Using signal generation to detect the location of a line bre

E

Eric Livingston

Guest
I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.

Thanks,
Eric
 
Eric Livingston wrote:

I have three speaker wires running just behind sheetrock along a wall
in my house that have breaks in them somewhere (I believe from the
contractor firing nails through the wires when putting up the
sheetrock). Two of the wires are shorted from one end (wall terminal)
and open from the other. The third is open from both ends. I figure
in all cases a nail-gunned nail went through the wire in question,
and in two cases the nail is probably shorting one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a
strong magnet, and it works to a degree but not enough - I need a
stronger magnet or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as
an antenna, generating some kind of signal, I could use a receiver
held up to the wall to detect that signal, and thus detect the break.
Would this work? How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the
cut (i.e. open) wires in the walls due to the capacitance of the
wire, though there's no closed circuit. Can I use something to detect
the AC Current in the wires behind the wall? Could this work even
with the broken (not shorted) wires, relying on nothing but the wire
capacitance to allow a trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it
should be possible.

Thanks,
Eric
Click to expand...
yes its possible - but what are you going to do once you locate the
wires? dig holes in the wall?
rw
 
"Rein Wiehler" <rwiehler@netscape.net> wrote in message
news:mrQtb.14181$j1d.13744@news04.bloor.is.net.cable.rogers.com...
Eric Livingston wrote:

I have three speaker wires running just behind sheetrock along a wall
in my house that have breaks in them somewhere (I believe from the
contractor firing nails through the wires when putting up the
sheetrock). Two of the wires are shorted from one end (wall terminal)
and open from the other. The third is open from both ends. I figure
in all cases a nail-gunned nail went through the wire in question,
and in two cases the nail is probably shorting one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a
strong magnet, and it works to a degree but not enough - I need a
stronger magnet or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as
an antenna, generating some kind of signal, I could use a receiver
held up to the wall to detect that signal, and thus detect the break.
Would this work? How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the
cut (i.e. open) wires in the walls due to the capacitance of the
wire, though there's no closed circuit. Can I use something to detect
the AC Current in the wires behind the wall? Could this work even
with the broken (not shorted) wires, relying on nothing but the wire
capacitance to allow a trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it
should be possible.

Thanks,
Eric

yes its possible - but what are you going to do once you locate the
wires? dig holes in the wall?
rw
Click to expand...
He'll have to, but it's better than having to tear into the wall along the
entire length of the cable.
 
"James Sweet" <jamessweet@hotmail.com> wrote in message
news:1vQtb.169394$ao4.548283@attbi_s51...
"Rein Wiehler" <rwiehler@netscape.net> wrote in message
news:mrQtb.14181$j1d.13744@news04.bloor.is.net.cable.rogers.com...
Eric Livingston wrote:

Are there other ways to do what I'm trying to do? It seems like it
should be possible.

Thanks,
Eric

yes its possible - but what are you going to do once you locate the
wires? dig holes in the wall?
rw

He'll have to, but it's better than having to tear into the wall along the
entire length of the cable.
Click to expand...
Right - I'll certainly have to punch through the wall to fix the break - but
that's just a single easily patched hole vs. ripping out a wall (which,
frankly, I won't do as it's not worth it).

If I can isolate the break, I can easily get through the wall to fix it. I
just need to find the break :)
 
I have three speaker wires running just behind sheetrock along a wall in
my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
Click to expand...
One possibilty is Time Domain Reflectometry (TDR)

Connect an oscilloscope and a pulse-generator ( with needle like pulses) to
the suspect wire and ensure it is terminated with the characteristic
impedance on both ends, something like 100 ohm for twisted pair.On the
oscilloscope you will see the pulse and a reflection at the short of open.
The speed of the signal in a cable is about 2/3 of the speed of light
(calibrate with a known piece of cable) so the fault will be at 0.5 (because
the signal has to go back and forth) * time / speed. Do not expect
millimeter accuracy, so you may still have to hack a long hole in the wall
:-(

Succes, Wim
 
"Eric Livingston" <eric@thelivingstons.org> went bleat in message
news:e0Qtb.18376$Dw6.84209@attbi_s02...

And cross posted it all over the shop.

This post comes from the design group. I am not representative but this is
where I spout my venom.

Kindly fuck off and lay some new speaker wires for your lo-fi under the
carpet.

It's certainly not my arse problem that you don't have the basic sensibility
in your head to realise that you had the wires in the first place and
couldn't tell your fuey schung 'architeks' about the situation.

As if you had the original installers do it properly in the first place

Try

news:/alt.house.redecorating.plaster.fell.of.the.clout.nails.after.I.painted
..it

And don't bint about the fact it doesn't exist.

Kindest regards

DNA
 
"Eric Livingston" <eric@thelivingstons.org> wrote in message
news:e0Qtb.18376$Dw6.84209@attbi_s02...
I have three speaker wires running just behind sheetrock along a wall in
my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other.
The
third is open from both ends. I figure in all cases a nail-gunned nail
went
through the wire in question, and in two cases the nail is probably
shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this
work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should
be
possible.

Thanks,
Eric

You could try a telephonce cable pair identifyer. The transmit a warbline
Click to expand...
tone which is picked up with a reciever. You follow the cable tehn at the
open there will be a peak in signal then nothing afterwards.
>
 
"Eric Livingston" <eric@thelivingstons.org> went bleat in message
news:e0Qtb.18376$Dw6.84209@attbi_s02...

And cross posted it all over the shop.

This post comes from the design group. I am not representative but this is
where I spout my venom.

Kindly fuck off and lay some new speaker wires for your lo-fi under the
carpet.

It's certainly not my arse problem that you don't have the basic sensibility
in your head to realise that you had the wires in the first place and
couldn't tell your fuey schung 'architeks' about the situation.

As if you had the original installers do it properly in the first place.

Try

news://alt.house.redecorating.plaster.fell.off.the.clout.nails.after.I.paint
ed.it

or

news://alt.binaries.pictures.erotica.here's-me-after-the-wife-found-out

or

news://alt.I.didn't.have.a.clue.in.the.first.place.but.it's.not.my.fault

And don't bint about the fact they don't exist.

See, we design people design things. Unfortunately we have to deal with the
crass stupidity of people like you and yours. It and you ain't fucking worth
it.

Kindest regards

DNA
 
On Sun, 16 Nov 2003 19:14:18 GMT, "Eric Livingston"
<eric@thelivingstons.org> wrote:

I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.
Click to expand...
For the wires that are shorted, if the nail is what's causing the short
you could check for continuity from the shorted end to the nails by
tying an ohmmeter to the end of the wire and probing the suspect
nailheads with a needle connected to the other ohmmeter lead. Find the
nailheads with a magnetic stud finder.

For the wire that's open on both ends, if you can just pull one end out
from behind the wall you'll know how long it is once you get it pulled
out and you'll know about where the break is (in X, anyway). Along
those lines, if you can pull on one of the wires and the other end moves
you might be able to use that wire to pull three new ones and forget
about having to damage the wall.

--
John Fields
 
Eric Livingston wrote:
I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.

Thanks,
Eric
Click to expand...
I'd vote for TDR. Know anybody who works for the cable company or the
phone company?

They make gizmos for finding hot power wires in the wall. Can get 'em
at any home depot. I'm guessing they just pick up the hum.
Don't know how much AC voltage you'd have to put on
your speaker wires to be detcted or whether that would be safe. You can
also
get fire extinguishers at home depot ;-)
mike

--
Bunch of stuff For Sale and Wanted at the link below.
laptops and parts Test Equipment
Honda CB-125S
TEK Sampling Sweep Plugin and RM564
Tek 2465 $800, ham radio, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
In article <e0Qtb.18376$Dw6.84209@attbi_s02>, eric@thelivingstons.org
mentioned...
I have three speaker wires running just behind sheetrock along a wall in my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the
wires are shorted from one end (wall terminal) and open from the other. The
third is open from both ends. I figure in all cases a nail-gunned nail went
through the wire in question, and in two cases the nail is probably shorting
one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a strong
magnet, and it works to a degree but not enough - I need a stronger magnet
or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as an
antenna, generating some kind of signal, I could use a receiver held up to
the wall to detect that signal, and thus detect the break. Would this work?
How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the cut
(i.e. open) wires in the walls due to the capacitance of the wire, though
there's no closed circuit. Can I use something to detect the AC Current in
the wires behind the wall? Could this work even with the broken (not
shorted) wires, relying on nothing but the wire capacitance to allow a
trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it should be
possible.
Click to expand...
A cable testing meter that has TDR, such as the Fluke DSP-2000 can
tell you where the break is, bow many feet from the end. Cat5 cable
installers use these, and they can be rented. For more cable info try
the comp.dcom.cabling newsgroup.

Thanks,
Eric
Click to expand...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article
<mrQtb.14181$j1d.13744@news04.bloor.is.net.cable.rogers.com>,
rwiehler@netscape.net mentioned...
Eric Livingston wrote:

I have three speaker wires running just behind sheetrock along a wall
in my house that have breaks in them somewhere (I believe from the
contractor firing nails through the wires when putting up the
sheetrock). Two of the wires are shorted from one end (wall terminal)
and open from the other. The third is open from both ends. I figure
in all cases a nail-gunned nail went through the wire in question,
and in two cases the nail is probably shorting one half of the wire.

I would like to detect where the breaks are in the wall.

I've tried generating emf in the shorted lines in the wall using a
strong magnet, and it works to a degree but not enough - I need a
stronger magnet or a more sensitive multimeter.

What I'm thinking now is that if I can use the wire(s) in the wall as
an antenna, generating some kind of signal, I could use a receiver
held up to the wall to detect that signal, and thus detect the break.
Would this work? How would I best do this?

Also, I've used a small electric motor as a generator to create an AC
current in the wires. This also works to a small degree even with the
cut (i.e. open) wires in the walls due to the capacitance of the
wire, though there's no closed circuit. Can I use something to detect
the AC Current in the wires behind the wall? Could this work even
with the broken (not shorted) wires, relying on nothing but the wire
capacitance to allow a trickle of AC current to get through?

Are there other ways to do what I'm trying to do? It seems like it
should be possible.

Thanks,
Eric

yes its possible - but what are you going to do once you locate the
wires? dig holes in the wall?
rw
Click to expand...
That's what people usually do. Cut a hole, and patch it after the
repair.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
There are devices that will tell you how long a cble is and can tell you
where shorts are. Pretty accurate, but expensive.

BEST ADVICE YET::

Don't tear a hole in the wall. At one end of the cable tightly tie on some
new cable, and at the other end pull the old cable though until you have
brand new wire in the wall. No wall repair required
 
Try a digital meter with a good capacitance range, calibrate on a
piece of cable. Measure the O/C ends and calculate distance. As a test
I measured
about 3.5 M of cable and got 180pF or about 50pF/M.
 
"mike" bravely wrote to "All" (16 Nov 03 15:41:33)
--- on the heady topic of "Re: Using signal generation to detect the location
of a line breakin my"

mi> From: mike <spamme0@juno.com>

mi> I'd vote for TDR. Know anybody who works for the cable company or the
mi> phone company?

mi> They make gizmos for finding hot power wires in the wall. Can get 'em
mi> at any home depot. I'm guessing they just pick up the hum.
mi> Don't know how much AC voltage you'd have to put on
mi> your speaker wires to be detcted or whether that would be safe. You
mi> can also
mi> get fire extinguishers at home depot ;-)

A small electronic metal detector will find wires in walls too.

.... I worked hard to attach the electrodes to it.
 
If you don't mind a drop in audio quality.....

Perhaps you could get by with a common earth return? eg....

Three speakers need only 4 wires (not 6).

Two speakers need only 3 wires.

Prerhaps you have enough working wires to get something going?

Colin



"red" <none@none.com> wrote in message
news:UEVtb.14346$up3.12534@fe1.columbus.rr.com...
There are devices that will tell you how long a cble is and can tell you
where shorts are. Pretty accurate, but expensive.

BEST ADVICE YET::

Don't tear a hole in the wall. At one end of the cable tightly tie on some
new cable, and at the other end pull the old cable though until you have
brand new wire in the wall. No wall repair required
Click to expand...
 
"red" <none@none.com> wrote in message
news:UEVtb.14346$up3.12534@fe1.columbus.rr.com...
There are devices that will tell you how long a cble is and can tell you
where shorts are. Pretty accurate, but expensive.

BEST ADVICE YET::

Don't tear a hole in the wall. At one end of the cable tightly tie on some
new cable, and at the other end pull the old cable though until you have
brand new wire in the wall. No wall repair required
Click to expand...
Cables are usually stapled in multiple places, it's unlikely that a new one
would pull through. Conduit would be ideal but is rarely used in residences.
 
"Wim Ton" <wimton@blueyonder.co.uk> writes:

I have three speaker wires running just behind sheetrock along a wall in
my
house that have breaks in them somewhere (I believe from the contractor
firing nails through the wires when putting up the sheetrock). Two of the

One possibilty is Time Domain Reflectometry (TDR)

Connect an oscilloscope and a pulse-generator ( with needle like pulses) to
the suspect wire and ensure it is terminated with the characteristic
impedance on both ends, something like 100 ohm for twisted pair.On the
oscilloscope you will see the pulse and a reflection at the short of open.
The speed of the signal in a cable is about 2/3 of the speed of light
(calibrate with a known piece of cable) so the fault will be at 0.5 (because
the signal has to go back and forth) * time / speed. Do not expect
millimeter accuracy, so you may still have to hack a long hole in the wall
:-(
Click to expand...
Plans for building one such pulse generating circuit can be found at
http://www.epanorama.net/circuits/tdr.html


--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
 
On Mon, 17 Nov 2003 08:59:41 GMT, "CWatters" <colin.watters@pandora.be>
wrote:

If you don't mind a drop in audio quality.....

Perhaps you could get by with a common earth return? eg....

Three speakers need only 4 wires (not 6).

Two speakers need only 3 wires.

Prerhaps you have enough working wires to get something going?
Click to expand...
---
Unfortunately, using a common return will cause a voltage drop in the
return conductor which will vary with the sum of the instantaneous
currents in all three speakers. This will hopelessly muddle the high
registers and reduce the transparency of the soundstage.

--
John Fields
 
"John Fields" <jfields@austininstruments.com> schreef in bericht
news:3vchrvgmqjh0u1ht29v0e56js1ketf7jnr@4ax.com...
On Mon, 17 Nov 2003 08:59:41 GMT, "CWatters" <colin.watters@pandora.be
wrote:

If you don't mind a drop in audio quality.....

Perhaps you could get by with a common earth return? eg....

Three speakers need only 4 wires (not 6).

Two speakers need only 3 wires.

Prerhaps you have enough working wires to get something going?

---
Unfortunately, using a common return will cause a voltage drop in the
return conductor which will vary with the sum of the instantaneous
currents in all three speakers. This will hopelessly muddle the high
registers and reduce the transparency of the soundstage.

--
Click to expand...
Not only that. I would not blindly trust that every amplifier
has common minus terminals. But you can always try ;-) Silence
can be beautiful too.


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top