Electric Window/Fence Charger

Here is the circuit of a
simple electric window charger. With a couple of minor circuit
variations, it can be used as an electric fence charger too. A standard
12V, 7Ah sealed maintenance-free (SMF) UPS
battery is required for powering the entire unit. Any component layout
and mounting plan can be used. However, try to keep the output terminals
of transformer X1 away from the circuit board. Timer NE555 (IC1) is
wired as a free-running oscillator with narrow negative pulse at the
output pin 3. The pulse frequency is determined by resistors R2 and R3,
preset VR1 and capacitor C3. The amplitude of the output pulse can be
varied to some extent by adjusting variable resistor VR1. You can vary
the frequency from 100 Hz to 150 Hz. X1 is a small, iron-core, step-down
transformer (230V AC primary to 12V, 1A secondary) that must be reverse
connected, i.e., the secondary winding terminals of the transformer
should be connected between the emitter and ground and the output taken
across the primary winding.

Switch S1 is used for power ‘on’/‘off’ and LED1 works as a
power-‘on’ indicator. LED2 is used to indicate the pulse activity. The
output pulse from pin 3 of IC1 drives pnp transistor T1 into conduction
for the duration of the time period. The collector of T1 is connected to
the base of driver transistor T2 through resistor R5. When transistor
T1 conducts, T2 also conducts. When T2 conducts, a high-current pulse
flows through the secondary winding of transformer X1 to generate a very
high-voltage pulse at the primary winding. This dangerously high
voltage can be used to charge the window rails/fences. Ordinary silicon
diode D1 (1N4001) protects T2 against high-voltage peaks generated by X1
inductance during the switching time. You can replace X1 with another
transformer rating, and, if necessary, replace T2 with another
higher-capacity transistor. The circuit can be used to charge a 1km
fence with some minor modifications in the output section.

Caution:
Take all the relevant electrical safety precautions when assembling, testing and using this high-voltage generator.

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