Here is a simple water level buzzer circuit which can be used to detect or sense the level of water in tank, pool, washing machines etc. When the two probes shown in this water level indicator circuit will detect water the buzzer will start producing sound. The circuit is very simple and low cost using
only few parts like Buzzer, Transistor, 300K variable resistor and a 9V battery or power supply. The circuit is using BC547B NPN transistor but you can use any other general purpose transistor in the place of this transistor like 2N2222 or 2N3904.
Working of the Circuit
Working of this water level sensor is simple; the transistor used in the circuit is working as a switch. When the two probes detect water the transistor becomes switched on and as a result the voltage start passing through the transistor, which will activate the buzzer.