We use water pump motors to draw groundwater and fill it in our tanks. There may be cases in which the user switches ON the motor and forgets it. This leads to wastage of water. Now to reduce these kinds of water wastage, we are going to build a water level indicator circuit using 555 timer IC. This is a useful project which detects the water level and gives a signal (buzzer) to the user indicating that the water has reached the desired level. To detect the water level we are going to attach two wires in the tank in a height where the user wants the water level to be maintained.  The other end of one wire is connected to VCC and the other end of the other wire is connected to pin 4 of the IC 555 timer. If the water level reaches the desired level it will short both the wires. Current flows from VCC to pin 4, which resets the flip flop and triggers the buzzer.

Required Components for Water Level Indicator

  1. 555 timer IC
  2. Buzzer
  3. Resistors (22K Ohm - 1, 570 Ohm - 1, 1K Ohm - 2)
  4. Capacitors (1 uF – 1)
  5. Breadboard
  6. Connecting wires
  7. Battery with Battery Snap Connector


Brief Overview of 555 timer IC

A 555 timer is an IC, which internally consists of transistors, resistors, and diodes. The IC consists of 8 pins. The pain diagram of the IC 555 timer is shown below:

555 Timer IC Pinout

As shown in the below block diagram the IC contains two comparators, one flip flop, one inverter, three resistors.

555 timer IC block diagram

The pin description of the IC 555 timer is as follows.


Pin Name

And Number

Pin Description


Ground (pin 1)

Ground Reference Voltage 0V


Trigger (pin 2)

The output (pin 3) will be high as long as the trigger pin falls below 1/3 of the VCC voltage)


Output (pin 3)

This pin high when the set pin is high and low when the reset pin is high


RESET(pin 4)

The reset pin is active low. When this pin is low the flip flop reset i.e. timing interval is reset and starts only when the reset rises above approx. 0.7 volts.


Control(pin 5)

By default, this pin has a voltage of 2/3 of VCC.


Threshold(pin 6)

When the voltage connected to pin 6 is higher than the voltage connected to pin 5 (by default the pin 5 voltage is connected to 2/3 of VCC) the flip flop will reset, which will stop the timer.


Discharge (pin 7)

The discharge pin internally consists of an open collector output, which is useful in discharging a capacitor between intervals


VCC (pin 8)

The supply voltage is connected to VCC pin


The IC 555 timer can be worked in 3 modes when connected with an extra external circuit. The 3 modes are 1) A-stable 2) Mono-stable 3) Bi-Stable. In astable mode, the timer contains no stable state, which means the output will be continuously varying in between high and low states. In monostable mode, the timer contains only one stable state, which is either high or low. If the stable state is low, when an interrupt occurs, the output state changes from low to high. When the interrupt passes, it will revert back to its initial state, which is LOW in this example. In Bistable mode, the IC 555 timer contains 2 stable states. If an interrupt occurs, the state changes to LOW or HIGH, state depending upon the previous state and stays in that state until unless another interrupt occurs. By using IC 555 timer in astable mode, it can be used as a clock, square wave generator. By using it in a bistable mode, it can be used in applications, where the control of the load should be done using a single button. By using it in monostable mode, it can be used in applications like manual clock generator for debugging purpose, etc.


Water level indicator circuit diagram

The circuit for a water level detector is shown below. Pin 1 is connected to the ground. Pin 2 and Pin 6 are shorted and connected to pin 7 through 570 Ohm resistor.  An electrolytic capacitor of 1 uF is connected to pin 6 and Ground. Pin 3 is connected to the buzzer’s positive terminal, and the buzzer’s negative terminal is connected to the ground. Pin 4 is grounded through a 1K Ohm resistor. VCC (supply voltage) is connected to pin 7 through a 22K Ohm resistor. Pin 8 is connected to VCC. A connection is taken from pin 4 and VCC is connected to beaker as shown in the figure.

Water Level Detector Circuit Diagram


Working of the Water Level Indicator Circuit

We will connect the wires ( the green wires, which shown in the circuit diagram ) to the beaker (NOTE: the distance between the wires when connected to the beaker should be less ). Connect the wires to the beaker in such a height that the user wants to maintain the water level.  Whenever water level crosses that level, it will short both the wires leading it to trigger a buzzer, letting the user that the water has crossed the desired level. By which the user can take the necessary actions.

After connecting with the beaker and circuit, our project looks like this.

Water Level Indicator Alarm Circuit



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