wire break indicator

I hope you can help or steer me in the right direction. Also, I'm pretty much clueless on electronics.

I am looking for something that will indicate a break in a wire, such as a light and/or sound.

Some background info:

I just purchased Pet Safe's Professional underground fence capable of

The reality is my property is not a nice square and it took 8000 feet of wire for the perimeter and 500 feet of twisted wire to go from the loop to the transmitter in the house. I'm told by Pet Safe after the installation, that because of the length of wire, the break indicator will not function. In fact, it was disconnected because it was indicating a break and there wasn't one.

Is there some way I can have a wire break indicator, in the house were the transmitter is? Thank you

if you see the dog jumping the line then you know its not working! :) get your self a wire tracer like a (Fox and Hound) and work the wire now and then. i am sure the sensing circuit in your unit could be modified to work on longer runs.

I don't know where you may find a cheap one, but your alarm may use a "time-domain reflectometer" for fault detection.

upnorthwi wrote:

In message , dated Mon, 14 Aug 2006, upnorthwi writes

It can be done, but maybe there is another way. Your wire has too much resistance, because it is too long and thin. If you've already installed it, it's too late, but basically what you would do is to look at the wire length (loop length plus twice the twisted length) you are supposed to use, and measure the diameter of the conductor. For your longer wire, you need the conductor diameter to be equal to (or greater than) that of the original conductor multiplied by the square root of (your new length divided by the old length). That gets the resistance of your new length the same as (or less than) that of the length you were supposed to use.

If you can't do that, you need to sense the loop current by including a low-value resistor in series with the loop at the transmitter end, and a circuit to sense the voltage across it. When the loop breaks, there is no voltage and that can be indicated with a light or (maybe preferably) a noise.

The type of sensing circuit you need depends on several details of the transmitter, mainly the frequency and the current. The best bet is for you to try to get local assistance, such as from your local amateur radio club.

Two ideas: First: It might be a simple as adding a resistor in parallel with the twisted wires, with an RF choke in series with the resistor. We can compute the parallel resistance needed if you post the wire size and max length that allows the break detector to work. You will need to be able to test that the addition of the choke & resistor does not interfere with the deterrent operation.

Second: You can test the wire manually. Use a DPDT relay, bulb, pushbutton switch & battery, or variations (wall wart, LED + resistor, whatever).

Perimeter Wire

--------------o o--------------+--------------+ | | | | .----. | | ----- [Battery] |Pet |-----o->| |