1

ACKNOWLEDGEMENT

We are happy to take this opportunity to thank to people who helped us in the making of

our project. We acknowledge the influence and inspiration of Nimsi Arun Kumar Lecturer

in Electronics & Communication Engineering who made the entire project an exciting and

enjoyable experience.

At the outset, we thank God almighty for making our endeavour a success. We also

express our gratitude to our beloved principal Dr. JOSEPHKUTTY JACOB, and Dr

MANOJ V.J. Head of the Department, for providing us with adequate facilities, ways and

means by which we were able to complete this project. We are also grateful to Mr. Anil

Kumar K, Miss Visanthi V P, Annu Varghese, Sreenath S M, Jisbe Karthik

and all other teachers of Electronics & Communication Engineering

Department for their invaluable teaching, help and support without which the successful

completion of this project would not have been possible.

We thank our Project Guide, Lecturer Miss Sandhya Rajan in Electronics &

Communication Engineering for assisting us in variable ways.

2

ABSTRACT

Water level indicator is an electronic device which senses water level inside the water tank and

indicates the level on the seven segment display. It also alerts us when water level is at its peak

by buzzer sound.

Sensors use the conducting nature of water as tap water is good conductor of electricity. Water

make close circuit connection between the sensors. Here we have four level sensor which

indicate four different levels that are low, half, full and over flow level. The low, half and full

level is indicated on seven segment displays Disp1,Disp2 and Disp3 by glowing ‘L’, ‘H’ and ‘F’

respectively. The overflow level is indicated by sounding the piezo-buzzer. The ground potential

sensor is at the lowest level of the water tank. If water rises then respective display will glow.

User can see present level of water on seven segment display. Buzzer starts sounding if water

overflow and user can switch off the motor. Thus large amount of water can conserve through

this device.

3

CONTENT

1. ACKNOWLEDGEMENT………………………………………………...…......1

2. ABSTRACT…………………………………………………………………......2

3. LIST OF FIGURES……………………………………………………….……..5

4. INTRODUCTION ……………………………………………………………....6

5. HOW IDEA LOOK UP……………………………………………………….…7

6. BLOCK DIAGRAM …………………………………….…………………...…8

7. CIRCUIT DIAGRAM ………….……………………………………….....……9

8. WORKING…………… ……………………………………………...………..10

9. MODIFICATIONS …………………………………………..…….…….…….11

9.1:1st modification……………………………………..………………….11

9.2:2nd modification…………………………………………………..…… 14

9.3:3rd modification…………………………………………………….... 23

10. COMPONENT DETAILS ………………………………………………… 29

10.1: Resistor………………………………………………………………..29

10.2: NOT gate………………………………………………………………34

10.3: AND gate…………………………………………………………..…..35

10.4: NOR gate……………………………………………………………….36

10.5: Piezo buzzer………………………………………………….……… 37

4

10.6 Relay…………………………………………………………………39

10.7 Seven segment display………………………………………………40

10.8 transistor (2N3904)…………………………………………………44

10.9 diode (1N4001)……………………………………………………..45

11. ADVANTAGES / DISADVANTAGES ……………………..……………47

12. CONCLUSION………………………………………………………….......48

13. BIBLIOGRAPHY ………………………………………………….………49

14. DATA SHEETS…………………………………………………………….50

5

LIST OF FIGURES

1. BLOCK DIAGRAM…………..………………………….…………..…8

2. CIRCUIT DIAGRAM……………………………………..……………...9

3. BLOCK DIAGRAM (1ST MODIFICATION) ……………...…………...11

4. CIRCUIT DIAGRAM (1ST MODIFICATION) …………........................12

5. BLOCK DIAGRAM (2nd MODIFICATION) ……….…………………..15

6. CIRCUIT DIAGRAM (2nd MODIFICATION)……..…………………...16

7. RISING /FALLING STATE………………………….…..……….……..17

8. STATE DIAGRAM…..………………………………………………….18

9. BLOCK DIAGRAM (3rd MODIFICATION) …………………………...24

10.CIRCUIT DIAGRAM (3rd MODIFICATION)………..…………………25

11.RISING FALLING STATE………….……………………..……………26

12.NOT GATE…………………………………………………...………….34

13.AND GATE…………..…………………………………….…………… 35

14.NOR GATE……………………………………………………….….….36

15.PIEZO BUZZER…………………………...…………………..…..…….37

16.RELAY…………………………………………….………..……….......39

17.SEVEN SEG. DISPLAY.

17.1Physical structure…………………...………….…………..…40

17.2 Virtual structure……………...........................………….…...40

17.3 Implementation………………………………..…………..…42

18. TRANSISTOR (2N3904)……………………………………………...…….44

19. DIODE(1N4001)…………………………………………………………….45

6

INTRODUCTION

Now a days, there is large loss of water due to laziness of people. We present here a very simple

remedy for providing water level, whenever water is being used or filled inside the tank at home

offices or at any place.

In this, we connect a circuit to water tank with conducting rods dipped inside water to indicate

the level up to which water is filled. We used here three seven segment display which gives an

indication to the user by showing…….

‘’L” for indicating ‘’Low level” that is there is need to start the motor to fill the tank.

‘’H’’ for indicating “Half level”

“F” for indicating “Full level” that is sufficient water for the user has been filled.

When water reaches up to peak of the tank (water touching to the upper most rod) buzzer starts

sounding indicating that user has to switch off the motor.

To reduce human effort further, we modified our circuit as “automatic water level control”.

We connect the motor with o/p of the modified circuit, which results automatic action. That is

motor switches off and on automatically, whenever it is needed.

7

HOW THE IDEA TOOK UP

Being citizen of India our aim is to look forward for the development of our country and to make

it economic superpower. For a country having such a huge population the conservation of pure

water is very important. In 1981 total utilization of India’s water source was 470 cubic meter per

person per year. According to “EXPERT COMITEE OF AND WATER CONSERVATION

“India water needs is estimated to be 1245cubic meter per person per year by 2031-32. This

estimation is actually based on a very optimistic projection of 9% GDP growth rate but going by

present trend of double digit in inflation and the overall global economic scenario, one tends to

be apprehensive that 9% GDP is too much to ask for. Even at this rapid growth we are going to

have water deficit of 25% by 2031-32 which is far more than India’s entire water resources.

Thus we see that it is very tough task to produce drinking as per our requirement, so we have to

go for optimum utilization of available water resources for this to happen we have to minimize

wastage of water as far as possible. By looking our daily schedule we come to conclusion that

there is huge loss of water due to our carelessness or laziness in our practical life.

Being a responsible part of society we think of innovating cheaper technology to reduce losses in

water. This is the basic idea behind selection of our mini project as “WATER LEVEL

INDICATOR”.

8

6. BLOCK DIAGRAM

Fig.1: block diagram of base circuit

9

7. CIRCUIT DIAGRAM

configuration of seven segment display for F,H and L respectively.

Fig2: circuit diagram

10

8. WORKING

This water-level indicator uses 7-segment display, to indicate the water level (low, half and

full) in the tank. Moreover, a buzzer is used to alert us of water overflowing from the tank. The

circuit shows the water level by displaying L, H and F for low, half and full, respectively. circuit

uses five sensors to sense the different water levels in the tank. Sensor A is connected to the

negative terminal (GND) of the power supply. The other four sensors (B through E) are

connected to the inputs of NOT gate IC 7404. When there is a high voltage at the input pin of

the NOT gate, it outputs a low voltage. Similarly, for a low voltage at the input pin of the NOT

gate, it outputs a high voltage.

When the tank is empty, the input pins of IC 7404 are pulled high via a 1-mega-ohm resistor. So

it outputs a low voltage. As water starts filling the tank, a low voltage is available at the input

pins of the gate and it outputs a high voltage. When the water in the tank rises to touch the

low level, there is a low voltage at input pin 5 of gate N3 and high output at pin 6. Pin 6 of the

gate is connected to pin 10 of gate N9, so pin 10 also goes high. Now as both pins 9 and 10 of

gate N9 are high, its output pin 8 also goes high. As a result, positive supply is applied to DIS3

which is configured to show ‘L’, indicating low level of water in the tank.

Similarly, when water in the tank touches the half level, pins 4 and 5 of AND gate N8

become high. As a result, its output also goes high and DIS2 shows ‘H’ indicating half level of

water in the tank. At this time, pin 9 of gate N9 also goes low via gate N4 and DIS3 stops

glowing.

When the water t a n k b e c o me s f u l l , the voltage at pin 1 of gate N1 and pin 3 of

gate N2 goes low. Output pin 3 of gate N 7 g o e s high a n d DIS1 shows ‘F’ indicating

that the water tank is full.

When water starts overflowing the tank, pin 13 of gate N6 goes low to make output pin 12.

The buzzer sounds to indicate that water is over- flowing the tank and we need to switch

off the motor pump.

11

9. MODIFICATION

9.1 Modification 1:

Water level indicator using single display:

Block diagram:

Fig 3: block diagram of 1st modification

12

Circuit diagram:

Fig4: circuit diagram of 1st modification

13

WORKING

In this modification circuit we use only one display instead of three displays, which show L,H

&F for their respective position of water in the tank.

The circuit uses five sensors to sense the different water levels in the tank. Sensor A is

connected to the negative terminal (GND) of the power supply. The other four sensors (B

through E) are connected to the inputs of NOT gate IC 7404. When there is a high voltage at the

input pin of the NOT gate, it outputs a low voltage. Similarly, for a low voltage at the input pin of

the NOT gate, it outputs a high voltage.

When the tank is empty, the input pins of IC 7404 are pulled high via a 1-mega-ohm

resistor. So it gives a low voltage. So display will not glow. As water starts filling the tank, a

low voltage is available at the input pins of the gate and it outputs a high voltage When the

water in the tank rises to touch the low level, there is a low voltage at input pin 5 of gate

N3 and high output at pin 6. Pin 6 of the gate is connected to pin 10 of gate N9, so pin 10 also

goes high. Now as both pins 9 and 10 of gate N9 are high, its output pin 8 also goes high. So

the display will glow L for which it is arranged through OR gate system as shown in the circuit

diagram. Similarly, when water in the tank touches the half level, pins 4 and 5 of AND

gate N8 become high. So display will glow through OR gate system which is arranged for

showing H in the display. When the water t a n k b e c o me s f u l l , the voltage at pin 1 of

gate N1 and pin 3 of gate N2 goes low. Output pin 3 of gate N7 goes h igh. So the display

will glow F through OR gate system as shown in the circuit diagram.

When water starts overflowing the tank, pin 13 of gate N6 goes low to make output pin 12. The

buzzer sounds to indicate that water is over- flowing the tank and you need to switch off

the motor pump.

14

9.2 Modification 2:-

Water level controller

Using SR latch:

INTRODUCTION

To reduce human effort further, we modified our circuit as “automatic water level control”.

“Automatic water level controller” is a circuit which restrict water level to rise or fall within

Two specified level automatically.

It is totally automatic device that is no human effort is needed.

We specified two level as low level and high levels, by dipping two level sensors A and B which

is denoted in fig. by letter “L” and “H” respectively.

When water level falls below level “L”, output becomes high which drives motor through relay

switch and motor starts pumping water inside the tank and keeps on pumping till level reaches up

to “H”. Again motor turns on through the relay switch when water level reaches below low level.

This cycle repeats automatically.

15

Block diagram

Fig5: block diagram of 2nd modification

16

Circuit diagram:

Fig6: circuit diagram of 2nd modification

17

Working:

when water remain below low level, no current flows. So, voltage at “A” is equal to +5v or we

can say that “A” is at high logic (A).

when water reaches up to low level, ”A” becomes grounded , that is “A” becomes low (A)

similarly “B” remains high when water level remain below high level, and becomes low when it

reaches up to high level.

So, logic state of A and B for different region is shown in figure.

Fig7: rising/falling state

.Possible input:-

For region below level L A B (both the terminal is connected to supply voltage)

For region between L&H A B (terminal A is grounded)

For region above level H A B (both the terminal is grounded)

Note :-the input A B can never come, we can easily observe it from figure.

18

We assume two states:-

Rise state: In this state water level is rising in the tank i.e motor is ON.

Fall state: In this state water level is falling i.e motor is off.

State diagram:-

Fig8: state diagram

19

Assuming it as a Moore machine i.e.

o/p = present state

assuming:

R=1

F=0

input

A B = 1 1

A B = 0 1

A B = 1 0

A B = 0 0

20

STATE TABLE

21

k-map solution for S-input

K- map solution for R-input

S = A

R = B

22

(moore machine)

So after solving logic with the help of SR flip flop we note that we should connect point ‘A’

directly to S input and point ‘B’ should be connected to input R through not gate and output Q

of the flip flop will be the output ‘Z’.

At the output relay switch is used to drive the motor.

Q = Z

23

9.3 Modification 3:

Water level control using feedback

INTRODUCTION:

It is totally also automatic device that is no human effort is needed .

We specified two level as low level and high levels, by dipping two level sensors A and B which

is denoted in fig. by letter “L” and “H” respectively as in the modification 2.

When water level falls below level “L”, output becomes high which drives motor through relay

switch and motor starts pumping water inside the tank and keeps on pumping till level reaches up

to “H”. Again motor turns on through the relay switch when water level reaches below low level.

This cycle repeats automatically.

Output Q can not be uniquely expressed with two variables A and B we need one more variable.

Here we used feedback circuit that is the third variable is Q itself.

24

Block diagram:

Fig9: block diagram of third modification

25

Circuit diagram:

Fig 10: circuit diagram of 3rd modificaton

26

Working:

Fig11:level logic

For water to be controlled within level L and H output Q as a function of A and B is given

following truth table.

A B Q

0 0 1

0 1 1,0

1 0 Ф

1 1 0

For A=0 and B=1 Q is not unique therefore Qcan’t be uniquely expressed with twovariables A

and B. We need one more variable.

27

We take Q itself as third variable.

Desired o/p Q for different possible input is given in following truth table……

Truth table:

A B Qin Qout

0 0 0 0

0 0 1 0

0 1 0 0

0 1 1 1

1 0 0 �

1 0 1 �

1 1 0 1

1 1 1 1

The above truth table can be reduced with help of K-map for output Qout

28

k-map reduction for Q

:

Q=A+BQ

So output Q is feedback and output of the AND gate having input B and Q is ORed to get desired

output Qout.. Motor is driven by the output Qout using relay switch.

29

10. Details of components:

10.1 Resistors

Resistors are the most common passive electronic component (one that does not require power to

operate). They are used to control voltages and currents. While a resistor is a very basic

component, there are many ways to manufacture them. Each style has its own characteristics that

make it desirable in certain types of applications. Choosing the right type of resistor is important

to making high-performance or precision circuits work well. This bonus chapter covers the

resistor types and helps with picking the right one for your project.

All resistors are basically just a piece of conducting material with a specific value of resistance.

For that piece of conducting material to be made into a practical resistor, a pair of electrodes and

leads are attached so current can flow. The resistor is then coated with an insulating material to

protect the conducting material from the surrounding environment and vice versa. There are

several different resistor construction methods and body styles (or packages) that are designed

for a certain range of applied voltage, power dissipation, or other considerations. The

construction of the resistor can affect its performance at high frequencies where it may act like a

small inductor or capacitor has been added, called parasitic inductance or capacitance.

Carbon-composition resistors

These are also known as carbon-comp resistors. “Composition” means that the resistive material

is a mix of carbon and stabilizing compounds. The amount of carbon in the mix determines the

resistance of the material. A small cylinder, like a pencil lead, is held between the two electrodes

and coated with resin or phenolic, making a non-inductive resistor (one with very low parasitic

inductance) that is often used in RF circuits.

Carbon-comp resistors are available with power ratings of 1⁄4- to 2 watts. They can also handle

temporary overloads much better than film resistors (more about those in a moment) because the

heat is distributed evenly throughout the cylinder of resistive material. That makes this type of

30

resistor a good choice for circuits that protect against and absorb pulses and transients (short

bursts of excess voltage or current),for example. Unfortunately, these resistors are also strongly

influenced by temperature and humidity and so are not good for circuits that depend on precise,

stable resistance values.

Film resistors

In a film resistor, the resistive material is a very thin coating of carbon or metal on an insulating

substrate, such as ceramic or glass. The value of the resistance is determined by the thickness of

the film and the amount of carbon or metal in it. These resistors are available with very accurate

and stable values. A drawback of film resistors is that they are unable to handle large amounts of

power because the film is so thin. Overloads can also damage the film by creating “hot spots”

inside the resistor, changing its value permanently. The value of film resistors is sometimes

adjusted before sealing by cutting away some of the film with a laser, a process called trimming.

Surface-mount resistors are almost always film resistors; the film is deposited on a ceramic

sheet. Because of their extremely small size, surface-mount resistors have very low power

ratings — from 1⁄10 to 1⁄4 watt.

Wire wound resistors

Common in power supplies and other equipment that dissipates lots of power, wire wound

resistors are made just as you might expect: A high-resistance wire is wound around an

insulating form — usually a ceramic tube — and attached to electrodes at each end. These are

made to dissipate a lot of power in sizes from 1-watt to hundreds of watts! Wire wound resistors

are usually intended to be air cooled, but some styles have a metal case that can be attached to a

heat sink or metal chassis to get rid of undesired heat. Because the resistive material in these

resistors is wound on a form, they also act like small inductors. For this reason, wire wound

resistors are not used in audio and RF circuits. Be careful when using a resistor from your junk

box or a grab bag in such a circuit! Small wire wound resistors look an awful lot like film or

carbon-comp resistors. There is usually a wide color band on wire wound resistors, but not

always. If you’re in doubt, test the resistor at the frequencies you expect to encounter.

31

Ceramic and metal oxide

If you need a high-power non-inductive resistor, you can use cermet (ceramic-metal mix) or

metal oxide resistors. These are constructed much like carbon-comp resistors, substituting the

cermet or metal oxide for the carbon-composition material.

Adjustable resistors

There are many different types of adjustable resistors. The simplest are wire wound resistors

with some of the wire exposed so a movable electrode can be attached. The most common are

adjusted with a rotary shaft. The element provides a fixed resistance between two terminals. The

wiper moves to contact the element at different positions, changing the resistance between the

end of the element and the wiper terminal.

If an adjustable resistor has only two terminals — one end of the element and the wiper — then

it’s called a rheostat and provides an adjustable value of resistance. Most rheostats are intended

for use in high-power circuits with power ratings from

several watts to several tens of watts.

If the adjustable resistor has three terminals, it is called a potentiometer (or “pot” for short).

Most pots are intended to act as voltage dividers; they can be made into rheostats by leaving one

of the element terminals unconnected. Miniature versions called trimmers, mounted on a circuit

board, are used to make small adjustments or calibrate a circuit. They are available in single-turn

or multi-turn versions. Larger pots (with shafts 1⁄8” or 1⁄4” in diameter) are intended as user

controls — for example, the volume and tone pots on an electric guitar or a radio. Pots are

available with resistance values from a few ohms to several mega ohms and with power ratings

up to 5 watts.

As with fixed-value resistors, the construction of the pot is important. Higher-power pots may

have a wire wound element that has enough inductance to be unsuitable for audio or RF signals.

Smaller pots, particularly trim pots, are not designed to be strong enough mechanically for use as

a frequently adjusted control.

32

Pots are also available with elements that have a non-linear taper or change of resistance with

wiper position. For example, a log taper pot has a resistance that changes logarithmically with

shaft rotation. This is useful in attenuator circuits. An audio taper pot is used to create a voltage

divider that mimics the loudness response of the human ear so volume appears to change linearly

with control rotation.

Resistor networks

Often resistor networks are used to save space on printed circuit boards. These networks are

miniature printed circuits themselves, placing several resistors on one substrate — where they

may be isolated from each other, share one common terminal, or be connected in series. You can

find various configurations of these resistors in any component supplier’s catalog.

Power Dissipation and Voltage Ratings

After value, power dissipation is the next most important characteristic of a resistor.

An overloaded resistor often changes in value over time and can often get hot enough to burn its

self and surrounding components. Every circuit designer learns the smell of burnt resistor sooner

or later!

The common rule is to calculate how much power the resistor will have to dissipate — and then

use the next largest size or a factor-of-two higher dissipation ratings, whichever is larger. The

power rating is based on unobstructed air circulation around the resistor. For resistors dissipating

more than a watt, arrange nearby components so air can circulate freely. If possible, mount

power resistors horizontally so convection cools all parts of the resistor equally. Another

important rating is maximum applied voltage. Voltages above this value may cause an arc

between the resistor terminals! At high voltages, leakage resistance from current across the

resistor’s body surfaces can also become significant — allowing current to leak around the

internal resistance. High-voltage resistors must be kept clean. Fingerprints, oil, dirt and dust all

create unwanted current paths, increasing leakage or even arcing. This is why resistors for use in

high-voltage circuits are long and thin, with their terminals far apart — to minimize leakage and

maximize their ability to withstand high voltage.

33

Choosing Resistors

Here’s a short list of special applications that require special types of resistors.

These aren’t hard and fast rules, but they can guide your initial selection. For most circuits, plain

old carbon-film or carbon-comp resistors work just fine.

ESD and transient protection: Carbon composition and metal oxide (they withstand short pulse

overloads and have low values of parasitic inductance).

Audio and instrumentation circuits: Metal film (low noise).

High voltage: Wire wound and metal oxide in high-voltage body styles.

RF: Carbon composition and metal oxide (low inductance).

Precision circuits: Carbon or metal film (fixed-value) and cermet (trimmers or controls).

Consider what’s most important for your particular circuit — value, power, voltage, stability,

cost — and then look for the resistor type that meets those requirements.

34

10.2 IC 74LS04&CD4069(NOT GATE)

In digital logic, an inverter or NOT gate is a logic gate which implements logical negation. The

truth table is shown on the right. This represents perfect switching behavior, which is the

defining assumption in Digital electronics. In practice, actual devices have electrical

characteristics that must be carefully considered when designing inverters. In fact, the non-ideal

transition region behavior of a CMOS inverter makes it useful in analog electronics as a class A

amplifier (e.g., as the output stage of an operational amplifier)

PINOUT TRUTH TABLE

Fig12:NOT gate ic

An inverter circuit outputs a voltage representing the opposite logic-level to its input. Inverters

can be constructed using a single NMOS transistor or a single PMOS transistor coupled with a

resistor. Since this 'resistive-drain' approach uses only a single type of transistor, it can be

fabricated at low cost. However, because current flows through the resistor in one of the two

states, the resistive-drain configuration is disadvantaged for power consumption and processing

speed. Alternatively, inverters can be constructed using two complimentary transistors in a

CMOS configuration. This configuration greatly reduces power consumption since one of the

transistors is always off in both logic states. Processing speed can also be improved due to the

relatively low resistance compared to the NMOS-only or PMOS-only type devices. Inverters can

also be constructed with Bipolar Junction Transistors (BJT) in either a resistor-transistor logic

(RTL) or a transistor-transistor logic (TTL) configuration.

INPUT OUTPUT

A B Y

0 0 0

0 1 0

1 0 0

1 1 1

35

10.3 IC 74LS08&CD4081( AND GATE)

The AND gate is a digital logic gate that implements logical conjunction - it behaves according

to the truth table to the right. A HIGH output (1) results only if both the inputs to the AND gate

are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results. In

another sense, the function of AND effectively finds the minimum between two binary digits,

just as the OR function finds the maximum.

PINOUT TRUTHTABLE

Fig 13: AND gate ic

36

10.4 74LS25 &CD4001NOR GATE

The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the

truth table to the right. A HIGH output (1) results if both the inputs to the gate are LOW (0). If

one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the negation of the

OR operator. NOR is a functionally complete operation—combinations of NOR gates can be

combined to generate any other logical function. By contrast, the OR operator is monotonic as it

can only change LOW to HIGH but not vice versa. In most, but not all, circuit implementations,

the negation comes for free—including CMOS and TTL. In such logic families, the only way to

implement OR is with 2 or more gates, such as a NOR followed by an inverter. A significant

exception is some forms of the domino logic family.7425 is 4 input TTL NOR GATE.

PINOUT TRUTHTABLE

Fig 14: NOR gate ic

37

10.5 Piezo buzzer:

A Piezo buzzer is made from two conductors that are separated by Piezo crystals. When a

voltage is applied to these crystals, they push on one conductor and pull on the other. The result

of this push and pull is a sound wave. These buzzers can be used for many things, like signaling

when a period of time is up or making a sound when a particular button has been pushed. The

process can also be reversed to use as a guitar pickup. When a sound wave is passed, they create

an electric signal that is passed on to an audio amplifier.

Fig 15: piezo buzzer

Instruction :

Carefully take the Piezo buzzer out of its packaging. If the metal piece inside is damaged

in any way, the buzzer will not work as well as it should.

1. 2

38

Strip each end of the audio cable.

2. 3

Connect the audio wire on one side of the audio cable to the center of the Piezo element.

3. 4

Using the same side of the audio cable, connect the ground/shielding wire to the brass

surface on the Piezo device.

4. 5

Connect the signal wire on the other side of the cable to the signal tab on your 1/4-inch

audio jack, located on the amplifier.

5. 6

Connect the ground/shielding wire to the ground tab on the audio jack.

39

10.6 RELAY

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism mechanically, but other operating principles are also used. Relays are used

where it is necessary to control a circuit by a low-power signal (with complete electrical isolation

between control and controlled circuits), or where several circuits must be controlled by one

signal. The first relays were used in long distance telegraph circuits, repeating the signal coming

in from one circuit and re-transmitting it to another. Relays were used extensively in telephone

exchanges and early computers to perform logical operations.

A simple electromagnetic relay consists of a coil of wire surrounding a soft iron core, an iron

yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one

or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke

and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so

that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition,

one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other

relays may have more or fewer sets of contacts depending on their function. The relay in the

picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit

between the moving contacts on the armature, and the circuit track on the printed circuit board

(PCB) via the yoke, which is soldered to the PCB.

10.7 Seven segment display

A seven-segment display, or seven

device for displaying decimal numerals

matrix displays. Seven-segment displays are widely used in

other electronic devices for displaying numerical information.

Fig 17.1:7 segment display (physical structure)

Concept and visual structure

Fig 17.2 :visual structure

gment display

seven-segment indicator, is a form of electronic display

numerals that is an alternative to the more complex

segment displays are widely used in digital clocks, electronic

other electronic devices for displaying numerical information.

Fig 17.1:7 segment display (physical structure)

Concept and visual structure

40

display

that is an alternative to the more complex dot-

, electronic meters, and

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A seven segment display, as its name indicates, is composed of seven elements. Individually on

or off, they can be combined to produce simplified representations of thearabic numerals. Often

the seven segments are arranged in an oblique (slanted) arrangement, which aids readability. In

most applications, the seven segments are of nearly uniform shape and size (usually

elongated hexagons, though trapezoids and rectangles can also be used), though in the case

of adding machines, the vertical segments are longer and more oddly shaped at the ends in an

effort to further enhance readability.

Each of the numbers 0, 6, 7 and 9 may be represented by two or more different glyphs on seven-

segment displays.

The seven segments are arranged as a rectangle of two vertical segments on each side with one

horizontal segment on the top, middle, and bottom. Additionally, the seventh segment bisects the

rectangle horizontally. There are also fourteen-segment displays and sixteen-segment

displays (for fullalphanumerics); however, these have mostly been replaced by dot-

matrix displays.

The segments of a 7-segment display are referred to by the letters A to G, as shown to the right,

where the optional DP decimal point (an "eighth segment") is used for the display of non-integer

numbers.

The animation to the left cycles through the common glyphs of the ten decimal numerals and the

six hexadecimal "letter digits" (A–F). It is an image sequence of a "LED" display, which is

described technology-wise in the following section. Notice the variation between uppercase and

lowercase letters for A–F; this is done to obtain a unique, unambiguous shape for each letter

(otherwise, a capital D would look identical to an 0 (or less likely O) and a capital B would look

identical to an 8).

Seven segments are, effectively, the fewest required to represent each of the ten Hindu-Arabic

numerals with a distinct and recognizable glyph. Bloggers have experimented with six-segment

and even five-segment displays with such novel shapes as curves, angular blocks and serifs for

segments; however, these often require complicated and/or non-uniform shapes and sometimes

create unrecognizable glyphs.[1]

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Implementations

Fig 17.3: 7 seg. Display implementation.

Seven-segment displays may use a liquid crystal display (LCD), arrays of light-emitting

diodes (LEDs), or other light-generating or controlling techniques such as cold cathode gas

discharge, vacuum fluorescent, incandescent filaments, and others. For gasoline price totems and

other large signs, vane displays made up of electromagnetically flipped light-reflecting segments

(or "vanes") are still commonly used. An alternative to the 7-segment display in the 1950s

through the 1970s was the cold-cathode, neon-lamp-like nixie tube. Starting in 1970, RCA sold a

display device known as the Numitron that used incandescent filaments arranged into a seven-

segment display. [2]

In a simple LED package, typically all of the cathodes (negative terminals) or all of

the anodes (positive terminals) of the segment LEDs are connected together and brought out to a

common pin; this is referred to as a "common cathode" or "common anode" device. Hence a 7

segment plus decimal point package will only require nine pins (though commercial products

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typically contain more pins, and/or spaces where pins would go, in order to match industry

standard pinouts).

Integrated displays also exist, with single or multiple digits. Some of these integrated displays

incorporate their own internal decoder, though most do not – each individual LED is brought out

to a connecting pin as described. Multiple-digit LED displays as used in pocket calculators and

similar devices used multiplexed displays to reduce the number of IC pins required to control the

display. For example, all the anodes of the A segments of each digit position would be connected

together and to a driver pin, while the cathodes of all segments for each digit would be

connected. To operate any particular segment of any digit, the controlling integrated circuit

would turn on the cathode driver for the selected digit, and the anode drivers for the desired

segments; then after a short blanking interval the next digit would be selected and new segments

lit, in a sequential fashion. In this manner an eight digit display with seven segments and a

decimal point would require only 8 cathode drivers and 8 anode drivers, instead of sixty-four

drivers and IC pins. Often in pocket calculators the digit drive lines would be used to scan the

keyboard as well, providing further savings; however, pressing multiple keys at once would

produce odd results on the multiplexed display.

Seven segment displays can be found in patents as early as 1908 (in U.S. Patent 974,943, F W

Wood invented an 8-segment display, which displayed the number 4 using a diagonal bar), but

did not achieve widespread use until the advent of LEDs in the 1970s. They are sometimes even

used in unsophisticated displays like cardboard "For sale" signs, where the user either applies

color to pre-printed segments, or (spray)paints color through a seven-segment digittemplate, to

compose figures such as product prices or telephone numbers.

For many applications, dot-matrix LCDs have largely superseded LED displays, though even in

LCDs 7-segment displays are very common. Unlike LEDs, the shapes of elements in an LCD

panel are arbitrary since they are formed on the display by a kind of printing process. In contrast,

the shapes of LED segments tend to be simple rectangles, reflecting the fact that they have to be

physically moulded to shape, which makes it difficult to form more complex shapes than the

segments of 7-segment displays.

10.8 transistor (2n3904)

The 2N3904 is a small, common

amplifying or switching applications. It is designed for low

voltage, and can operate at moderately high sp

It is a 200 milliamp, 40 volt

with a beta or current gain of 100 on average. It is used in a variety of analog amplification

and switching applications.

It is available in a variety of small through

92, SOT-23, and SOT-223, with package

1 watt.

A 2N3906 is a complementary (

transistor that can safely switch three times as much current as the 2N3904 but has

otherwise similar characteristics.

Fig.18 transistor 2n3904

transistor (2n3904)

is a small, common NPN BJT transistor used for general purpose low

or switching applications. It is designed for low current and power

, and can operate at moderately high speeds.

volt, 625 milliwatt transistor capable of amplifying up to 100

or current gain of 100 on average. It is used in a variety of analog amplification

and switching applications.

It is available in a variety of small through-hole and surface mount packages including

, with package-dependent thermal ratings from 625

is a complementary (PNP) transistor for the 2N3904. The 2N2222

transistor that can safely switch three times as much current as the 2N3904 but has

r characteristics.

44

used for general purpose low-power

power, medium

transistor capable of amplifying up to 100 MHz,

or current gain of 100 on average. It is used in a variety of analog amplification

hole and surface mount packages including TO-

ings from 625 milliwatts to

2N2222 is an NPN

transistor that can safely switch three times as much current as the 2N3904 but has

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10.9diode (1N4001)

In electronics, a diode is a two-terminal electronic component that conducts electric current in

only one direction. The term usually refers to a semiconductor diode, the most common type

today. This is a crystalline piece of semiconductor material connected to two electrical terminals.

The most common function of a diode is to allow an electric current to pass in one direction

(called the diode's forward direction) while blocking current in the opposite direction (the reverse

direction). Thus, the diode can be thought of as an electronic version of a check valve. This

unidirectional behavior is called rectification, and is used to convert alternating current to direct

current, and to extract modulation from radio signals in radio receivers. However, diodes can

have more complicated behavior than this simple on-off action. This is due to their complex non-

linear electrical characteristics, which can be tailored by varying the construction of their P-N

junction. These are exploited in special purpose diodes that perform many different functions.

For example, specialized diodes are used to regulate voltage (Zener diodes), to electronically

tune radio and TV receivers (varactor diodes), to generate radio frequency oscillations (tunnel

diodes), and to produce light (light emitting diodes). Tunnel diodes exhibit negative resistance,

which makes them useful in some types of

Fig.19 DIODE 1N4001

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A modern semiconductor diode is made of a crystal of semiconductor like silicon that has

impurities added to it to create a region on one side that contains negative charge carriers

(electrons), called n-type semiconductor, and a region on the other side that contains positive

charge carriers (holes), called p-type semiconductor. The diode's terminals are attached to each

of these regions. The boundary within the crystal between these two regions, called a PN

junction, is where the action of the diode takes place. The crystal conducts conventional current

in a direction from the p-type side (called the anode) to the n-type side (called the cathode), but

not in the opposite direction. Another type of semiconductor diode, the Schottky diode, is formed

from the contact between a metal and a semiconductor rather than by a p-n junction.

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11. Advantages:

Low power consumption

User friendly

Automatic control of water level in water tank.

Compactable circuit.

Economical circuit.

Handy, potable and easily applicable.

Most effective circuit.

Reduces human effort.

Disadvantage:

Corrosion of the level sensor takes place.

So there is need to change the level sensor time to time .

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Conclusion:

The spark has finally shown its valor. We take pride in declaring that we have finally

substantiated our vision and ideas, and hence been successful in creating an electronic gadget of

public utility.

It took a couple of months well co-ordinated team work, several failures, disappointments, tiring

endeavors, experienced and valuable guidance by our guide to mould to this project into a

success.

We finally give a sigh of relief and content for our successful effort.

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BIBLIOGRAPHY

REFERENCE BOOKS:

Digital Circuit A. Anand Kumar

Electronics Lab Manual (vol-1) K.A. Navas

Digital systems and hardware Milos D Ercegovac, Tomas Lang

REFERENCE WEBSITES:

http://en.wikipedia.org

http://www.electronicsforu.com

http://www.allaboutcircuits.com

http://www.alldatasheet.com