project report on REMOTE SENSING THERMOMETER

A

Project Report

ON

“REMOTE SENSING THERMOMETER”

Submitted

in partial fulfillment

for the award of the Degree of

Bachelor of Technology

in Department of Electronics & Communication Engineering

Submitted to: Submitted by:

Ved Prakesh Yadav Vikas Yadav (10ESMEC094)

Asst. Prof. EIC Vijay Singh Yadav (10ESMEC093)

Sandeep Kumar (10ESMEC074)

Department of Electronics and Communication Engineering

SMEC Neemrana

Rajasthan Technical University, Kota

May, 2014

1

Department of Electronics & Communication Engineering St. Margaret Engineering College Neemrana, NH-8, Alwar, Rajasthan

CERTIFICATE

This is to certify that the Project titled “REMOTE SENSING THERMOMETER” submitted

by Mr. VIKAS YADAV, VIJAY SINGH YADAV, SANDEEP KUMAR in partial fulfillment

of the course work requirement for B.Tech. Program in the Department of Electronics &

Communication Engineering, St. Margaret Engineering College Neemrana have been

completed by him under my guidance and supervision. This Project Report has been found quite

satisfactory.

Head of Department Project Guide

Rakesh Chauhan Ved Prakesh YadavAsst. Prof. Asst. Prof.Department of ECE Department of EIC SMEC, Neemrana SMEC,Neemrana

2

ACKNOWLEDGEMENT

The satisfaction and euphoria that accompany the successful completion of any task would be

incomplete without the mentioning of the people whose constant guidance and encouragement

made it possible. We take pleasure in presenting before you, our project, which is result of

studied blend of both research and knowledge. We express our earnest gratitude to our internal

guide, Assistant Professor Mr. VED PRAKASH YADAV Department of EIC. Our project

guide and project lab assistant Mr. SURENDRA YADAV for his constant support,

encouragement and guidance. We are grateful for his cooperation and his valuable suggestions.

Vikas Yadav (10ESMEC094)

Vijay Singh Yadav (10ESMEC093)

Sandeep Kumar(10ESMEC074)

3

ABSTRACT

Ever since the invention of thermometer, various techniques have been developed and used to measure temperature of solid, liquid and gaseous matters. But none of these techniques could measure the temperature from a remote place, which sometimes becomes a necessity particularly when the object under testis in a dangerous or inaccessible area. Presented here is a remote sensing thermometer to measure the temperature from a remote place.

The temperature of the object under test is sensed by a temperature sensor convert the sensed voltage into equivalent frequency by using a voltage-to frequency (V-F) converter and send the same to the remote end through a transmitter. At the remote end, a frequency-to-voltage (F-V) converter is used to retrieve the original signal from the received frequency-encoded signal for display or control process.

It can measure from -55°C to 150°C. In a properly calibrated system, meter reading should increase or decrease@ 10mV/°C. Therefore a 0.250V reading on the mV meter indicates 25°C temperature.

4

INDEX

CONTENT……………………………………………………..PAGE NO.

CERTIFI CATE ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

CHAPTER 1: INTRODUCTION 8-10

CHAPTER 2: LITERATURE SURVEY 11-12

CHAPTER 3: LM35 TEMPERATURE SENSER 13-15

3.1 Introduction 14

3.2 How does LM35 work’s 14

3.3 Features 15

CHAPTER 4: KA331 IC 16-17

4.1 Introduction 16

4.2: KA331 Internal Structure 16

4.3: Features 17

CHAPTER 5: CA3140 (op-amp IC) 18-22

5.1 Introduction 18

5.2 Internal Structure 19

5.3 Circuit Description 19

5.3.1 Input Stage 20

5.3.2 Second Stage 20

5

5.3.3 Output Stage 20

5.3.4 Bias Circuit 21

5.4 Features 22

CHAPTER 6: MC2TE (OPTO-COUPLER) 23-27

6.1 Introduction 23

6.2 Electric isolation 24

6.3 Types of Opto-Isolators 26

6.4 Application 27

CHAPTER 7: ASK MODULATION 28-32

7.1 Introduction 28

7.2 ASK Transmitter and Receiver Module(433MHz) 29

7.3 Characteristics of ASK Tx/Rx Module 32

7.4 Features 32

CHAPTER 8: VOLTAGE REGULATOR IC 33-36

8.1: Introduction 33

8.1.1 7805 IC 33

8.1.2 7905 IC 34

CHAPTER 9: TRANSISTOR 37-38

9.1 Introduction 37

9.2 BC547 38

6

CHAPTER 10: DIODE 39-43

10.1 Introduction 39

10.2 V-I Characteristics 39

10.3 1N4007 (Rectifier Diode) 42

10.3.1 Features 43

CHAPTER 11: LED (LIGHT EMITTING DIODE) 44-47

11.1 Introduction 44

11.2 Internal Description of LED 44

11.3 Advantages of using LEDs 46

11.4 Disadvantage of using LEDs 47

CHAPTER 12: SWITCH 48-49

12.1 Introduction 48

CHAPTER 13: RESISTOR 50-54

13.1 Introduction 50

13.2 Electronic symbols and notation 51

13.3 Theory of operation 52

13.4 Resistor color coding 53

CHAPTER 14: CAPACITOR 55-59

14.1 Introduction 55

14.2 Theory of operation 57

14.2.1 Energy of electric field 58

14.2.2 Current-voltage relation 58

7

CHAPTER 15: TRANSFORMER 60-62

15.1 Introduction 60

15,2 Working Principle of Transformer 61

15.2.1 Basic Theory of Transformer 61

CHAPTER 16: PROJECT DESCRIPTION 63-72

16.1 Introduction 63

16.2 Component used 63

16.3 Circuit Diagram 65

16.4 Working 66

16.5 Construction 68

16.6 Adjustment for Transmitter Unit 70

16.7 Adjustment for Receiver Unit 71

CONCLUSION 73

REFERENCE 74

8

LIST OF FIGURES

SR. NO. NAME OF FIGURE…. …………………………………PAGE NO.

1.1 Block diagram of remote sensing thermometer 10

3.1 LM35 Temperature sensor 13

3.2 Basic Centigrade Temperature Sensor 14

3.3 Full-Range Centigrade Temperature Sensor 14

4.1 IC KA331 IC 16

4.2 Internal diagram of KA331 16

5.1 CA3140 (op-amp IC) 18

5.2 Internal Diagram of CA3140 IC 19

6.1 MC2TE IC 23

6.2 Electric isolation MC2TE IC 24

7.1 ASK Waveform 28

7.2 ASK Mathematical Notation 29

7.3 ASK Transmitter & Receiver Module 30

7.4 ASK Mathematical Notation Diagram 31

8.1 7805 IC 34

8.2 7905 IC 35

9.1 Transistor 37

9.2 BC547 Transistor 38

9

10.1 Diode Symbol 39

10.2 V-I Characteristics of Diode 41

10.3 1N4007 Rectifier Diode 42

11.1 Light Emitting Diode 44

11.2 Internal description of LED 45

11.3 Electronic Symbol of LED 46

12.1 Switches 48

13.1 Resistors 50

13.2 Electronic Symbols 51

13.3 Resistor color coding 53

14.1 Capacitors 55

14.2 Varieties of Capacitors 56

14.3 Theory of operation of capacitor 57

15.1 Transformer

60

15.2 Principle of Transformer 61

16.2 Transmitter Circuit 65

16.3 Receiver Circuit 66

16.4 An actual size, single side PCB for transmitter circuit 68

16.5 An actual size, single side PCB for Receiver circuit 69

16.6 Component layout for the Transmitter circuit 69

10

16.7 Component layout for Receiver circuit 70

11

LIST OF TABLES

SR. NO. NAME OF TABLE…….…………………………………PAGE NO.

6.1 Types of opto isolator 26

13.1 Standard Resistor Color Code 54

12

Chapter 1

INTRODUCTION

The temperature of the object under test is sensed by a temperature sensor IC LM 35 and

temperature is converted into voltage and convert this sensed voltage into equivalent frequency

by using a voltage-to frequency (V-F) converter and send the same to the remote end through a

transmitter. At the remote end, a frequency-to-voltage (F-V) converter is used to retrieve the

original signal from the received frequency-encoded signal for display the temperature in form of

voltage. Temperature is measured by calibrating the voltage. Remote sensing thermometer is

based on ASK modulation process, for this purpose ASK transmitter (433MHz) and ASK

receiver (433MHz) is used.

The transmitter power supply consists of step down transformer 230/9-0-9V(500mA). This

transformer step down 230V AC to 9V AC. Now the 9V AC is converted into 9V DC with the

help of bridge rectifier. After that 1000/25V capacitor is used to filter the ripples and then it

passes through voltage regulator 7805 and 7905 which regulates it to 5V and -5V respectively.

LED acts as the power indicator.

To derive power supply for the receiver circuit, the 230V AC mains is stepped down by trans-

former to deliver a secondary output of 9 V, 500 mA. The transformer output is rectified by a

full-wave rectifier filtered by capacitor and regulated by IC 7805.LED acts as the power

indicator.

Transmitter:

The temperature is sensed by a LM35. The resultant voltage developed at the output of the

sensor cannot be sent to a remote destination through normal wired path as its magnitude is

generally very low and would be highly attenuated during transit. One way to solve this problem

is to convert the sensed voltage into equivalent frequency by using a voltage-to frequency (V-F)

converter and send the same to the remote end through a transmitter.

13

Receiver:

At the remote end, a frequency-to-voltage (F-V) converter is used to retrieve the original signal

from the received frequency-encoded signal for display or control process. The circuit of the

transmitter unit. It comprises temperature sensor LM35 (IC1), two CA3140 operational

amplifiers (IC2 and IC3), voltage-to-frequency converter KA331 (IC4), opto-coupler MC2TE

(IC5), 433MHz ASK transmitter, regulators 7805 (IC6) and 7905 (IC7), and a few discrete

components. Temperature sensor IC1 develops a voltage at its output pin 2, which is equivalent

to the temperature being sensed. It can measure from -55°C to 150°C. LED1 connected to pin 3

of IC1 raises its output by a few hundred millivolts. Thus the voltage obtained at the output is the

sum of LED voltage and the sensed voltage. This voltage enhancement is required to transmit the

frequency-encoded signal for 0°C and below-0°C temperatures. The output from IC1 is fed to

input of the unity-gain inverting amplifier built around operational amplifier IC2. The output

signal from pin 6 of IC2 is further fed to V-F converter section comprising an integrator wired

around operational amplifier IC3 and V-F converter IC4. Integrator IC3 improves the V-F

converter’s linearity in conversion process. The frequency encoded temperature data is then sent

to transmitter module TX1 via opto-coupler IC5 and buffer transistor T1. Flickering of LED2

indicates ongoing V-F conversion.

Power Supply:

To derive power supply for the circuit, the 230V AC mains is stepped down by transformer X1

to deliver a secondary output of 9V-0-9V, 500 mA. The transformer output is rectified by a full-

wave rectifier comprising diodes D1 through D4, filtered by capacitors C1 and C2, and regulated

by ICs 7805 and 7905 (IC6 and IC7) for +5V and -5V, respectively. Capacitors C3 and C4

bypass ripples present in the regulated supply. Fig. 3 shows the receiver circuit. It comprises

NAND gate IC 7400 (IC9), F-V converter KA331 (IC10), regulator 7805 (IC8), 433MHz ASK

receiver module (RX1) and a few discrete components. RX1 is used to receive and demodulate

the ASK-modulated RF signal transmitted from the transmitter unit. The demodulated output is a

train of rectangular pulses as already explained in the transmitter section. Transistor T2 is used to

14

amplify and at the same time limit the amplitude of the pulse between 0 and 5 V. This TTL

compatible output is then fed to IC9.

The NAND gate helps to get perfectly rectangular wave shaped pulses. LED3 at pin 3 of IC9

flickers to indicate reception of the demodulated signal. The output of IC9 is also fed to F-V

converter IC10 through capacitor C8. It generates a voltage equivalent to the frequency of the

demodulated signal from receiver module RX1. To get the actual sensed signal voltage

developed by sensor LM35, the voltage output at pin 1 of IC10 has to be reduced by a voltage

equal to the reference voltage developed by LED1 of the transmitter unit. In order to do this, a

stable voltage is first developed across LED4. The required reference voltage is then achieved by

adjusting preset VR5. Preset VR5 is pre-adjusted during calibration to generate this reference

voltage. To derive power supply for the receiver circuit, the 230V AC mains is stepped down by

transformer X2 to deliver a secondary output of 9 V, 500 mA. The transformer output is

rectified by a full-wave rectifier comprising diodes D6 through D9, filtered by capacitor C11 and

regulated by IC 7805 (IC8). Capacitor C12 bypasses ripples present in the regulated supply.

LED5 acts as the power indicator and R24 limits the current through LED5.

Fig.1.1 Block diagram of remote sensing thermometer

15

Chapter 2

LITERATURE SURVEY

Literature survey 1.

Analysis and synthesis of Remote Sensing of Environment Temperature

Department of Geography, University of Western Ontario, London, ON, Canada N6A 5C2

Date of Conference: 15 Aug 2003Author(s): J.A Voogt and T.R Oke

Volume: 86, Issue 3

Page(s):370-384Product Type: Conference Publications

Abstract

Thermal remote sensing has been used over urban areas to assess the urban heat island, to

perform land cover classifications and as input for models of urban surface atmosphere

exchange. Here, we review the use of thermal remote sensing in the study of urban climates,

focusing primarily on the urban heat island effect and progress made towards answering the

methodological questions posed by Roth et al. [International Journal of Remote Sensing 10

(1989) 1699]. The review demonstrates that while some progress has been made, the thermal

remote sensing of urban areas has been slow to advance beyond qualitative description of

thermal patterns and simple correlations. Advances in the application of thermal remote sensing

to natural and agricultural surfaces suggest insight into possible methods to advance techniques

and capabilities over urban areas. Improvements in the spatial and spectral resolution of current

and next-generation satellite-based sensors, in more detailed surface representations of urban

surfaces and in the availability of low cost, high resolution portable thermal scanners are

16

expected to allow progress in the application of urban thermal remote sensing to the study of the

climate of urban areas.

Literature survey 2.

Analysis and synthesis of Remote Sensing Device

California Air Resources Board, Haagen-Smit Laboratory 9528 Telstar AvenueEl Monte, CA 91734

Date of Conference: 26 Aug 2004Author(s): Tom Austin, Sierra Research, Andrew D. Burnette, Eastern Research Group, Inc. Rob Klausmeier de la Torre Consulting, Inc.

ERG No:187.00.002.001Product Type: Conference Publications

Abstract

This report is intended to fulfill one objective (i.e., Task 2) of the Pilot Remote Sensing Study,

specifically, to “provide an organized synthesis and critical assessment of previous and current

studies on relevant remote sensing programs. The information obtained from this task would be

used to help answer the questions identified in Task 1, define research gaps, establish the need

for further studies, and resolve controversies, if any.” If possible, research gaps, controversies,

etc. would be resolved by performing the rest of the Pilot Remote Sensing Study.

Remote sensing measurements can be used to identify some of the vehicles with excessive

tailpipe emissions that should receive a Smog Check in the near future. Since whether a vehicle

can be classified as a “high emitter” or not depends upon the standards it was designed to meet, a

“high emitter” manufactured recently may actually emit much less than an older high emitter.

Below certain emission levels, RSD’s ability to distinguish between a “normal” emitter and a

“high” emitter is greatly diminished, so newer vehicles may be difficult for RSD to identify as

being high emitters.

17

Chapter 3

LM35 TEMPERATURE SENSER

3.1 Introduction

The LM35 is an integrated circuit sensor that can be used to measure temperature with an

electrical output proportional to the temperature (in oC). The LM35 thus has an advantage over

linear temperature sensors calibrated in ˚ Kelvin, as the user is not required to subtract a large

constant voltage from its output to obtain convenient Centigrade scaling.

Fig.3.1 LM35 Temperature sensor

3.2 How does LM35 work’s

It has an output voltage that is proportional to the Celsius temperature.

The scale factor is .01 V/degree centigrade.

18

The LM35 does not require any external calibration or trimming and maintain an

accuracy of +/- 0.4 degree centigrade. At room temperature. And +/- 0.8 degree

centigrade over a range of degree centigrade to +100 degree centigrade.

Another important characteristic of the LM35DZ is that it draws only 60 micro amps

from its supply and possesses a low self-heating capability. The Sensor Self-Heating

causes less than 0.1degree centigrade temperature rise in still air.

Fig.3.2 Basic Centigrade Temperature Sensor

Fig.3.3 Full-Range Centigrade Temperature Sensor

19

The LM35 datasheet specifies that this ICs are precision integrated-circuit temperature sensors,

whose output voltage is linearly proportional to the Celsius (Centigrade) temperature.

The LM35 thus has an advantage over linear temperature sensors calibrated in ˚ Kelvin, as the

user is not required to subtract a large constant voltage from its output to obtain convenient

Centigrade scaling.

3.3 Features:

It can measure temperature more accurately than a using a thermistor.

The sensor circuitry is sealed and not subject to oxidation.

The LM35 generates a higher output voltage than thermocouples and may not require that

the output voltage be amplified.

It has an output voltage that is proportional to the Celsius temperature.

The scale factor is .01V/oC.

Chapter 4

20

KA331 IC

4.1 Introduction

This voltage to frequency converter provides the output pulse train at a frequency precisely

proportional to the applied input voltage. The KA331 can operate at power supplies as low as

4.0V and be changed output frequency from 1Hz to 100KHz. It is ideally suited for use in simple

low-cost circuit for analog-to digital conversion, long term integration, linear frequency

modulation or demodulation, frequency-to-voltage conversion, and many other functions.

Fig.4.1 IC KA331

4.2 KA331 Internal Structure

Fig. 4.2 Internal diagram of KA331

This IC works in two modes:

21

Voltage to Frequency convertor

Frequency to Voltage convertor

4.3 Features

Guaranteed linearity: 0.01% max.

Low power dissipation: 15mW at 5V

Wide range of full scale frequency: 1Hz to 100KHz

Pulse output compatible with all logic forms.

Wide dynamic range: 100dB min at 10KHz full scale Frequency.

Applications:

Desktop Pc

Mobile Handsets

Graphics Card

Broadband Modem

`

Chapter 5

CA3140 (op-amp IC)

22

5.1 Introduction

CA3140 is the 4.5MHz BiMOS Operational Amplifier with MOSFET inputs and bipolar output.

This Op Amp combines the advantage of PMOS transistors and high voltage bipolar transistors.

The CA3140A and CA3140 are integrated circuit operational amplifiers that combine the

advantages of high voltage PMOS transistors with high voltage bipolar transistors on a single

monolithic chip. The CA3140A and CA3140 BiMOS operational amplifiers feature gate

protected MOSFET (PMOS) transistors in the input circuit to provide very high input

impedance, very low input current, and high speed performance.

The CA3140A and CA3140 operate at supply voltage from 4V to 36V (either single or dual

supply). These operational amplifiers are internally phase compensated to achieve stable

operation in unity gain follower operation, and additionally, have access terminal for a

supplementary external capacitor if additional frequency roll-off is desired. Terminals are also

provided for use in applications requiring input offset voltage nulling.

The use of PMOS field effect transistors in the input stage results in common mode input voltage

capability down to 0.5V below the negative supply terminal, an important attribute for single

supply applications. The output stage uses bipolar transistors and includes built-in protection

against damage from load terminal short circuiting to either supply rail or to ground.

Fig. 5.1 CA3140 (op-amp IC)

5.2 Internal Structure

23

Fig.5.2 Internal Diagram of CA3140

5.3 Circuit Description

As shown in the block diagram, the input terminals may be operated down to 0.5V below the

negative supply rail. Two class A amplifier stages provide the voltage gain, and a unique class

AB amplifier stage provides the current gain necessary to drive low-impedance loads. A biasing

circuit provides control of cascoded constant current flow circuits in the first and second stages.

The CA3140 includes an on chip phase compensating capacitor that is sufficient for the unity

gain voltage follower configuration.

5.3.1 Input Stage

24

The schematic diagram consists of a differential input stage using PMOS field-effect transistors

(Q9, Q10) working into a mirror pair of bipolar transistors (Q11, Q12) functioning as load

resistors together with resistors R2 through R5. The mirror pair transistors also function as a

differential-to-single-ended converter to provide base current drive to the second stage bipolar

transistor (Q13). Offset nulling, when desired, can be effected with a 10kΩ potentiometer

connected across Terminals 1 and 5 and with its slider arm connected to Terminal 4. Cascode-

connected bipolar transistors Q2, Q5 are the constant current source for the input stage. The base

biasing circuit for the constant current source is described subsequently. The small diodes D3,

D4, D5 provide gate oxide protection against high voltage transients, e.g., static electricity.

5.3.2 Second Stage

Most of the voltage gain in the CA3140 is provided by the second amplifier stage, consisting of

bipolar transistor Q13 and its cascode connected load resistance provided by bipolar transistors

Q3, Q4. On-chip phase compensation, sufficient for a majority of the applications is provided by

C1. Additional Miller-Effect compensation (roll off) can be accomplished, when desired, by

simply connecting a small capacitor between Terminals 1 and 8. Terminal 8 is also used to strobe

the output stage into quiescence. When terminal 8 is tied to the negative supply rail (Terminal 4)

by mechanical or electrical means, the output Terminal 6 swings low, i.e., approximately to

Terminal 4 potential.

5.3.3 Output Stage

The CA3140 Series circuits employ a broad band output stage that can sink loads to the negative

supply to complement the capability of the PMOS input stage when operating near the negative

rail. Quiescent current in the emitter-follower cascade circuit (Q17, Q18) is established by

transistors (Q14, Q15) whose base currents are “mirrored” to current flowing through diode D2

in the bias circuit section. When the CA3140 is operating such that output Terminal 6 is sourcing

current, transistor Q18 functions as an emitter-follower to source current from the V+ bus

(Terminal 7), via D7, R9, and R11. Under these conditions, the collector potential of Q13 is

sufficiently high to permit the necessary flow of base current to emitter follower Q17 which, in

25

turn, drives Q18. When the CA3140 is operating such that output Terminal 6 is sinking current to

the V- bus, transistor Q16 is the current sinking element. Transistor Q16 is mirror connected to

D6, R7, with current fed by way of Q21, R12, and Q20. Transistor Q20, in turn, is biased by

current flow through R13, zener D8, and R14. The dynamic current sink is controlled by voltage

level sensing. For purposes of explanation, it is assumed that output Terminal 6 is quiescently

established at the potential midpoint between the V+ and V- supply rails. When output current

sinking mode operation is required, the collector potential of transistor Q13 is driven below its

quiescent level, thereby causing Q17, Q18 to decrease the output voltage at Terminal 6. Thus,

the gate terminal of PMOS transistor Q21 is displaced toward the V- bus, thereby reducing the

channel resistance of Q21. As a consequence, there is an incremental increase in current flow

through Q20, R12, Q21, D6, R7, and the base of Q16. As a result, Q16 sinks current from

Terminal 6 in direct response to the incremental change in output voltage caused by Q18. This

sink current flows regardless of load; any excess current is internally supplied by the emitter-

follower Q18. Short circuit protection of the output circuit is provided by Q19, which is driven

into conduction by the high voltage drop developed across R11 under output short circuit

conditions. Under these conditions, the collector of Q19 diverts current from Q4 so as to reduce

the base current drive from Q17, thereby limiting current flow in Q18 to the short circuited load

terminal.

5.3.4 Bias Circuit

Quiescent current in all stages (except the dynamic current sink) of the CA3140 is dependent

upon bias current flow in R1. The function of the bias circuit is to establish and maintain

constant current flow through D1, Q6, Q8 and D2. D1 is a diode connected transistor mirror

connected in parallel with the base emitter junctions of Q1, Q2, and Q3. D1 may be considered

as a current sampling diode that senses the emitter current of Q6 and automatically adjusts the

base current of Q6 (via Q1) to maintain a constant current through Q6, Q8, D2. The base currents

in Q2, Q3 are also determined by constant current flow D1. Furthermore, current in diode

connected transistor Q2 establishes the currents in transistors Q14 and Q15.

5.4 Features:

26

Very High Input Impedance (ZIN) -1.5TΩ (Typ)

Very Low Input Current (Il) -10pA (Typ) at ±15V

Wide Common Mode Input Voltage Range (VlCR) - Can be Swung 0.5V Below

Negative Supply Voltage Rail.

Output Swing Complements Input Common Mode Range.

Chapter 6

27

MC2TE (Opto-coupler IC)

6.1 Introduction

The MCT2XXX series opto isolators consist of a gallium arsenide infrared emitting diode

driving a silicon phototransistor in a 6-pin dual in-line package. MCT2 and MCT2E are also

available in white package by specifying –M suffix, e.g. MCT2-M.

The frequency-encoded temperature data is then sent to transmitter module via opto-coupler IC.

Fig. 6.1 MC2TE

An opto-isolator, also called an opto coupler, photo coupler, or optical isolator, is a component

that transfers electrical signals between two isolated circuits by using light.  Opto-isolators

prevent high voltages from affecting the system receiving the signal. Commercially available

opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds

up to 10 kV/μs.A common type of opto-isolator consists of an LED and a phototransistor in the

same opaque package. Other types of source-sensor combinations include LED-photodiode,

LED-LASCR, and lamp-photo resistor pairs. Usually opto-isolators transfer digital (on-off)

signals, but some techniques allow them to be used with analog signals.

28

6.2 Electric isolation

Fig. 6.2 Electric isolation MC2TE IC

Planar (top) and silicone dome (bottom) layouts - cross-section through a standard dual in-line

package. Relative sizes of LED (red) and sensor (green) are exaggerated Electronic equipment

and signal and power transmission lines can be subjected to voltage surges induced

by lightning, electrostatic discharge, radio frequency transmissions, switching pulses (spikes)

and perturbations in power supply. Remote lightning strikes can induce surges up to 10 kV, one

thousand times more than the voltage limits of many electronic components. A circuit can also

incorporate high voltages by design, in which case it needs safe, reliable means of interfacing its

high-voltage components with low-voltage ones.

The main function of an opto-isolator is to block such high voltages and voltage transients, so

that a surge in one part of the system will not disrupt or destroy the other parts. Historically, this

function was delegated to isolation transformers, which use inductive coupling between galvanic

ally isolated input and output sides. Transformers and opto-isolators are the only two classes of

electronic devices that offer reinforced protection they protect both the equipment and the human

user operating this equipment. They contain a single physical isolation barrier, but provide

protection equivalent to double isolation.

29

An opto-isolator connects input and output sides with a beam of light modulated by input

current. It transforms useful input signal into light, sends it across the dielectric channel, captures

light on the output side and transforms it back into electric signal. Unlike transformers, which

pass energy in both directions with very low losses, opto-isolators are unidirectional

(see exceptions) and they cannot transmit power. Typical opto-isolators can only modulate the

flow of energy already present on the output side. Both transformers and opto-isolators are

effective in breaking ground loops, common in industrial and stage equipment, caused by high or

noisy return currents in ground wires.

The physical layout of an opto-isolator depends primarily on the desired isolation voltage.

Devices rated for less than a few kV have planar (or sandwich) construction. The sensordie is

mounted directly on the lead frame of its package (usually, a six-pin or a four-pin dual in-line

package). The sensor is covered with a sheet of glass or clear plastic, which is topped with the

LED die. The LED beam fires downward. The optical channel is made as thin as possible for a

desired breakdown voltage. For example, to be rated for short-term voltages of 3.75 kV and

transients of 1 kV/μs, the clear polyimide sheet in the Avago ASSR-300 series is only 0.08 mm

thick. Breakdown voltages of planar assemblies depend on the thickness of the transparent sheet

and the configuration of bonding wires that connect the dies with external pins. Real in-circuit

isolation voltage is further reduced by creepage over the PCB and the surface of the package.

Opto-isolators rated for 2.5 to 6 kV employ a different layout called silicone dome. Here, the

LED and sensor dies are placed on the opposite sides of the package; the LED fires into the

sensor horizontally. The LED, the sensor and the gap between them are encapsulated in a blob,

or dome, of transparent silicone. The dome acts as a reflector, retaining all stray light and

reflecting it onto the surface of the sensor, minimizing losses in a relatively long optical

channel. In double mold designs the space between the silicone blob ("inner mold") and the outer

shell ("outer mold") is filled with dark dielectric compound with a matched coefficient of

thermal expansion.

30

6.3 Types of opto-isolators

Device type Source of light Sensor type SpeedCurrent transfer

ratio

Resistive opto-

isolator

(Vactrol)

Incandescent light bulb

CdS or CdSe photoresistor  (LDR)

Very low

<100%Neon lamp Low

GaAs infrared LED Low

Diode opto-

isolatorGaAs infrared LED Silicon photodiode Highest 0.1–0.2%[22]

Transistor opto-

isolatorGaAs infrared LED

Bipolar silicon phototransistor Medium 2–120%[22]

Darlingtonphototransistor Medium 100–600%[22]

Opto-isolated SCR GaAs infrared LED Silicon-controlled rectifierLow to

medium>100%[23]

Opto-isolated triac GaAs infrared LED TRIACLow to

mediumVery high

Solid-state relayStack of GaAs infrared

LEDs

Stack of photodiodes driving

a pair of MOSFETs or an IGBT

Low to

high[note 7]

Practically

unlimited

Table6.1 Types of opto isolator

31

6.4 Application:

Power supply regulators. Digital logic inputs. Microprocessor inputs. Coupling between transmitter and receiver.

32

Chapter 7

ASK MODULATION

7.1 Introduction

Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as

variations in the amplitude of a carrier wave. In an ASK system ,binary symbol 1 is represented

by transmitting carrier wave of fixed amplitude and fixed frequency for the bit duration T

second.

Fig. 7.1 ASK Waveform

Three parameters specify a sinusoidal carrier wave: amplitude, frequency, and phase. An

individual parameter or combination of parameters may be modulated by a message to

communicate information. The most basic modulation schemes switch a single parameter

between two values to signal a binary 0 or binary 1.

In this project, construct and study a transmitter that switches the carrier wave's amplitude

between zero and a non-zero value. The term switching is also called keying (as in a telegraph

key), and so the transmitter in this project can be said to use binary amplitude shift

keying (binary ASK).

33

Bandpass channels possess a non-zero lower cutoff frequency, and therefore cannot transmit

a baseband signal. For example, the channel established between two voice-grade telephones

begins at 300 Hz and ends at 3,000 Hz. A digital signal (baseband type) must be shifted in

frequency so that its significant frequency components all exist within the 300 to 3,000 Hz range.

Frequency shifting may be accomplished by impressing the baseband signal onto a

sinusoidal carrier wave.

A sinusoidal carrier wave c(t)=Ac cos(2πfct+ϕc) possesses three parameters that can be switched

(or keyed) by a binary message signal: amplitude, frequency, and phase; the resulting digital

continuous wave modulation schemes are called ASK (amplitude shift keying), FSK (frequency

shift keying), and PSK (phase shift keying), respectively.

Fig. 7.2 ASK Mathematical Notation

7.2 ASK Transmitter and Receiver Module (433MHz)

We will be using ASK (Amplitude shifting keying) based Tx/Rx (Transmitter/Receiver) pair

operating at 433 mhz. The transmitter module accepts serial data at a maximum of xx baud rate.

It can be Directly interfaced with a microcontroller or can be used in remote control applications

with the help of encoder/decoder ICs.

34

Fig. 7.3 ASK Transmitter & Receiver Module

Any digital modulation scheme uses a finite number of distinct signals to represent digital data.

ASK uses a finite number of amplitudes, each assigned a unique pattern of binary digits. Usually,

each amplitude encodes an equal number of bits. Each pattern of bits forms the symbol that is

represented by the particular amplitude. The demodulator, which is designed specifically for the

symbol-set used by the modulator, determines the amplitude of the received signal and maps it

back to the symbol it represents, thus recovering the original data. Frequency and phase of the

carrier are kept constant.

35

Fig. 7.4 ASK Mathematical Notation Diagram

The simple circuit consists of a transmitter/receiver pair and functions as an automobile antitheft

alert system. The premise for the design is straightforward. You place the transmitter in a vehicle

parked outside your home and leave the receiver in your house. When the vehicle leaves the area,

this circuit sounds an alarm because the distance between the transmitter and receiver increases

and the received power level falls below a predetermined level (threshold). The circuit is, in

effect, warning of a potential auto theft. This circuit can also be applied to other applications for

security purposes, such as securing USB flash drives or monitoring a child's presence.

ASK transmitter system with a carrier frequency of 315MHz. IC1 is the ICM7555, a 555-based

timer that provides a bilevel oscillation signal. IC2, the MAX1472 ASK transmitter, has an

adjustable output power level of up to +10dBm. The encoder IC takes in parallel data which is to

be transmitted, package it into serial format and then transmits it with the help of the RF

transmitter module. At the receiver end the decoder IC receives the signal via the RF receiver

module, decodes the serial data and reproduce the original data in the parallel format. Now in

order to control say a dc motor, we require 2 bits of information (switching on/off) while we

need 4 bits of information to control 2 motors. HT12E and HT12D are 4 channel

encoder/decoder ICs directly compatible with the specified RF module.

36

7.3 Characteristics of ASK Tx/Rx Module:

7.4 Features:

Frequency Range 433MHz

Data Rate 8kbps

Supply voltage +5V.

Power supply and all input/output pins 0-5V.

Non operating case temperature -20 to +85.

Soldering temperature(10 seconds) 230.

37

Chapter 8

VOLTAGE REGULATOR IC

8.1 Introduction

Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output

voltages. They are also rated by the maximum current they can pass. Negative voltage regulators

are available, mainly for use in dual supplies. Most regulators include some automatic protection

from excessive current ('overload protection') and overheating ('thermal protection').

They include a hole for attaching a heat sink if necessary.

8.1.1 7805 IC:

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.

The 7805 provides circuit designer with an easy way to regulate DC voltage to 5v. Encapsulated

in a single chip/package(IC), the 7805 is a positive voltage DC regulator that has only 3

terminals. They are input voltage, Ground, Output voltage. Although the 7805 is primarily

designed for a fixed-voltage output (5v), it is indeed possible to use external components in order

to obtain Dc output voltages of : 5V, 6V, 8V, 9V, 10V, 12V, 15, 18V, 20V, 24V.

Note :- The input voltage must, of course, be greater that the required output voltage, so it can

regulated Downwards.

38

Fig. 8.1 7805 IC

Features:

Output Current up to 1 A

Output Voltages: 5, 6, 8, 9, 10, 12, 15, 18, 24 V

Thermal Overload Protection

Short-Circuit Protection

Output Transistor Safe Operating Area Protection

LM78L05 in micro SMD package.

Output voltage tolerances of +- 5% over the temp. range.

Output current of 100ma.

Internal thermal overload protection.

Internal short circuit current limit.

Available in plastic TO-92 and plastic SO-8 low profile package.

No external components.

8.1.2 7905 IC:

The LM79XX series of 3-terminal regulators is available with fixed output voltages of b5V,

b8V, b12V, and b15V. These devices need only one external component a compensation

capacitor at the output. The LM79XX series is packaged in the TO-220 power package and is

capable of supplying 1.5A of output current. These regulators employ internal current limiting

39

safe area protection and thermal shutdown for protection against virtually all overload

conditions. Low ground pin current of the LM79XX series allows output voltage to be easily

boosted above the present value with a resistor divider. The low quiescent current drain of these

devices with a specified maximum change with line and load ensures good regulation in the

voltage boosted mode.

Fig. 8.2 7905 IC

The LM7905 three terminal negative voltage regulator IC is available in TO-220 package and

with a fixed output voltage of -5 volt, making it useful in a wide range of applications. Each type

employs internal current limiting, thermal shut down and safe operating area protection, making

it essentially indestructible.

Features:

Thermal, short circuit and safe area protection

High ripple rejection

1.5A output current

4% tolerance on preset output voltage

Output Current in Excess of 1A

Output Voltages of -5V

40

Internal Thermal Overload Protection

Short Circuit Protection

Output Transistor Safe Operating Area Compensation 

Chapter 9

41

TRANSISTOR

9.1 Introduction

A transistor is a semiconductor device used to amplify and switch electronic signalsand electrical

power. It is composed of semiconductor material with at least three terminals for connection to

an external circuit. A voltage or current applied to one pair of the transistor's terminals changes

the current through another pair of terminals. Because the controlled (output) power can be

higher than the controlling (input) power, a transistor can amplify a signal. It is of two type NPN

and PNP, which are shown below in fig.

Fig. 9.1 Transistor

Transistors are commonly used as electronic switches, both for high-power applications such

as switched-mode power supplies and for low-power applications such as logic gates.

Advantages:

Less power consumption.

Small size and minimal weight, allowing the development of miniaturized electronic devices.

Low operating voltages compatible with batteries of only a few cells.

No warm-up period for cathode heaters required after power application.

42

Lower power dissipation and generally greater energy efficiency.

Higher reliability and greater physical ruggedness.

9.2 BC547

BC547 is an NPN bi-polar junction transistor. A transistor, stands for transfer of resistance, is

commonly used to amplify current. A small current at its base controls a larger current at

collector & emitter terminals.

Fig. 9.2 BC547 Transistor

BC547 is mainly used for amplification and switching purposes. It has a maximum current gain

of 800. Its equivalent transistors are BC548 and BC549.

The transistor terminals require a fixed DC voltage to operate in the desired region of its

characteristic curves. This is known as the biasing. For amplification applications, the transistor

is biased such that it is partly on for all input conditions. The input signal at base is amplified and

taken at the emitter. BC547 is used in common emitter configuration for amplifiers. The voltage

divider is the commonly used biasing mode. For switching applications, transistor is biased so

that it remains fully on if there is a signal at its base. In the absence of base signal, it gets

completely off.

Chapter 10

43

DIODE

10.1 Introduction

A diode is a two-terminal electronic component with asymmetric conductance, it has low (ideally

zero) resistance to current flow in one direction, and high (ideally infinite) resistance in the other.

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

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

(the reverse direction). Thus, the diode can be viewed as an electronic version of a check valve.

This unidirectional behavior is called rectification, and is used to convert alternating

current to direct current, including extraction of modulation from radio signals in radio receivers

—these diodes are forms of rectifiers

Fig. 10.1 Diode Symbol

10.2 V-I Characteristics

A semiconductor diode's behavior in a circuit is given by its current–voltage characteristic, or I–

V graph (see graph below). The shape of the curve is determined by the transport of charge

carriers through the so-called depletion layer or depletion region that exists at the p–n

junction between differing semiconductors. When a p–n junction is first created, conduction-

band (mobile) electrons from the N-doped region diffuse into the P-doped region where there is a

large population of holes (vacant places for electrons) with which the electrons "recombine".

When a mobile electron recombines with a hole, both hole and electron vanish, leaving behind

an immobile positively charged donor (dopant) on the N side and negatively charged acceptor

44

(dopant) on the P side. The region around the p–n junction becomes depleted of charge

carriers and thus behaves as an insulator.

However, the width of the depletion region (called the depletion width) cannot grow without

limit. For each electron–hole pair that recombines, a positively charged dopant ion is left behind

in the N-doped region, and a negatively charged dopant ion is left behind in the P-doped region.

As recombination proceeds more ions are created, an increasing electric field develops through

the depletion zone that acts to slow and then finally stop recombination. At this point, there is a

"built-in" potential across the depletion zone.

If an external voltage is placed across the diode with the same polarity as the built-in potential,

the depletion zone continues to act as an insulator, preventing any significant electric current

flow (unless electron–hole pairs are actively being created in the junction by, for instance, light;

see photodiode). This is the reverse bias phenomenon. However, if the polarity of the external

voltage opposes the built-in potential, recombination can once again proceed, resulting in

substantial electric current through the p–n junction (i.e. substantial numbers of electrons and

holes recombine at the junction). For silicon diodes, the built-in potential is approximately 0.7 V

(0.3 V for Germanium and 0.2 V for Schottky). Thus, if an external current passes through the

diode, the voltage across the diode increases logarithmic with the current such that the P-doped

region is positive with respect to the N-doped region and the diode is said to be "turned on" as it

has a forward bias. The diode is commonly said to have a forward "threshold" voltage, which it

conducts above and is cutoff.

A diode's I–V characteristic can be approximated by four regions of operation:

At very large reverse bias, beyond the peak inverse voltage or PIV, a process called

reverse breakdown occurs that causes a large increase in current (i.e., a large number of

electrons and holes are created at, and move away from the p–n junction) that usually

damages the device permanently. The avalanche diode is deliberately designed for use in

the avalanche region. In the Zener diode, the concept of PIV is not applicable. A Zener

diode contains a heavily doped p–n junction allowing electrons to tunnel from the

valence band of the p-type material to the conduction band of the n-type material, such

45

that the reverse voltage is "clamped" to a known value (called the Zener voltage), and

avalanche does not occur. Both devices, however, do have a limit to the maximum

current and power in the clamped reverse-voltage region. Also, following the end of

forward conduction in any diode, there is reverse current for a short time. The device

does not attain its full blocking capability until the reverse bias.

Fig. 10.2 V-I Characteristics of Diode

At reverse biases more positive than the PIV, has only a very small reverse saturation

current. In the reverse bias region for a normal P–N rectifier diode, the current through

the device is very low (in the µA range). However, this is temperature dependent, and at

sufficiently high temperatures, a substantial amount of reverse current can be observed

(mA or more).

46

With a small forward bias, where only a small forward current is conducted, the current–

voltage curve is exponential in accordance with the ideal diode equation. There is a

definite forward voltage at which the diode starts to conduct significantly. This is called

the knee voltage or cut-in voltage and is equal to the barrier potential of the p-n junction.

This is a feature of the exponential curve, and is seen more prominently on a current scale

more compressed than in the diagram here.

At larger forward currents the current-voltage curve starts to be dominated by the ohmic

resistance of the bulk semiconductor. The curve is no longer exponential, it is asymptotic

to a straight line whose slope is the bulk resistance. This region is particularly important

for power diodes. The effect can be modelled as an ideal diode in series with a fixed

resistor.

10.3 1N4007 (Rectifier Diode)

This is a simple, very common rectifier diode. Often used for reverse voltage protection, the

1N4007 is a staple for many power, DC to DC step up, and breadboard projects. 1N4007 is rated

for up to 1A/1000V

Fig. 10.3 1N4007 Rectifier Diode

47

10.3.1 Features:

Diffused Junction

High Current Capability and Low Forward Voltage Drop

Surge Overload Rating to 30A Peak

Low Reverse Leakage Current

48

Chapter 11

LED (LIGHT EMITTING DIODE)

11.1 Introduction

Fig.11.1 Light Emitting Diode

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps

in many devices and are increasingly used for other lighting. Appearing as practical electronic

components in 1962, early LEDs emitted low-intensity red light, but modern versions are

available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

11.2 Internal Description of LED

When a light-emitting diode is forward-biased (switched on), electrons are able to recombine

with electron holes within the device, releasing energy in the form of photons. This effect is

called electroluminescence and the color of the light (corresponding to the energy of the photon)

is determined by the energy gap of the semiconductor. An LED is often small in area (less than 1

mm2), and integrated optical components may be used to shape its radiation pattern.

49

Fig. 11.2 Internal description of LED

LEDs present many advantages over incandescent light sources including lower energy

consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.

LEDs powerful enough for room lighting are relatively expensive and require more precise

current and heat management than compact fluorescent lamp sources of comparable output.

50

Fig.11.3 Electronic Symbol of LED

Light-emitting diodes are used in applications as diverse as aviation lighting, automotive

lighting, advertising, general lighting, and traffic signals. LEDs have allowed new text, video

displays, and sensors to be developed, while their high switching rates are also useful in really be

advanced communications technology. Infrared LEDs are also used in the remote control units of

many commercial products including televisions, DVD players, and other domestic appliances.

11.3 Advantages of using LEDs

LEDs produce more light per watt. Than do incandescent bulbs; this is useful in battery

powered or Energy saving device.

LEDs can emit light of an intended color without the use of colour filters that traditional

lighting methods require. This is more efficient and can lower initial costs.

The solid package of LED can be designed to focus it’s light. Incandescent and florescent

sources often require an external reflector to collect light and direct it in a usable manner.

When use in application where dimming is require, LED’s do not change their colour tint

as the current passing through them is lowered, unlike incandescent lamps, which turn

yellow.

LEDs are Ideal for use in applications that are subject to frequent on-off cycling, unlike

fluorescent lamps that burn out more quickly when cycled frequently, or HID lamps that

require a long time before restarting.

LEDs being solid state components, are difficult to damage with external shock.

Fluorescent and incandescent bulbs are easily broken if dropped on the ground.

51

LEDs have extremely long life span. One manufacturer has calculated the ETTF

(Estimated Time To Failure) for their LEDs to be between 100,000 and 1,000,000 hour’s.

Fluorescent tubes typically are rated at about 30,000 hours, and incandescent light bulbs

at 1,000- 2,000 hours.

11.4 Disadvantages of using LEDs

LEDs are currently more expensive, price per lumen, on an initial capital cost basis, than

more conventional lighting technologies.

LEDs Performance largely depends on the ambient temperature of the operating

environment. Driving an LED hard in high ambient temperature may result in

overheating of the LED package. Eventually leading to device failure. Adequate heat-

sinking is required to maintain long life. This is especially important when considering

automotive, medical, and military applications where the device must operate over a large

range of temperature, and are required to have a low failure rate.

Voltage sensitivity.

52

Chapter 12

SWITCH

12.1 Introduction

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting

the current or diverting it from one conductor to another.

Fig.12.1 Switches

The momentary push-button switch is a type of biased switch. The most common type is a

"push-to-make" (or normally-open or NO) switch, which makes contact when the button is

pressed and breaks when the button is released. Each key of a computer keyboard, for example,

53

is a normally-open "push-to-make" switch. A "push-to-break" (or normally-closed or NC)

switch, on the other hand, breaks contact when the button is pressed and makes contact when it is

released. An example of a push-to-break switch is a button used to release a door held open by

an electromagnet. The interior lamp of a household refrigerator is controlled by a switch that is

held open when the door is closed.

The most familiar form of switch is a manually operated electromechanical device with one or

more sets of electrical contacts. Each set of contacts can be in one of two states: either 'closed'

meaning the contacts are touching and electricity can flow between them, or 'open', meaning the

contacts are separated and non-conducting.

A switch may be directly manipulated by a human as a control signal to a system, such as a

computer keyboard button, or to control power flow in a circuit, such as a light switch.

Automatically-operated switches can be used to control the motions of machines, for example, to

indicate that a garage door has reached its full open position or that a machine tool is in a

position to accept another work piece.

The common feature of all these usages is they refer to devices that control a binary state: they

are either on or off, closed or open, connected or not connected.

54

Chapter 13

RESISTOR

13.1 Introduction

A resistor is a passive two-terminal electrical component that implements electrical resistance as

a circuit element

Fig.13.1 Resistors

The current through a resistor is in direct proportion to the voltage across the resistor's terminals.

This relationship is represented by Ohm's law:

Where I is the current through the conductor in units of amperes, V is the potential difference

measured across the conductor in units of volts, and R is the resistance of the conductor in units

of ohms. The ratio of the voltage applied across a resistor's terminals to the intensity of current in

the circuit is called its resistance, and this can be assumed to be a constant (independent of the

voltage) for ordinary resistors working within their ratings.

55

Resistors are common elements of electrical networks and electronic circuits and are ubiquitous

in electronic equipment. Practical resistors can be made of various compounds and films, as well

as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome).

Resistors are also implemented within integrated circuits, particularly analog devices, and can

also be integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common commercial

resistors are manufactured over a range of more than nine orders of magnitude. When specifying

that resistance in an electronic design, the required precision of the resistance may require

attention to the manufacturing tolerance of the chosen resistor, according to its specific

application. The temperature coefficient of the resistance may also be of concern in some

precision applications. Practical resistors are also specified as having a maximum power rating

which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is

mainly of concern in power electronics applications. Resistors with higher power ratings are

physically larger and may require heat sinks. In a high-voltage circuit, attention must sometimes

be paid to the rated maximum working voltage of the resistor.

Practical resistors have a series inductance and a small parallel capacitance; these specifications

can be important in high-frequency applications. In a low-noise amplifier or pre-amp, the noise

characteristics of a resistor may be an issue. The unwanted inductance, excess noise, and

temperature coefficient are mainly dependent on the technology used in manufacturing the

resistor.

13.2 Electronic symbols and notation

The symbol used for a resistor in a circuit diagram varies from standard to standard and country

to country. Two typical symbols are as follows.

56

Fig.13.2 Electronic Symbols

13.3 Theory of operation

Ohm's law

The behavior of an ideal resistor is dictated by the relationship specified by Ohm's law:

Ohm's law states that the voltage (V) across a resistor is proportional to the current (I), where the

constant of proportionality is the resistance (R). Equivalently, Ohm's law can be stated:

57

This formulation states that the current (I) is proportional to the voltage (V) and inversely

proportional to the resistance (R).

Series and parallel resistors

In a series configuration, the current through all of the resistors is the same, but the voltage

across each resistor will be in proportion to its resistance. The potential difference (voltage) seen

across the network is the sum of those voltages, thus the total resistance can be found as the sum

of those resistances:

Resistors in a parallel configuration are each subject to the same potential difference (voltage),

however the currents through them add. The conductance of the resistors then add to determine

the conductance of the network. Thus the equivalent resistance (Req) of the network can be

computed:

13.4 Resistor color coding

Fig.13.3 Resistor color coding

58

To distinguish left from right there is a gap between the C and D bands.

Band A is first significant figure of component value (left side)

Band B is the second significant figure

Band C is the decimal multiplier

Band D if present, indicates tolerance of value in percent (no band means 20%)

For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow

in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that

the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.

The Standard Resistor Color Code

Table 13.1 Standard Resistor Color Code

59

Chapter 14

CAPACITOR

14.1 Introduction

A capacitor (originally known as condenser) is a passive two-terminal electrical component used

to store energy in an electric field. The forms of practical capacitors vary widely, but all contain

at least two electrical conductors separated by a dielectric (insulator); for example, one common

construction consists of metal foils separated by a thin layer of insulating film. Capacitors are

widely used as parts of electrical circuits in many common electrical devices.

Fig.14.1 Capacitors

Features: ceramic disc capacitor

Linear temperature coefficient of capacitance.

High Stability of capacitance.

Low loss at wide range of frequency.

60

Specification

Operating temp. range -25 to +85 degree centigrade.

Rated working voltage DC 50V, 500v.

Test Voltage 3 times of the rated voltage.

Capacitance within the tolerance and Q-Factor at 1 Mhz, 1+- 0.2 Vrms.25 degree

centigrade.

Insulation Resistance 10,000 M ohm min.

When there is a potential difference (voltage) across the conductors, a static electric field

develops across the dielectric, causing positive charge to collect on one plate and negative charge

on the other plate. Energy is stored in the electrostatic field.

An ideal capacitor is characterized by a single constant value, capacitance, measured in farads.

This is the ratio of the electric charge on each conductor to the potential difference between

them. The capacitance is greatest when there is a narrow separation between large areas of

conductor, hence capacitor conductors are often called "plates," referring to an early means of

construction. In practice, the dielectric between the plates passes a small amount of leakage

current and also has an electric field strength limit, resulting in a breakdown voltage, while the

conductors and leads introduce an undesired inductance and resistance.

Fig.14.2 Varieties of Capacitors

61

Practical capacitors are available commercially in many different forms. The type of internal

dielectric, the structure of the plates and the device packaging all strongly affect the

characteristics of the capacitor, and its applications.

Capacitors are widely used in electronic circuits for blocking direct current while allowing

alternating current to pass, in filter networks, for smoothing the output of power supplies, in the

resonant circuits that tune radios to particular frequencies, in electric power transmission systems

for stabilizing voltage and power flow, and for many other purposes.

14.2 Theory of operation

A capacitor consists of two conductors separated by a non-conductive region. The non-

conductive region is called the dielectric. In simpler terms, the dielectric is just an electrical

insulator. Examples of dielectric media are glass, air, paper, vacuum, and even a

semiconductor depletion region chemically identical to the conductors.

Fig.14.3 Theory of operation of capacitor

A capacitor is assumed to be self-contained and isolated, with no net electric charge and no

influence from any external electric field. The conductors thus hold equal and opposite charges

on their facing surfaces, and the dielectric develops an electric field. In SI units, a capacitance of

62

one farad means that one coulomb of charge on each conductor causes a voltage of one volt

across the device.

The capacitor is a reasonably general model for electric fields within electric circuits. An ideal

capacitor is wholly characterized by a constant capacitance C, defined as the ratio of charge ±Q

on each conductor to the voltage V between them.

Sometimes charge build-up affects the capacitor mechanically, causing its capacitance to vary. In

this case, capacitance is defined in terms of incremental changes:

14.2.1 Energy of electric field

Work must be done by an external influence to "move" charge between the conductors in a

capacitor. When the external influence is removed the charge separation persists in the electric

field and energy is stored to be released when the charge is allowed to return to its equilibrium

position. The work done in establishing the electric field, and hence the amount of energy stored,

is given by:

14.2.2 Current-voltage relation

The current i(t) through any component in an electric circuit is defined as the rate of flow of a

charge q(t) passing through it, but actual charges, electrons, cannot pass through the dielectric

layer of a capacitor, rather an electron accumulates on the negative plate for each one that leaves

the positive plate, resulting in an electron depletion and consequent positive charge on one

electrode that is equal and opposite to the accumulated negative charge on the other.

Thus the charge on the electrodes is equal to the integral of the current as well as proportional to

the voltage as discussed above. As with any anti-derivative, a constant of integration is added to

represent the initial voltage v (t0). This is the integral form of the capacitor equation,

63

Taking the derivative of this, and multiplying by C, yields the derivative form

The dual of the capacitor is the inductor, which stores energy in a magnetic field rather than an

electric field. Its current-voltage relation is obtained by exchanging current and voltage in the

capacitor equations and replacing C with the inductance L.

64

Chapter 15

TRANSFORMER

15.1 Introduction

A transformer is an electrical equipment that transfers energy by inductive coupling between its

winding circuits. A varying current in the primary winding creates a varying magnetic flux in the

transformer's core and thus a varying magnetic flux through the secondary winding. This varying

magnetic flux induces a varying  voltage in the secondary winding. Transformers can be used to

vary the relative voltage of circuits or isolate them, or both.

Electrical Power Transformer is a static device which transforms electrical energy from one

circuit to another without any direct electrical connection and with the help of mutual induction

between two windings. It transforms power from one circuit to another without changing its

frequency but may be in different voltage level. This is very short and simple definition of

transformer, as we will go through this portion of tutorial related to Electrical Power

Transformer, we will understand more clearly and deeply "what is transformer ?" and

basic theory of transformer.

Fig. 15.1 Transformer

65

15,2 Working Principle of Transformer

Fig. 15.2 Principle of Transformer

The working principle of transformer is very simple. It depends upon Faraday's law of

electromagnetic induction. Actually mutual induction between two or more winding is

responsible for transformation action in an electrical transformer.

Faraday's Laws of Electromagnetic Induction:

"Rate of change of flux linkage with respect to time is directly proportional to the induced EMF

in a conductor or coil"

15.2.1 Basic Theory of Transformer

Say you have one winding which is supplied by an alternating electrical source. The alternating

current through the winding produces a continually changing flux or alternating flux surrounds

the winding. If any other winding is brought nearer to the previous one, obviously some portion

of this flux will link with the second. As this flux is continually changing in its amplitude and

direction, there must be a change in flux linkage in the second winding or coil. According to

66

Faraday's law of electromagnetic induction, there must be an EMF induced in the second. If the

circuit of the latter winding is closed, there must be an electric current flows through it. This is

the simplest form of electrical power transformer and this is most basic of working principle of

transformer.

67

Chapter 16

PROJECT DESCRIPTION

16.1 Introduction

The temperature of the object under test is sensed by a temperature sensor IC LM 35 and

temperature is converted into voltage, and convert this sensed voltage into equivalent frequency

by using a voltage-to frequency (V-F) converter and send the same to the remote end through a

transmitter. At the remote end, a frequency-to-voltage (F-V) converter is used to retrieve the

original signal from the received frequency-encoded signal for display the temperature in form of

voltage. Temperature is measured by calibrating the voltage.

Remote sensing thermometer is based on ASK modulation process, for this purpose ASK

transmitter (433MHz) and ASK receiver(433MHz) is used.

The transmitter power supply consists of step down transformer 230/9-0-9V(500mA). This

transformer step down 230V AC to 9V AC. Now the 9V AC is converted into 9V DC with the

help of bridge rectifier. After that 1000/25V capacitor is used to filter the ripples and then it

passes through voltage regulator 7805 and 7905 which regulates it to 5V and -5V respectively.

LED acts as the power indicator.

To derive power supply for the receiver circuit, the 230V AC mains is stepped down by trans-

former to deliver a secondary output of 9 V, 500 mA. The transformer output is rectified by a

full-wave rectifier filtered by capacitor and regulated by IC 7805.LED acts as the power

indicator.

16.2 Component used:

IC1 - LM35 temperature sensor IC2, IC3 - CA3140 operational amplifier IC4, IC10 - KA331 voltage-to-frequency converter

68

IC5 - MC2TE opto-coupler IC6, IC8 - 7805, 5V regulator IC7 - 7905 -5V regulator IC9 - 7400 NAND gate T1, T2 - BC547 NPN transistor D1-D9 - 1N4007 rectifier diode LED1-LED5 - 5mm LED TX1 - 433MHz ASK transmitter module RX1 - 433MHz ASK receiver module Resistors :

R1 - 91-kilo-ohm R2-R4,R17 -100-kilo-ohm R5 - 2.2-kilo-ohm R6, R7, R9, R15, R18, R19, R22, R25, R26 - 10-kilo-ohm R8, R20 - 6.8-kilo-ohm R10, R14 - 1-kilo-ohm R11, R12, R13 - 3.3-kilo-ohm R16, R24 - 470-ohm R21 - 68-kilo-ohm R23 - 4.7-kilo-ohm VR1, VR2,VR4, VR5 - 10-kilo-ohm trim potmeter VR3 - 20-kilo-ohm trim potmeter

Capacitors: C1, C2, C11 - 1000μF, 25V electrolytic C3, C4, C12 - 0.1μF ceramic disk C5, C7, C9 - 0.01μF ceramic disk C6, C10 - 1μF, 16V electrolytic C8 - 1nF ceramic disk

Transformers: X1 - 230V AC primary to 9V-0-9V,500mA secondary transformer X2 - 230V AC primary to 9V, 500Ma secondary transformer

69

Fig.16.1 Block Diagram of Project

16.3 Circuit Diagram:

Fig.16.2 Transmitter Circuit

70

Fig.16.3 Receiver Circuit

16.4 Working:

The temperature of the object under test is sensed by a temperature sensor. The resultant voltage

developed at the output of the sensor cannot be sent to a remote destination through normal

wired path as its magnitude is generally very low and would be highly attenuated during transit.

One way to solve this problem is to convert the sensed voltage into equivalent frequency by

using a voltage-to frequency (V-F) converter and send the same to the remote end through a

transmitter. At the remote end, a frequency-to-voltage (F-V) converter is used to retrieve the

original signal from the received frequency-encoded signal for display or control process. Fig.

shows the circuit of the transmitter unit. It comprises temperature sensor LM35 (IC1), two

CA3140 operational amplifiers (IC2 and IC3), voltage-to-frequency converter KA331 (IC4),

opto-coupler MC2TE (IC5), 433MHz ASK transmitter, regulators 7805 (IC6) and 7905 (IC7),

and a few discrete components. Temperature sensor IC1 develops a voltage at its output pin 2,

which is equivalent to the temperature being sensed. It can measure from -55°C to 150°C. LED1

71

connected to pin 3 of IC1 raises its output by a few hundred millivolts. Thus the voltage obtained

at the output is the sum of LED voltage and the sensed voltage. This voltage enhancement is

required to transmit the frequency-encoded signal for 0°C and below-0°C temperatures. The

output from IC1 is fed to input of the unity-gain inverting amplifier built around operational

amplifier IC2. The output signal from pin 6 of IC2 is further fed to V-F converter section

comprising an integrator wired around operational amplifier IC3 and V-F converter IC4.

Integrator IC3 improves the V-F converter’s linearity in conversion process. The frequency

encoded temperature data is then sent to transmitter module TX1 via opto-coupler IC5 and buffer

transistor T1. Flickering of LED2 indicates ongoing V-F conversion.

To derive power supply for the circuit, the 230V AC mains is stepped down by transformer X1

to deliver a secondary output of 9V-0-9V, 500 mA. The transformer output is rectified by a full-

wave rectifier comprising diodes D1 through D4, filtered by capacitors C1 and C2, and regulated

by ICs 7805 and 7905 (IC6 and IC7) for +5V and -5V, respectively. Capacitors C3 and C4

bypass ripples present in the regulated supply. Fig. 3 shows the receiver circuit. It comprises

NAND gate IC 7400 (IC9), F-V converter KA331 (IC10), regulator 7805 (IC8), 433MHz ASK

receiver module (RX1) and a few discrete components. RX1 is used to receive and demodulate

the ASK-modulated RF signal transmitted from the transmitter unit. The demodulated output is a

train of rectangular pulses as already explained in the transmitter section. Transistor T2 is used to

amplify and at the same time limit the amplitude of the pulse between 0 and 5 V. This TTL

compatible output is then fed to IC9.

The NAND gate helps to get perfectly rectangular wave shaped pulses. LED3 at pin 3 of IC9

flickers to indicate reception of the demodulated signal. The output of IC9 is also fed to F-V

converter IC10 through capacitor C8. It generates a voltage equivalent to the frequency of the

demodulated signal from receiver module RX1. To get the actual sensed signal voltage

developed by sensor LM35, the voltage output at pin 1 of IC10 has to be reduced by a voltage

equal to the reference voltage developed by LED1 of the transmitter unit. In order to do this, a

stable voltage is first developed across LED4. The required reference voltage is then achieved by

adjusting preset VR5. Preset VR5 is pre-adjusted during calibration to generate this reference

72

voltage. To derive power supply for the receiver circuit, the 230V AC mains is stepped down by

transformer X2 to deliver a secondary output of 9 V, 500 mA. The transformer output is

rectified by a full-wave rectifier comprising diodes D6 through D9, filtered by capacitor C11 and

regulated by IC 7805 (IC8). Capacitor C12 bypasses ripples present in the regulated supply.

LED5 acts as the power indicator and R24 limits the current through LED5.

16.5 Construction

An actual-size, single-side PCB for the transmitter circuit is shown in Fig.16.4 and its component

layout in Fig.16.6. PCB for the receiver circuit is shown in Fig.16.5 and its component layout in

Fig.16.7. Assemble the circuits on PCBs to minimize time and assembly errors. Carefully

assemble the components and double-check for any overlooked error. Use IC base and, before

inserting the IC, check the supply voltage. Refer test points given in the table to check the circuit

for proper functioning.

For proper operation of the remote sensing thermometer, pre-adjustment of some components is

necessary.

Fig. 16.4 An actual size, single side PCB for transmitter circuit

73

Fig.16.5 An actual size, single side PCB for Receiver circuit

Fig.16.6 Component layout for the Transmitter circuit

74

Fig.16.7 Component layout for Receiver circuit

16.6 Adjustment for Transmitter Unit

Offset adjustment: Measure the voltage at TP3 with respect to ground by using a digital

voltmeter. Disconnect R1 and short the inverting input to ground. Switch on the ±5V supply.

Adjust preset VR2 to get 0V reading on the voltmeter.

Gain adjustment: Operational amplifier IC2 acts as a unity-gain amplifier. Reconnect resistor

R1. Connect pin 3 of IC1 directly to ground by shorting LED1. Keep sensor IC1 at a fixed

temperature. If room temperature is constant, keep the sensor free to sense the room temperature.

Measure output voltage of the sensor with a digital mV meter. Connect another digital mV meter

to read the output voltage at TP3. Adjust preset VR1 to get the same voltage reading on TP3 but

with negative polarity. If required, change the value of R1.

V-F gain adjustment: The V-F converter should generate frequency in hertz exactly equal to the

voltage input in millivolts. To get this, the gain of the V-F converter is to be adjusted. For this,

connect a frequency counter between test point TP5 and ground, and a digital mV meter between

75

TP3 and ground. Adjust VR3 to get a frequency in Hz that is equal to the meter reading in mV.

Sensor IC1 must be kept at a fixed temperature.

16.7 Adjustment for Receiver Unit

F-V gain adjustment: The F-V converter should generate output voltage in millivolts exactly

equal to the input frequency in Hz. To get this, the gain of the F-V converter is adjusted. To do

this, connect a frequency counter to pin 3 of IC9 and a digital millivolt meter at pin 1 of F-V

converter IC10. Switch on the transmitter and the receiver units. The frequency counter should

display the frequency transmitted from the transmitter unit. LED3 connected to output pin 3 of

the NAND gate indicates the incoming frequency signal. Adjust preset VR4 to get a mV reading

on the voltmeter that equals the frequency in Hz displayed on the frequency counter.

Adjustment of reference voltage: As already stated in the transmitter unit description, pin 3 of

temperature sensor IC1 is raised above the ground potential by the reference voltage developed

across LED1. At the receiver end, this voltage is to be subtracted to get the actual temperature-

sense voltage developed by sensor IC1. To do this, connect the positive lead of the millivolt

meter to pin 1 of F-V converter IC10 and negative lead of the meter to the rotary arm of preset

VR5. Now adjust preset VR5 to get actual temperature on the meter’s screen.

In a properly calibrated system, meter reading should increase or decrease @ 10mV/°C.

Therefore a 0.250V reading on the mV meter indicates 25°C temperature.

Final Project PCB

To make the final project PCB firstly at the transmitter side we take wooden board then we place

a transformer and transmitter PCB circuit on it. At the Receiver side we take a wooden board

then we place transformer and Receiver PCB circuit on it. These Tx/Rx transmit and receive

signal by ASK modulation, which have range up to 50ft. Working of project as described above

section.

76

Fig.16.8 Actual PCB of Transmitter Unit

Fig.16.9 Actual PCB of Receiver Unit

77

CONCLUSION

Ever since the invention of thermometer, various techniques have been developed and used to

measure temperature of solid, liquid and gaseous matters. But none of these techniques could

measure the temperature from a remote place, which sometimes becomes a necessity,

particularly when the object under test is in a dangerous or inaccessible area. Presented here is a

remote sensing thermometer to measure the temperature from a remote place.

The main scope of this project is to measure the temperature in industries where human can not

reach. This project will monitor the temperature from remote area and show the temperature at

receiver side in the form of voltage, with the help of calibration between temperature and

voltage. We measure the temperature of the machine in industries at critical area where

temperature of machine is not measured directly.

78

REFERENCE

http://www.ehow.com/about_4697090_what-do-optocouplers-do.html#ixzz30M7ZnkHm

http://www.efymag.com/previousissue.asp?month=June&year=2013&tot=1&id=12

“Analysis and synthesis of Remote Sensing of Environment Temperature”

Department of Geography, University of Western Ontario, London, ON, Canada N6A

5C2,Author(s) : J.A Voogt and T.R Oke Volume: 86, Issue 3,Page(s):370-384 Product

Type: Conference Publications

http://www12.fairchildsemi.com/ds/KA/KA331.pdf

http://multyremotes.com/DOWNLOAD/MCT2E.PDF

http://www.intersil.com/content/dam/Intersil/documents/ca31/ca3140a.pdf

“Analysis and synthesis of Remote Sensing Device”

California Air Resources Board, Haagen-Smit Laboratory 9528 Telstar Avenue

El Monte, CA 91734 Author(s) : Tom Austin, Sierra Research, Andrew D. Burnette,

Eastern Research Group, Inc. Rob Klausmeier de la Torre Consulting, Inc.

ERGNo.:187.00.002.001 Product Type: Conference Publications

http://en.wikipedia.org/wiki/Voltage_regulator

http://www.technologystudent.com/elec1/transis1.html

http://en.wikipedia.org/wiki/Transformer

http://letstalkaboutscience.wordpress.com/2012/05/28/how-resistors-and-capacitors-

work/

http://www.allaboutcircuits.com/vol_4/chpt_4/1.html

79