Most water-level indicators for water tanks are based upon the number of LEDs that glow to indicate the corresponding level of water in the container. Here we present a digital version of the water-level indicator. It uses a 7-segment display to show the water level in numeric form from’0′ to ‘9’
When the tank is empty, all the inputs of 74HC147 remain high. As a result, its output also remains high, making all the inputs of CD4511 low. Display on 7 segment at this stage shows ‘ 0, ‘ which means the tank is empty. Similarly, when the water level reaches Level-1 position, the display shows ‘1, ‘and when the water level reaches Level-8 position, the display shows ‘8.’ Finally, when the tank is full, all the inputs of 74HC147 become low and its output goes low to make all the inputs of CD4511 high. Display at 7 segment led now shows ‘9,’ which means the tank is full.