how to detect a break in a single wire? - Page 1
Forum section: electronics / beginners

author: daslolo
author_rank: Regular Contributor
timestamp: May 21, 2021, 03:35:47 am
content: I have a radio fence for the dogs, somewhere along the 1500+ feet there is a break.It's one wire, a control box pulses a signal that radiate around the wire.I'm wondering if there is a way to induce some other pulse in a way that another induction coil or even better a AM radio can detect?

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2021, 04:04:35 am
content: They sell wire detector tools, and they are not that expensive in a grand scheme of things. You will waste a lot of time trying homegrown solutions.

author: daslolo
author_rank: Regular Contributor
timestamp: May 21, 2021, 04:16:20 am
content: haven't ffound a wire tester that uses radio frequency or induction, got a link?(and I hhave plenty of time)PS: all double letters are the fruit of Asus G14 buggy keyboard driver, I keep it there as warning for those in the market for a laptop

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2021, 04:31:08 am
content: Search amazon for "Wire Break Locator" or "Underground Cable Locator".Here is one (no idea if it is any good, have not used them) -https://www.amazon.com/F02-Underground-Locator-Tracker-Earphone/dp/B01GDZLZOU/ref=bmx_4/132-7556038-5640200

author: daslolo
author_rank: Regular Contributor
timestamp: May 21, 2021, 04:32:20 am
content: thanks. so one connector to the wire and the other to the ground.does the power of the transmitter matter?

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2021, 04:37:43 am
content: It would obviously matter to some extent. I have no idea what specific signals will work.The issue with anything you will do at home is that you will have to prove that it works on a known break, so you would need to bury a model broken wire firstOtherwise you will just dig up your lawn on false positives from an unproven technology.

author: daslolo
author_rank: Regular Contributor
timestamp: May 21, 2021, 04:47:21 am
content: I'll iterate through Amazon's choices, starting with the cheapest with a 1000' range.https://www.amazon.com/gp/product/B00ADHQCIO/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2021, 04:59:55 am
content: That looks super dodgy and is not explicitly advertised as detecting breaks. It just detects wires. The break may sound different though, I'm not sure.Why not start and finish at something reasonable instead of buying a lot of cheap garbage first?

author: daslolo
author_rank: Regular Contributor
timestamp: May 21, 2021, 05:01:14 am
content: yes the sound changes, somewhere on the description it says it works with dog fence, we'll see, repurpose if not

author: Berni
author_rank: Super Contributor
timestamp: May 21, 2021, 05:48:58 am
content: Just take the dogs collar off and carry it along the fence to see where it stops triggering it. If its some sort of shock collar id assume it also has some sort of warning beep before the shock to give them a chance to back off.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 21, 2021, 06:35:05 am
content: You have TDR (Time domain reflectometer) equipment who could do the job, but they can cost a lot ?? maybe overkill tooUsed some of them in the past, they could locate a broken wire at feet precision ??

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2021, 06:48:35 am
content: TDR will generally not work for the buried cables. It will tell you the distance along the cable. But unless the area consists of perfectly linear segments and you know all the bending points, there is no way to fing the break point based on the distance.

author: Zero999
author_rank: Super Contributor
timestamp: May 21, 2021, 02:31:14 pm
content: Quote from: Berni on May 21, 2021, 05:48:58 amIf it doesn't have a warning, just connect a small neon lamp to it. Keep it shaded from bright light, otherwise you won't see it flash, when the collar shocks.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 24, 2021, 04:46:19 am
content: Quote from: Berni on May 21, 2021, 05:48:58 am... then make sure you put it around your neck tightly so you won't miss it triggering.And insert fresh batteries first.Also make sure you're crawling around close enough to the ground, as these things don't have much reach.Where is it, can I come watch?Popcorn time.

author: james_s
author_rank: Super Contributor
timestamp: May 24, 2021, 05:05:18 am
content: I suppose you could connect a neon sign transformer to the loop and look for smoke. I've used that trick to find breaks in shorter pieces of wire, and even a broken winding in a transformer once. Turn off the light and power up the HV transformer briefly and see where it arcs.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 24, 2021, 06:14:41 am
content: That probably wont work too good for underground buried cables.

author: bob91343
author_rank: Super Contributor
timestamp: May 24, 2021, 06:26:50 am
content: I would use a nanoVNA to measure the length of the wire. You can set the frequency down in the kHz region and see what the electrical length is. I have measured lots of lines with this amazing tool. A new one is around $50 and you need a cheap adapter to attach to it.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 24, 2021, 07:19:13 am
content: My first try would be to use Time Domain Reflectometry (TDR)

author: IDEngineer
author_rank: Super Contributor
timestamp: May 24, 2021, 03:55:54 pm
content: During a remodel, a drywall subcontractor covered one of the outlet boxes that had TV coax. It was flush enough to the stud that they could not find a "bulge" with a long level. It was somewhere in a few feet of the wall, at a known height, but they didn't want to "just start cutting" because of all the patchwork that might result.My solution was to turn off the breakers that serviced that portion of the house. Then I connected the other end of the coax shield and center conductor together and tied them to one phase of the incoming 240VAC two-phase power. This meant that coax was the only thing in that wall with AC. Then I handed them an electrician's electric field tester - available for a few dollars at any hardware store - and had them use that to find the now "hot" coax. They found the field - and where it stopped - in seconds. I disconnected the coax, they drilled a pilot hole which went right into the box, and finished with a RotoZip to open up the rectangle. Presto... the box was exposed with zero additional drywall damage.An electric field probe can be a very handy device for determining the presence or absence of an electric field if you have a conductor available to carry it. Even if only one end of the conductor is accessible!Disclaimers: I am NOT advocating anyone do this. I am NOT advocating that anyone try this with a dog fence wire. I AM advocating that you avoid mains power, hire licensed and bonded professionals, take out a large umbrella liability insurance policy, and not be on the premises when they're working. YMMV.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 24, 2021, 04:44:59 pm
content: Have you tried just sniffing around it with a pocket radio?

author: IDEngineer
author_rank: Super Contributor
timestamp: May 24, 2021, 05:06:22 pm
content: Quote from: RoGeorge on May 24, 2021, 07:19:13 amScroll to ~9:13 in the video to learn why this won't work with a single wire.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 24, 2021, 06:10:14 pm
content: Won't work with a single wire coiled.Should work with a single wire in an electric fence, where the second wire is the Earth.