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.
The numeric water indicator circuit works off 5V regulated power supply. It is built around priority encoder IC 74HC147 (IC1), BCD-to-7-segment decoder IC CD4511 (IC2), 7-segment display LTS543 (DIS1) and a few discrete components.
When the water tank is empty, all the inputs of IC1 remain high. As a result, its output also remains high, making all the inputs of IC2 low. Display LTS543 at this stage shows ‘0,’ which means the tank is empty. Similarly, when the water level reaches L-1 position, the display shows ‘1,’ and when the water level reaches L-8 position, the display shows ‘8.’ Finally, when the tank is full, all the inputs of IC1 become low and its output goes low to make all the inputs of IC2 high. Display LTS543 now shows ‘9,’ which means the tank is full.
Assemble the water level indicator circuit on a general-purpose PCB and enclose in a box. Mount 7-segment LTS543 on the front panel of the box. For sensors L-1 though L-9 and ground, use corrosion free conductive-metal (stainless-steel) strips.