This circuit was cobbled together many years back to help keep a fox away from some domestic ducks. It seems that the fox was canny enough to work out the time period between shocks of an of the peg fencer unit so something operating more frequently was required.
The timing is derived from a classic 555 timer chip. Transistor Q1 acts as a buffer and inverter. Transistor Q2 is a power Darlington and switches the current through a conventional car ignition coil. There is no advantage is increasing the ON time as the value of R2 ensures that the coil has fully saturated before the current is turned off. If a spark with lesser energy is required then increase the value of R2 and also save battery energy.
Resistor R1 sets the time interval between pulses.
Capacitor C5 is a very high voltage capacitor.
Eventually a Printed Circuit Board was laid out for the electronic components.
It is vital that this unit is NOT used to electrify anything that people or sensitive animals could come into contact with.
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