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Electric fence

     Electric fence is device used to keep pets in a particular area, to protect them from predators or to keep wild animals away from the fields or objects. It is formed by one or more wires stretched obove the ground and isolated from ground. In the wires there are high-voltage pulses causing electric shocks. Pulse is short and the current is small, so it is not dangerous for people or animals when the electric fence is properly constructed, but causes unpleasant electric shock. The animal will then begin to avoid contact with the electric fence. Electric fence replaces conventional fence or enclosure, which would be much more difficult and expensive to build and maintain. It can also be used in combination with the conventional fence, If the animals are trying to overcome it or damaging it.
     To create a high-voltage pulse a common automotive ignition coil is used. The MOSFET transistor driven by 555 circuit ensures the interruptions. Pulse repetition frequency is around 1.3 Hz. Switching has about 2% duty cycle. The repetition frequency is determined by R1 (higher resistance - lower frequency). The ON time of the transistor, and thus the intensity of the pulse, is affected by R2 (higher resistance - higher intensity). C1 affects both the frequency and intensity (higher C - lower frequency, greater intensity). A significant increase in the intensity or frequency might require the use of more powerful transistor.

     Construction and use of this electric fence is at your own risk. This equipment can cause electric shock. The author is not responsible for any damage or consequences of your use of this device.

Schematic of the homemade electric fence.

Electric fence - 555 and MOSFET

Electric fence built into the ATX box

Completed Electric fence