This document describes the design and operation of a water level indicator circuit with alarm. The circuit uses transistors, resistors, LEDs, and a buzzer. As water fills the tank, the LEDs light up sequentially to indicate the water level. When the tank is full, the buzzer sounds an alarm. The circuit works by using the water to complete conductive paths between sensors to trigger the LEDs and buzzer. It provides a simple way to monitor water levels and alert users when the tank is full.

2. Report of
Major exam working project
LED WATER LEVEL
INDICATOR WITH ALARM

3. Contents
 Introduction
 Water Level Indicator Circuit Diagram
 Components used in leveller
 Components description
 Assembling the components
 Levels in indicator
 How water level indicator circuit works
Water Level Indicator Project Application’s

4. Introduction:
A water level indicator is used to show the
level of water in an over head tank. This
keeps the user informed about the water level
at all times and avoids the situation of water
running out when it is most needed. There are
ton of water level indicator circuits on the
web. But this one is unique because this water
level indicator circuit also has an alarm
feature. It not only indicates the amount of
water present in the overhead tank but also
gives an alarm when the tank is full.

5. Component used in leveller:
 Transistor BC548 { 4 }
 220 ohm resistors { 3 }
 Colour L.E.D { 3 }
 Buzzer { 1 }
 9v battery + battery clip { 1 }
 P.C.B BORD { 1 }
There are Four parts in this project:-
(i) The Sensor Part
It is generally a fixed support inside the tank having some nuts and bolt with
wires coming out.
(ii) The Circuit Part
It comprises the brain of the module, where in all the various inputs from the
sensors are fed. It is the unit from where you will get all the information of how
much of water is in the tank.
(iii) The Power Supply
It is the part where in you will be converting the A/C voltage to a regulated
voltage of 5V to the Circuit.
(IV) The Buzzer Part
It is responsible for bringing up the sound when the water level fills up in the
tank. It will also be having a speaker or a buzzer to alert.

6. Water leveller indicator diagram

7. ASSEMBLING THE COMPONENTS:
Preparing the soldering iron: • Place the soldering iron in its stand and plug in. The iron will
take a few minutes to reach its operating temperature of about 400°C. • Dampen the
sponge in the stand. • Wait a few minutes for the soldering iron to warm up. You can check
if it is ready by trying to melt a little solder on the tip. • Wipe the tip of the iron on the damp
sponge. This will clean the tip. Melt a little solder on the tip of the iron.
Soldering the components: • Use the component overlay on the PCB
to insert the components and solder them in the following order: 1. Resistors
2. Transistors 3. LED 4. Electric Buzzer
Hold the soldering iron like a pen, near the base of the handle. Touch the
soldering iron onto the joint to be made. Make sure it touches both the
component lead and the track. • Hold the tip there for a few seconds and feed
a little solder onto the joint. It should flow smoothly onto the lead and track to
form a volcano shape. Apply the solder to the joint, not the iron. • Remove the
solder, then the iron, while keeping the joint still. • After all the components
have been soldered, check the soldering closely for any breaks. Inspect your
work carefully under a bright light. The solder joints should have a ‘shiny’ look
about them. Check that there are no solder this placement, fill the tank at least
up to the MDL. • This should cause the loudspeaker to generate an alarm. If
this does not happen then check whether the toggle switch is in the ON
position or not. If not, change the position of the toggle switch to hear the
alarm sound. • When the alarm is generated, it can be silenced by
disconnecting the AC supply from the circuitry.

8. Component description:
Transistor:A transistor is a semiconductor device used
to amplify and switch electronic signals and electrical power. Itis composed
of semiconductor material with at least three terminals for connection to an
external circuit. A voltage or current applied to one pair of the transistor's
terminals changes the current through another pair of terminals. Because the
controlled (output) power can be higher than the controlling (input) power, a
transistor can amplify a signal. Today, some transistors arepackaged
individually, but many more are found embedded in integrated circuits.
Transistor asa switch
Transistors arecommonly used as electronic switches, both for high-power
applications such as switched mode power supply and for low-power
applications such as logic gate.
Transistor asan amplifier
The common-emitter amplifier is designed so that a small change in voltage
(Vin) changes thesmall currentthrough the baseof the transistor; the
transistor's currentamplification combined with the properties of the circuit
mean that small swings in Vin producelargechanges in Vout .
Resistors
A resistor is a passivetwo-terminalelectrical component that
implements electrical resistanceas a circuit element. Resistors actto reduce
currentflow, and, at the same time, act to lower voltage levels within circuits.
In electronic circuits resistors areused to limit currentflow, to adjustsignal
levels, bias active elements, terminate transmission lines among other uses.
High-power resistors thatcan dissipate many watts of electrical power as heat
may be used as part of motor controls, in power distribution systems, or as
test loads for generator. Fixed resistors haveresistances thatonly change
slightly with temperature, time or operating voltage. Variableresistors can be

9. used to adjustcircuit elements (such as a volume controlor a lamp dimmer), or
as sensing devices for heat, light, humidity, force, or chemical activity
COLOUR L.E.D
A light-emitting diode (LED) is a two-lead semiconductor light source. Itis a p
n-junction diode, which emits light when activated. When suitable voltage is
applied to the leads, electrons are able to recombine with electro holes within
the device, releasing energy in the form of photons.
This effect is called called electroluminescence, and the colour of the light
(corresponding to the energy of the photon) is determined by the energy band
gap of the semiconductor.
Piezoelectric Buzzer:
A piezoelectric element may be driven by an oscillating electronic circuit or
other audio singles source, driven with a piezoelectric audio amplifier. Sounds
commonly used to indicate that a button has been pressed are a click, a ring or
a beep.
Battery:
An electric battery is a device consisting of two or more electrochemical cells
that convert stored chemical energy into electrical energy. Each cell contains a
positive terminal, or cathode, and a negative terminal,
or anode. Electrolytes allow ions to move between the electrodes and
terminals, which allows currentto flow out of the battery to performwork.

10. The operation of this projectis very simple and can be understood easily. In
our project “water level indicator” there are 3 main conditions:
1. There is no water available in the sourcetank.
2. Intermediate level i.e. either first level to third level .
3. There is ample amountof water available in the sourcetank.
So let us discuss more about these 3 conditions
CONDITION 1: Water not available
When water is not available in water tank the circuit is not completed and
because of this neither led nor buzzer is started .
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 getsufficient biasing at their base, they starts conducting and now.
The yellow led starts glowing .
CONDITION 3: mid level
When the tank becomes half completed the green led will startglowing .
Condition 4 : full level
When the tank become full completed with water red light will glowing .
Condition 5 : overflowing level
When tht tank become full completed with water buzzer will start.

13. How circuit works:
When the water is empty the wires in the tank are open circuited and the resistors pulls the
switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first
the wire in the tank connected to S1 and the + supply are shorted by water. This closes the
switch S1 and turns the LED1 ON. As the water continues to fill the tank, the LEDs 2 , 3 and
3 light up gradually.
When the water is full, the base of the transistor B548 is pulled high by the water and this
saturates the transistor, turning the buzzer ON. The SPST switch has to be opened to turn the
buzzer OFF.
Since it uses CMOS switches the current flowing through the wires is very less and hence
the corrosion of electrodes is very minimum.
Remember to turn the switch ON while pumping water otherwise the buzzer will not sound