05-04-11 docuentation completed

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CHAPTER-1

TRANSMISSION LINES

1.1 Introduction:

The Automation is the current trend, which transforms the merely conveyer to well

equipped transmission lines to monitor the faults in the main line. As the country is opened to

globalization, people’s income is rising. And the automation is now become essential part of

the life. So, governments prefer not only to raise their automatic monitoring quality but also

the faults of it. As a result, transmission lines are flowing throughout the country like blood

veins. This leads to more number of transmission towers, and government prefer to monitor

with there own techniques.

This increase in number of transmission line towers in forest areas brings not only big issue

to monitor where exactly the fault is but also headache to check the faults, Electric

Department, and others too. It is hard to keep & maintain the details of the each tower, which

is placed in the forest areas. This inefficiency sets some evil things to work on forest areas.

Such as, in case of transmission line cut or short circuit in the transmission line or any such

faults which occurs in the transmission line, Electric board may not trace the exact location of the towers in which fault is occurred very easily, as the tower details are not monitored

individually. Suppose the power generation plants wants to transmit the power to the city or

rural areas in between while transmitting the power if any this happens in the transmission

line then its some what difficult to monitor the things and as we know its some what hectic

job to even monitor where exactly the fault is and in which part of the transmission line. how

to do it?

As we know that if any faults occur in any of the system it takes time to discover the fault

and location of the fault in order to over come this major disadvantages of finding out the

faults in transmission line PHS (Personal Handy System) system is being introduced .

In this system, vehicles are tracked using Earth Orbit Satellites continuously. Not only this,

the electric can see the road map of the location on which transmission line is heading

towards or forecast of the locality or whether the heading road is clear or any fault occurred

in the line and if fault is occured then with the help of PHS system its very easy to monitor

where exactly the location of the faulty transmission line.

2



The Project is not about the PHS, but about alternative technology which is much

economical, simple and Indigenous in design. There by resulting in an effective system for

our own network system of tracking & monitoring the various parameters of the line and

keep the updated information to the electric department.

With help of this project, it is possible to easily track particular vehicle for its geographical

locations on a computer screen. The operator can see the towers current location in real time

mode. Here the communication network is comparable to the cellular network in operation.

So whenever a tower is equipped with it PHS Transmitter enters a “cell” / geographical

location, that particular “Cell Unit” or “Cell Broadcaster” sends a wireless message to the

centralized base unit. In turn the base unit receives the VHF message from the “Cell

Broadcaster” and after processing & decoding displays the geographical location of the faulty

tower location on a graphical form on the computer monitor screen. This way the user can

find the whereabouts of the transmission tower in real time mode.

Whenever a fault is occurred an wireless information will be sent to the base station or

electric department.If the transmission line is in city limits where by there are GSM or mobile

signals are available then at that time if any faults occurs in the transmission line then with

the help of GSM technology we can monitor the faults and even we can monitor in which

tower the fault occurred but what about not reachable areas where there is no network

available to track, at that time we are going to use PHS system, where by in not reachable

areas this PHS system communicates with satellite and sends the information to the base

station if the faults occur in the city limits then the same PHS system acts like an GSM

transmitter and starts transmitting the signals to the board.

In this way we can keep an eye on all the transmission lines and keep on monitoring

MAIN FEATURES OF THE PROJECT

1. Effective in implementation.

2. Low power consumption, and compact size,

3. High reliability, due to the usage of power semiconductor devices,

6. Greater control range due the usage of Frequency Modulation with a PC.

7. Vehicles monitored from a remote area (no need of 'line-of-sight’ arrangement).

3



1.2 Rf Trans-Receiver Module:

This module explains the Radio Frequency transmitter and receiver units used in this system

to transmit code signal from Railway Station end/Train Engine end.

1.3 RF Transmitter Module:

ASIC: Application Specific Integrated Circuit [ASIC] is another option for embedded

hardware developers. The ASIC needs to be custom-built for a specific application, so it is

costly. If the embedded system being designed is a consumer item and is likely to be sold in

large quantities, then going the ASIC route is the best option, as it considerably reduces the

cost of each unit. In addition, size and power consumption will also be reduced. As the chipcount (the number of chips on the system) decreases, reliability increases.

If the embedded system is for the mass market, such as those used in CD players, toys, and

mobile devices, cost is a major consideration. Choosing the right processor, memory devices,

and peripherals to meet the functionality and performance requirements while keeping the

cost reasonable is of critical importance. In such cases, the designers will develop an

Application Specific Integrated Circuit or an Application Specific Microprocessor to reduce

the hardware components and hence the cost. Typically, a developer first creates a prototype

by writing the software for a general-purpose processor, and subsequently develops an ASIC

to reduce the cost.

Oscillator: An electronic device that generates sinusoidal oscillations of desired frequency is

known as a sinusoidal oscillator. Although we speak of an oscillator as “generating” a

frequency, it should be noted that it does not create energy, but merely acts as an energy

converter. It receives d.c. energy and changes it into a.c energy of desired frequency. The

frequency of oscillations depends upon the constants of the device.

A circuit which produces electrical oscillations of any desired frequency is known as an

oscillatory circuit or tank circuit . A simple oscillatory circuit consists of a capacitor (C ) and

inductance coil (L) in parallel. This electrical system can produce electrical oscillations of

frequency determined by the values of L and C . The sequence of charge and discharge results

in alternating motion of electrons or an oscillating current. The energy is alternately stored in

4



the electric field of the capacitor and the magnetic field of the inductance coil. This

intercharge of energy between L and C is repeated over and again resulting in the production

of oscillations.

In order to obtain continuous undamped a.c. output from the tank circuit, it is necessary to

supply the correct amount of power to the circuit. The most practical way to do this is to

supply d.c. power to some device which should convert it to necessary a.c. power for supply

to the tank circuit. This can be achieved by employing a transistor circuit. Because of its

ability to amplify, a transistor is very efficient energy converter i.e. it converts d.c. power to

a.c. power. If the damped oscillations in the tank circuit are applied to the base of transistor, it

will result in an amplified reproduction of oscillations in the collector circuit. Because of this

amplification more energy is available in the collector circuit than in the base circuit. If a part

of this collector-circuit energy is feedback by some means to the base circuit in proper phase

to aid the oscillations in the tank circuit, then its losses will be overcome and continuous

undamped oscillations will occur.

Hartley Oscillator is very popular and is commonly used as a local oscillator in radio

receivers. It has two main advantages viz., adaptability to a wide range of frequencies and is

easy to tune.

5



Fig. 1.1 The Radio Frequency Spectrum

6

FM broadcasting

TV bands 1V/V

3M

Hz

100m

Very high frequency, VHF

SW broadcasting

MW broadcastingMedium frequency,

MF

300 KHz 1 Km

LW broadcastingLow frequency, LF

10 Km30 KHz

3 GHz 10 cm

Frequency Wavelength

30 MHz 10 m

30 MHz 1 m

Ultra high frequency, UHF

High frequency, HF



1.4 RADIO FREQUENCY CIRCUIT TECHNIQUES

Radio must surely be one of the most fascinating aspects of electronics. This part of

explanation provides a brief introduction to radio communication before describing the

circuitry of RF receivers and transmitters. The aim has been to provide the user withsufficient information to what his or her appetite for a subject which has a broad appeal to a

large number of dedicated enthusiasts all over the world.

Radio Frequency Signals:

Radio frequency signals are generally understood to occupy a frequency range, which

extends from a few tens of kilohertz to several hundred giga-hertz. The lowest part of radio

frequency range, which is of practical use (below 30 kHz), is only suitable for narrow-band

communications. At this frequency, signals propagate as ground waves (following the

curvature of the earth) over very long distance. At the other extreme, the highest frequency

range, which is of practical importance, extends above 30GHz. At these ‘microwave’

frequencies, considerable bandwidths are available (sufficient to transmit many television

channel using point-to-point links or to permit very high definition radar systems) and signals

tend to propagate strictly along ‘line-of-sight’ paths.

At other frequencies, signals may propagate by various means, including reflection from

ionized layers in the ionosphere. At frequencies between 3MHz and 30MHz, for example,

ionospheric propagation regularly permits intercontinental broadcasting and communications

using simple equipment within the scope of the enthusiastic radio amateur and short-wave

listener.

For convenience, the radio frequency spectrum is divided into a number of bands, each

spanning a decade of frequency. The use to which each frequency range is put depends upon

a number of factors, paramount amongst which is the propagation characteristic within the

band concerned. Other factors, which need to be taken into account, include the efficiency of

practical aerial system in the range concerned and the bandwidth available. It is also worth

noting that, although it may appear from Figure A that a great deal of the radio frequency

spectrum is not used, it should be stressed that competition for frequency space is fierce.

Frequency allocations are, therefore, ratified by international agreement and the various user

services carefully safeguard their own areas of the spectrum.

7



Frequency and Wavelength:

Radio waves propagate in air (or space) at the speed of light (300 million meters per second).

The velocity of propagation[v], wavelength[λ ] and frequency [f] of a radio wave are related

by the equation:

V = f λ = 3 X 108 m/s

This equation can be arranged to make f or λ the subject, as follows:

F = 3 X 108/ λ Hz and λ = 3 X 108 / fm

As an example, a signal at a frequency of 1 MHz will have a wavelength of 300 m whereas a

signal at a frequency of 10 MHz will have a wavelength of 30m.

Modulation:

In order to convey information using a radio frequency carrier, the signal information must be

superimposed or ‘modulated’ onto the carrier. Modulation is the name given to the process of

changing a particular property of the carrier wave in sympathy with the instantaneous voltage

(or current) signal.

The most commonly used methods of modulation are amplitude modulation (AM) and

frequency modulation (FM). In the former case, the carrier amplitude (its peak voltage) varies

according to the voltage, at any instant, of the modulating signal. In the latter case, the carrier

frequency is varied in accordance with the voltage, at any instant, of the modulating signal.

Figure B shows the effect of amplitude and frequency modulating a sinusoidal carrier (note

that the modulating signal is, in the case, also sinusoidal). In practice, many more cycles of

the radio frequency carrier would occur in the time span of the cycle of the modulating

signal.

The term ‘angle modulation’ is the generic term encompassing both frequency modulation

and phase modulation. Frequency modulation involves operating directly upon the frequency

determining elements of an oscillator stage (e.g. by means of a variable capacitance diode

placed across the oscillator-tuned circuit or connected in series with a quartz crystal).

8



Phase modulation, on the other hand, acts indirectly by changing the phase of the signal in a

subsequent stage (e.g. by means of a variable capacitance diode acting in a phase shifting

circuit).

Fig .1.2 Amplitude And Frequency Modulation

Modulating signal (audio) is correctly tailored prior to its application to the phase modulated

stage, the end result is identical to that of frequency modulation. The reason for this is that, in

a true FM system, the deviation produced is the same for all modulating signals of equal

amplitude (i.e. the amount frequency deviation is independent of the frequency of the

modulating signal). In a phase-modulated system, on other hand, the amount of frequency

deviation is proportional to both modulating signal amplitude and modulating signal

frequency. Thus in a phase modulated system without audio tailoring, a modulation signal of

2 kHz will produce twice as much frequency deviation as an equal amplitude modulating

signal of 1 kHz. The desired audio response required to produce FM, therefore, is one, which

9



rolls off the frequency response by half for each doubling of frequency (equivalent to 6-dB

per octave roll-off). This can be easily achieved using a simple R-C low-pass filter

Demodulation:

Demodulation is the reverse of modulation and is the means by which the signal information

is recovered from the modulated carrier. Demodulation is achieved by means of a

demodulator consists of a reconstructed version of the original signal information present at

the input of the modulator stage within the transmitter.

Figure C shows the simplified block schematic of a simple radio communication system

comprising on AM transmitter and a ‘tuned radio frequency’ (TRF) receiver. Within the

transmitter, the carrier wave (of constant frequency) is generated by means of a radio

frequency oscillator stage. In order to ensure that the carrier is both accurate and within in

frequency, this stage would normally employ a quartz crystal within its frequency generating

circuitry.

The output of the modulator (a modulated carrier) is amplified before outputting to the aerial

system. The output is usually carefully filtered to remove any spurious signals (harmonics)

which may be present and which may otherwise cause interference to other services.

At the receiver, the signal produced by the receiving aerial is a weak copy of the transmitted

signal (its level is usually measured in a µ V). Also present will be countless other signals at

different frequencies (and some with appreciably larger amplitude than the desired signal).

These unwanted signals must be rejected by the receiver’s radio frequency tuned circuits if

they are no to cause problems in later stages.

10



1.5 Radio Communication System

Fig.1.3 RF TRANSMITTER AND RECEIVER

11

AFamplifier

RFoscillator

Modulator RF

amplifier

Mic.

Demodulator

RFamplifier

AFamplifier

LS



CHAPTER-2

RF TRANSMITTER MODULE

2.1 INTRODUCTION

The RF transmitter is built around the common passive and active components, which are

very is to obtain from the material shelf. The circuit works on Very High Frequency band

with wide covering range.

2.2 RF TRANSMITTER

The RF transmitter is built around the ASIC and common passive and active components,

which are very easy to obtain from the material shelf. The circuit works on Very High

Frequency band with wide covering range. The Carrier frequency is 147 MHz and Data

frequencies are 17 MHz, 19 MHz,22 MHz & 25 MHz. It should be noted that ASIC or

Application Specific Integrated Circuit is proprietary product and data sheet or pin details or

working principles are not readily available to the user.

CIRCUIT DESCRIPTION

The ASIC Transmitter IC has four inputs and only one output pin. The four inputs are for the

frequency range of 17 KHz, 19 KHz, 22 KHz and 25 KHz and four switches are provided for

each range. When any one switch is selected, that frequency is added to the Transmitter

circuit as data frequency and transmitted in the air. The Crystal X1 with two coupling

capacitor provides the working oscillator frequency to the circuit. The Capacitors C6 and C7

are to stabilize the crystal oscillator frequency.

2.3 Part List

12



The ASIC output is added to the transmitter circuit’s oscillator transistor T1s base. The data

frequency is added with carrier frequency 147 MHz and aired for transmitting purpose. The

transistor T1 is heart of the Hartely Oscillator and oscillates at carrier frequency of 147 MHz

along with tuned circuit formed by coil L1 and capacitor C4. The Data frequency is fed to T1

on base through resistors R4 and R5. Capacitors C1 and C3 and for stabilizing the tuned

circuit along with resistor R3.

To increase the range of the circuit, transmitting signals must be strong enough to travel the

long distance [i.e., upto 100 meters in this prototype]. So the generated signals are made

strong by amplifying to certain level with the help of Transistor T2 and associated circuit.

The Radio frequency thus generated is fed to pre-amplifier transistor T2 on base terminal.

The resistor R6 provides the bias voltage to T2 and capacitors C5 & C7 removes the noise

and harmonics present in the circuit. The antenna coil L2 transmits the radio frequency in the

air.

13

SEMICONDUCTORS:

IC ASIC 1

T1 BC 547 NPN Transistor 1

T2 BF 494 NPN Transistor 1RESISTORS:

R1 & R2 2.7 K Ohm ¼ Watt 2

R3 & R6 330 K Ohm ¼ Watt 2

R4 1 K Ohm ¼ Watt 1


CAPACITORS:

C1, C2 0.001 Pico Farad Capacitor 2

C3 & C7 0.022 Pico Farad Capacitor 2

C4 4.7 Pico Farad Capacitor 1

C5 & C6 0.01 Micro Farad Capacitor 2

MISCELLANEOUS:X1 1.44 MHz Crystal 1

S1 to S4 ON/OFF SWITCHES 4

L1 RF Coil 200mH 1

L2 Aerial or Telescopic Antenna 1



Fig.2.1 Circuit Diagram Of RF Transmitter

14



1



2.4 RF RECEIVER

This circuit is built around the ASIC i.e., Application Specific Integrated Circuit, hence less

circuitry is observed. The Radio Frequency tuned circuit has 147 M Hz carrier frequencywith four options viz., 17Khz, 19Khz, 22KHz and 25KHz.

The transmitted signals are received on coil L1 which acts as receiver antenna. The oscillator

transistor removes the received signals from 147MHz carrier frequency and fed to ASIC. The

tank circuit formed by C1 and L1 gives the carrier frequency range. The current limiting

resistor R1 and bypass capacitor C5 stabilizes the oscillator. The resistor R2, R3 and R4

provide the biasing voltage to the oscillator transistor T1. Capacitors C2 and C3 are there to

bypass the noise and harmonics present in the received signals. Through coupling capacitor

C7 output of the RF Receiver is fed to ASIC.

The ASIC manipulates the received signal and gives out four channels as output viz., 17KHz,

19KHz, 22KHz and 25KHz. Each channel is amplified by pre-amplifier transistor T2 along

with bias resistor R9. The output of the pre-amplifier transistor is fed to relay driver stage to

activate the

respective

relay ON.

The

Darlington

pair T3 and

T4 are

arranged in

driver stage

to drive the

low

impedance

relay.

2.3 Part

List

SEMICONDUCTORS:

IC ASIC 1

T1 BC 547 NPN Transistor 1

T2 BF 494 NPN Transistor 4

T3&T4 BC 548 NPN Transistor 8

RESISTORS:

R1 & R2 270 K Ohm ¼ Watt 2

R3 & R6 220 Ohm ¼ Watt 2

R4 2.2 K Ohm ¼ Watt 1

R5 2.2 M Ohm ¼ Watt 1


R8 100 Ohm ¼ Watt 4R9 560 Ohm ¼ Watt 4

CAPACITORS:

C1, C2 0.001 Pico Farad Capacitor 2

C3 & C7 0.022 Pico Farad Capacitor 2

C4 4.7 Pico Farad Capacitor 1

C5 & C6 0.01 Micro Farad Capacitor 2

L1 RF Coil 200mH 1

2



3



Fig. 2.2 RF Receiver

..........................



2.5 CIRCUIT DIAGRAM & ITS DESCRIPTION

The Obstacle Detection System is having circuit blocks as follows: IR Trans-receiver

Module, Variable Power Supply and finally Power Supply.

IR TRANS-RECEIVER MODULE

These IR Transmitter and two IR Receivers are fitted on front side of vehicle and are

continuously switched ON for obstacle detection purpose.

The circuit components are explained as:

IR TRANSMITTER

IR LED: The IR LED or Infra Red Light Emitting Diode is an electronic device which gives

off or emits light when current is passed through it. Like general diode, this IR LED passes

current only in one direction and requires forward operation voltage of about 2V and forward

operation current in 10 to 20 mA range. Maximum reverse voltage that the IR LED can

withstand is typically 3 to 5V, more than this could damage the component. It does not have

any current control function, so, when the IR LED is used in a circuit, a resistor must be used

in series to limit the current flow through it. If greater range is required, this resistor may be

reduced to a minimum value with a consequent adverse effect on current consumption. Do

not reduce the value of resistor unless you do require the greater range, otherwise the relay

may not trip reliably close in due to reflections caused by the high light output. For a good

range, the current through the LEDs must be large. Since, however, currents, the pulses must

be short, and this is why PDM is used (In this type of modulation, the time of occurrence of the first and last transition edge, is varied from its unmodulated position).

When the IR LED is used in an application such as the remote controlling transmitter, where

the battery is the main source of current, providing continuous high current to keep the IR

LED ON will consume too much of power. So when the power is applied to the IR LED, the

supply is provided as pulses. If the pulse repetition frequency is rapid enough (more than 50



Hz) then to the receiver eye the IR LED will appear as continuously ON. For example,

instead of supplying 25 mA current continuously, one can provided 50 mA current as pulse to

get brighter light output with the same power consumption. The Infrared diode used is of

plastic pack and is similar in appearance to the familiar Red LED, except that the plastic

encapsulation is deep violet colour.

As stated earlier, the IR Remote Controlling system consists of a set of an IR transmitter and

an IR receiver. Whenever the IR transmitter is activated, it generates a invisible Infra-red

light beam signal and transmits an it towards the IR receiver. The transmitters and receivers

are positioned facing each other.

The source of light in the transmitter is an Infrared LED and rather than merely providing a

continuous source of light, it is flashed on and off at about 10Khz.This is done so that the

receiver can selectively amplify the signal from the transmitter and completely reject ambient

light.

PCM I



Fig.2.3 Pin Diagram Of 708A

The information is passed from the IR Transmitter and Receiver in the form of combinational

digital pulse signals. These pulses are transmitted to the receiver by modulating a carrier

frequency using Pulse Code Modulation [PCM] method. That means it uses pulse-duration

(pulse-width) modulation. The modulated signal is produced in the traditional manner of

having the audio signal set against a pure high-frequency triangular signal generator can be

found on 55. If another generator is used, make sure that its off-set is equal to half the supply

voltage of 5 V and its peak value is 2.5 V pp.

2.6 PCM IR Transmitter IC: This 20 pin DIL packaged IC has integrated all the necessary

stages to transmit the IR pulse beams to the receiver. As the pin-out diagram of the IC shows,

pin-20 is supply pin and pin-18 is ground pin. Since the IC has in-built Oscillator circuit,

whose frequency can be adjusted between 445 K Hz and 510 K Hz, it needs outer

components to oscillate with transmitter circuit needs. SO to get the calculated frequency

range, specific value crystal and capacitors are connected to the pin-2 [OSC IN] and output is

taken on pin-3 [OSC OUT]. This frequency is used by the IC as a reference frequency to

oscillate. The pin-19 is the out pin, which is fed to the transmitter circuit.

The IC can be used in two modes: Flash Mode, where pin-1 [Transmission Mode pin] is

connected with Supply pin and the average current consumption is 6.5 mA; Carrier Mode,

where pin-1 is connected to ground and average current consumption is around 13 mA.

The address information send in the control word depends on the value of these two pins.

Different combination of Low and High (L & H) value on these two pins will transmit

different address codes as shown in the table.



Circuit Diagram Of IR Transmitter

Fig.2.4 IR TRANSMITTER

Parts List

Circuit Description:

IC1 M708/708A PCM Remote Control Transmitter IC 1

T1 BC377 NPN Transistor 1

T2 BC237 NPN Transistor 1

D1& D2 1N4148 Diode 3

D3 & D4 INFRARED LEDs 2

R1 33 Ohm, ¼ Watt 1

R2 820 Ohm, ¼ Watt 1

R3 0.39 Ohm, ¼ Watt 1

C1 220µ F/25V Electrolytic Capacitors 1

C2,C3 0.1µ F Ceramic Disc Capacitors 2

X1 Crystal 1

RL1 12 V, 200 Ohm DPDT Relay 1

S1 Switch 1

S1

T2

C3

C2

Infra-RedLEDs

R2

R1

T1

2

3

SignalDiodes R3

C1

+Vcc

X1

IC1

20 1

18

15

19



The Infra Red Transmitter is made very simple by employing the dedicated & commercially

available IC1. Here the IC1 is used in flash mode by connecting Transmission Mode Pin 1 to

+Vcc, and thus reduces average current consumption to 6.5 mA. In this mode minimum and

maximum transmission times are 2.1 milliseconds and 3.6 milliseconds respectively and the

duty cycle is 0.7%.

Since the Circuit is intended to send only one signal code, IC1 is configured for address one

[refer the table in IC description] by making all the Address Input pins, Code pins to zero or

ground. As soon the switch S1 is switched ON, the circuit gets its working voltage of 9 Volts

through pin-20. Inside the IC, it creates the address 1 as a command code and sent to the

output pin-19.

This command signal output from the IC1 is given through a resistor R1 to the base of the

Transistor T1. The output from this transistor T1 is fed to the base of another Transistor T2.

These two transistors amplify the command signal to the sufficient level and then drive the IR

LEDs. The Collector of both the transistors is connected to the pair of Infra Red LEDs. When

the transistor T2 goes to saturation region, that means starts conducting, the current will flow

through the two series IR LEDs. Thus they illuminate for that period and gets off. This

process continues as per the switch S1 is pushed ON and the pulses will be sent through IR

LEDs continues. Thus the command signal is transmitted to IR receiver successfully.

2.7 IR Receiver, Driver & Circuit Breaker:

The ‘packets’ of infra-red light transmitted from the IR Transmitter of the user remote control

are received on a sensor module which is sensitive to infra-red light. Next, the signal is

converted back into electrical pulses by a 36 KHz receiver and an associated detector. And

that electrical pulse is fed to driver circuit, which in result supply trigger pulse to Schmitt

Trigger circuit. The circuit components are explained as:



IR RECEIVER EYE: An IR Receiver Eye is a module, which is encapsulated with Photo

Transistor whose semiconductor junction is mounted beneath an optical lens. It is normally

used in its open base configuration and act as a light-to-voltage converter. The base is open;

the value of the reverse current across collector and emitter will depend on the amount of

illumination on the base face. In dark conditions it is near zero and under bright light it is tens

or hundreds of mA.


This circuit activates the relay whenever there is a presence of Infra Red Rays. The working

principle of this module is very simple:

Power Supply: The mains voltage is step-down to 6V using a transformer. This secondary 6V

is rectified using full-wave rectifier, which is composed by D1 & D2 diodes. This is further

filtered using electrolytic capacitor C2 and fed to regulator IC1. This three-terminal IC

stabilizes the input and gives out the constant +5V as working voltage for the circuit.

IR Receiver : The IR Sensor Module has 3 terminals: signal input, supply pin and the ground

pin. This module works on regulated +5Votls, and exceeding this limit may cause the damage

of it. So, this Sensor is given Vcc through a biasing resistor R1 and grounded pin is given to

negative terminal of the supply. Whenever the Infra Red rays falls on this Sensors eye [that

black mole on Sensor] it produces varying signal voltages at output pin. This is given to

amplifier stage built by an PNP transistor TR1 through an current limiting resistor R2. The

output of this amplifier is fed to a buffer situated in IC2. This buffer or converter enhances

the current capacity of the signal and send to driver stage. The signal output is monitored by

observing the glowing indicator LED D4.

Driver & Circuit Breaker: The driver is built around TR1 and a low-impedance relay. The

signal diode D3 is there to prevent the back e.m.f produced by the switching action of the

relay. When user doesnot press any key, the receiver does not receive any IR rays from the

opposite end, and hence No signals to TR2 base.

As this E-Power Supply unit’s Receiver senses interrupt of IR Rays from the opposite IR

Transmitter, it alerts driver section. The IR signal from the buffer enters the base of TR2, it



undergoes saturation and activates the relay RL1. Since, relay RL1’s N/O [Normally Open]

pins are connected to Schmitt Trigger Circuit.

Note: The circuit is fully stabilized from the false triggering and other interferences. This is

achieved by using capacitors at proper places. As this is an Unlatch Circuit the relay actuates

only when the IR beams are present at the ‘eye’ of the sensor module. And releases the

switching as-soon-as there are no IR radiations.

CHAPTER-3

CONSTRUCTION GUIDELINES FOR INFRA RED TRANS-RECEIVER

3.1 Introduction



The IR remote control circuit is very simple in design. Basically it consists of a pair of IR

transmitter and receiver. To use it as a ‘remote controlling’ device, the transmitter and the

receiver must be positioned facing each other with the maximum tolerance of 60˚. When the

light beam which is being transmitted by IR transmitter towards the IR receiver falls on the

Infra-Red sensor of the receiving unit, IR light sensor senses this special invisible light, and

this variation in the intensity of IR light beam is immediately sensed by the IR sensor located

at the IR receiver unit, and in turn it activates a electromechanical relay.

The range of the unit, i.e. the maximum distance between transmitter and receiver is almost

about 5 to 7 feet. No lenses are used and no adjustment of sensitivity is required just point the

transmitter in the general direction of the receiver and you are in business. If greater range is

desired, the transmitter current can be increased.

When the unit is fully assembled the photo transistor must be kept about 20mm from the light

beam entry hole of the box. This does not reduce the range of the unit, but is intended to

prevent direct light from falling on the photo transistor & thus reducing the sensitivity. We

still found that when used outdoors, strong sunlight reduces the range of the unit, but this can

be readily cured by fitting a smalt tube of non-reflective material 20-30mm in diameter of

about 50mm long in front of the receiver.

It was practical observed that light from flourescent lamps working with electronics ballasts

slightly interferes with the circuit. This is because the electronic ballasts working on high

frequency produce a lot of harmonics while lie within the range of signal frequency of the

receiver circuit and act as a source of sustained noise. In that case the sensor module should

be properly oriented to minimise the effect.

Alternatively the sensor should be covered with a dark red glass plate. This will slightly

reduce the range light from other sources like flourescent lamps working on ordinary chokes;

incandescent lamps and sunlight do not have any effect on the circuit.

ADJUSTMENTS: Keep the receiver about 3 meters away from the transmitter and press S1.

If led on receiver section, does not glow adjust the sensors line-of-sight alignment and



increase the range. The transmitter need supply 9V battery. The current consumption of

transmitter is moderate.

3.2 TESTING

When the transmitter & the receiver are completely assembled, the combination can then be

tested as follows:

Switch the Receiver ON.

2. When the transmitter is OFF the Relay should

turnON.

3. Now switch the transmitter ON & aim it at the receiver the Relay

should turn off. Finally, check that the Relay is activated whenever

the beam is interrupted.

Note :

1. The IR LED & photo transistor both of them have their sensitive area on their tip and

their anode lead is longer than the cathode.

2. Because the information is passed as light beam, if any opaque object comes in the path between the remote control transmitter and the receiver, the signal will not be

able to reach the receiver. But this doesn’t intended that the transmitter and receiver

need to be pointed directly at each other. The receiver can be anywhere in the active

area of the transmitter IR beam, only requirement is there should not be any opaque

object in the line of sight t create a blind area.

3. Battery supplied with this kit is only for general use. For using this unit regularly a9V DC Adaptor is suggested with a battery backup for full protection, even in case

of power failure.



3.3 Buffer, Driver & Switching Module:

When the user programs the schedule for the automation using GUI [Graphical User

Interface] software, it actually sends 5-bit control signals to the circuit. The present circuit provides interfacing with the printer port of the Personal Computer and the controlling

circuitry. This circuit takes the 5-bit control signal, isolates the PC from this circuitry, boosts

control signals for required level and finally fed to the driver section to actuate relay. These

five relays in turn sends RC5 coded commands with respect to their relay position.

First the components used in this Module are discussed and then the actual circuit is dealt in

detail.

Fig.3.1 Buffer Circuit

1

2

6

3

16

5

15

4

14

10

11

12

13

7

Vcc

Vss8 9

IC4050



HEX BUFFER / CONVERTER [NON-INVERTER] IC 4050: Buffers does not affect the

logical state of a digital signal (i.e. logic 1 input results into logic 1 output where as logic 0

input results into logic 0 output). Buffers are normally used to provide extra current drive at

the output, but can also be used to regularise the logic present at an interface. And Inverters

are used to complement the logical state (i.e. logic 1 input results into logic 0 output and vice

versa). Also Inverters are used to provide extra current drive and, like buffers, are used in

interfacing applications. This 16-pin DIL packaged IC 4050 acts as Buffer as-well-as a

Converter . The input signals may be of 2.5 to 5V digital TTL compatible or DC analogue the

IC gives 5V constant signal output. The IC acts as buffer and provides isolation to the main

circuit from varying input signals. The working voltage of IC is 4 to 16 Volts and

propagation delay is 30 nanoseconds. It consumes 0.01 mill Watt power with noise immunity

of 3.7 V and toggle speed of 3 Megahertz.

Fig.3.2 Driver Circuit

Vcc

116

2

3

4

5

6

7

8

11

12

14

15

13

10

9

IC ULN 2004



ULN 2004: Since the digital outputs of the some circuits cannot sink much current, they are

not capable of driving relays directly. So, high-voltage high-current Darlington arrays are

designed for interfacing low-level logic circuitry and multiple peripheral power loads. The

series ULN2000A/L ICs drive seven relays with continuous load current ratings to 600mA

for each input. At an appropriate duty cycle depending on ambient temperature and number

of drivers turned ON simultaneously, typical power loads totalling over 260W [400mA x 7,

95V] can be controlled. Typical loads include relays, solenoids, stepping motors, magnetic

print hammers, multiplexed LED and incandescent displays, and heaters. These Darlington

arrays are furnished in 16-pin dual in-line plastic packages (suffix A) and 16-lead surface-

mountable SOICs (suffix L). All devices are pinned with outputs opposite inputs to facilitate

ease of circuit board layout.

The input of ULN 2004 is TTL-compatible open-collector outputs. As each of these outputs

can sink a maximum collector current of 500 mA, miniature PCB relays can be easily driven.

No additional free-wheeling clamp diode is required to be connected across the relay since

each of the outputs has inbuilt free-wheeling diodes. The Series ULN20x4A/L features series

input resistors for operation directly from 6 to 15V CMOS or PMOS logic outputs.

1N4148 signal diode: Signal diodes are used to process information (electrical signals) in

circuits, so they are only required to pass small currents of up to 100mA. General

purpose signal diodes such as the 1N4148 are made from silicon and have a forward

voltage drop of 0.7V.



CIRCUIT DIAGRAM OF BUFFER, DRIVER & SWITCHING STAGE

Fig.3.3 Buffer Driver And Switching Stage

5

3

9

7

8

1

11

4

2

10

6

12

14

15

RL2

RL3

RL4

RL5

IC

1

IC

2

2

1

4

3

8

9

5

15

16

13

12

611

14

7

10

R1 TO

R5

D1 TOD5

+5

V

Gn

d

+12V

Commands

from PC

D6-D10

R6-R10

RL1

N/C

COM-1

N/C

COM-2

N/C

COM-3

N/C

COM-4

N/C

COM-5



Parts List

3.4 Voltage Regulation


The Hex Buffer/Inverter IC1’s working voltage of +5V is applied at pin-1 and five control

signals are applied at input pins 3, 5, 7, 9 & 11. Thus the signal supplying circuit [i.e. PC] is

isolated from this Buffer & Driver circuit. Further the grounding resistors R1 to R5 prevents

the abnormal voltage levels passing inside the IC1. The buffered outputs are acquired at pins

2, 4, 6, 10, & 12. Thus the varying input is further stabilized and fed to signal diodes [D1 to

D5]. As the load is inductive, there is a chance of producing back e.m.f. So to cope with this

back e.m.f, signal diodes are used. But this signal level is not strong enough to drive the lowimpedance relay. So, IC2 Darlington driver is used. Its working voltage is +12 V and only

five input/output pins are used. The output signal from the Darlington driver IC is strong

enough to actuate five relays.

These relays with +12V working voltage can be used to produce five command signals with

RC5 format. The N/O [Normally Open] contact of each relay produces one command signal

with the help of RC5 Transmitter Circuit. The five relays activation with their corresponding

command signal production is tabulated as below:

SEMICONDUCTORS

IC1 4050 HEX BUFFER/CONVERTER(NON-

INVERTER)

1

IC2 2004 DARLINGTON ARRY 1

RESISTORS

R1 to R5 220 Ohm ¼ Watt Carbon Resistors 5

R6 to R10 2.2 K Ohm ¼ Watt Carbon Resistors 5

DIODES

D1to D5 1N4148 SIGNAL Diodes 5

D6 to D10 Red Indicator LEDs 5

MISCELLANEOUS

RL1-RL5 12 V, 700 Ohm DPDT Reed Relays 5



RELAY COMMAND NUMBER COMMAND SIGNAL

RL1 COM-1 TURN LEFT

RL2 COM-2 TURN RIGHT

RL3 COM-3 MOVE BACKWARDRL4 COM-4 MOVE FORWARD

RL5 COM-5SWITCH ON/OFF THE

SUCKING DEVICE

Table.1: Relay Table

The circuit needs two different voltages, +5V & +12V, to work. These dual voltages are

supplied by this specially designed power supply.

The power supply, unsung hero of every electronic circuit, plays very important role in

smooth running of the connected circuit. The main object of this ‘power supply’ is, as the

name itself implies, to deliver the required amount of stabilized and pure power to the circuit.

Every typical power supply contains the following sections:

1. Step-down Transformer: The conventional supply, which is generally available to the

user, is 230V AC. It is necessary to step down the mains supply to the desired level. This is

achieved by using suitably rated step-down transformer. While designing the power supply, it

is necessary to go for little higher rating transformer than the required one. The reason for

this is, for proper working of the regulator IC (say KIA 7805) it needs at least 2.5V more than

the expected output voltage

2. Rectifier stage: Then the step-downed Alternating Current is converted into Direct

Current. This rectification is achieved by using passive components such as diodes. If the

power supply is designed for low voltage/current drawing loads/circuits (say +5V), it is

sufficient to employ full-wave rectifier with centre-tap transformer as a power source. While

choosing the diodes the PIV rating is taken into consideration.

3. Filter stage: But this rectified output contains some percentage of superimposed a.c.

ripples. So to filter these a.c. components filter stage is built around the rectifier stage. The

cheap, reliable, simple and effective filtering for low current drawing loads (say upto 50 mA)



is done by using shunt capacitors. This electrolytic capacitor has polarities, take care while

connecting the circuit.

4.Voltage Regulation: The filtered d.c. output is not stable. It varies in accordance with the

fluctuations in mains supply or varying load current. This variation of load current is

observed due to voltage drop in transformer windings, rectifier and filter circuit. These

variations in d.c. output voltage may cause inaccurate or erratic operation or even

malfunctioning of many electronic circuits. For example, the circuit boards which are

implanted by CMOS or TTL ICs.

Fig.3.4 voltage series

The stabilization of d.c. output is achieved by using the three terminal voltage regulator IC.

This regulator IC comes in two flavors: 78xx for positive voltage output and 79xx for

negative voltage output. For example 7805 gives +5V output and 7905 gives -5V stabilized

output. These regulator ICs have in-built short-circuit protection and auto-thermal cutout provisions. If the load current is very high the IC needs ‘heat sink’ to dissipate the internally

generated power.

3.5 Full Wave Regulator

1 2 3

KIA 78xx

Series



Circuit description:

A d.c. power supply which maintains the output voltage constant irrespective of a.c. mains

fluctuations or load variations is known as regulated d.c. power supply. It is also referred as

full-wave regulated power supply as it uses four diodes in bridge fashion with the

transformer. This laboratory power supply offers excellent line and load regulation and

output voltages of +5V & +12 V at output currents up to one amp.

Fig.3.5:Full Wave Regulator of +5V &+12V

230AC

X

1

C1

D21

C2C3

IC17812

D11

9V

C4

IC1780

5

+12V

+5V



1. Step-down Transformer: The transformer rating is 230V AC at Primary and 12-0-

12V, 1Ampers across secondary winding. This transformer has a capability to deliver a

current of 1Ampere, which is more than enough to drive any electronic circuit or varying

load. The 12VAC appearing across the secondary is the RMS value of the waveform and the

peak value would be 12 x 1.414 = 16.8 volts. This value limits our choice of rectifier diode as

1N4007, which is having PIV rating more than 16Volts.

2. Rectifier Stage: The two diodes D1 & D2 are connected across the secondary winding

of the transformer as a full-wave rectifier. During the positive half-cycle of secondary

voltage, the end A of the secondary winding becomes positive and end B negative. This

makes the diode D1 forward biased and diode D2 reverse biased. Therefore diode D1

conducts while diode D2 does not. During the negative half-cycle, end A of the secondary

winding becomes negative and end B positive. Therefore diode D2 conducts while diode D1

does not. Note that current across the centre tap terminal is in the same direction for both

half-cycles of input a.c. voltage. Therefore, pulsating d.c. is obtained at point ‘C’ with respect

to Ground.

3. Filter Stage: Here Capacitor C1 is used for filtering purpose and connected across the

rectifier output. It filters the a.c. components present in the rectified d.c. and gives steady d.c.

voltage. As the rectifier voltage increases, it charges the capacitor and also supplies current to

the load. When capacitor is charged to the peak value of the rectifier voltage, rectifier voltage

starts to decrease. As the next voltage peak immediately recharges the capacitor, the

discharge period is of very small duration. Due to this continuous charge-discharge-recharge

cycle very little ripple is observed in the filtered output. Moreover, output voltage is higher as

it remains substantially near the peak value of rectifier output voltage. This phenomenon is

also explained in other form as: the shunt capacitor offers a low reactance path to the a.c.

components of current and open circuit to d.c. component. During positive half cycle the

capacitor stores energy in the form of electrostatic field. During negative half cycle, the filter

capacitor releases stored energy to the load.



4. Voltage Regulation Stage: Across the point ‘D’ and Ground there is rectified and

filtered d.c. In the present circuit KIA 7812 three terminal voltage regulator IC is used to get

+12V and KIA 7805 voltage regulator IC is used to get +5V regulated d.c. output. In the

three terminals, pin 1 is input i.e., rectified & filtered d.c. is connected to this pin. Pin 2 iscommon pin and is grounded. The pin 3 gives the stabilized d.c. output to the load. The

circuit shows two more decoupling capacitors C2 & C3, which provides ground path to the

high frequency noise signals. Across the point ‘E’ and ‘F’ with respect to ground +5V &

+12V stabilized or regulated d.c output is measured, which can be connected to the required

circuit.

Note: While connecting the diodes and electrolytic capacitors the polarities must be taken

into consideration. The transformer’s primary winding deals with 230V mains, care should be

taken with it.



3.6 POWER SUPPLY UNIT

Description: The circuit needs two different voltages, +5V & +9V, to work. The +9Volts

is provided by power packt, which contains six alkaline batteries in series. The +5 voltage is

supplied by this specially designed power supply.

A d.c. power supply which maintains the output voltage constant irrespective of a.c. mains

fluctuations or load variations is known as regulated d.c. power supply. It is also referred as

full-wave regulated power supply as it uses two diodes in full wave fashion with centre tap

transformer.

1.Step-down Transformer : The transformer rating is 230V AC at Primary and 12-0-12V,

1Ampers across secondary winding. This transformer has a capability to deliver a current of

1Ampere, which is more than enough to drive any electronic circuit or varying load. The

12VAC appearing across the secondary is the RMS value of the waveform and the peak value

would be 12 x 1.414 = 16.8 volts. This value limits our choice of rectifier diode as 1N4007,which is having PIV rating more than 16Volts.



Power Supply Diagram:

+5V

B

230AC

X

1

0 V

IC 1

C1

D2221

C2C3

D1111

A

O

CD

Ground

E



2. Rectifier Stage: The two diodes D1 & D2 are connected across the secondary winding of

the transformer as a full-wave rectifier. During the positive half-cycle of secondary voltage,

the end A of the secondary winding becomes positive and end B negative. This makes the

diode D1 forward biased and diode D2 reverse biased. Therefore diode D1 conducts while

diode D2 does not. During the negative half-cycle, end A of the secondary winding becomes

negative and end B positive. Therefore diode D2 conducts while diode D1 does not. Note that

SEMICONDUCTORS

Fig.3.6:+5vfullwaveregulator Power Supply

IC1 7805 Regulator IC 1

D1,D2 1N4007 Rectifier Diodes 2

CAPACITORS

C1 1000 µf/25V Electrolytic 1

C2,C3 0.1µF Ceramic Disc type 2

MISCELLANEOUS

X1 230V AC Pri,12-0-12 1Amp Sec Transformer 1



current across the centre tap terminal is in the same direction for both half-cycles of input a.c.

voltage. Therefore, pulsating d.c. is obtained at point ‘C’ with respect to Ground.

3. Filter Stage: Here Capacitor C1 is used for filtering purpose and connected across the

rectifier output. It filters the a.c. components present in the rectified d.c. and gives steady d.c.

voltage. As the rectifier voltage increases, it charges the capacitor and also supplies current to

the load. When capacitor is charged to the peak value of the rectifier voltage, rectifier voltage

starts to decrease. As the next voltage peak immediately recharges the capacitor, the

discharge period is of very small duration. Due to this continuous charge-discharge-recharge

cycle very little ripple is observed in the filtered output. Moreover, output voltage is higher as

it remains substantially near the peak value of rectifier output voltage. This phenomenon is

also explained in other form as: the shunt capacitor offers a low reactance path to the a.c.

components of current and open circuit to d.c. component. During positive half cycle the

capacitor stores energy in the form of electrostatic field. During negative half cycle, the filter

capacitor releases stored energy to the load.

4. Voltage Regulation Stage: Across the point ‘D’ and Ground there is rectified and filtered

d.c. In the present circuit KIA 7805 voltage regulator IC is used to get +5V regulated d.c.

output. In the three terminals, pin 1 is input i.e., rectified & filtered d.c. is connected to this

pin. Pin 2 is common pin and is grounded. The pin 3 gives the stabilized d.c. output to the

load. The circuit shows two more decoupling capacitors C2 & C3, which provides ground

path to the high frequency noise signals. Across the point ‘E’ and ground +5V stabilized or

regulated d.c output is measured, which can be connected to the required circuit.





CHAPTER-4

PHERIPHERAL INTERFACE STANDARDS

4.1 Introduction:

The large variety of plug-ins, add-ons and ancillary equipment’s force the user to look a littlecarefully into the hardware and software aspects of interfacing various peripherals to a PC.

The open architecture of the IBMPC has helped its 62-pin I/O channel bus in becoming a

universally accepted interface standard for joining extra hardware to a PC.

A peripheral, in strict sense, is a piece of equipment which in itself is a separate entity and

gets attached to the PC through a specific connection protocol called Interface Standard.

The block diagram in Fig. 1 illustrates a typical scheme chosen for peripheral interface. Here

different sockets have been provided for each one of the peripherals, which are not



interchangeable among themselves. If one looks inside a PC, all these sockets originate from

printed circuit cards, which share a common bus, called I/O, channel bus, and sometimes PC

bus a name given to the set of signals available on 62-pin edge connectors on the PC

motherboard.

4.2 PHERIPHERAL INTERFACE:

The interface standards have evolved over a period of time depending upon the need of the

users and support from the originating manufacturer. The data transfer, by large, involves a

series of 8-bit bytes, or even wider, to be transferred over a set of physical wires or optical

fibers.

The data transfer may take place in bit serial, word serial or bit parallel word serial form. The

serial transfer requires a lesser number of physical interconnections as compared to the

parallel one, and the user is tempted to choose it for the sake of sheer simplicity. However,

the speed of data transfer is degraded by a factor of eight, which may be determining factor in

quite a few cases.

PC

CPU+

MEMORY

SERIALPORTPRINTERINTERFACE

FLOPPY

DISC DRIVECONTROLLER

PRINTER PLOTTER FDD

PRINTER

PLOTTER

MOUSE



Fig.4.1 Peripherals On A PC Bus

Use of RS 232 C is limited to a data transfer rate of 19,200 bits per second at a

distance of 15 meters. The RS 423/ RS 422 have evolved to remove some of the

shortcomings of the RS 232C.

RS 232 C signals: The signals of RS 232 C may be separated into five groups, as given

below:

PARALLEL SERIAL

GENERALPURPOSE

SPECIALPURPOSE

SPECIALPURPOSE

GENERALPURPOSE

SCSI1

50-PIN2.5MM

IEEE-4881

24-PIN

PRINTER(CENTRONICS)

36-PIN

PERTEC MAG.TAPE

PCB EDGE36-PINX 30.38MM

HARDDISC

DRIVE

FLOPPY DISCDRIVE

(34-PIN, 2.5MM)

RS 423A

RS422A

RS 232C25 PIN D

OR9-PIN D

PERIPHERAL INTERFACE



Fig 4.2: Peripheral Interface standards.

1) Ground Lines: Pin1 used as protective ground while pin 7 is used as signal ground.

Accordingly, pin 1 should be connected to the instrument body and pin 7 to the ground

line of the drivers/ receivers.

2) Transmit Signals or source: Signals on pins 2,4, and 20 are transmit data (TXD),

request to send (RTS), and data terminal ready (DTR) signals respectively. They are

sourced by the host computer called the Data Terminal Equipment (DTE).

3) Receive Signals: These are the receive data (RXD) on pin 3, clear to send (CTS) on pin

5, and data set ready on pin 6.

4) Modem control lines: The ring indicator on pin 22 and the carrier detect (CD) on pin 8

are used by the modem. The car detect signal is used by the computer to send a logon

message. Some other pins are used on synchronous modems and cater for data clock.These include data signaling rate selection pin 23 and transmitter signal element timing

on pin 24. Pin 15 serves the same function at the receiving end and pin 17 provides the

receive signal element timing.

5) Auxiliary or secondary control signals: These are the transmit data on pin 14, request

to send on pin 19, as transmit signals and receive data, clear to send and receive line

signal detect on pins 16, 13, 12 respectively.



Out of these 21 wires we may drop the ones relate d to synchronous modem as well as

those required to the secondary communication channel. The result is the shortened RS

232C, which only requires a 9-pin D connector with saving in back panel space.

The RS 232 C specifies +3 to +25 volts at the transmit end as space and –3 to –25 volts as

mark. At the receive end the levels are +5 to –25 volts for space and –5 to – 25 volts as mark.

These are quire special drivers.

The large voltage excursion is needed to combat noise level on the lines. It is. However,

possible to reduce this level if balanced mode of transmission is employed, and that’s exactly

what has been done in case RS 422. The mark and space levels have been reduced to + and –

200 millivolts with less critical grounding requirements. These can easily be handled by

lower supply voltages of +5 and –5 volts.

The RS 422 is not compatible to RS 232 C, and that compatibility has been provided in a

variant of RS 422, i.e. RS 423. The signals incase of RS 423 are +4 and –4 volts, which are

good enough for RS 232C. The RS 423 receivers are sensitive enough for +200mV signals

of the RS 422 as well and can, therefore, cater for RS 422 as well as RS 232C. The RS-422

and RS-423 can transfer data much faster than RS 232 C.

RS 449: RS 449 is a new standard which covers all the signals of RS 232C, with facility for

balanced output and input for some of the signals. It also has a facility for some extra signals.

The total number of signals is 46, which requires two connector- one of 37-pin and the other

of 9-pin type. The second channel is catered for by the 9-pin connector and may be dropped if

not needed. Inter-comparison of different types of serial interfaces has been shown in table 1.









PRINTED CIRCUIT BOARD

A printed circuit board is used to avoid most as all disadvantages of conventional

breadboards. They are small in size, efficient in performance. The only disadvantage is that

once the board is prepared no more changes are possible. It gives all the information on the

board. This involves the clear conception and details of the circuit before the actual layout

can be a board

Types Of Board:

The two most popular boards are the Single sided boards & Double sided board.

The single sided printed circuit boards are widely used for general-purpose application where

the cost is to be high and the layout is simple. However the circuit performance is also to be

considered in selecting the appropriate board. To jump over a conducting tracks jumper wires

are used. If the number of jumper wires the board is more than the double-sided printed

circuit boards are preferred. Even in the board the minimum for are liability the cost of

double sided printed circuit board without plated through holes is considered through contact

are made by soldering the component lead on both side.

Preperation Of Printed Circuit Board :

The drawing or art work as is the 1st steps on the preparation of printed circuit board. A

perfect drawing overcomes problem like inaccurate registration, broken annual rings and

critical spacing. A good method of artwork tabs is of the smallest details.

The pads are available in two varieties the self-adhesive and transfer type.

Self adhesive pads are supplied sticking on a backing paper .The pad is pulled from the

backing pad paper and positioned where required and then slightly pressed. If the position of

the pads is to be shifted it can be pulled off again placed in the position required and prepared

firmly again.

The term transfer pads are pointed on a thin adhesive film. The thin film is mounted on the

carrier strip on to the art work by rubbing with a wooden stick on the carrier strip while the



pad is exactly positioned on the art work case. The carrier strip can there after be lifted from

the art work leaving behind pad.

To prepare Printed Circuit Board following apparatus are required.

1. Copper Board.

2. Ferric Chloride.

3. Attaching stickers.

4. Drill machine, etc.

To design a Printed circuit board, we have to proceed as follows.

Draw the component layouts on a graph paper systematically i.e., for I.C base, place the IC

on graph paper and mark it. If more ICs are present draw the other too keeping an adequate

gap between the two ICs. Gap should be selected taking into the account of the other

components, which also have to be connected. The layout should be such that there must not

be jumpers, similarly positive and negative power supply lines should be kept apart sufficient

otherwise the two may create capacitance. Also the width of negative line should be thick

depending upon the current flowing through it. After completion of drawing layout on graph

paper the same drawing should be attached on copper plate by attaching stickers. Then the

copper plate should be dropped into ferric chloride solution, till a required copper portion is

dissolved. Now ferric chloride becomes greenish from bluish color. If even more time

required the plate should be allowed to be in the solution. Now the PCB will be in trace with

the attached stickers, now deep the copper plate in the fresh water so that all the impurities

left over copper plate are washed out. Now dry the copper plate, wipe with the help of

blotting paper and not with cloth. Then remove stickers with help of spirit petrol or nail

polish remover. Now we will get the desired layout of the circuit on the printed circuit board,

further drilling should be done to provide inspiration of components having more than 5000

rpm. The result will be the printed circuit board ready for connecting circuit.



CHAPTER- 5

GENERAL COMPONENTS



CHAPTER-5

GENERAL COMPONENTS

5.1 Introduction

In many electronic circuit applications the resistance forms the basic part of the circuit. The

reason for inserting the resistance is to reduce current or to produce the desired voltage drop .

These components which offer value of resistance are known as resistors . Resistors may

have fixed value i.e., whose value cannot be changed and are known as fixed resistors . Such

of those resistors whose value can be changed or varied are known as variable resistors.

There are two types of resistors available. They are :

1. Carbon resistors .

2. Wire wound resistors .

Carbon resistors are used when the power dissipation is less than 2W because they are

smaller and cost less. Wire wound resistors are used where the power dissipation is more than

5W . In electronic equipments carbon resistors are widely used because of their smaller size .

All resistors have three main characteristics:(i) Its resistance R in ohms (from 1 ohm to many mega ohms ).

(ii) Power rating (from several 10 W to 0.1 W ) .

(iii) Tolerance (in percentage ) .

5.2:Resistor color coding:

The carbon resistors are small in size and are color coded to indicate their resistance value in

ohms. Different colors are used to indicate the numeric values . The dark colors represent

lower values and the lighter colors represent the higher values . The color code has been

standardized by the electronic industries association .

The color bands are printed at one end of the resistors and are read from the left to right. The

first color band closed to the edge indicates the first digit in the value of resistance .The

second band gives the second digit. The third band gives the number of zero’s after two digits



. The resulting number is the resistance in ohms . A fourth band indicates the tolerance i.e., to

indicate how accurate the resistance value is , the bands are shown in the figure 1.

Fig.5.1: Colour code for resistor with four bands

PRESET:

There are two general categories of variable resistors:

1. General purpose resistors.

2. Precision resistors.

The general purpose type can again be wire wound type and carbon type .These follows

either linear or logarithmic law. The precision type are always wire wound and follow a

linear law .The variable resistors can be broadly classified as potentiometer , rheostats ,

presets and decade resistance boxes.

1St Color BandBlack0Brown1Red2Orange3Yellow4Green5Blue6Vio

let7Gray8White9

2nd Color BandBlack0Brown1Red2Orange3Yellow4Green5Blue6Violet

7Gray8White9

3rd Color BandMultiplyBySilver0.01Gold0.1Black1Brown10Red100Orange1,000Yellow10,000Green100,0

00Blue1,00,000

4th Color Band[Tolerance]Red±2%Gol

d±5%Silver±10%NoColor±20%



The general purpose wire wound potentiometers are available in 1, 2, 3 and 4 watts. The

usual tolerances ratings 10 % and 20% are available. The widely used potentiometers are of

the standard diameters 19mm, 31mm, and 44mm. The temperature coefficient depends on the

wire used and on the resistors values. The resolution of these wire wound resistors is proper

than carbon resistors because the wiper has to move from one winding to the other, where as

in carbon potentiometers it is continuous. These resistors are highly linear, the linearity

falling with 1%.

5.3 CAPACITORS:

Devices which can store electronic charge are called capacitors. Capacitance can be

understood as the ability of a dielectric to store electric charges. Its unit is Farad, named after

the Michael Faraday. The capacitors are named according to the dielectric used. Most

common ones are air, paper, and mica, ceramic and electrolytic capacitors.

Physically a capacitor has conducting plates separated by an insulator or the dielectric. The

plates of the capacitor have opposite charge, this gives rise to an electric field .In capacitor

the electric field is concentrated in the dielectric between the plates.

Like resistors, capacitors are also crucial to the correct working of nearly every electronic

circuit and provide us with a means of storing electrical energy in the form of an electric

field. Capacitors have numerous applications including storage capacitors in power supplies,

coupling of A.C. signals between the stages of an amplifier, and decoupling power supply

rails so that, As far as A.C. signal components are concerned, the supply rails are

indistinguishable from zero volts.

5.3.1types Of Capacitors:

Ceramic Capacitors :

The Ceramic Capacitors use ceramic dielectric with thin film as electrodes bonded to the

ceramic .these capacitors are available as low permittivity, medium permittivity and high

permittivity types .The ceramic is used is generally thick because they cannot with stand



high potential gradients .The leads are soldered to metal electrodes and the entire assembly is

enclosed in a ceramic or epoxy molded cases. Capacitors are available as tubular ,disk,

monolithic and barrier type.

Disc Capacitors :In the disk form, silver is fired on to both sides of the ceramic to form the conductor plates.

The sheets are then baked and cut to the appropriate shape and size & attached by pressure

contact and soldering . These have high capacitance per unit volume and are very

economical. The disks are lacquered or encapsulated in plastic or Phenolic molding. Round

disk are used at high voltages the capacitance of values upto 0.01F can be obtained. They

have tolerance of +20% or –20%. In general these capacitors have voltage ratings upto 750 V

d.c.

Electrolytic Capacitors :

These capacitors derive the name from electrolyte which is used as a medium to produce high

dielectric constants. These capacitors have low value for large capacitances at low working

voltages.

There are two types of Electrolytic capacitors:

1. Aluminum Electrolytic capacitors .

2. Tantalum electrolytic capacitors .

Electrolytic capacitors are used in circuits that have combination of D.C. voltage and A.C.

The D.C. voltage maintains the polarity . They are used as ‘ripple filter ‘ where large

capacitance are required at low cost in small space . They are also used as ‘biased capacitors ‘

and ‘decoupling capacitors ‘ and even as ‘coupling capacitors ‘ in R- C amplifier.



5.5 DIODES:

To ensure unidirectional flow of liquid we use mechanical valves in its path. By properly

arranging these valves in a system we get useful devices such as pumps and locomotives.

In the field of electronics too we have a valve called semiconductor diode (a counterpart

of thermionic valve) for controlling the flow of electric current in one direction. But we

use these diodes in circuits for limited purposes like converting AC to DC, by passing

EMF etc. a diode allows current to pass through it provided it is forward biased and the

biasing voltage is more than potential barrier (forward voltage drop) of the diode.

An uninterrupted power supply (UPS) is necessary for a main operated clock. This

facility is very useful in transistors and two in ones for recording or listening to news

programs. A relay can do this job with a battery backup. But the relay takes several

milliseconds before it makes contact. Moreover, it is costly and occupies space.

The same task can be achieved with a single diode. Just connect a germanium diode

DR50 (D1) as shown in fig 1.when the power is available form the eliminator or the

external power source, the gadget will use the power from it. As points A and B are at

same potential, the external power is remove, point B will be at higher potential that point

A i.e. D1 is forward biased and current flows from the battery. In no case the voltage of

the eliminator or the external power source should be less than the voltage of the battery.

Otherwise, the current will flow from the battery during mains operation also and the

battery will be drained quickly.



Fig.5.2 AUTOMATIC SWITCHOVER TO BATTERY



5.6 TRANSISTOR

Introduction

The transistor an entirely new type of electronic device is capable of achieving amplification

of weak signals in a fashion comparable and often superior to that realized by vacuum tubes.

Transistors are far smaller than vacuum tube, have no filaments and hence need no heating

power and may be operates in any position. They are mechanically strong, hence practically

unlimited life and can do some jobs better than vacuum tubes.

Invented in 1948 by J. Bardeen and W.H.Brattain of Bell Telephone Laboratories, a transistor

has now become the heart of most electronic appliance. Though transistor is only slightly

more the 45 years old, yet it is fast replacing vacuum tubes in almost all applications.

Transistor:

A transistor consists of two pn junction formed by sand witching either p-type or n-type

semiconductor between a pair of opposite type. Accordingly, there are two types of

transistors namely:

1) n-p-n transistor

2) p-n-p transistor

An n-p-n is composed of two n-type semiconductors separated a by thin section of p-type.

However, a p-n-p is formed by two p-section separated by a thin section of n-type.

1) These are two pn junctions. Therefore, a transistor may be regarded as a combination of

two diodes connected back to back.

2) There are 3 terminals, taken from each type of semiconductor.

3) The middle section is very thin layer. This is the most important factor in the functioning

of a transistor.



Origin of the name “transistor “: When new devices are invented, scientists often try to

device a name that will appropriately describe the device. A transistor has two pn junctions.

As the discussed later one junction is forward biased and the other is reversed biased.

The forward biased junction has low resistance path whereas the reverse biased junction has

low resistance path whereas the reverse biased junction has a high resistance path. The weak

signal is introduced in the low resistance circuit and output is taken from the high resistance

circuit. Therefore, a transistor transfers a signal from a low resistance to high resistance.

The prefix ‘tans’ means the signal transfer property of the device while ‘istor’ classifies it as

a solid element in the same general family with resistors.



Transistor Terminals:

A transistor (pnp or npn) has three sections of doped semiconductors. The section on one side

is the emitter and the section on the opposite side is the collector. The middle section is called

the base and forms two junctions between the emitter and collector.

1) Emitter: The section on one side that supplies charge carriers (electrons or holes) is

called the emitter. The emitter is always forward biased w.r.t base so that it can supply a

large number of majority carriers.

2) Collector: The section on the other side that collects the charge is called the collector.

The collector is always reversing biased. Its function is to remove charges from its

junction with the base.3) Base: The middle section, which forms to pn junctions between the emitter and collector,

is called bas. The base emitter junction is forward biased, allowing low resistance for the

emitter circuit. The base-collector junction is reversed biased and provides high resistance

in the collector circuit.

5.6.1 Charcteristics Of Transistors

Whenever we have to decide about the applications of a transistor certain question arises.

Some of these are – how much amplification gets from it? What is the highest frequency upto

which it can be used? How much power output could we get from it? And what should be the

values of different components used in the circuits? The answers to these entire questions lie

in the electrical properties of the transistor. These properties depend on the size,

manufacturing techniques and materials used in the manufacturer of transistor and are know

as characteristics. Transistor manufacturers give these characteristics in the data sheets

published by them.

(a) Current gain factor ‘alpha’ (α )

(b) Current gain factor ‘beta’ (β )

(c) Input resistance (Rin)

(d) Output resistance (Rout)

(e) Cut-off frequency (F α and Fβ )

(f) Leakage current (I ‘co)



(g) Maximum permissible limits:

1) Maximum collector voltage (Vceo)

2) Maximum emitter current (IC Max)

3) Maximum Power dissipation (P max)

5.6.2 Introduction To Integrated Circuits

All modern digital systems rely on the use of integrated circuits in which hundreds of

thousands of components are fabricated on a single chip of silicon. A relative measure of the

number of individual semiconductor devices within the chip is given by referring to its ‘scale

of integration’. The following terminology is commonly applied.

Scale of integration Abbreviation Number of logic gates

Small SSI 1 to 10

Medium MSI 10 to 100

Large LSI 100 to 1000

Very large VLSI 1000 to 10,000

Super large SLSI 10,000 to 100,000

Table.2: Types Of Integration Table

5.6.3 Encapsulation

The most common package used to encapsulate an integrated circuit, and that with which

most reader will be familiar, is the plastic dual-in-line (DIL) type. These are available with a

differing number of pins depending upon the complexity of the integrated circuit in question

and, in particular, the need to provide external connections to the device. Conventional logic

gates, for example, are often supplied in 14-pin or 16-pin DIL packages, whilst

microprocessors (and their more complex support devices) often require 40-pins or more.



5.6.4 Identification

When delving into an unfamiliar piece of equipment, one of the most common problems is

that of identifying the integrated circuit devices. To aid us in this task, manufacturers providesome coding on the upper surface of each chip. Such a coding generally includes the type

number of the chip (including some of the generic coding), the manufacturer’s name (usually

in the form of prefix letters), and the classification of the device (in the form of a prefix, infix

or suffix).

In many cases the coding is further extended to indicate such things as encapsulation, date of

manufacture, and any special characteristics of the device. Unfortunately, all of this

potentially useful information often leads to some considerable confusion due to

inconsistencies in marking from one manufacturer to the next!

5.6.5 Logic Families

The integrated circuit device on which modern digital circuitry depends belongs to one or

other of several ‘logic families’. The term simply describes the type of semiconductor

technology employed in the fabrication of the integrated circuit. This technology is

instrumental in determining the characteristics of a particular device. This, however, is quite

different from its characteristics, and encompasses such important criteria as supply voltage,

power dissipation, switching speed and immunity to noise.

The most popular logic families, at least as far as the more basic general purpose devices are

concerned, are complementary metal oxide semiconductor (CMOS) and transistor transistor

logic (TTL). TTL also has a number of sub-families including the popular low power

Schottky (LS-TTL) variants.

The most common range of conventional TTL logic devices is known as the ‘74’ series.

These devices are, not surprisingly, distinguished by the prefix number 74 in their coding.

Thus devices coded with the numbers 7400, 7408, 7432 and 74121 are all members of this

family which is often referred to as ‘Standard TTL’. Low power Schottky variants of these

devices are distinguished by an LS infix. The coding would then be 74LS00, 74LS08,

74LS32 and 74LS121.



5.7 POWER TRANSFORMER

The power supply, unsung hero of every electronic circuit, plays very important role in

smooth running of the connected circuit. The main object of this ‘power supply’ is, as the

name itself implies, to deliver the required amount of stabilized and pure power to the circuit.

Every typical power supply contains one transformer which steps-down the main voltage,

which is 230V AC, to the required level. The national standard for line frequency of the

mains supply is 50 Hz.

The transformer simply transfers 230 Voltage Alternating Current from primary side to

secondary side, without altering the voltage and frequency. The secondary voltage is depends

on the number of turns in secondary winding. This turns ration of primary to secondary

windings gives the rating of the transformer.

The transformers are classified on various parameters: based on the core – air core, ferrite

core, iron core etc.; based on the turns ration- step up, step down, isolation etc; based on the

tapping- centre tap or normal etc. As per the circuit requirements one can choose the correct

type of transformer.

The conventional supply, which is generally available to the user, is 230V AC. It is necessary

to step down the mains supply to the desired level. This is achieved by using suitably rated

step-down transformer. While designing the power supply it is necessary to go for higher

rating transformer than the required one. There are three reasons for this. First reason is,

across the secondary winding of the transformer there is no guarantee of getting the equal

voltages. Secondly, for proper working of the regulator IC it needs at least 2.5V more than

the expected output voltage. Last reason is to compensate the power loss offered by the

transformer windings and power supply circuit itse

If the power supply is designed for low voltage/current drawing loads/circuits (say +5V), it

is sufficient to employ full-wave rectifier with centre-tap transformer as a power source. The

transformer rating is 230V AC at Primary and 12-0-12V, 1Ampers across secondary winding.

This transformer has a capability to deliver a current of 1Ampere, which is more than enough

to drive any electronic circuit or varying load. The 12VAC appearing across the secondary is

the RMS value of the waveform and the peak value w



BIBLIOGRAPHY

• Electronic Communication Systems – George Kennedy

• Electronics in Industry - George M.Chute

• Principles of Electronics - V.K.Mehta

• www.electronicsforu.com

• www.howstuffworks.com

• Telecommunication Switching, Traffic and Networks –

J.E.Flood• The 8051 Microcontroller & Embedded Systems - Mazidi

• The Microcontroller Idea Book - Axelson

Documents

05-04-11 docuentation completed