I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Wiki didn't have the answer to this, so I provided it.
http://wiki.answers.com/Q/What_is_th...BhbnN3ZXJzIQ==



In switch language, open means to disconnect, or break the
circuit. Some people call this "turned off". Closed, is to
connect, or make the circuit. Some people call this turned
on.

In the case of a normally open switch, the switch is open
(off) unless something takes action on the switch. Pushes a
button for example, or holds a magnet near the switch, or
other active force. A normally closed switch is closed (on)
unless some force causes the switch to be opened.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted
on my
garage door that controls a signal light in the house that
comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current
flows) when the
magnet is near the switch and CLOSED (meaning current flows)
when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed
one? Different
manufacturers/vendors seem to use the terms differently. Is
it "normal"
when the magnet is near the switch-- or away from it?

Normal is when the magnet is away. Which is the unactivated
condition. When the magnet is near the reed switch, that's
not considered normal -- it's considered activated.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted
on my
garage door that controls a signal light in the house that
comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current
flows) when the
magnet is near the switch and CLOSED (meaning current flows)
when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed
one? Different
manufacturers/vendors seem to use the terms differently. Is
it "normal"
when the magnet is near the switch-- or away from it?

"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do you
have to close the switch in order to turn on the light? If so, then you
need a normally open switch. Conversely, if the switch is open when the
light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

"Stormin Mormon" wrote in message
...
Normal is when the magnet is away. Which is the unactivated
condition. When the magnet is near the reed switch, that's
not considered normal -- it's considered activated.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.


Your description is about as clear as mud. Try again!

"MLD" wrote in message
...

"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do you
have to close the switch in order to turn on the light? If so, then you
need a normally open switch. Conversely, if the switch is open when the
light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger -- both
the semantic snafu, and that Stormin actually grokked it.
--
EA

Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do you
have to close the switch in order to turn on the light? If so, then you
need a normally open switch. Conversely, if the switch is open when the
light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger -- both
the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.

On Apr 29, 9:07*am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

On Thu, 29 Apr 2010 09:32:45 -0700 (PDT), Bob Villa
wrote:

On Apr 29, 9:07*am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

Normally = Energized = most of the time.
Except fire alarm systems

Upload the wiring diagram to be sure.

On Thu, 29 Apr 2010 10:07:15 -0400, Bitzer wrote:

I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Or you can look at the switch you pulled out and wire the new one the
same way.

"Bitzer" wrote in message
...
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on
when the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do
you have to close the switch in order to turn on the light? If so, then
you need a normally open switch. Conversely, if the switch is open when
the light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as
both states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no
natural "return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or
are you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger --
both the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who thought
it was a doorbell. RS seems to mainly sell cell phones and electronic toys
these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or so-- but it's
really unclear if they will keep the circuit open when the magnet is near
or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.

Radio shack ain't what it used to be.

Oh, you know, these magnetic switches were common in the old alarms systems,
that you would put on doors, windows, etc.
--
EA

"Metspitzer" wrote in message
news
On Thu, 29 Apr 2010 09:32:45 -0700 (PDT), Bob Villa
wrote:

On Apr 29, 9:07 am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

Normally = Energized = most of the time.

Not in relays.
--
EA




Except fire alarm systems

Upload the wiring diagram to be sure.

"Bitzer" wrote in message
...
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on
when the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do
you have to close the switch in order to turn on the light? If so, then
you need a normally open switch. Conversely, if the switch is open when
the light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as
both states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no
natural "return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or
are you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger --
both the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who thought
it was a doorbell. RS seems to mainly sell cell phones and electronic toys
these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or so-- but it's
really unclear if they will keep the circuit open when the magnet is near
or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.

If you find one that says SPDT or DPDT, then it can be used as either NC or
NO.
Often, the screw terminals or lugs themselves are labeled NO and NC, but not
the switch as a whole.
--
EA

On Thu, 29 Apr 2010 13:29:25 -0400, "Existential Angst"
wrote:

"Metspitzer" wrote in message
news
On Thu, 29 Apr 2010 09:32:45 -0700 (PDT), Bob Villa
wrote:

On Apr 29, 9:07 am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

Normally = Energized = most of the time.

Not in relays.

I meant De energized in motor relays and Energized in fire alarm
systems.

On Apr 29, 11:56*am, Bitzer wrote:
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?
Forget current flows or doesn't flow--that is confusing. *Instead, do you
have to close the switch in order to turn on the light? *If so, then you
need a normally open switch. *Conversely, if the switch is open when the
light is on, then you need a normally closed switch. *From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? *Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: *"closed" in
switching has the opposite meaning to a valve, ito flow. *Go figger -- both
the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or *so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.- Hide quoted text -

- Show quoted text -

"Radio Shack seems to mainly sell cell phones and electronic toys
these days-- no more electronic components."

Well, since you brought it up...

I was working at an event this weekend and somebody broke the 1/4 mono
jack for one of the loudspeakers.

I went over to the nearest Radio Shack to get a new jack. Since the
young lady was nice enough to approach me and ask if she could help, I
started to explain to her what I needed - quickly noticing the glaze
that was coming over her eyes.

Her response was "You'll have to speak to one of those guys. I know a
lot about cell phones, but not much about that kind of stuff."

So what's the deal? Does Radio Shack *expect* that everyone that walks
into the store wants a cell phone? If not, why would someone who knows
nothing about their other products approach me?

"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong

On Apr 29, 9:07*am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You use a reed switch, with TWO magnets. When the door is down, place
the two magnets so they oppose each other, the reed switch will stay
open if you position the magnets correctly. one magnet on the door,
one on the frame next to the reed relay/switch. When the door goes
up, the one magnet will move away from the reed relay/switch and the
remaining magnet will close the switch and turn on your alarm/light
bulb/whatever. This is high-school 9th grade stuff, not rocket
science!!!!

On Thu, 29 Apr 2010 13:49:12 -0700 (PDT), DerbyDad03
wrote:

On Apr 29, 11:56*am, Bitzer wrote:
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?
Forget current flows or doesn't flow--that is confusing. *Instead, do you
have to close the switch in order to turn on the light? *If so, then you
need a normally open switch. *Conversely, if the switch is open when the
light is on, then you need a normally closed switch. *From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? *Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: *"closed" in
switching has the opposite meaning to a valve, ito flow. *Go figger -- both
the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or *so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.- Hide quoted text -

- Show quoted text -

"Radio Shack seems to mainly sell cell phones and electronic toys
these days-- no more electronic components."

Well, since you brought it up...

I was working at an event this weekend and somebody broke the 1/4 mono
jack for one of the loudspeakers.

I went over to the nearest Radio Shack to get a new jack. Since the
young lady was nice enough to approach me and ask if she could help, I
started to explain to her what I needed - quickly noticing the glaze
that was coming over her eyes.

Her response was "You'll have to speak to one of those guys. I know a
lot about cell phones, but not much about that kind of stuff."

So what's the deal? Does Radio Shack *expect* that everyone that walks
into the store wants a cell phone? If not, why would someone who knows
nothing about their other products approach me?

Radio Shack should expect everyone to buy a cellphone.

They left me with a bad taste in my mouth when I bought my first
compute from them.

I used to buy everything at Radio Shack. I can't remember the last
time I have been in one of their stores. Several years.

I know your situation was that you needed something that day. I let
Newegg bring the stuff to my door.

hr(bob) wrote:
On Apr 29, 9:07 am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You use a reed switch, with TWO magnets. When the door is down, place
the two magnets so they oppose each other, the reed switch will stay
open if you position the magnets correctly. one magnet on the door,
one on the frame next to the reed relay/switch. When the door goes
up, the one magnet will move away from the reed relay/switch and the
remaining magnet will close the switch and turn on your alarm/light
bulb/whatever. This is high-school 9th grade stuff, not rocket
science!!!!


If I recall, the first thing they taught back in 9th grade was to answer
the question that was asked, not tell the inquirer how to build a
convoluted Rube Goldberg device ;-)

On Thu, 29 Apr 2010 16:49:51 -0400, "RBM" wrote:


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong


Yeah, then you can put one wire on the "common" and flip a coin.

Wire it NO and if the light goes off when it should come on then wire
it NC.

My best guess is that you should wire it NO and the magnet will close
the switch.

"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on
my garage door that controls a signal light in the house that
comes on when the door is open.

Thus, I need a switch that is OPEN (meaning no current flows)
when the magnet is near the switch and CLOSED (meaning current
flows) when the magnet is removed from the switch.

So do I need a normally open switch or a normally closed one?
Different manufacturers/vendors seem to use the terms
differently. Is it "normal" when the magnet is near the switch--
or away from it?


NC

--
Nonny
On most days,
it's just not worth
the effort of chewing
through the restraints..

On Thu, 29 Apr 2010 11:56:39 -0400, Bitzer wrote:

Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

Forget current flows or doesn't flow--that is confusing. Instead, do you
have to close the switch in order to turn on the light? If so, then you
need a normally open switch. Conversely, if the switch is open when the
light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger -- both
the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.
Go to the Borg or any other reasonably well stocked shop and get a
normally closed magnetic alarm switch. Install it so the magnet (on
the door) is in proximity to the switch with the door closed, and the
light will come on when the magnet leaves the switch.

On Thu, 29 Apr 2010 13:07:44 -0400, Metspitzer
wrote:

On Thu, 29 Apr 2010 09:32:45 -0700 (PDT), Bob Villa
wrote:

On Apr 29, 9:07Â*am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

Normally = Energized = most of the time.
Except fire alarm systems

Upload the wiring diagram to be sure.
Actually, even with fire alarms you can have series string (normally
closed) or parallel string(normally open) circuits.

On Thu, 29 Apr 2010 17:54:39 -0400, Metspitzer
wrote:

On Thu, 29 Apr 2010 16:49:51 -0400, "RBM" wrote:


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong


Yeah, then you can put one wire on the "common" and flip a coin.

Wire it NO and if the light goes off when it should come on then wire
it NC.

My best guess is that you should wire it NO and the magnet will close
the switch.
That's fine if he wants to know when the door is CLOSED - Generally
people set it up that they know when it is OPEN. (or NOT closed)

On Thu, 29 Apr 2010 22:12:35 -0400, wrote:

On Thu, 29 Apr 2010 13:07:44 -0400, Metspitzer
wrote:

On Thu, 29 Apr 2010 09:32:45 -0700 (PDT), Bob Villa
wrote:

On Apr 29, 9:07*am, Bitzer wrote:
I'm replacing a broken surface mount magnetic switch mounted on my
garage door that controls a signal light in the house that comes on when
the door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

You need a NC switch as you describe it.

Normally = Energized = most of the time.
Except fire alarm systems

Upload the wiring diagram to be sure.
Actually, even with fire alarms you can have series string (normally
closed) or parallel string(normally open) circuits.

Fire alarm relays are "normal" in the energized state so they fail
safe.

On Thu, 29 Apr 2010 22:19:30 -0400, wrote:

On Thu, 29 Apr 2010 17:54:39 -0400, Metspitzer
wrote:

On Thu, 29 Apr 2010 16:49:51 -0400, "RBM" wrote:


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong


Yeah, then you can put one wire on the "common" and flip a coin.

Wire it NO and if the light goes off when it should come on then wire
it NC.

My best guess is that you should wire it NO and the magnet will close
the switch.
That's fine if he wants to know when the door is CLOSED - Generally
people set it up that they know when it is OPEN. (or NOT closed)

No. I think you and I disagree whether the switch is "normal" with
the magnet near or far.

I don't know. I am guessing.

On Thu, 29 Apr 2010 22:19:30 -0400, wrote:

On Thu, 29 Apr 2010 17:54:39 -0400, Metspitzer
wrote:

On Thu, 29 Apr 2010 16:49:51 -0400, "RBM" wrote:


"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong


Yeah, then you can put one wire on the "common" and flip a coin.

Wire it NO and if the light goes off when it should come on then wire
it NC.

My best guess is that you should wire it NO and the magnet will close
the switch.
That's fine if he wants to know when the door is CLOSED - Generally
people set it up that they know when it is OPEN. (or NOT closed)


Oh yeah...........never mind

Reminds me of when we installed some lights in an underpass. The
emergency lights burned all the time and the main lights came on in
the daytime.

Metspitzer wrote:
On Thu, 29 Apr 2010 13:49:12 -0700 (PDT), DerbyDad03
wrote:

On Apr 29, 11:56 am, Bitzer wrote:
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.
Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.
So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?
Forget current flows or doesn't flow--that is confusing. Instead, do you
have to close the switch in order to turn on the light? If so, then you
need a normally open switch. Conversely, if the switch is open when the
light is on, then you need a normally closed switch. From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD
Actually, not correct, either in analogy or in answer.
The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.
A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.
To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? Wouldn't they be able to just supply the right part, or are
you kluging your own solution?
Remarkably, Stormin brought up a good point semantically: "closed" in
switching has the opposite meaning to a valve, ito flow. Go figger -- both
the semantic snafu, and that Stormin actually grokked it.
I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.- Hide quoted text -

- Show quoted text -
"Radio Shack seems to mainly sell cell phones and electronic toys
these days-- no more electronic components."

Well, since you brought it up...

I was working at an event this weekend and somebody broke the 1/4 mono
jack for one of the loudspeakers.

I went over to the nearest Radio Shack to get a new jack. Since the
young lady was nice enough to approach me and ask if she could help, I
started to explain to her what I needed - quickly noticing the glaze
that was coming over her eyes.

Her response was "You'll have to speak to one of those guys. I know a
lot about cell phones, but not much about that kind of stuff."

So what's the deal? Does Radio Shack *expect* that everyone that walks
into the store wants a cell phone? If not, why would someone who knows
nothing about their other products approach me?

Radio Shack should expect everyone to buy a cellphone.

They left me with a bad taste in my mouth when I bought my first
compute from them.

I used to buy everything at Radio Shack. I can't remember the last
time I have been in one of their stores. Several years.

I know your situation was that you needed something that day. I let
Newegg bring the stuff to my door.



I went to a Shack store in a small town outside of Birmingham the
other day to get a toggle switch to repair a neon sign for a store
belonging to a customer of mine. The Shack (new name) has nowhere
near the number of electronic parts they used to carry but I can
usually find what I need because the morons there have no clue
what parts they carry. I worked for their repair division more than
30 years ago, I wound up with all kinds of discrete components.

TDD

RBM wrote:
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it. My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong



He he he, most electricians I come across are befuddled by three way and
four way switches. I had to explain it to my electrical superintendent
and foreman on a government job I worked on some years ago. Normally
open and normally closed had to be explained to them using the
illustration of the difference between a virtuous woman and a slut.
*snicker*

TDD

RBM wrote:
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it.

I agree.

In all the following the contacts are closed with the magnet next to the
reed switch.

From an alarm perspective *NC* ("normal" is when the door is closed):

http://en.wikipedia.org/wiki/Burglar..._control_panel
"Most switching devices are N.C. (normally closed) circuits, so when the
device is not in an alarm condition, the circuit is closed."

http://www.alibaba.com/product-gs/21...ch_5C_31A.html
"Output signal: normally closed (switch contact is closed when the door
closed)"



From a component manufacturer *NO*

C&K: "ELECTRICAL CIRCUIT: SPST NO (Contact Form A). Reed switch
opens when magnet is removed from proximity. Contacts are
held closed when magnet is within actuation range."


To know what the switch does you need to have a description like all of
the above.

My solution is to always buy
devices that come in the "form C" which is both open and closed circuits,
this way you can't go wrong

For the magnetic switches I looked at from alarm companies, none said NO
or NC. A few said NC loop. They were probably all "NC" from an alarm
perspective. Except a few were Form C.

--
bud--

On Apr 29, 5:33*pm, Metspitzer wrote:
On Thu, 29 Apr 2010 13:49:12 -0700 (PDT), DerbyDad03





wrote:
On Apr 29, 11:56*am, Bitzer wrote:
Existential Angst wrote:
"MLD" wrote in message
...
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the
door is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?
Forget current flows or doesn't flow--that is confusing. *Instead, do you
have to close the switch in order to turn on the light? *If so, then you
need a normally open switch. *Conversely, if the switch is open when the
light is on, then you need a normally closed switch. *From what you
describe, I would think that you need a normally open switch---light off
when door is closed.
MLD

Actually, not correct, either in analogy or in answer.

The answer is normally closed -- as others have said, the state with no
outside force acting on it.
Same thing with relays -- IF the relay is "single throw".
If the relay is "double throw", then again, NO or NC doesn't apply, as both
states can be wired in as normal.

A toggle light switch also has two "normal" states, even tho it single
throw -- because the "outside force" is, well, you, so there is no natural
"return position"..
Ditto with any rotary-type multi-position switch, for fan speeds, etc.:
every position is normal.

To the OP, curious as to where you would get this kind of switch -- oem,
from the garage door mfr??
How much $$?? *Wouldn't they be able to just supply the right part, or are
you kluging your own solution?

Remarkably, Stormin brought up a good point semantically: *"closed" in
switching has the opposite meaning to a valve, ito flow. *Go figger -- both
the semantic snafu, and that Stormin actually grokked it.

I bought the switch for about two bucks 15-20 years ago at Radio Shack--
along with the wire, transformer and LED indicator light i needed for my
custome designed system. A contractor bashed the existing switch so I've
been to a few Radio Shack stores around town but the clerks didn't know
wht I was talking about. I showed the broken one to one clerk who
thought it was a doorbell. RS seems to mainly sell cell phones and
electronic toys these days-- no more electronic components.

I see lots of them on line and on Ebay for around $10 or *so-- but it's
really unclear if they will keep the circuit open when the magnet is
near or away. I guess I'll just buy one of each kind-- an NO and an NC--
and toss the one I don't need.- Hide quoted text -

- Show quoted text -

"Radio Shack seems to mainly sell cell phones and electronic toys
these days-- no more electronic components."

Well, since you brought it up...

I was working at an event this weekend and somebody broke the 1/4 mono
jack for one of the loudspeakers.

I went over to the nearest Radio Shack to get a new jack. Since the
young lady was nice enough to approach me and ask if she could help, I
started to explain to her what I needed - quickly noticing the glaze
that was coming over her eyes.

Her response was "You'll have to speak to one of those guys. I know a
lot about cell phones, but not much about that kind of stuff."

So what's the deal? Does Radio Shack *expect* that everyone that walks
into the store wants a cell phone? If not, why would someone who knows
nothing about their other products approach me?

Radio Shack should expect everyone to buy a cellphone.

They left me with a bad taste in my mouth when I bought my first
compute from them.

I used to buy everything at Radio Shack. *I can't remember the last
time I have been in one of their stores. *Several years.

I know your situation was that you needed something that day. *I let
Newegg bring the stuff to my door.- Hide quoted text -

- Show quoted text -

"I let Newegg bring the stuff to my door."

As you surmised, I needed the jack rather quickly.

"Normally" (thread-based pun intended) I go to the one remaining
*real* electronics parts store in my town where if they don't have it,
they can get it the next day - without trying to sell me a cell phone.

On Apr 30, 9:02 pm, wrote:
On Fri, 30 Apr 2010 10:41:41 -0500, bud--
wrote:



RBM wrote:
"Bitzer" wrote in message
...
I'm replacing a broken surface mount magnetic switch mounted on my garage
door that controls a signal light in the house that comes on when the door
is open.

Thus, I need a switch that is OPEN (meaning no current flows) when the
magnet is near the switch and CLOSED (meaning current flows) when the
magnet is removed from the switch.

So do I need a normally open switch or a normally closed one? Different
manufacturers/vendors seem to use the terms differently. Is it "normal"
when the magnet is near the switch-- or away from it?

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it.

I agree.

Not quite right. An alarm SYSTEM being normally closed requires
normally open SWITCHES. This is a series string system, where when one
- any one - switch opens, the "normally closed" loop is open and the
alarm sounds. The SWITCHES are normally open, and closed when the
magnet activates the switch.

A Normally OPEN system is a parallel string circuit - where the
normally CLOSED switches are activated when the doores are closed and
the magnet is close - and ANY ONE switch being CLOSED activates the
system.

The techs (if they know what they are doing and talking about) KNOW
this.


I think Bud and RBM who are both electricians have this one right.
There is no consistency on this. At the very least, I can show you
an alarm switch I quickly found that clearly calls switches that are
CLOSED when the magnet is next to them NORMALLY CLOSED SWITCHES. You
can pull up the PDF "manual" as well and it is consistent with that
terminology. It didn't take long to find this, it was the first place
I looked after googling alarm switch.

I think Buds statement that you have to carefully read the full
description to figure it out is spot on. And even then, in some
descriptions you may not be able to tell because they really don't
say. In this one, it is very clear:

http://www.smarthome.com/7113-10/Sur...10-Pack/p.aspx

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack

Essential Info
The most basic sensors of any alarm system are the door and window
Surface Mount Magnetic Contact Switches. There are 10 pairs of
switches included in this kit allowing you to monitor multiple areas
around your home. This type of contact switch is for normally closed
circuits; this means that the when the magnets are lined up, the
switch is closed."

Note that they call the circuit normally closed and also call the
switch for that circuit normally closed.


It all gets back to what your definition of "normal" is. If it means
the condition with no outside signal or magnet on it, which is
reasonable and how we approach relays then I agree with your
interpretation. But I also see how what RBM said is true. That in
the alarm industry, which BTW is an obvious big user of these devices,
they call a switch "normal" if the window is shut and the magnet is
next to it. It becomes not-normal when the window is moved away and
it trips the alarm.

On Sat, 1 May 2010 06:31:46 -0700 (PDT), wrote:



As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it.

I agree.

Not quite right. An alarm SYSTEM being normally closed requires
normally open SWITCHES. This is a series string system, where when one
- any one - switch opens, the "normally closed" loop is open and the
alarm sounds. The SWITCHES are normally open, and closed when the
magnet activates the switch.

A Normally OPEN system is a parallel string circuit - where the
normally CLOSED switches are activated when the doores are closed and
the magnet is close - and ANY ONE switch being CLOSED activates the
system.

The techs (if they know what they are doing and talking about) KNOW
this.


I think Bud and RBM who are both electricians have this one right.
There is no consistency on this. At the very least, I can show you
an alarm switch I quickly found that clearly calls switches that are
CLOSED when the magnet is next to them NORMALLY CLOSED SWITCHES. You
can pull up the PDF "manual" as well and it is consistent with that
terminology. It didn't take long to find this, it was the first place
I looked after googling alarm switch.

I think Buds statement that you have to carefully read the full
description to figure it out is spot on. And even then, in some
descriptions you may not be able to tell because they really don't
say. In this one, it is very clear:

http://www.smarthome.com/7113-10/Sur...10-Pack/p.aspx

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack

Essential Info
The most basic sensors of any alarm system are the door and window
Surface Mount Magnetic Contact Switches. There are 10 pairs of
switches included in this kit allowing you to monitor multiple areas
around your home. This type of contact switch is for normally closed
circuits; this means that the when the magnets are lined up, the
switch is closed."

Note that they call the circuit normally closed and also call the
switch for that circuit normally closed.


No, they do not call the switch a "normally closed" switch. They say
when the magnets are lined up they are normally closed.
The definition of a "normally open" switch meets that spec.

You DO have to read carefully what they are saying - and you have to
understand what is really going on.

It all gets back to what your definition of "normal" is. If it means
the condition with no outside signal or magnet on it, which is
reasonable and how we approach relays then I agree with your
interpretation. But I also see how what RBM said is true. That in
the alarm industry, which BTW is an obvious big user of these devices,
they call a switch "normal" if the window is shut and the magnet is
next to it. It becomes not-normal when the window is moved away and
it trips the alarm.

On May 1, 10:53 am, wrote:
On Sat, 1 May 2010 06:31:46 -0700 (PDT), wrote:

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it.

I agree.

Not quite right. An alarm SYSTEM being normally closed requires
normally open SWITCHES. This is a series string system, where when one
- any one - switch opens, the "normally closed" loop is open and the
alarm sounds. The SWITCHES are normally open, and closed when the
magnet activates the switch.

A Normally OPEN system is a parallel string circuit - where the
normally CLOSED switches are activated when the doores are closed and
the magnet is close - and ANY ONE switch being CLOSED activates the
system.

The techs (if they know what they are doing and talking about) KNOW
this.

I think Bud and RBM who are both electricians have this one right.
There is no consistency on this. At the very least, I can show you
an alarm switch I quickly found that clearly calls switches that are
CLOSED when the magnet is next to them NORMALLY CLOSED SWITCHES. You
can pull up the PDF "manual" as well and it is consistent with that
terminology. It didn't take long to find this, it was the first place
I looked after googling alarm switch.

I think Buds statement that you have to carefully read the full
description to figure it out is spot on. And even then, in some
descriptions you may not be able to tell because they really don't
say. In this one, it is very clear:

http://www.smarthome.com/7113-10/Sur...-Contact-Switc...

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack

Essential Info
The most basic sensors of any alarm system are the door and window
Surface Mount Magnetic Contact Switches. There are 10 pairs of
switches included in this kit allowing you to monitor multiple areas
around your home. This type of contact switch is for normally closed
circuits; this means that the when the magnets are lined up, the
switch is closed."

Note that they call the circuit normally closed and also call the
switch for that circuit normally closed.

No, they do not call the switch a "normally closed" switch. They say
when the magnets are lined up they are normally closed.
The definition of a "normally open" switch meets that spec.

You DO have to read carefully what they are saying - and you have to
understand what is really going on.



Yeah YOU sure do need to read carefully what they are saying. And you
obviously didn't. Because if your read the description in the link I
provided, they CLEARLY call that switch normally closed. It's right
in the freaking one line TITLE:

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack)"


Here's another link to a switch supplier that discusses the issue and
says this:

http://www.iheartswitch.com/blog/cho...h-your-project

"For unknown reasons, there are some companies classifying their
magnetic switches against the grain. Their NC switches turn things OFF
when the two halves are apart, while NO does the opposite. This is why
even some salespersons are confused as well. Therefore, before
purchasing any magnetic switches, read the product descriptions
carefully."

The OP can make up his own mind. Listen to two electricians and a
switch company that says confusion does exist and the only way to know
is to carefully read the description, if it's even contained in the
description. Or you, who says the terms are only used one way.
Clearly in the case I just showed you, if you went by the one line
title of the switch, you'd be getting the opposite of what you
expect. And in most cases, that one line is about all they say about
the switch, ie there is no further explanation.





It all gets back to what your definition of "normal" is. If it means
the condition with no outside signal or magnet on it, which is
reasonable and how we approach relays then I agree with your
interpretation. But I also see how what RBM said is true. That in
the alarm industry, which BTW is an obvious big user of these devices,
they call a switch "normal" if the window is shut and the magnet is
next to it. It becomes not-normal when the window is moved away and
it trips the alarm.

wrote in message
...
On Sun, 2 May 2010 06:34:49 -0700 (PDT), wrote:

On May 1, 10:53 am, wrote:
On Sat, 1 May 2010 06:31:46 -0700 (PDT), wrote:

As an electrician, I've been through this numerous times over the
years. It
clearly depend on who you are talking to, and what trade they're
in. IMO,
the "normal" position is the state the switch is in when nothing
affects it.
Alarm people have the opposite take on it.

I agree.

Not quite right. An alarm SYSTEM being normally closed requires
normally open SWITCHES. This is a series string system, where when
one
- any one - switch opens, the "normally closed" loop is open and the
alarm sounds. The SWITCHES are normally open, and closed when the
magnet activates the switch.

A Normally OPEN system is a parallel string circuit - where the
normally CLOSED switches are activated when the doores are closed and
the magnet is close - and ANY ONE switch being CLOSED activates the
system.

The techs (if they know what they are doing and talking about) KNOW
this.

I think Bud and RBM who are both electricians have this one right.
There is no consistency on this. At the very least, I can show you
an alarm switch I quickly found that clearly calls switches that are
CLOSED when the magnet is next to them NORMALLY CLOSED SWITCHES. You
can pull up the PDF "manual" as well and it is consistent with that
terminology. It didn't take long to find this, it was the first place
I looked after googling alarm switch.

I think Buds statement that you have to carefully read the full
description to figure it out is spot on. And even then, in some
descriptions you may not be able to tell because they really don't
say. In this one, it is very clear:

http://www.smarthome.com/7113-10/Sur...-Contact-Switc...

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack

Essential Info
The most basic sensors of any alarm system are the door and window
Surface Mount Magnetic Contact Switches. There are 10 pairs of
switches included in this kit allowing you to monitor multiple areas
around your home. This type of contact switch is for normally closed
circuits; this means that the when the magnets are lined up, the
switch is closed."

Note that they call the circuit normally closed and also call the
switch for that circuit normally closed.

No, they do not call the switch a "normally closed" switch. They say
when the magnets are lined up they are normally closed.
The definition of a "normally open" switch meets that spec.

You DO have to read carefully what they are saying - and you have to
understand what is really going on.



Yeah YOU sure do need to read carefully what they are saying. And you
obviously didn't. Because if your read the description in the link I
provided, they CLEARLY call that switch normally closed. It's right
in the freaking one line TITLE:

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack)"


Here's another link to a switch supplier that discusses the issue and
says this:

http://www.iheartswitch.com/blog/cho...h-your-project

"For unknown reasons, there are some companies classifying their
magnetic switches against the grain. Their NC switches turn things OFF
when the two halves are apart, while NO does the opposite. This is why
even some salespersons are confused as well. Therefore, before
purchasing any magnetic switches, read the product descriptions
carefully."

The OP can make up his own mind. Listen to two electricians and a
switch company that says confusion does exist and the only way to know
is to carefully read the description, if it's even contained in the
description. Or you, who says the terms are only used one way.
Clearly in the case I just showed you, if you went by the one line
title of the switch, you'd be getting the opposite of what you
expect. And in most cases, that one line is about all they say about
the switch, ie there is no further explanation.





It all gets back to what your definition of "normal" is. If it means
the condition with no outside signal or magnet on it, which is
reasonable and how we approach relays then I agree with your
interpretation. But I also see how what RBM said is true. That in
the alarm industry, which BTW is an obvious big user of these devices,
they call a switch "normal" if the window is shut and the magnet is
next to it. It becomes not-normal when the window is moved away and
it trips the alarm.


A doorbell button is a clear and easy to understand example of a
normally open switch.

Indeed, it must be....
Assuming you didn't get some behind-the-scenes tutoring.
--
EA

On Sun, 02 May 2010 09:56:37 -0400, wrote:

On Sun, 2 May 2010 06:34:49 -0700 (PDT), wrote:

On May 1, 10:53 am, wrote:
On Sat, 1 May 2010 06:31:46 -0700 (PDT), wrote:

As an electrician, I've been through this numerous times over the years. It
clearly depend on who you are talking to, and what trade they're in. IMO,
the "normal" position is the state the switch is in when nothing affects it.
Alarm people have the opposite take on it.

I agree.

Not quite right. An alarm SYSTEM being normally closed requires
normally open SWITCHES. This is a series string system, where when one
- any one - switch opens, the "normally closed" loop is open and the
alarm sounds. The SWITCHES are normally open, and closed when the
magnet activates the switch.

A Normally OPEN system is a parallel string circuit - where the
normally CLOSED switches are activated when the doores are closed and
the magnet is close - and ANY ONE switch being CLOSED activates the
system.

The techs (if they know what they are doing and talking about) KNOW
this.

I think Bud and RBM who are both electricians have this one right.
There is no consistency on this. At the very least, I can show you
an alarm switch I quickly found that clearly calls switches that are
CLOSED when the magnet is next to them NORMALLY CLOSED SWITCHES. You
can pull up the PDF "manual" as well and it is consistent with that
terminology. It didn't take long to find this, it was the first place
I looked after googling alarm switch.

I think Buds statement that you have to carefully read the full
description to figure it out is spot on. And even then, in some
descriptions you may not be able to tell because they really don't
say. In this one, it is very clear:

http://www.smarthome.com/7113-10/Sur...-Contact-Switc...

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack

Essential Info
The most basic sensors of any alarm system are the door and window
Surface Mount Magnetic Contact Switches. There are 10 pairs of
switches included in this kit allowing you to monitor multiple areas
around your home. This type of contact switch is for normally closed
circuits; this means that the when the magnets are lined up, the
switch is closed."

Note that they call the circuit normally closed and also call the
switch for that circuit normally closed.

No, they do not call the switch a "normally closed" switch. They say
when the magnets are lined up they are normally closed.
The definition of a "normally open" switch meets that spec.

You DO have to read carefully what they are saying - and you have to
understand what is really going on.



Yeah YOU sure do need to read carefully what they are saying. And you
obviously didn't. Because if your read the description in the link I
provided, they CLEARLY call that switch normally closed. It's right
in the freaking one line TITLE:

"Surface Mount Magnetic Contact Switch, Normally Closed (10-Pack)"


Here's another link to a switch supplier that discusses the issue and
says this:

http://www.iheartswitch.com/blog/cho...h-your-project

"For unknown reasons, there are some companies classifying their
magnetic switches against the grain. Their NC switches turn things OFF
when the two halves are apart, while NO does the opposite. This is why
even some salespersons are confused as well. Therefore, before
purchasing any magnetic switches, read the product descriptions
carefully."
From the site referenced :

Surface Mounted Normally Open Magnetic Reed Switch
Philmore # 30-17050

Use this switch if you'd like to turn something OFF when the two
halves of your switch are apart. Commonly used with security systems.


Specifications


Action: Closed Loop / Normally Open (when magnet is beyond the
actuations range)
Maximum Gap (actuation range): 1-1/4" Max
Mounting Hole Centers: 2-3/32"
Terminal Type: Screw
Type: SPST
Current Rating: 0.5A @ 100VDC


There is NOTHING contrary in this description. With the magnet beyond
actuation range, the NO switch is turned off - exactly as it should
be.

Radio Shack's is normally closed when contacts are apart (poor
description - but basically when magnet is beyond actuation range)

Digi-Key gives no description other than "normally closed"


The OP can make up his own mind. Listen to two electricians and a
switch company that says confusion does exist and the only way to know
is to carefully read the description, if it's even contained in the
description. Or you, who says the terms are only used one way.
Clearly in the case I just showed you, if you went by the one line
title of the switch, you'd be getting the opposite of what you
expect. And in most cases, that one line is about all they say about
the switch, ie there is no further explanation.





It all gets back to what your definition of "normal" is. If it means
the condition with no outside signal or magnet on it, which is
reasonable and how we approach relays then I agree with your
interpretation. But I also see how what RBM said is true. That in
the alarm industry, which BTW is an obvious big user of these devices,
they call a switch "normal" if the window is shut and the magnet is
next to it. It becomes not-normal when the window is moved away and
it trips the alarm.


A doorbell button is a clear and easy to understand example of a
normally open switch.