Water Level Indicator using 7-segment display

This water level indicator uses a 7-segment display to indicate the water level L(low), H(half) and F(full) in the tank. This water level indicator circuit is based on the 7408 (U2) quad two inputs AND gates IC (that contains four input independent gates) and a 7404 (U1) hex inverting gates IC.
When the tank is full a buzzer is used to alert and it can be OFF by the Switch(SW).

This water level indicator shows the water level by displaying L, H and F for low, half and full, respectively.
The circuit uses five level sensors to sense the different water levels ( one for common GND, one for low, one for high one for half and one for overflow ) .
A high voltage at the input pin of the NOT gate, it outputs a low voltage . For a low voltage at the input pin of the NOT gate, it outputs a high voltage.
When the tank is empty, the input pins of IC 7404 are pulled high via a 1-mega-ohm resistor.
When the water is at the low sensor the common cathode 7 segments Display shows L indicating low level of water in the tank.
When the water is at the half sensor the Display shows H indicating half level of water in the tank.
When the water is at the low sensor the Display shows F indicating that the tank is full.

When water is at the overflow sensor ( buzzer sensor ) the pin 13 of gate in U1 goes low to make output pin 12 and the buzzer will sound .
All water sensors must be constructed from noncorrosive material . For powering this electronic circuit you must to use a regulated 5V to power the circuit.