Report Arun

MINIPROJECT REPORT APRIL 2014 INTELLIGENT POLLUTION CONTROL SYSTEM

CHAPTER-1

INTRODUCTION

In major cities there exist a mandatory system for

inspection and maintenance but it is now increasingly felt to upgrade the present system to a

more effective one in the near future. But now the present system is not implemented

effectively and many automobiles are running without pollution check. To overcome this

kind of problems we have come up with a new idea of designing a new project called

intelligent pollution control system through which we can save our mother earth from

pollution.

In this project we are going to design a prototype which detects the amount of CO in

the vehicle. When the amount of the CO is reached to a threshold limit

(dangerous/maximum), buzzer and led indication produces simultaneously.

Carbon monoxide (CO) is a colourless, odourless, and tasteless gas that is slightly less

dense than air. It is toxic to humans and animals when encountered in higher concentrations,

although it is also produced in normal animal metabolism in low quantities, and is thought to

have some normal biological functions. In the atmosphere, it is spatially variable and short

lived, having a role in the formation of ground-level ozone.

Carbon monoxide consists of one carbon atom and one oxygen atom, connected by

a triple bond that consists of two bonds as well as one dative covalent bond. It is the

simplest Oxo carbon, and isoelectronic with the cyanide ion and molecular nitrogen.

Incoordination complexes the carbon monoxide ligand is called carbonyl.

Carbon monoxide is produced from the partial oxidation of carbon-containing

compounds; it forms when there is not enough oxygen to produce carbon dioxide (CO2), such

as when operating a stove or an internal combustion engine in an enclosed space. In the

presence of oxygen, including atmospheric concentrations, carbon monoxide burns with a

blue flame, producing carbon dioxide. Coal gas, which was widely used before the 1960s for

domestic lighting, cooking, and heating, had carbon monoxide as a significant fuel

DEPARTMENT OF ELECTRONICS AND COMMUNICATION,SBCE 1


constituent. Some processes in modern technology, such as iron smelting, still produce

carbon monoxide as a by-product.

Worldwide, the largest source of carbon monoxide is natural in origin, due

to photochemical reactions in the troposphere that generate about 5×1012 kilograms per

year. Other natural sources of CO include volcanoes, forest fires, and other forms of

combustion.

The components which we are going to use in this

project are CO sensor, relay unit, ignition unit (DC motor). When the CO concentration is

high then relay circuit will be activated which in turn turns ON LED.

The project uses regulated 5V, 500mA power supply.

7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave

rectifier is used to rectify the ac output of secondary of 230/20V step down transformer.



CHAPTER-2

BLOCK DIAGRAM DESCRIPTION

2.1 BLOCK DIAGRAM

Fig2.1: Block Diagram

2.2 WORKING PRINCIPLE

The power supply from socket is connected to the step down transformer inorder to

step down the voltage from 230v to 12 or 18v and the output of step down transformer is 12v

0r 18v ac is connected to rectifier to convert it to pulsating dc from rectifier we will get 12v

0r 18v pulsating dc. The rectifier output is connected to capacitive filter of 100 micro farads

it will blocks DC and allows total ac ripples/contents to ground from that we will get pure DC



and is given to voltage regulator to get constant output voltage of 5v.

2.3 DESCRIPTION Initially the car engine is in on condition i.e., it is default driving which is indicated

by a DC motor running and a continuous on and off of an LED array. The prototype makes

use of alcohol sensor to detect the presence of alcohol or carbon monoxide gas present in the

car. Whenever the driver or the person driving the car consumes alcohol, the sensor senses it

and gives a signal to the buzzer for indicating the presence. This indication is also given to

the relay which makes the engine of the car to stop. When the car is stopped the LED

indication also gets stopped. The sensing and detection of the alcohol present in the car goes

on continuously by the indication of buzzer until and unless the alcohol present gets

vanished. Once the alcohol gets vanished the buzzer comes in the initial position i.e it gets

stopped. By using this simple and efficient prototype for the alcohol detection a much

important and costlier life can be saved by avoiding the occurrence of accidents.



CHAPTER-3

CIRCUIT DESCRIPTION

3.1 CIRCUIT DIAGRAM

Fig 3.1 Circuit diagram of Intelligent Pollution Control System



3.2 OVEARALL WORKING OF THE CIRCUIT

This circuit consists of a voltage regulator , a gas sensor, two comparator

stages , a bipolar junction Junction transistor and a relay switch The input voltage is passed

through a diode and a capacitor which acts as a Half wave rectifier. The output of this section

is a DC voltage. This voltage is passed to a Voltageregulator. 7805 is a voltage regulator

integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The

voltage source in a circuit may have fluctuations and would not give the fixed voltage output.

The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx

indicates the fixed output voltage it is designed to provide. 7805 provides +5V regulated

power supply. Capacitors of suitable values can be connected at input and output pins

depending upon the respective voltage levels.An LED (here LED1) is provided to show the

flow of regulated dc power supply to the Gas Sensor.Here the Gas Sensor used is MQ-6. It's

an ideal sensor used to detect the presence of a dangerous LPG leak in your Home, car or in

a service station, storage tank environment. Its highly sensitive to LPG , and such gases. It

provides with a fast response and requires only a simple drive circuit. Its heater voltage is

equal to 5V. It’s a 3-pin IC, they are

*Vcc

*outputpin

* Ground pin

Sensitive material of MQ-6 gas sensor is SnO2, which with lower conductivity in clean

air. When the target combustible gas exist, the sensor’s conductivity is more higher along

with the gas concentration rising. Please use simple electro circuit, Convert change of

conductivity to correspond output signal of gas concentration. MQ-6 gas sensor has high

sensitivity to Propane, Butane and LPG, also response to Natural gas. The sensor could be

used to detect different combustible gas, especially Methane; it is with low cost and suitable

for different application. Gas leak detection is the process of identifying potentially

hazardous gas leaks by means of various sensors. These sensors usually employ an audible

alarm to alert people when a dangerous gas has been detected. Common sensors used today

include Infrared Point Sensor, Ultrasonic gas detectors, Electrochemical gas detectors,

and Semiconductor Sensors. These sensors are used for a wide range of applications, and can



be found in industrial plants, refineries, wastewater treatment facilities, vehicles, and around

the home.

The IC used here is LM358N . The LM158 series consists of two independent, high gain,

internally frequency compensated operational amplifiers which were designed specifically to

operate from a single power supply over a wide range of voltages. Operation from split power

supplies is also possible and the low power supply current drain is independent of the

magnitude of the power supply voltage.

The LM358 series can be directly operated off of the standard +5V power supply voltage

which is used in digital systems and will easily provide the required interface electronics

without requiring the additional +/- 15V power supplies. Across pin 4 & 8 a ceramic

capacitor is placed so that only dc voltage passes through the devices.

Resistors R2 and R3 are potentiometers used to set various level of gases detected. LED’s

are provided to show which level is deducted. A BJT transistor BC548 is provided here,

which acts as a switch and a relay switch is provided to connect various alarms in the circuit.

The alarm may be of various types: an LED, Buzzer, automatic brake and such. Thew device

can be placed in the ignition of the vehicle or any place that can provide sufficient power

supply for the operation of the circuit.



CHAPTER-4

COMPONENT STUDY

4.1 RESISTOR

Resistors "Resist" the flow of electrical current. The higher the value ofresistance

(measured in ohms) the lower the current will be. Resistance is the propertyof a component

which restricts the flow of electric current. Energy is used up as thevoltage across the

component drives the current through it and this energy appears asheat in the component.

Fig 4.1.1 Specification of a resister

Table 4.1.1: Resistor and its colour code details



The unit for measuring resistance is the OHM. (the Greek letter Ω - called Omega).

Higher resistance values are represented by "k" (kilo-ohms) and M (meg ohms). For example,

120 000 Ω is represented as 120k, while 1 200 000 Ω is represented as 1M2. The dot is

generally omitted as it can easily be lost in the printing process.In some circuit diagrams, a

value such as 8 or 120 represents a resistance in ohms. Another common practice is to use the

letter E for resistance in ohms. The letter R can also be used. For example, 120E (120R)

stands for 120 Ω, 1E2 stands for 1R2 etc.

Resistance values detailed above are a constant and do not change if the voltage or

current-flow alters. But there are circuits that require resistors to change value with a change

in temperate or light. This function may not be linear, hence the name NONLINEAR

RESISTORS.

There are several types of nonlinear resistors, but the most commonly used

include :NTC resistors (figure a) (Negative Temperature Co-efficient) - their resistance

lowers with temperature rise. PTC resistors (figure b) (Positive Temperature Co-efficient) -

their resistance increases with the temperature rise. LDR resistors (figure c) (Light Dependent

Resistors) - their resistance lowers with the increase in light. VDR resistors (Voltage

dependent Resistors) - their resistance critically lowers as the voltage exceeds a certain value.

Symbols representing these resistors are shown below.

4.2 CAPACITOR

Capacitors store electric charge. They are used with resistorsintiming circuits

because it takes time for a capacitor to fill with charge. They are used to smooth varying DC

supplies by acting as a reservoir of charge. They are also used in filter circuits because

capacitors easily pass AC (changing) signals but they block DC (constant) signals.



Fig4.2.1-Symbol of Capacitor

Electrolytic capacitors are polarized and they must be connected the correctway round, at least one of their leads will be marked + or -.

Fig4.2.2 Electrolytic Capacitor

The general definition of a capacitor (also called a condenser in older books) is any

conductor which can store charge. When we connect a wire between a charged capacitor and

ground, current will flow until the capacitor is left with no net charge. Since any conductor

has a capacity to hold charge, any conductor can be a capacitor

To charge a capacitor, all we need to do is connect the positive terminal of a battery to

one conductor and the negative terminal to the other conductor. Charge will continue to flow

onto the conductors until the voltage across the capacitor is equal in magnitude and opposite

indirection to the voltage across the battery. That means that an electron in a wire between

the battery and thecapacitor is pushed one direction by the battery with the same force that it

is pushed the other direction by the capacitor, so no current will flow in the circuit.

Capacitance is defined by the relation Q = CV.



4.3 DIODES

Diodes allow electricity to flow in only one direction. The arrow of the circuitsymbol shows the direction in which the current can flow. Diodes are the electrical version of a valve and early diodes were actually called valves.

Fig4.3.:- Circuit Symbol

Diodes must be connected the correct way round, the diagram may be + for anode and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is marked by a line painted on the body. Diodes are labelled with their code in small print; you may need a magnifying glass to read this on small signal diodes.1N4004

FEATURES :

* High current capability

* High surge current capability

* High reliability

* Low reverse current

* Low forward voltage drop

MECHANICAL DATA :

* Case : DO-41 Molded plastic

* Epoxy : UL94V-O rate flame retardant

* Lead : Axial lead solderable per MIL-STD-202,

Method 208 guaranteed

* Polarity :Colour band denotes cathode end

* Mounting position : Any



* Weight : 0.34 gram

MAXIMUM RATINGS AND ELECTRICAL CHARACTERISTICS

Rating at 25 °C ambient temperature unless otherwise specified.

Single phase, half wave, 60 Hz, resistive or inductive load.

4.4 LIGHT-EMITTING DIODE (LED):

The longer lead is the anode (+) and the shorter lead is the cathode (&minus). In the schematic symbol for an LED (bottom), the anode is on the left and the cathode is on the right. Light emitting diodes are elements for light

Fig4.4:- Circuit Symbol

They are manufactured in different shapes, colors and sizes. For their lowprice, low

consumption and simple use, they have almost completely pushed aside other light sources-

bulbs at first place. It is important to know that each diode will be immediately destroyed

unlessits current is limited. This means that a conductor must be connected in parallel to a

diode. In order to correctly determine value of this conductor, it is necessary to know diode’s

voltage drop in forward direction, which depends on what material a diode is made of and

what colors it is. Values typical for the most frequently used diodes are shown in table below:

As seen, there are three main types of LEDs. Standard ones get full brightness at current of

20mA. Low Current diodes get full brightness at ten time’s lower current while Super Bright

diodes produce more intensive light than Standard ones.

Since the 8052 microcontrollers can provide only low input current and sincetheir pins

are configured as outputs when voltage level on them is equal to 0, directconfectioning to

LEDs is carried out as it is shown on figure (Low current LED, cathode is connected to

output pin).



4.5 SWITCHES AND PUSHBUTTONS

A push button switch is used to either close or open an electrical circuitdepending on

the application. Push button switches are used in various applications such as industrial

equipment control handles, outdoor controls, mobile communication terminals, and medical

equipment, and etc. Push button switches generally include a push button disposed within

housing. The push button may be depressed to cause movement of the push button relative to

the housing for directly or indirectly changing the state of an electrical contact to open or

close the contact. Also included in a pushbutton switch may be an actuator, driver, or plunger

of some type that is situated within a switch housing having at least two contacts in

communication with an electrical circuit within which the switch is incorporated.

Fig 4.5:- Pushbutton

Typical actuators used for contact switches include spring loaded force capactuators

that reciprocate within a sleeve disposed within the canister. The actuator is typically coupled

to the movement of the cap assembly, such that the actuator translates in a direction that is

parallel with the cap. A push button switch for a data input unit for a mobile communication

device such as a cellular phone, a key board for a personal computer or the like is generally

constructed by mounting a cover member directly on a circuit board. Printed circuit board

(PCB) mounted pushbutton switches are an inexpensive means of providing an operator

interface on industrialcontrol products. In such push button switches, a substrate which



includes a pluralityof movable sections is formed of a rubber elastomeric. The key top is

formed on a top surface thereof with a figure, a character or the like by printing, to thereby

provide acover member. Push button switches incorporating lighted displays have been used

in a variety of applications. Such switches are typically comprised of a pushbutton, an opaque

legend plate, and a back light to illuminate the legend plate.

4.6 VOLTAGE REGILATOR

DESCRIPTION

The MC78XX/LM78XX/MC78XXA series of threeterminal positive regulators are

available in theTO-220/D-PAK package and with several fixed outputvoltages, making them

useful in a wide range ofapplications. Each type employs internal current limiting,thermal

shut down and safe operating area protection,making it essentially indestructible. If adequate

heat sinkingis provided, they can deliver over 1A output current.Although designed primarily

as fixed voltage regulators,these devices can be used with external components toobtain

adjustable voltages and currents.

Fig 4.6.1:-Voltage regulator IC



Table 4.6.1: Absolute Maximum Ratings

Fig 4.6.2:- Internal block diagram of Voltage Regulatopr IC

4.7 MQ-6 GAS SENSOR

FEATURES

* High sensitivity to LPG, iso-butane, propane* Small sensitivity to alcohol, smoke.* Fast response . * Stable and long life * Simple drive circuit

APPLICATION

They are used in gas leakage detecting equipments in family and industry, are suitable for detecting ofLPG, iso-butane, propane, LNG, avoid the noise of alcohol and cooking fumes and cigarette smoke.

SPECIFICATIONS

a.Standard work condition



b.Enviornment condition

c.Sensitivity characterstics

4.8 LM358/LM358A /LM258A (DUAL OPERATIONAL AMPLIFIER)

FEATURES

• Internally Frequency Compensated for Unity Gain

• Large DC Voltage Gain: 100dB

• Wide Power Supply Range:

LM258/LM258A, LM358/LM358A: 3V~32V (or ±1.5V~ 16V)

LM2904 : 3V~26V (or ±1.5V ~ 13V)

• Input Common Mode Voltage Range Includes Ground

• Large Output Voltage Swing: 0V DC to Vcc -1.5V DC

• Power Drain Suitable for Battery Operation

DESCRIPTION



The LM2904,LM358/LM358A, LM258/LM258A consist oftwo independent, high gain,

internally frequencycompensated operational amplifiers which were designedspecifically to

operate from a single power supply over awide range of voltage. Operation from split power

suppliesis also possible and the low power supply current drain isindependent of the

magnitude of the power supply voltage.Application areas include transducer amplifier, DC

gainblocks and all the conventional OP-AMP circuits which nowcan be easily implemented

in single power supply systems.

Fig 4.8.1:-LM358/LM358A /LM258A

Fig4.8.2 Internal Block Diagram of LM358



4.9 NPN GENERAL PURPOSE TRANSISTORS(BC 548)

FEATURES

· Low current (max. 100 mA)· Low voltage (max. 65 V).

APPLICATIONS

· General purpose switching and amplification.

DESCRIPTION

NPN transistor in a TO-92; SOT54 plastic package.

PNP complements: BC556, BC557 and BC558.

PINNING

Fig 4.9:- Simplified outline (TO-92: S0T54) and symbol.



Table 4.9.1 Quick Reference Data

4.10 TRANSFORMER

A transformer is a device that transfers electrical energy from one circuit to another

through inductively coupled conductors—the transformer's coils. A varying current in the

first or primary winding creates a varying magnetic flux in the transformer's core, and thus a

varying magnetic field through the secondary winding. This varying magnetic field induces a

varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is

called mutual induction.

Figure 4.10.1: Transformer Symbol

Transformer is a device that converts the one form energy to another form of energy like a

transducer.



Fig 4.10.2: Transformer

BASIC PRINCIPLE:

A transformer makes use of Faraday's law and the ferromagnetic properties of an iron

core to efficiently raise or lower AC voltages. It of course cannot increase power so that if the

voltage is raised, the current is proportionally lowered and vice versa.

Fig 4.10.3: Basic Principle



TRANSFORMER WORKING:

A transformer consists of two coils (often called 'windings') linked by an iron core, as

shown in figure below. There is no electrical connection between the coils; instead they are

linked by a magnetic field created in the core.

Fig 4.10.4: Basic Transformer

Transformers are used to convert electricity from one voltage to another with minimal

loss of power. They only work with AC (alternating current) because they require a changing

magnetic field to be created in their core. Transformers can increase voltage (step-up) as well

as reduce voltage (step-down). Alternating current flowing in the primary (input) coil creates

a continually changing magnetic field in the iron core. This field also passes through the

secondary (output) coil and the changing strength of the magnetic field induces an alternating

voltage in the secondary coil. If the secondary coil is connected to a load the induced voltage

will make an induced current flow. The correct term for the induced voltage is 'induced

electromotive force' which is usually abbreviated to induced e.m.f. The iron core is laminated

to prevent 'eddy currents' flowing in the core. These are currents produced by the alternating

magnetic field inducing a small voltage in the core, just like that induced in the secondary

coil. Eddy currents waste power by needlessly heating up the core but they are reduced to a

negligible amount by laminating the iron because this increases the electrical resistance of the

core without affecting its magnetic properties.

Transformers have two great advantages over other methods of changingvoltage:

1. They provide total electrical isolation between the input and output, so they can be safely

used to reduce the high voltage of the mains supply.



2. Almost no power is wasted in a transformer. They have a high efficiency (power out /

power in) of 95% or more.

CLASSIFICATION OF TRANSFORMER:

Step-Down Transformer

Step-Up Transformer

Step-down transformer:

Step down transformers are designed to reduce electrical voltage. Their primary voltage is

greater than their secondary voltage. This kind of transformer "steps down" the voltage

applied to it. For instance, a step down transformer is needed to use a 110v product in a

country with a 220v supply. Step down transformers convert electrical voltage from one level

or phase

configuration usually down to a lower level. They can include features for electrical isolation,

power distribution, and control and instrumentation applications. Step down transformers

typically rely on the principle of magnetic induction between coils to convert voltage and/or

current levels. Step down transformers are made from two or more coils of insulated wire

wound around a core made of iron. When voltage is applied to one coil (frequently called the

primary or input) it magnetizes the iron core, which induces a voltage in the other coil,

(frequently called the secondary or output). The turn’s ratio of the two sets of windings

determines the amount of voltage transformation.

Fig4.10.5: Step-Down Transformer

An example of this would be: 100 turns on the primary and 50 turns on the secondary,

a ratio of 2 to 1.



Step down transformers can be considered nothing more than a voltage ratiodevice.

With step down transformers the voltage ratio between primary and secondary will

mirror the "turn’s ratio" (except for single phase smaller than 1kva which have compensated

secondary). A practical application of this 2 to 1 turn’s ratio would be a 480 to 240 voltage

step down. Note that if the input were 440 volts then the output would be 220 volts. The ratio

between input and output voltage will stay constant. Transformers should not be operated at

voltages higher than the nameplate rating, but may be operated at lower voltages than rated.

Because of this it is possible to do some non-standard applications using standard

transformers. Single phase step down transformers 1kva and larger may also be reverse

connected to step-down or step-up voltages. (Note: single phase step up or step down

transformers sized less than 1 KVA should not be reverse connected because the secondary

windings have additional turns to overcome a voltage drop when the load is applied. If

reverse connected, the output voltage will be less than desired.)

Step-Up Transformer:

A step up transformer has more turns of wire on the secondary coil, which makes a

larger induced voltage in the secondary coil. It is called a step up transformer because the

voltage output is larger than the voltage input.Step-up transformer 110v 220v design is one

whose secondary voltage is greater than its primary voltage. This kind of transformer "steps

up" the voltage applied to it. For instance, a step up transformer is needed to use a 220v

product in a country with a 110v supply. A step up transformer 110v, 220v converts

alternating current (AC) from one voltage to another voltage. It has no moving parts and

works on a magnetic induction principle; it can be designed to "step-up" or "step-down"

voltage. So a step up transformer increases the voltage and a step down transformer decreases

the voltage. The primary components for voltage transformation are the step up transformer

core and coil. The insulation is placed between the turns of wire to prevent shorting to one

another or to ground. This is typically comprised of Mylar, nomex, Kraft paper, varnish, or

other materials. As a transformer has no moving parts, it will typically have a life expectancy

between 20 and 25 years.



Fig 4.10.6: Step-Up Transformer

APPLICATIONS:

Generally these Step-Up Transformers are used in industries applications only.

TYPES OF TRANSFORMER:

Mains Transformers:

Mains transformers are the most common type. They are designed to reduce the AC

mains supply voltage (230-240V in the UK or 115-120V in some countries) to a safer low

voltage. The standard mains supply voltages are officially 115V and 230V, but 120V and

240V are the values usually quoted and the difference is of no significance in most cases.

Fig 4.10.7: Main Transformer

To allow for the two supply voltages mains transformers usually have two separate

primary coils (windings) labeled 0-120V and 0-120V. The two coils are connected in series

for 240V (figure 2a) and in parallel for 120V (figure 2b). They must be wired the correct way

round as shown in the diagrams because the coils must be connected in the correct sense

(direction): Most mains transformers have two separate secondary coils (e.g. labeled 0- 9V,

0-9V) which may be used separately to give two independent supplies, or connected in series

to create a center-tapped coil (see below) or one coil with double the voltage. Some mains

transformers have a centre-tap halfway through the secondary coil and they are labeled 9-0-

9V for example. They can be used to produce full-wave rectified DC with just two diodes,

unlike a standard secondary coil which requires four diodes to produce full-wave rectified

DC.



A mains transformer is specified by:

1. Its secondary (output) voltages Vs.

2. Its maximum power, Pmax, which the transformer can pass, quoted in VA (voltamp). This

determines the maximum output (secondary) current, Imax... Where Vs is the secondary

voltage. If there are two secondary coils the maximum power should be halved to give the

maximum for each coil.

3. Its construction - it may be PCB-mounting, chassis mounting (with solder tag connections)

or steroidal (a high quality design).

Audio Transformers:

Audio transformers are used to convert the moderate voltage, low current output of an

audio amplifier to the low voltage, high current required by a loudspeaker. This use is called

'impedance matching' because it is matching the high impedance output of the amplifier to

the low impedance of the loudspeaker.

Fig 4.10.8: Audio transformer

Radio Transformers:

Radio transformers are used in tuning circuits. They are smaller than mains and audio

transformers and they have adjustable ferrite cores made of iron dust. The ferrite cores can be

adjusted with a non-magnetic plastic tool like a small screwdriver. The whole transformer is

enclosed in an aluminum can which acts as a shield, preventing the transformer radiating too

much electrical noise to other parts of the circuit.

Fig 4.10.9: Radio Transformer



Turns Ratio and Voltage:

The ratio of the number of turns on the primary and secondary coils determines the

ratio of the voltages......where Vp is the primary (input) voltage, Vs is the secondary (output)

voltage, Np is the number of turns on the primary coil, and Ns is the number of turns on the

secondary coil.

4.11 RECTIFIER:

The purpose of a rectifier is to convert an AC waveform into a DC waveform (OR)

Rectifier converts AC current or voltages into DC current or voltage. There are two different

rectification circuits, known as 'half-wave' and 'full-wave' rectifiers. Both use components

called diodes to convert AC into DC.

The Half-wave Rectifier:

The half-wave rectifier is the simplest type of rectifier since it only uses one

diode, as shown in figure.

Fig4.11.1: Half Wave Rectifier

Figure 2 shows the AC input waveform to this circuit and the resulting output.As you can see,

when the AC input is positive, the diode is forward-biased and lets the current through. When

the AC input is negative, the diode is reverse-biased and the diode does not let any current

through, meaning the output is 0V. Because there is a 0.7V voltage loss across the diode, the

peak output voltage will be 0.7V less thanVs.



Fig 4.11.2: Half-Wave Rectification

While the output of the half-wave rectifier is DC (it is all positive), it would not be suitable as

a power supply for a circuit. Firstly, the output voltage continually varies between 0V and

Vs-0.7V, and secondly, for half the time there is no output at all.

The Full-wave Rectifier:

The circuit in figure 3 addresses the second of these problems since at no time is the output

voltage 0V. This time four diodes are arranged so that both the positive and negative parts of

the AC waveform are converted to DC. The resulting waveform is shown in figure 4.

Figure4.11.3: Full-Wave Rectifier



Fig 4.11.4: Full-Wave Rectification

When the AC input is positive, diodes A and B are forward-biased, while diodes C and D are

reverse-biased. When the AC input is negative, the opposite is true - diodes C and D are

forward-biased, while diodes A and B are reverse-biased. While the full-wave rectifier is an

improvement on the half-wave rectifier, its output still isn't suitable as a power supply for

most circuits since the output voltage still varies between 0V and Vs-1.4V. So, if you put

12V AC in, you will 10.6V DC out

CAPACITOR FILTER:

The capacitor-input filter, also called "Pi" filter due to its shape that looks like the Greek

letter pi, is a type of electronic filter. Filter circuits are used to remove unwanted or

undesired frequencies from a signal.

Fig 4.11.5: Capacitor Filter



A typical capacitor input filter consists of a filter capacitor C1, connected across the rectifier

output, an inductor L, in series and another filter capacitor connected across the load.

1. The capacitor C1 offers low reactance to the AC component of the rectifier output while it

offers infinite reactance to the DC component. As a result the capacitor shunts an appreciable

amount of the AC component while the DC component continues its journey to the inductor

L

2. The inductor L offers high reactance to the AC component but it offers almost zero

reactance to the DC component. As a result the DC component flows through the inductor

while the AC component is blocked.

3. The capacitor C2 bypasses the AC component which the inductor had failed to block. As a

result only the DC component appears across the load RL.

4.12 VOLTAGE REGULATOR:

A voltage regulator is an electrical regulator designed to automatically maintain a

constant voltage level. It may use an electromechanical mechanism, or passive or active

electronic components. Depending on the design, it may be used to regulate one or more AC

or DC voltages.

There are two types of regulator are they.

Positive Voltage Series (78xx) and

Negative Voltage Series (79xx)

78xx:

’78’ indicate the positive series and ‘xx’ indicates the voltage rating. Suppose

7805 produces the maximum 5V.’05’indicates the regulator output is 5V.

79xx:

’78’ indicate the negative series and ‘xx’ indicates the voltage rating. Suppose 7905 produces

the maximum -5V.’05’indicates the regulator output is -5V.



These regulators consists the three pins there are

Pin1: It is used for input pin.

Pin2: This is ground pin for regulator

Pin3: It is used for output pin. Through this pin we get the output.

Figure4.12: Regulator

4.13 RELAYS

A relay is an electrically controllable switch widely used in industrial controls,

automobiles and appliances. The relay allows the isolation of two separate sections of a

system with two different voltage sources i.e., a small amount of voltage/current on one side

can handle a large amount of voltage/current on the other side but there is no chance that

these two voltages mix up.

Inductor

Fig4.13.1: Circuit symbol of a relay



OPERATION:

When a current flow through the coil, a magnetic field is created around the coil i.e.,

the coil is energized. This causes the armature to be attracted to the coil. Thearmature’s

contact acts like a switch and closes or opens the circuit. When the coil is not energized, a

spring pulls the armature to its normal state of open or closed. There are all types of relays for

all kinds of applications.

Fig4.13.2: Relay Operation and use of protection diodes

Transistors and ICs must be protected from the brief high voltage 'spike' produced when the

relay coil is switched off. The above diagram shows how a signal diode (eg 1N4148) is

connected across the relay coil to provide this protection. The diode is connected 'backwards'

so that it will normally not conduct. Conduction occurs only when the relay coil is switched

off, at this moment the current tries to flow continuously through the coil and it is safely

diverted through the diode. Without the diode no current could flow and the coil would

produce a damaging high voltage 'spike' in its attempt to keep the current flowing.

In choosing a relay, the following characteristics need to be considered:

1. The contacts can be normally open (NO) or normally closed (NC). In the NC type, the

contacts are closed when the coil is not energized. In the NO type, the contacts are closed

when the coil is energized.

2. There can be one or more contacts. i.e., different types like SPST (single pole single

throw), SPDT (single pole double throw) and DPDT (double pole double throw) relay.



3. The voltage and current required to energize the coil. The voltage can vary from a few

volts to 50 volts, while the current can be from a few milliamps to 20milliamps. The relay has

a minimum voltage, below which the coil will not be energized. This minimum voltage is

called the “pull-in” voltage.

4. The minimum DC/AC voltage and current that can be handled by the contacts. This is in

the range of a few volts to hundreds of volts, while the current can be from a few amps to

40A or more, depending on the relay. A relay is used to isolate one electrical circuit from

another. It allows a low current control circuit to make or break an electrically isolated high

current circuitpath. The basic relay consists of a coil and a set of contacts. The most common

relay coil is a length of magnet wire wrapped around a metal core. When voltage is applied to

the coil, current passes through the wire and creates a magnetic field. This magnetic field

pulls the contacts together and holds them there until the current flow in the coil has stopped.

The diagram below shows the parts of a simple relay.

Fig 4.13.4: Relay Operation:

When a current flows through the coil, the resulting magnetic field attracts an armature that is

mechanically linked to a moving contact. The movement either makes or breaks a connection

with a fixed contact. When the current is switched off, the armature is usually returned by a

spring to its resting position shown in figure 6.6(b).

Latching relays exist that require operation of a second coil to reset the contact position.

By analogy with the functions of the original electromagnetic device, a solid-state relay

operates a thyristor or other solid-state switching device with a transformer or light-emitting

diode to trigger it.



POLE AND THROW:

SPST

SPST relay stands for Single Pole Single Throw relay. Current will only flow through the

contacts when the relay coil is energized.

Fig 4.13.5: SPST Relay

SPDT Relay

SPDT Relay stands for Single Pole Double Throw relay. Current will flow between the

movable contact and one fixed contact when the coil is De-energized and between the

movable contact and the alternate fixed contact when the relay coil is energized. The most

commonly used relay in car audio, the Bosch relay, is a SPDT relay.

Fig 4.13.6: SPDT Relay

DPST Relay

DPST relay stands for Double Pole Single Throw relay. When the relay coil is energized, two

separate and electrically isolated sets of contacts are pulled down to make contact with their

stationary counterparts. There is no complete circuit path when the relay is De-energized.



Fig 4.13.7: DPST Relay

DPDT RelayDPDT relay stands for Double Pole Double Throw relay. It operates like the SPDT relay but

has twice as many contacts. There are two completely isolated sets of contacts.

Fig 4.13.8: DPDT Relay

Pole Double Throw Relay

This is a 4 Pole Double Throw relay. It operates like the SPDT relay but it has 4 sets

of isolated contacts.

Fig 4.13.9: 4 Pole Double Throw relay

TYPES OF RELAY:

1. Latching Relay

2. Reed Relay

3. Mercury Wetted Relay

4. Machine Tool Relay



5. Solid State Relay (SSR)

Latching relay:

Latching relay, dust cover removed, showing pawl and ratchet mechanism. The ratchet

operates a cam, which raises and lowers the moving contact arm, seen edge-on just below it.

The moving and fixed contacts are visible at the left side of the image.

A latching relay has two relaxed states (bi-stable). These are also called "impulse", "keep",

or "stay" relays. When the current is switched off, the relay remains in its last state. This is

achieved with a solenoid operating a ratchet and cam mechanism, or by having two opposing

coils with an over-center spring or permanent magnet to hold the armature and contacts in

position while the coil is relaxed, or with a remnant core. In the ratchet and cam example, the

first pulse to the coil turns the relay on and the second pulse turns it off. In the two coil

example, a pulse to one coil turns the relay on and a pulse to the opposite coil turns the relay

off. This type of relay has the advantage that it consumes power only for an instant, while it is

being switched, and it retains its last setting across a power outage. A remnant core latching

relay requires a current pulse of opposite polarity to make it change state.

Figure4.13.10: Latching relay

Reed relay:

A reed relay has a set of contacts inside a vacuum or inert gas filled glass tube, which

protects the contacts against atmospheric corrosion. The contacts are closed by a magnetic

field generated when current passes through a coil around the glass tube. Reed relays are

capable of faster switching speeds than larger types of relays, but have low switch current

and voltage ratings.



Mercury-wetted Relay:

A mercury-wetted reed relay is a form of reed relay in which the contacts are wetted

with mercury. Such relays are used to switch low-voltage signals (one volt or less) because of

their low contact resistance, or for high-speed counting and timing applications where the

mercury eliminates contact bounce. Mercury wetted relays are position-sensitive and must be

mounted vertically to work properly. Because of the toxicity and expense of liquid mercury,

these relays are rarely specified for new equipment. See also mercury switch.

Machine tool relay:

A machine tool relay is a type standardized for industrial control of machine tools, transfer

machines, and other sequential control. They are characterized by a large number of contacts

(sometimes extendable in the field) which are easily converted from normally-open to

normally-closed status, easily replaceable coils, and a form factor that allows compactly

installing many relays in a control panel. Although such relays once were the backbone of

automation in such industries as automobile assembly, the programmable logic controller

(PLC) mostly displaced the machine tool relay from sequential control applications.

Solid-state relay:

A solid state relay (SSR) is a solid state electronic component that provides a similar function

to an electromechanical relay but does not have any moving components, increasing long-

term reliability. With early SSR's, the tradeoff came from the fact that every transistor has a

small voltage drop across it. This voltage drop limited the amount of current a given SSR

could handle. As transistors improved, higher current SSR's, able to handle 100 to 1,200

Amperes, have become commercially available. Compared to electromagnetic relays, they

may be falsely triggered by transients.

Figure4.13.11: Solid relay, which has no moving parts



SPECIFICATION:

Number and type of contacts – normally open, normally closed, (doublethrow)

Contact sequence – "Make before Break" or "Break before Make". For example, the old

style telephone exchanges required Make-before-break so that the connection didn't get

dropped while dialing the number.

Rating of contacts – small relays switch a few amperes, large contactors are rated for up to

3000 amperes, alternating or direct current

Voltage rating of contacts – typical control relays rated 300 VAC or 600 VAC, automotive

types to 50 VDC, special high-voltage relays to about 15 000 V

Coil voltage – machine-tool relays usually 24 VAC, 120 or 250 VAC, relays for

switchgear may have 125 V or 250 VDC coils, "sensitive" relays operate on a few milli-

amperer.

APPLICATIONS:

Relays are used:

To control a high-voltage circuit with a low-voltage signal, as in some types of modems,

To control a high-current circuit with a low-current signal, as in the starter solenoid of an

automobile,

To detect and isolate faults on transmission and distribution lines by opening and closing

circuit breakers (protection relays),

To isolate the controlling circuit from the controlled circuit when the two are at different

potentials, for example when controlling a mains-powered device from a low-voltage switch.

The latter is often applied to control office lighting as the low voltage wires are easily

installed in partitions, which may be often moved as needs change. They may also be

controlled by room occupancy detectors in an effort to conserve energy,

To perform logic functions. For example, the Boolean AND function is realized by

connecting relay contacts in series, the OR function by connecting contacts in parallel. Due to

the failure modes of a relay compared with a semiconductor, they are widely used in safety

critical logic, such as the control panels of radioactive waste handling machinery.

As oscillators, also called vibrators. The coil is wired in series with the normally closed

contacts. When a current is passed through the relay coil, the relay operates and opens the

contacts that carry the supply current. This stops the current and causes the contacts to close



again. The cycle repeats continuously, causing the relay to open and close rapidly. Vibrators

are used to generate pulsed current.

To generate sound. A vibrator, described above, creates a buzzing sound because of the

rapid oscillation of the armature. This is the basis of the electric bell, which consists of a

vibrator with a hammer attached to the armature so it can repeatedly strike a bell.

To perform time delay functions. Relays can be used to act as an mechanical time delay

device by controlling the release time by using the effect of residual magnetism by means of

a inserting copper disk between the armature and moving blade assembly.

4.14 BUZZER

An electric coil is wound on a plastic bobbin, the latter having a central sleeve

within which a magnetic core is slide ably positioned. One end of the sleeve is closed and

projects beyond the coil. An inverted cup-shaped housing surrounds the coil and bobbin and

has a central opening through which the closed end of the sleeve projects. The core projects

into the closed end of the sleeve beyond the margin of the opening in the housing to augment

the magnetic coupling between the housing and the core. The open end of the housing is

attached to a support bracket of magnetic material, there being a spring between the bracket

and bobbin normally urging the core toward the closed end of the sleeve. For a self- drive

buzzer (DC/ circuit- built), either pizeo or magnetic just apply the rated current and voltage.

For the external-drive buzzer, it depends on

1. We should give magnetic buzzer 1/2 square wave, and provide it at least 3 times the

amount of the rated consumptive current.

2. Otherwise, we give square wave to the peizo buzzer instead of 1/2 square wave, because

the half wave might cause the buzzer does not work.

Therefore, voltage control is an important factor for a peizo buzzer which is driven by

the voltage.



CHAPTER-5

PCB DESIGN AND FABRICATION

When we look at a finished printed circuit board with an often-complex circuit

pattern and a mixture of through-hole and surface mount components we may think creating

your own boards would be a difficult, time-consuming task that would require specialized

tools and expertise. However, fabricating your own printed circuit boards can be broken

down into the following relatively simple steps:

1 Generation of the schematic.

2 Placement and routing of the circuit board.

3 Generation of artwork.

4 Exposing and developing the resist layer.

5 Etching the printed circuit board.

6 Tin plating of the printed circuit board.

7 Drilling and shaping, including barrels.

Depending upon our particular situation, you may not need to complete all of the

steps listed above. The most popular board types are

SINGLE-SIDED BOARDS: ‘Single-sided’ means that wiring is available only on one

side of the insulating substrate. The side which contains the circuit pattern is called

the ‘solder side’ whereas the other is called the ‘component side’. These type of

boards are mostly used in the case of simple circuitry and where the manufacturing

cost are kept to be minimum. Nevertheless, they represent a large volume of printed

circuit boards currently produced for professional and nonprofessional grades. The

single sided boards are manufactured commonly by the ‘print and etch’ or by ‘diecut’

technique by using a die that carries an image of the wiring pattern; and the die is

either photoengraved or machine engraved. They are mainly used in entertainment

electronics where manufacturing costs have to be kept at the minimum.



DOUBLE-SIDED BOARDS: ‘Double-sided’ printed circuit board have writing

pattern on both side of the insulating material. The circuit is available both on the

components side and solder side. Obviously, the component density and the conductor

lines are higher than the single sided boards. Double sided PCBs can be made with or

without plated through holes. Double sided PTH board has circuitry on both sides of

an insulating substrate, which is connected by metalizing the wall of a hole in the

substrate that intersects the circuitry on both sides. Double sided non-PTH board is

only an extension of a single sided board. Its low cost is considerably lower because

plating can be avoided. In this case through contacts are made by soldering the

components lead on both sides of the board, wherever required. The production of

boards with plated through holes is fairly expensive.

5.1 MANUFACTURING PROCESS

First, the wanted circuit is drawn on paper and it is modified or designed PCB layout

is to be drawn on the plain copper coated board. These boards are available in two types:

Phenolic

Glass epoxy

Most computers PCBs are glass epoxy. To draw circuit diagram we can use the black

color paints. Before that the required size of the plane PCB board is determined from the

roughly drawn PCB layout. Using black paint the desired circuit is drawn on the board.

5.1.1 Safety Measures

We can't stress safety enough! While the techniques described in this project are not

inherently dangerous, we must wear appropriate protective clothing when required or

exercise care and good judgment when handling chemicals or using required tools. In

particular, always wear gloves and eye protection whenever we work with chemicals and

always wear eye protection when drilling or machining a board. The chemicals used in the



processes are relatively safe; however, always follow the procedures below when using any

chemical:

Always store your chemicals in tightly sealed plastic or glass containers.

Make sure each container is clearly labeled with the contents and the

date it was stored.

Don't use expired chemicals.

Make sure your work area is properly ventilated and lighted.

Make sure your work area is clean.

5.2 PCB FABRICATION

5.2.1 Layout Approaches

The first rule is to prepare each and every PCB layout as viewed from the component

side. Another important rule is not to start the designing of a layout unless an absolutely clear

circuit diagram is available, if necessary, with a component lists. Among the components the

larger ones are placed first and the space between is filled with smaller ones. Components

requiring input / output connections come near the connectors. All components are placed in

such a manner that disordering of the components is not necessary if they have to be

replaced. In the designing of a PCB layout it is very important to divide the circuit into

functional subunits. Each of these subunits should be realized on a defined portion of the

board. In the designing the inter connections which are usually done by pencil lines, actual

space requirements in the artwork must be considered. In addition the layout can be rather

roughly sketched and will still be clear enough for artwork designer.

5.2.2 Board Cleaning

The cleaning of the copper surface prior to resist applications in an essential step for

any types of PCB process using etch or plating resist. Insufficient cleanings is one of the



reasons most often encountered for difficulties in PCB fabrication although it might not

always be immediately recognized as this. But it is quiet often the reasons of poor-resist

adhesion, uneven photo-resist films, pinholes, poor plating adhesion, etc .Where cleaning has

to be done with simplest means or only for a limited quantity of PCBs, manual-cleaning

process is mainly used. In the process we require just a sink with running water, pumice

powder, scrubbing brushes and suitable tanks.

5.2.3Screen Printing

This process is particularly suitable for large production schemes. However the

preparation of a screen can also be economically attractive for series of 1000 PCBs. While

photo printing is basically the non-accurate method to transfer a pattern on to a board surface,

with the screen-printing process one can produce PCBs with a conduction of as low as 0.5 +

or – and a registration error of 0.1mm on an industrial scale with a high reliability. In its basic

form, a screen fabric with uniform meshes and opening is stretched and fixed on a solid

frame of metal or wood. The circuit pattern is photographically transferred onto the screen,

leaving the meshes in the pattern open, while the meshes in the rest of the area are closed. In

the actual printing step, ink is forced by the moving squeegee through the open meshes onto

the surface of the material to be printed.

5.2.4 Plating

From a practical stand port, printed circuit boards may have to be stocked before

being taken for assembly of components. It is expected that the circuit board retain its solder

ability for long periods of several months so that reliable solder joints can be produced ring

assembly. Plating of a metal can be accomplished on a copper pattern.

5.2.5 Etching

This can be done both by manual and mechanical ways by immersing the board onto a

solution of formic chloride and hydrochloric acid and finally cleaning the board by soap. In

all subtractive PCB processes, etching is one of the most important steps. The copper pattern

is formed by selective removal of all unwanted copper, which is not protected by an etch

resist. This looks very simple at first glance but in practice there are factors like under



etching and overhang which complicate the matter especially in the production of fine and

highly precise PCBs. Etching of PCBs as required in modern electronic equipment

production, is usually done in spray type etching machines.

5.2.6 Drilling

Drilling is the most important mechanical machining operation in PCB production

processes. Holes are made by drilling wherever a superior hole finish for plated-through

hole processes is required and where the tooling costs for a punching tool cannot be

justified. Therefore drilling is applied for all the professional grade PCB manufacturers and

generally in smaller PCB production laboratories. The importance of hole drilling into PCB

has further gone up with electronic component miniaturization and it needs smaller hole

diameters and higher package density.

5.3 COMPONENT PLACING

The actual location of components in the layout is responsible for the problems to be

placed during routing of the interconnections. In a highly sensitive circuit the critical

components are placed first and in such a manner as to require minimum length for the

critical conductors. In less critical circuit the components are arranged exactly in the order of

signal flow. This will result in a minimum overall conductor length. In a circuit where a few

components have considerably more connecting points than the others. These key

components are placed first and the remaining ones are grouped around them. The general

result to be aimed at is always to get shortest possible interconnections. The bending of the

axial component leads is done in a manner to guarantee an optimum retention of the

component of the PCB. The lead bending radius should be approximately two times the lead

diameter. Horizontally mounted resistors must touch the board surface to avoid lifting of

solder joints along with the copper pattern under pressure on the resistor body. Vertically

mounted resistors should not be flush to the board surface to avoid strain on the solder joints

as well as on the component lead junction due to different thermal expansion coefficients of

lead and board materials, where necessary resilient spaces to be provided. Coated or sealed

components should to be mounted in such to provide a certain length along the leads.



Especially when plated through holes where the solder flows up in the hole, clean lead of at

least 1 mm above the board are recommended.

5.4 SOLDERING

Soldering is a process for the joining of metal parts with the aid of a molten

metal (solder), where the melting temperature is suited below that of the material joined, and

whereby the surface of the parts are wetted, without then becoming molten. Soldering

generally implied that the joining process occurs at temperatures below 450-degree

centigrade. Solder wets and alloys with the base metals and gets drawn, by capillary action,

into the gap between them. This process forms a metallurgical bond between the parts of the

joint. Therefore solder acts by wetting of base metal surfaces forming joint flowing between

these surfaces, which result in a completely filled space between them. Soldering consists of

the relative positioning of the surfaces to be joined, wetting these surfaces with molten solder

and allowing the solder to cool down until it has solidified. During this soldering operation,

an auxiliary medium is mostly used to increase the flow properties of molten solder or to

improve the degree of wetting. Such a medium is called flux mounted only one side of the

board. In double-sided PCBs, the component side is usually opposite to the major conductor

pattern side, unless otherwise dictated by special design requirements. The performance and

reliability of solder joints give best result covered with solder and here with contributing to

the actual solder connections. Generally applied soldering methods are iron soldering, torch

soldering, mass soldering, and electrical soldering, furnace soldering and other methods.

Components are basically cutting after soldering is still common in particular in smaller

industries where hand soldering is used. The problems usually arise at a much later than

during the final functioning testing of the board in the factory. Among the contaminants, we

can typically find flux, chips of plastics, metals and other constructional materials, plating

sails, oils greases environmental soil and other processing materials. The following

performances are expected from the cleaning procedure with the appropriate cleaning

medium:

Dissolution or dissolving of organic liquids and solids, e.g., oils, greases, resin flux.

Removal of plating salts and silicone oils.

Displacing of particulate and other insoluble matters, e.g., chips, dust, and lint.



No severe attacks on boards and components to be cleaned, no alteration of ink or paint

notations and last but not the least, compatibility with healthy environmental working

conditions.

5.5 PCB LAYOUT



CHAPTER 6

ADVANTAGES AND APPLICATIONS

6.1 APPLICATIONS

Automobiles. Industrial and mining applications. Carbon monoxide monitoring and leakage detection

6.2 ADVANTAGES

Content of Pollution in environment can be reduced.

Due to the implementation of this project we can maintain the co level in atmosphere

which can reduce adverse effects on environment and on human life.

Vehicle can work smoothly and no need to pay challans to pollution control board

Check and repair exhaust system leaks.

Long life and low cost

Ease of operation

Highly sensitive

Fit and Forget system

Low cost

Simple and Reliable circuits



CHAPTER 7

CONCLUSION

The project “INTELLIGENT POLLUTION CONTROL SYSTEM “is implemented

successfully for automotives and industrial application for reducing and maintaining CO level

which is harmful for ecosystem and which is affordable from small to large scale industries

for maintaining pollution norms. The project is implemented through a DC motor for

symbolic representation of vehicle and user get alert through a beep sound and if the content

of CO is more automatically indicates with flash lights.



CHAPTER 8REFERENCE

1. Wikipedia

2. Embedded systems by Rajkamal

3. Magazines

4. Electronics for you

5. Electrikindia

6. www.Electronic projects.com




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