Water level indicator using LM358 IC

Circuit Design:

1. LM358 Connections:
   • Connect the VCC pin (pin 8) of the LM358 IC to the positive supply voltage (e.g., 9V).
   • Connect the GND pin (pin 4) of the LM358 IC to the ground (0V) of the circuit.
2. Voltage Divider:
   • Create a voltage divider using two resistors (e.g., 10kΩ and 100kΩ).
   • Connect one end of the 10kΩ resistor to the positive supply voltage.
   • Connect the other end of the 10kΩ resistor to the non-inverting input (pin 3) of the LM358.
   • Connect the junction between the two resistors to the inverting input (pin 2) of the LM358.
   • Connect the end of the 100kΩ resistor to the ground.
3. Water Sensing Probes:
   • Connect one sensing probe to the inverting input (pin 2) of the LM358.
   • Connect the other sensing probe to the ground.
4. Output Stage:
   • Connect the output (pin 1) of the LM358 to an LED or a series of LEDs representing the water level.
   • Optionally, for a more precise indication, you can use a 7-segment display and appropriate driver circuitry.

Working Principle:

• The LM358 is configured as a comparator with a voltage divider setting a reference voltage.
• The water sensing probes act as a variable resistor depending on the water level.
• When the water level rises and contacts the sensing probes, the resistance between the probes changes.
• This change in resistance alters the voltage at the inverting input.
• The LM358 compares the water level voltage with the reference voltage and activates the output accordingly.