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This circuit not
only indicates the amount of water present in the overhead tank
but also gives an alarm when the tank is full.
The circuit uses the widely available CD4066, bilateral switch
CMOS IC to indicate the water level through LEDs.
When the water is empty the wires in the tank are open circuited
and the 180K resistors pulls the switch low hence opening the
switch and LEDs are OFF. As the water starts filling up, first the
wire in the tank connected to S1 and the + supply are shorted by
water. This closes the switch S1 and turns the LED1 ON. As the
water continues to fill the tank, the LEDs2 , 3 and 4 light up
gradually.
The no. of levels of indication can be increased to 8 if 2 CD4066
ICs are used in a similar fashion.
When the water
is full, the base of the transistor BC148 is pulled high by the
water and this saturates the transistor, turning the buzzer ON.
The SPST switch has to be opened to turn the buzzer OFF.
Remember to turn the switch ON while pumping water otherwise the
buzzer will not sound!
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