Wastage of water is quite prominent in urban as well as rural areas and overflowing of water tanks is a major reason for that. This water tank overflow circuit described here starts ringing as soon as the water tank becomes full. Thus, by warning the user, the project avoids the need to check overflow and prevents wastage of water.
This water tank overflow circuit is based on LM324 whose output voltage is many times higher than the voltage difference between the input terminals.
The project comprises a sensor part built using only one op-amp (N1) of quad op-amp IC LM324. Op-amp N1 is configured here as a comparator. Two stiff copper wires are inserted in the tank containing water. As long as the tank is empty copper wire does not conduct and the circuit remains off. When the water touches sensors, an alarm rings, indicating the user to switch off the motor pump.
When the tank dries out, the resistance between the copper wires (sensor probes A and B) increases. As a result output of opamp is high and LED will glow to indicate that tank is empty.
If the resistance increases beyond the preset limit, output pin 1 of op-amp N1 goes ‘low’. This will trigger timer IC2 and buzzer will start sounding.
The threshold point at which the output of op-amp N1 goes ‘low’ can be changed with the help of preset VR1.