A Simple Water level indicator circuit indicating 5 stage water levels in the tank. LED1 glows when the water tank is empty. LED 5 glows when the tank is full. LED 2 indicated 40%, LED 3 indicates 60% and LED 4 indicates 80% water in the tank. LEDs glows one by one when the water tank fills and turns off one by one when the water level drops.
The Common probe (Com) gives 12 volt DC to water. It should be fixed at the bottom of tank using a pin. Fix Probes C1 to C5 at different heights using pins. Probe 5 should be just below the upper end of tank to indicate Full level. When the water shorts each probe and Com probe, current flows to the base of corresponding transistor and it conducts. LED glows one by one indicating the water level in the tank. Use thin wires to connect probes with the points marked as Com, C1,C2,C3,C4 and C5 . Probes can be paper pins. For easy fixing, use a straw and pin the probes at the required heights. Fix the straw inside the tank.