't know this for sure, that's why I'm asking
you guys.

I have another reason why I'd prefer to use normally-CLOSED
switches. Currently I only have the basement door wired because
that was the easiest one to start with. I'd like to do the main
floor door as well, and ultimately the windows too, but there's no
point in starting any of that until I understand what's causing my
false alarm problems.

It doesn't much matter what sort of hardware installation I use on
the basement door because nobody except me ever sees that. On the
main floor though I'd prefer to use those nifty little cylindrical
concealed switches. Except Radio Shack only sells those as
normally-CLOSED switches and don't carry them as normally-OPEN. I
know, I know, I shouldn't be buying crap from Radio Shack...

So the question is how would I be able to use normally-CLOSED reed
switches in my system if my FreezeAlarm auxiliary alarm triggers on
a closed circuit? I suppose I could use a normally-CLOSED circuit
to power a relay switch, holding the relay in the open position, so
if a door is opened one of the reed switches in the circuit opens,
the relay switch then closes to trigger the alarm terminals. But, I
don't want this system tripping a door alarm every time the power
goes off momentarily (which it does a lot at our cottage).

Any suggestions?

-Ferdinand-
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
Robert said:
Olson is correct that it's a good idea to first eliminate the possibility
that a hardware fault (susceptibility to static, etc..) is involved...

I suppose it is possible that the hardware is at fault, but I doubt
it. It worked fine for most of a year with no other false alarms.
It was only after I wired up the basement door alarm that I started
getting these false alarms. Unless I've buggered up the box
somehow.
... before rewiring the place.

Rewiring is not a big deal at this point as it's just the one door
at the moment. There's only about 15 feet of wire in a straight run
between the door and the alarm box.

I was hoping to wire the rest of the place someday, but I'm not
going to start on that before solving this problem.
However, I would not be surprised if the cable is the problem given what
you've said so far. Give it a try. A few feet of shielded cable won't
cost much anyway.

I have a good feeling about this shielded cable idea. It sounds
right to me.

I went to Home Depot last night looking for 22-gauge 2-conductor
shielded cable and the guy there had never heard of it nor had any
idea where to get stuff like that. Nuts. They're usually very
helpful there.

So I stopped by a local electronics store and he said, no problem,
how much do you want? It's not expensive at all, so I got enough to
wire up everything. I'm itching to go up to the cottage right away
now to install the new cable. But I won't know for sure whether
that's cured my problem until after the next thunderstorm which is
unlikely to occur until next summer.

I'll be sure to give y'all an update then.

-Ferdinand-
 
F

Ferdinand Trauttmansdorff

Jan 1, 1970
0
Alarminex
Have you determined what happens to the alarm output when you remove power and
then re-apply it? Does the system come back in a momentary alarm condition? How
about when power is intermittantly applied and removed? ... I would guess that
the device is not sophisticated enough to have a backup standby battery.

It does have a 9v backup battery and continues to function while
there is a power failure. It will also call out a "low battery
alarm" if the backup battery voltage ever falls below a safe level.
You might say that you don't get a freeze alarm during a thunder storm, but it
could be that the freeze alarm has a delay or lag, built in, so that momentary
cold ( such as opening a door ) periods would not cause the unit to trip. This
just might allow the freeze alarm to not react to a power failure in the same
way the alarm circuit does.

The FreezeAlarm is quite a sophisticated gizmo. It has a series of
dip switches to allow it to be configured in different ways.

The temperature alarm can be set to trigger immediately if the
temperature goes above or below the alarm set points. If that trips
too easily, such as in the case when a cold draft comes in whenever
you open the door, you can flip the dip switch the other way and the
temperature alarm will only trip if the temperature stays outside
the acceptable temperature range for more than 45 minutes.

Similarly the power failure alarm can be configured to trigger an
alarm callout immediately if the power is interrupted, in which case
it calls out every time there is so much as a momentary blip in the
power supply. Or it can be configured to wait until the power has
been off for more than an hour continuously. While the power is off
the FreezeAlarm continues to function, monitoring the status of the
other alarm conditions, even performing alarm callouts, as it's
running off the 9v backup battery.
If you find that the system is tripping during a momentary power outage, you
might try using a old computer UPS that would act, at least, as a temporary
buffer against losing power altogether.

My door alarm problem is definitely not being caused by momentary
power outages. We quite often have momentary power blips at the
cottage and the door alarm has never been tripped by that.
Another thing. I don't know if you are aware or not but if you don't have a
phase coupler, a whole house filter and a blocking filter on your electrical
wiring, you are likely to continue to have the problems you have been having
with the X10 devices. Unfortunately, X10 is very susceptible to spikes noise
and from signals coming down the line from neighbors, who may have their X10
devices programed to the same, or close to the codes you are using.

We're getting off topic here, but yes the X-10 modules can be
problematic. I only started into this X-10 stuff, using an X-10
Universal Relay, because I needed some way to remotely arm/disarm
the door alarm so I could could get in and out without tripping an
alarm callout each time. The FreezeAlarm auxiliary alarm port that
I've hooked the door switch to cannot be set to delay. If it's
tripped it starts dialing out immediately.

I ended up buying a bunch of other stuff from X-10 including those
Motion Detector Floodlights. I have since learned all about the
need for a phase coupler. For now I'm using the simple capacitor
trick across a 220v breaker to couple the phases together and that
seems to be working quite nicely.

I'm still undecided about potential X-10 line interference from
neighbours. We don't have a lot of neighbours around our cottage
and I very much doubt any of them are using X-10 components.
Someday I might do the whole house filter thing, but I really hadn't
intended to spend a lot of money on this stuff.

-Ferdinand-
 
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