Water Level Indicator:

The Water Level Indicator employs a simple
mechanism to detect and indicate the water
level in an overhead tank or any other water
container. The sensing is done by using a set
of nine probes which are placed at nine
different levels on the tank walls (with probe9
to probe1 placed in increasing order of
height, common probe (i.e. a supply carrying
probe) is placed at the base of the tank).
The level 9 represents the “tank full”
condition while level 1 represents the “tank
empty” condition.

When the water-level is below the minimum
detectable level (MDL), the seven segment
displays is arranged to show the digit 1,
indicating that the tank is empty, When the
water reaches level1 (but is below level2) the
connection between the probes gets
completed (through the conducting medium
– water) and the base voltage of transistor
increases. This causes the base-emitter
junction of transistor to get forward biased,
this switches transistor from cut-off to
conduction mode thus PIN (B0) of
microcontroller is pulled to ground hence, the
corresponding digit displayed by the seven
segment display is 2. The similar mechanism
applies to the detection of all the other
levels. When the tank is full, all inputs to
microcontroller become low and all its
outputs go high. This causes the display
shows a 9 also in this case a buzzer sound is
given, thereby indicating a “tank full”

Most water level indicators are equipped to
indicate and detect only a single level. The
Water Level Indicator implemented here can
indicate up to nine such levels and the
microcontroller displays the level number on a
seven segment display. So, not only is the
circuit capable of cautioning a person that
the water tank has been filled up to a certain
level, it also indicates that the water level has
fallen below the minimum detectable level.
This circuit is important in appliances such
as the water cooler where there is a danger
of motor-burnout when there is no water in
the radiator used up also it can be used in
fuel level indication.

Read the related post:
Water Level Indicator Using 555 Alarm

In this project we show the water level
indicator using eight transistors which
conducts as level rises, a buzzer is also
added which will automatically start as the
water level becomes full, auto buzzer start
with the help of microcontroller. With the help
of this project we not only show the level of
water with the help of seven segment display
but also a buzzer.

Water Level Indicator Project

1.Easy installation.

2.Low maintenance.

3.Compact elegant design.

4.The Automatic water level controller
ensures no overflows or dry running of
pump there by saves electricity and

5.Avoid seepage of roofs and walls due
to overflowing tanks.

6.Fully automatic, saves man power.
Consume very little energy, ideal for
continuous operation.

7.Automatic water level controller
provides you the flexibility to decide for
yourself the water levels for operations
of pump set.

8.Shows clear indication of water levels
in the overhead tank.

9.Hardware Description:
Water Level Indicator Project

Block Diagram:


Figure 2.1.1 Block diagram

Water Level Indicator Project
Circuit Diagram:


Water Level Indicator Project

This is the circuit diagram and description for
water level indicator:

A constant 5v power supply is given to
the microcontroller and rest of the
circuit from a battery.

The tank has 9 conductive type sensors
(other types of sensors have been
mentioned earlier but in our project
only conductive type are used)
embedded into it and 8 wires of
sensors out of 9 are connected to
transistors and the 9th is connected to
5v+ supply.

The use of transistor is it acts as
inverter (i.e. in on state gives low
voltage at output and in non
conducting state gives high voltage at
its output), all transistors outputs are
connected to 1,2,3,4,5,6,7,8 pins
(PORTB) of microcontroller.

Seven segment display is connected to
pin no. 33 to 40 (PORTA). It is
connected in common cathode fashion.
The Output for the 7th level is not only
shown in seven segment display but
also indicated with a discontinuous
buzzer sound.

Output for the 8th level (i.e. tank full
condition) is not only shown in seven
segment display but also indicated
with a continuous buzzer sound.


The operation of this project is very simple
and can be understood easily. In our project
“water level indicator” there are 3 main

1. There is no water available in the
source tank.

2. Intermediate level i.e. either of 3rd to
7th level.

3. There is ample amount of water
available in the source tank.

So let us discuss on the more about these 3

CONDITION 1: Water not available

When the tank is empty there is no
conductive path between any of the 8
indicating probes and the common probe(which is connected to 5v+ supply) so the transistor base emitter region will not have sufficient biasing voltage hence it remains in cut off region and the output across its collector will be Vc approximately 4.2v. As in this case the microcontroller is used in the active low region (which means it considers
0-2 volts for HIGH and 3-5 volts for LOW)
now the output of transistor which is 4.2v approximately will be considered as LOW by the microcontroller and hence the default value given by microcontroller to the seven
segment display is 1 which indicates as the tank is empty.

CONDITION 2: Intermediate levels

Now as the water starts filling in the tank a conductive path is established between the sensing probes and the common probe and the corresponding transistors get sufficient biasing at their base, they starts conducting
and now the outputs will be Vce (i.e.
1.2v-1.8v) approximately which is given to microcontroller. Here the microcontroller is programmed as a priority encoder which detects the highest priority input and displays
corresponding water level in the seven
segment display. In this project while the
water level reaches the 7th level i.e. last but one level along with display in seven segment a discontinuous buzzer is activated which warns user that tank is going to be full soon.

CONDITION 3: Water full

When the tank becomes full, the top level probe gets the conductive path through water and the corresponding transistor gets into
conduction whose output given to
microcontroller with this input microcontroller
not only displays the level in seven segment display but also activates the continuous buzzer by which user can understand that tank is full and can switch off the motor and save water.

Flow Chart:


Figure 4.2.1 Flow chart

Flow chart gives the clear and easy
understanding of the project. The process goes on as follows:
The microcontroller checks if the tank is full if the condition is satisfied it indicates the same on display unit and also sounds a buzzer if the condition fails it checks if the tank is filled upto level 7 and this process continues and the corresponding level is
indicated in the display unit.

Conclusion and Scope:

Applications of Water Level

Automatic Water level Controller can be
used in Hotels, Factories, Homes
Apartments, Commercial Complexes,
Drainage, etc., It can be fixed for single
phase motor, Single Phase
Submersibles, Three Phase motors.
(For 3Æ and Single Phase Submersible
Starter is necessary) and open well,
Bore well and Sump. We can control
two motor and two sumps and two
overhead tanks by single unit.

Automatic water level controller will
automatically START the pump set as
soon as the water level falls below the
predetermined level (usually 1/2 tank)
and shall SWITCH OFF the pump set
as soon as tank is full.

Fuel level indicator in vehicles.

Liquid level indicator in the huge
containers in the companies.

Note: Various Water Level Indicator Project Videos are given below for your reference. All these are collected from various resources.

How to Make Water Level Indicator – Video
Resource Link: http://www.youtube.com/

Simple Water Level Indicator Using
Transistors – Video 2:
Resource Link: http://www.youtube.com/

Demonstration of Water Level Indicator
Project – Video 3:
Resource Link: http://www.youtube.com/

Water Level Indicator (from Sunday Projects)
– Video 4:
Resource Link: http://www.youtube.com/

Water Level Indicator Using 2n2222 – Video
Resource Link: http://www.youtube.com/

Simple Water Level Indicator – Video 6:
Resource Link: http://www.youtube.com/

Simple Water Level Circuit – Video 7:
Resource Link: http://www.youtube.com/

Water Level Indicator – Video 8:
Resource Link: http://www.youtube.com/

Tank Water Level Indicator – Video 9
Resource Link: http://www.youtube.com/

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