Friday, July 1, 2016

Water Level Controller

Water Level Controller:

This system mainly works on a principle that “water conducts electricity”. The four wires which are dipped into the tank will indicate the different water levels. Based on the outputs of these wires, microcontroller displays water level on LCD as well as controls the motor.

Components Required:

  • At89c51 controller
  • At89c51 programming board.
  • 16*2 LCD
  • 5V Relay
  • Bc547 (NPN) transistors – 5
  • Resistors (1K) – 4
  • Resistor – 330 ohm
  • AC Motor
  • Pot – 10k
  • Programming cable
  • Connecting wires


The main heart of this project is AT89C51 microcontroller. The water level probes are connected to the P3.0, P3.1, P3.2, and P3.3 through the transistors. Port P2 connected to the data pins of LCD and control pins RS, RW and EN of LCD are connected to the P1.0, P1.1, and P1.2 respectively.
Initially when tank is empty, LCD will display the message EMPTY and motor runs automatically. When water level reaches to quarter level, now LCD displays QUARTER and still motor runs. For further levels, LCD displays the messages HALF and ¾ FULL.
When tank is full, LCD displays FULL and motor automatically stops. Again motor runs when tank is empty.


  • First configure the controller pins P3.0, P3.1, P3.2 and P3.3 as inputs and P3.4 as output.
  • Now initialize the LCD.
  • Continuously check the water level input pins P3.0, P3.1, P3.2, and P3.3
  • If all the pins are low then display tank is empty on LCD and make P3.4 pin high to run the motor automatically.
  • High pulse on the pin P3.0 indicates quarter level, display the same thing on LCD.
  • If P3.1 is high then water level is half.
  • High pulse on P3.2 indicates 3/4th full of the tank.
  • If P3.3 is high then tank is full, now make P3.4 pin is low to turn off the motor automatically.

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