Indicator with alarm Click here for Circuit Diagram.
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.
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!