LED Electric Fence Monitor

[DairyFarmer]

I run a dairy farm. I am looking into building my own LED pulse indicators to be attached all over the farm to monitor the electric fences.

The farm is divided into blocks. Each block is further divided into pastures. All is fenced by single strand electric fencing. What happens is that the fences short out or are broken by the cows.

I have three controller boxes with LED indicators that show the strength of the pulse it is sending out. I also have hand held testers that give a 0.1 - 9.9 readout of the pulse.

I am currently reorganising the fences so that I can isolate a block to be able to do any repairs. It is no fun using a wire stretcher when high voltage pulses are running through the wire. Isolating the blocks also gives me the ability to turn blocks off when not in use or to turn off a block where there is a short so as not to affect the other blocks that are being used.

Now to my question. I would like to have pulse indicators all over the farm so that I can see if a block is live or not without having to run around with a tester. Basically a LED attached to a fence pole, connected to the fence that illuminates when the fence is live.

Would it be as simple as a LED and resistor that is connected to the fence and earthed?

It would be nice to have a 3 LED indicator to show the strength of the fence at that point (red < 3, yellow < 5, green > 5), but this may not be financially viable.

I know the farm will look like a Christmas tree at night, but at least I will know the fences are working.

Any help would be appreciated.

 

[crutschow]

You would have to know the voltage of the pulse at the desired strengths to know how to select the resistors for the LED indicators. Also LED's take several mA of current and that may seriously load down the fence controller signal.

What type of indicator does the hand-held tester have?

 

[Mike_2545]

The hand held testers I used were neon bulbs with a gnd probe.

 

[crutschow]

I believe neon bulbs, such as the NE-2, are more efficient than LEDs for monitoring the high voltage of a fence controller. I would suggest buying some of these bulbs and a number of resistors ranging from 1MΩ to 10MΩ. Try the bulbs with various resistor combinations (more than one resistor in series if necessary) to get the desired brightness for various fence conditions.

 

[DairyFarmer]

Energizer (StaFix 18, mains only)- Up to 18 Joules, 9 000V (5 100V @ 100 ohms load).

Digital Voltmeter (StaFix)- 100V to 10,000V (shows kV on screen, i.e. 8.7)

Trying to source bulbs and resistors locally.

So if I have the following, does this mean:
Fence wire -> resistor (90Ω) -> bulb -> earth = light on when power is at 90% +

Fence wire -> resistor (50Ω) -> bulb -> earth = light on when power is at 50% +

Fence wire -> resistor (30Ω) -> bulb -> earth = light on when power is at 30% +

 

[chemelec]

The Neon Bulbs will indicate that the fence is OK.
BUT it sounds like you want a LOT of Indicators and the more bulbs you use the Greater the load will be. And This load Will Pull Down your Fence Voltage.
Possibly even to a point where it is no longer Effective.

QUOTE: So if I have the following, does this mean:
Fence wire -> resistor (90Ω) -> bulb -> earth = light on when power is at 90% +

Fence wire -> resistor (50Ω) -> bulb -> earth = light on when power is at 50% +

Fence wire -> resistor (30Ω) -> bulb -> earth = light on when power is at 30% +

NO it Doesn't work that way.

 

[Boncuk]

18 Joule is quite a serious shocking power.

My electric fence uses 250 to 450mJ which are shocking pretty strongly already.

By the number of "segments" I suggest to use inductors for HV-coupling into a comparator circuit (self contained battery or low voltage power supply from mains).

By inductive coupling there will be a very small power loss on the HV-wire.

Another possible solution would be measuring conductance of the segments during HV pulse pauses.

Boncuk