# Electric fence energiser

Discussion in 'General Electronics Discussion' started by piczim, Mar 31, 2013.

1. ### piczim

23
0
Dec 13, 2012
I would like to make an electric fence energiser. I am aware of all the laws pertaining to the electric fences in Zimbabwe.

If my understanding is correct a energiser consists of an oscillator which induces a high voltage, with very little current in an HT transformer. This is then pulsed down the fence.

The system is a closed loop which if cut activates an alarm, or if shorted to earth activates an alarm.

A battery,12 Volt, runs the system. So would need a charger.

The questions in this are.

1. Is this an accurate assumption of how an electric fence energiser works.
2. Does anyone have a circuit diagram or circuit diagrams of either a completed electric fence energiser or the individual circuits that could be used to make up an electric fence energiser.

Many thanks

Rodney

2. ### Harald KappModeratorModerator

11,662
2,697
Nov 17, 2011
Your assumptions are right. The alarm feature may or may not be included. Google "electric fence circuit" (without the quotation marks) to find a bunch of circuits.

3. ### duke37

5,364
772
Jan 9, 2011
A possibility
An oscillator is used to charge a capacitor to about 300V. The capacitor is discharged with a SCR which is triggered by a pulse each second. The circuit needs to be designed to allow the SCR to turn off.The current from discharging the capacitor is fed to a high voltage transformer with a ratio of about 20:1 so getting an output voltage of 6kV.

The capacitor should be able to store over 1J and may be difficult to find.(E=C*V*V/2) A motor run capacitor may do if it does not have an internal resistor.

The output transformer needs to be quite special with very good insulation to withstand the working voltage and lightning strikes.

There should be a spark gap on the output of about 3mm with a thick earth lead directly to earth. An inductance can be used on the output to reduce the effect of lighning, this can be made from a few turns, spaced 25mm on a 300mm former.

If you have a complete loop then the received pulse can be used to reset a charging capacitor which otherwise would generate an alarm.