Electric fence

This circuit controls an electric fence. A 08 picaxe drives a BUK555 mosfet directly. This switches a car ignition coil (always available second hand on ebay). The coil has three connections. One goes to 12V. One goes to the fence (the high tension stub). And the third is a common earth for both the primary and the secondary and this goes to a good earth stake and also to the drain of the mosfet. This somewhat unorthodox circuit means the earth's earth is not connected to the 0V of the supply and so must be run from a 12V battery and the battery 0V/12V must be floating so it has to be charged from a solar panel or a transformer charger (NOT a switchmode charger). A 100mA solar panel (36 cells) keeps an old car battery charged in normal conditions. Ok, there is no overcharge protection, but in practice old car batteries are free, they last for many years, and a quick word out to friends ensures a continuous supply. Top them up with a bit of water from time to time. Test with a bit of green grass.

BUK555 pinout is pin 1 = gate, pin 2 is the drain and goes to the joint primary/secondary connection of the ignition coil, and pin 3 is the source which goes to the battery 0V.

The picaxe 08 code is ridiculously simple. Use a 78L05, 33uF and 0.1uF on the power supply.

main: high 2
pause 1
low 2
pause 999
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