Here is a useful project of a wireless water level indicator circuit. The circuit can be used for many different water level indicator tasks for example you can use it as a water level alarm for water tanks, swimming pools, washing machines, aquariums or any type of liquid level detector task you want.
The good feature of the circuit is that it will detect your selected level of water and inform you wirelessly on a long distance by transmitting a beautiful melody on your fm radio. The circuit is ideal to use if you want to monitor the level of water from distance.
The project is using a UM66 CMOS melody IC and an FM transmitter circuit to transmit the melody on FM receiver. The 10K variable resistor is used to adjust the volume of transmitting melody. Coil L1 is equal to 2 turns of # 24 wire wound on 5mm form (Air Core) remove the form after winding the coil. TR is equal to 1to 30 pF trimmer capacitor which is used to adjust the transmitting frequency. For antenna use any 12 inch wire or for maximum range use 30 inch wire.
For tuning the circuit first of all connect the power and enter the two probes in water or use a 100 ohms resistor between them to switch-on the BC547B transistor to activate the melody and transmitter circuit (remember to remove this 100 ohms resistor after tuning the circuit) now tune your FM receiver on a blank dial and adjust the trimmer capacitor until you hear a melody.
Note: It is better to tune the circuit from a distance of 10 meters to make sure you have tuned a real frequency not harmonics.