1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Broken wire detection Idea

Discussion in 'Microcontrollers' started by georgetwo, May 29, 2013.

  1. georgetwo

    georgetwo Member

    Joined:
    Jul 30, 2009
    Messages:
    197
    Likes:
    8
    Location:
    DELTA state Nigeria
    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
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,178
    Likes:
    644
    Location:
    Ex Yorks' Hants UK
    hi george,
    What lengths of wire are you testing,?
     
  3. ClydeCrashKop

    ClydeCrashKop Well-Known Member

    Joined:
    Apr 28, 2005
    Messages:
    1,018
    Likes:
    171
    Location:
    Florida
    Last edited: May 29, 2013
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. georgetwo

    georgetwo Member

    Joined:
    Jul 30, 2009
    Messages:
    197
    Likes:
    8
    Location:
    DELTA state Nigeria

    the length of wire should be between 1 to 20 meters
     
  6. mab2

    mab2 Member

    Joined:
    Oct 9, 2009
    Messages:
    106
    Likes:
    15
    Sounds like Time-domain reflectometry would work to me:-

    http://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.
     
    • Like Like x 1
  7. georgetwo

    georgetwo Member

    Joined:
    Jul 30, 2009
    Messages:
    197
    Likes:
    8
    Location:
    DELTA state Nigeria
    @ 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.
     
  8. bryan

    bryan Member

    Joined:
    Jun 21, 2003
    Messages:
    416
    Likes:
    3
    Location:
    Vancouver, Canada
  9. Dr_Doggy

    Dr_Doggy Well-Known Member

    Joined:
    Aug 11, 2007
    Messages:
    1,715
    Likes:
    37
    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.....
     
    Last edited: May 29, 2013
  10. georgetwo

    georgetwo Member

    Joined:
    Jul 30, 2009
    Messages:
    197
    Likes:
    8
    Location:
    DELTA state Nigeria
    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.
     
  11. ClydeCrashKop

    ClydeCrashKop Well-Known Member

    Joined:
    Apr 28, 2005
    Messages:
    1,018
    Likes:
    171
    Location:
    Florida
    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.
     
  12. Dr_Doggy

    Dr_Doggy Well-Known Member

    Joined:
    Aug 11, 2007
    Messages:
    1,715
    Likes:
    37
    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.
     
    Last edited: May 30, 2013
  13. georgetwo

    georgetwo Member

    Joined:
    Jul 30, 2009
    Messages:
    197
    Likes:
    8
    Location:
    DELTA state Nigeria
    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
     
  14. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,908
    Likes:
    1,094
  15. Dr_Doggy

    Dr_Doggy Well-Known Member

    Joined:
    Aug 11, 2007
    Messages:
    1,715
    Likes:
    37
    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..
     
  16. manoj soorya

    manoj soorya Member

    Joined:
    Aug 23, 2014
    Messages:
    238
    Likes:
    4
    Location:
    India
    Hello All

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

    Check it please....
     

    Attached Files:

Share This Page