Broken wire detection Idea

[georgetwo]

Hi
For some time, I have been trying to construct a broken wire detector that can detect broken shielded wire without having to strip or pinch a hole in the wire.

I tried some circuits online, but there is a problem of false signal due to presence of electric field in the environment.

I had an idea of generating a high frequency signal that will be sent into the wire from one end and use a sensing circuit to sense that signal and maybe give out a sound.

I don't have a clue on how to achieve this. I need ideas

 

[ericgibbs]

hi george,
What lengths of wire are you testing,?

 

[ClydeCrashKop]

I have used a Fox and Hound tool with mixed results on boats. Everything is bonded and grounded. Instructions were vague.
https://www.youtube.com/watch?v=Y0HjaR0tj7Q
I'm not sure how well it works on shielded wire.

Instructions https://www.electro-tech-online.com/custompdfs/2013/05/84-863.pdf

 

[georgetwo]

the length of wire should be between 1 to 20 meters

 

[mab2]

Sounds like Time-domain reflectometry would work to me:-

https://en.wikipedia.org/wiki/Time-domain_reflectometer

In theory, all you need is a fast scope and a fast pulse gen, although, I'm not sure how fast they need to be to work over 1 - 20 m. I suspect they would need to be quite expensively fast TBH.

 

[georgetwo]

@ ClydeCrashKop
Will it be possible for me to build somthing like that Fox and Hound?
I can program pic micro,if it gets to that.
what should be d best way to generate high frequency signal even if it does not sound like that of Fox and Hound.

 

[bryan]

Sounds like Time-domain reflectometry would work to me:-

https://en.wikipedia.org/wiki/Time-domain_reflectometer

In theory, all you need is a fast scope and a fast pulse gen, although, I'm not sure how fast they need to be to work over 1 - 20 m. I suspect they would need to be quite expensively fast TBH.

Here you go.

https://youtu.be/9cP6w2odGUc

 

[Dr_Doggy]

you are just looking for holes in wire? is it burried? you just feed a RF into the wire and use a receiver across the length of the cable, you will find holes in shield of cable where the receiver picks up a higher signal bleed, fox/hound as described. i could even recommend building an 10meter FM Radio Transmitter circuit to hook up to the cable, then you can detect the hole with just a FM radio
however it will be hard to detect a difference in values with just the audio off of the wand/radio, maybe if you replaced the speaker with a DB meter and noise filter...

when i test a cable wire i put a 75 ohm resistor on one of the ends then measure the resistance on the other side across center pin and shield, digital cable is about 6ohms per 100ft, i think,, so if i get a resistance of anything other than 81 ohms i know ther is either a partial open or partial short on the line, that number usually goes up with damages.

My TDR is a few hundred dollars and it can measure the length of cable in FT up to the cut/short, other TDR's for a few thousand dollars give you graphic display which show you on a distance/impedance graph for all faults, splitters, and connectors on that line.

However a TDR has to be super fast since RF travels 80% speed of light on cable so a PIC could work but it would have very bad resolution
Be Careful though a TDR left on equipment for any length of time can potentially fry that said piece of equipment.

maybe you can elaborate what you are doing, sniffing out broken wires is what i do best.....

 

[georgetwo]

Thanks for the reply,
I will try out TDR
Coaxial cables are quite different compared
to normal power cable I dont know if the signal will
reflect, Ill give it a try.

 

[ClydeCrashKop]

It looks like Fox and Hound won't work.
From the Fox and Hound manual:
Because of the way that coax is constructed, it is not possible
to find an open in the center conductor. It is possible to
find an open in the shield, if the shield is not shorted to the
center conductor or ground.

 

[Dr_Doggy]

just so i'm clear, i am referring to coax 75ohm type RG6, which is what my tdr is programmed for..
but what are you testing for,
are you hunting to find where the cut exactly is or do you just need a average distance,
also where is the coax now, is it underground, or is it in the walls of your home? or is this just a piece you have laying around?do you have access to both ends of the cable?

bad cable -- which is different from a cut- TEST FOR OHMS
looking for distance of cut -- TDR
finding CUT exact location (on braid)! --- use fox hound (may need to amplify feed tone if you are too far away) - works great on cable though, put black on the braid. tone doesn't bleed well on a good piece of coax.

ALSO if there is just say a large pinhole in braid from removed staple or nail, and not a cut, TDR may not detect it, but bleeding will occur



btw, due to curiosity, i took the liberty of testing TDR on phone wire, seems to work as long as i hookup 2 parallel wires, even on different pairs in strand.

if you are testing center pin the rule of thumb is that dc will not pass through a cut but (AC)RF will... TDR will tell you the distance regardless if there is open or short.

 

[georgetwo]

Im trying to build a circuit that can detect d point of conduction breakeage in an insulated wire without pinching through wire insulation.

Either in a wall, burried in the ground, or visible, any one will do provided it can be trusted.
If length of wire needs to be considered, it hould be between 1 to 20M.
I have access to both ends of the wire.
Thanks

 

[KeepItSimpleStupid]

Maybe not the greatest, but cheap: **broken link removed**

 

[Dr_Doggy]

OHM test is the best way to test for flaws, tdr will give you distance if flaw is big enough.....expensive tdr will show every little thing at every distance..

 

[manoj soorya]

Hello All

I got a comple project with source code of the same....

Check it please....