A water level sensor or liquid level detector is a very useful device for measuring or detecting a required level of water, liquid or fluid in a tank, pool, well, aquarium, washing machines etc. The water level indicator shown here is very simple but can perform a great task as a monitor for desired level of
any liquid, it will activate the LED when the two probes shown in the circuit will detect liquid. The circuit is using only four components and can be built in few minutes if all parts are available with you.
Working of the circuit is simple, the circuit is based on a NPN transistor 2N2222 which is working as a switch, when water level will touch the two probes the transistor become switched on and the LED in the circuit will become activated. The circuit can be operated with two 1.5V batteries of any size.