Water level indicator circuit diagram based on 7-segment LED

The water level indicator here uses a 7-segment display that shows the water level in the tank (low, half and full). Additionally, a buzzer is used to warn you that water is overflowing from the tank. This circuit displays the water level by displaying L, H and F as low, half and full respectively.

This circuit uses five sensors to detect different water levels in the tank. Sensor A is connected to the negative terminal (GND) of the power supply. The other four sensors (B to E) are connected to the inputs of the NOT gate IC7404. When there is a high voltage on the input pin of the NOT gate, it outputs a low voltage. Likewise, for a low voltage at the NOT gate input pin, it outputs a high voltage.

When the tank is empty, the input pin of the IC7404 is pulled high through a 1 megohm resistor. So it outputs a low voltage. When water starts filling the tank, a low voltage appears on the input pin of the gate and a high voltage is output.

When the water in the water tank rises to a low level, the input of pin 5 of gate N3 is low voltage, and the output of pin 6 is high level. Pin 6 of the door is connected to pin 10 of the N9 door, so pin 10 is also higher. Now, since both pins 9 and 10 of gate N9 are high, its output pin 8 also becomes high. Therefore, positive supply is applied to DIS3 and displays an "L", indicating that the water level in the tank is low.

Similarly, when the water in the water tank reaches half level, pins 4 and 5 of AND gate N8 become high level. As a result, its output also becomes high, and DIS2 displays "H", indicating that the water level in the tank is half full. At this time, pin 9 of the N9 gate also changes to low level through the N4 gate, and DIS3 stops emitting light.

When the water tank is full, the voltage at pin 1 of the N1 door and pin 3 of the N2 door becomes low. The output pin 3 of gate N7 changes to high level, and DIS1 displays "F" to indicate that the water tank is full.

When water begins to overflow the water tank, pin 13 of the N6 door becomes low, causing pin 12 to output. The buzzer sounds, indicating that water has overflowed the tank and the electric pump needs to be shut down.

Build and build the circuit on a universal PCB and package it in a suitable box. Use non-corrosive materials such as steel straps for the five sensors and hang them in the tank as shown in the circuit diagram. Use a regulated 5V power supply or battery to power the circuit.