Water Level Indicator using 7-segment display

We could know the water level in the tank by showing L(low), H(half), and F(full) on a 7-segment-display. This water level indicator circuit is designed by using the 7408 (U2) quad two-input AND gate IC (that contains four independent gates) and a 7404 (U1) hex inverting gate IC. When the tank is full a buzzer gives sound to alert and a Switch(SW) is used to turn off the buzzer.


We could know the water level by displaying L, H, and F on behalf of low, half, and full. This circuit has five-level sensors to sense the different water levels (one for common GND for all sensors, one for low level, one for high level, one for half level, and one for detect water overflow). When a high-level voltage at the input pin of the NOT-gate, then it's output will be low-level voltage. For a low-level voltage at the input pin of the NOT gate, it's output will be a high-level voltage.

When the tank is empty, the input pins of IC 7404 are pulled high via a 1-mega-ohm resistor. If the water level touches the level-1 sensor, then the common-cathode 7-segment display will show L that means a low level of water is there in the tank.

When the water level touches the level-2 sensor then Display shows H that indicates there is the water half level in the tank. When the water is at the level-3 sensor, then display shows 'F', it indicates that the tank is full. When the water reaches overflow-sensor(level-4) the pin-13 of U1 goes low voltage level that makes the output pin-12 high and the buzzer will make a buzzer sound.


All water level sensor materials should be non-corrosive material. To power this electronic circuit, you could use a 5V DC Power supply.

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