Mybtechproject-180429062425.pdf

PROTECTION OF TRANSFORMER FROM OVERLOADING USING MICROCONTRLLER BASED RELAY Main Project Report Submitted in partial fulfilment of the requirement for the award of the degree BACHELOR OF TECHNOLOGY IN ELECTRICAL AND ELECTRONICS ENGINEERING Submitted by ALLA JITHENDRA PRASAD (15U45A0203) Under the Esteemed Guidance of Mrs A.LAKSHMI DURGA,

M Tech

Assistant Professor, Dept. of EEE

DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

DADI INSTITUTE OF ENGINEERING & TECHNOLOGY (Approved by A.I.C.T.E., New Delhi & Affiliated to JNTU, Kakinada) (NAAC Accredited Institute) An ISO 9001:2008 Certified Institute, NH-5, GAVARAPALEM, ANAKAPALLE– 531002, Visakhapatnam, Andhra Pradesh, INDIA 2014-2018

DADI INSTITUTE OF ENGINEERING & TECHNOLOGY (Approved by A.I.C.T.E., New Delhi & Affiliated to JNTU, Kakinada) (NAAC Accredited Institute) An ISO 9001:2008 Certified Institute NH-5, GAVARAPALEM, ANAKAPALLE – 531002, Visakhapatnam, Andhra Pradesh, INDIA 2014-2018 DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING

CERTIFICATE This is to certify that the project work entitled “PROTECTION OF TRANSFORMER FROM OVERLOADING USING MICROCONTROLLER BASED RELAY” is the bonafide work by ALLA JITHENDRA PRASAD (15U45A0203) In partial fulfilment of the curriculum of 4th year 2nd semester ELECTRICAL AND ELECTRONICS ENGINEERING during the academic year 2017-2018.

INTERNAL GUIDE A LAKSHMI DURGA, M Tech Assistant Professor, Dept. of EEE

HEAD OF THE DEPARTMENTEEE PROF.R.V.S LAKSHMI KUMARI M.Tech (Ph.d)

EXTERNAL EXAMINER

ACKNOWLEDGEMENT We wish to express our deepest gratitude to A LAKSHMI DURGA Assistant Professor [EEE Dept.], for their wholehearted co-operation, unfailing inspiration and the guidance and constant encouragement. We consider it as our privilege to express our deepest gratitude to Prof. R.V.S LAKSHMI KUMARI HOD Department of Electrical and Electronics Engineering for her inspiring guidance and for allocating her valuable time for our project. We consider it our privilege to express our sincere and utmost thank to Dr.CH.PRABHAKARA RAO, principal [DIET], for providing us the opportunity to complete this project. We great solemnity and sincerity, we thank SRI.DADI RATNAKAR, Correspondent[DIET] for providing all the resources that greatly helped the project work in getting completed successfully. We sincerely thank all the numbers of Electrical and Electronics DEPT. For their continuous help in our pursuit. We thank all those who contributed directly or indirectly in successfully carrying out this work.

PROJECT ASSOCIATES G.OOHA

(15U45A0214)

C.V.S.ANIRUDH

(15U45A0210)

A.JITHENDRA PRASAD

(15U45A0203)

E.RUPENDRA KRISHNA

(15U45A0213)

A.TRINADH

(15U45A0201 )

DECLARATION We hereby declare that the industry oriented Mini project report entitled “PROTECTION

OF

TRANSFORMER

FROM

OVERLOODING

USING MICROCONTRLLER BASED RELAY” is entirely original and has been carried out in the presence of A LAKSHMI DURGA, Assistant Professor, DIET. This report is being submitted in partial fulfilment of degree of bachelor of technology in Electrical and Electronics Engineering IN Dadi Institute of Engineering & Technology, Anakapalle, Affiliated to Jawaharlal Nehru Technological University, Kakinada. We hereby state that this report is not submitted in any other college/University or published at any time before

PROJECT ASSOCIATES G.OOHA

(15U45A0214)

C.V.S.ANIRUDH

(15U45A0210)

A.JITHENDRA PRASAD

(15U45A0203)

E.RUPENDRA KRISHNA

(15U45A0213)

A.TRINADH

(15U45A0201)

LIST OF CONTENTS

1. CHAPTER: INTRODUCTION

1-7

1.1 Background

1

1.2 Problem statement

2

1.3 Objectives

3

1.4 Scope work

3

1.5 Literature review

4

2. CHAPTER: ELECTRICAL AND ELECTRONIC COMPONENTS 2.1 Microcontroller

8-44 8

2.1.1

Microcontroller Vs microprocessor

9

2.1.2

Advantages of microcontrollers

9

2.1.3

Types of 8051 microcontroller

9

2.1.4

The major manufacturers

10

2.2 Microcontroller Architectural Block Diagram

11

2.3 Atmel At89c51 Pin out and Description

11

2.3.1

Why we go for AT89C51

12

2.3.2

Features of AT89C51

12

2.3.3

PIN DIAGRAM

13

2.3.4

Memory in 8051 Microcontroller

17

2.3.5

ROM memory

18

2.3.6

RAM Memory

18

2.3.7

Bit Memory

19

2.3.8

Special Function Register (SFR) Memory

19

2.3.9

SFR Registers

20

2.3.10 Timers

21

2.3.11 11.0592MHZ CRYSTAL

24

i

2.4

Liquid Crystal Display

24

2.5 Relay

28

2.6 OP AMP LM358

29

2.7 Comparator ADC MCP3202

30

2.8 Relay Driver IC

31

2.9 Relay Driver IC Circuit

33

2.10 Driver Circuits

33

2.11 DC Relay Driver Circuit

36

2.12 AC Relay Driver Circuit

38

2.13

Relay Driver IC ULN2003

38

2.14

Buzzer

40

2.15

Energy meter

42

3 .HARDWARE DISCRIPTION

45-75

3.1 Hardware design

45

3.1.1 POWER SUPPLY

45

3.2 Hardware

46

3.2.1 Interfacing LCD to the microcontroller

47

3.2.2 Warning devices and relay control

49

3.2.3 The Oscillator

52

3.3 PCB design

52

3.3.1 PCB design using Software.

53

3.3.2 Soldering

54

3.3.3 Electrical Testing and Troubleshooting

54

3.4 Software description and coding

54

3.5 Software used

54

3.6 Tools used

54

3.7 Definition of Embedded System

54

3.8 Introduction to Keil Cx51 Complier

55

ii

3.8.2 Support for all 8051 Variants

56

3.8.3 Compiling with the Cx51 Compiler

57

3.8.4 Running Cx51 from the Command Prompt

58

3.8.5 Cx51 Output Files

59

3.8.6 Debugging

62

3.8.7 Complier Limits

62

3.9 About KEIL

63

3.10 Getting started and creating applications

64

3.10.1 Evaluation kits and production kits

64

3.10.2 Types of users

65

3.10.3 Evaluation users

65

3.11 New users

65

3.12 Experienced users

65

3.13 Development tools

66

3.14 Micro vision2 integrated development environment

66

3.15 About the environment

67

3.16 Menu commands, toolbars and shortcuts

67

3.17 C51 optimizing c cross compiler

67

3.18 Micro vision provides unique features

68

3.19 Advantages

69

3.20 Programming the chip

70

3.20.1 Intelligent Universal Programmer

70

3.20.2 Features of IUP

71

3.20.3 Universal pin driver--True universal programming

71

3.20.4 Unbeatable programming speed

71

3.20.5 Device insertion and contact checks

72

3.20.6 EPROM and Flash memory ID detection

72

3.21 Auto-Sensing and self-programming

72

3.22 Memory buffer auto Increment

72

3.22.1 User-selectable verify voltage, one- or two-pass verification

iii

73

4. CHAPTER

3.22.2 Easy operation--Get to work immediately

73

3.22.3 Project file save option

73

3.22.4 Non-DIP device support through versatile converters

73

APENDIX A: CIRCUIT DESIGN

75

APENDIX B: ASSEMBLY LANGUAGE

75

RESULT AND DISCUSSION

81

5. CHAPTER CONCLUSION AND FUTURE RECOMMENDATION

iv

82

LIST OF FIGURES Figure 2.1

Microcontroller Block Diagram

8

Figure 2.2

Microcontroller Architectural Block Diagram

11

Figure 2.3

PINOUT DIAGRAM

13

Figure 2.4

Reset Circuit

14

Figure 2.5

Clock Circuit.

15

Figure 2.6

Memory Block Diagram

17

Figure 2.7

Ram Memory

19

Figure 2.8

Special Function Registers

20

Figure 2.9

The structure of an LCD

25

Figure 2.10

LCD pin arrangement

26

Figure 2.11

Photodiode and LM358

29

Figure 2.12

ADC MCP3202

30

Figure 2.13

Relay Driver IC Circuit

32

Figure 2.14

Driver Circuit

34

Figure 2.15

DC Relay Driver IC Circuit

36

Figure 2.16

AC Relay Driver IC Circuit

37

Figure 2.17

Relay Driver IC ULN2003

38

Figure 2.18

Buzzer

39

Figure 2.19

Energy meter

42

Figure 2.20

Single Phase Electromechanical Induction Energy meter

43

Figure 3.1

POWER SUPPLY

45

Figure 3.2

Microcontroller-LCD interface

49

Figure 3.3

Microcontroller-LED connection

50

Figure 3.4

Microcontroller-relay interface

52

Figure 3.5

complete circuit PCB design

53

Figure3.6

intelligent universal programmer

69

Figure 3.7

CIRCUIT DESIGN

74

Figure4.1

Transformer Current analysis

79

v

LIST OF TABLES Table2.1 AMONG THE MAJOR MANUFACTURERS Table2.2 The individual bits of TMOD

10 22

Table2.3 Specify a mode of operation. Modes of operation

23

Table2.4 TCON (88h) SFR

23

Table2.5 LCD pins description

27

Table2.6 LCD Instructions

28

Table2.7 HD44780 instruction set

29

Table2.8 Comparator ADC MCP3202

31

Table2.9 Microcontroller Pin Usage

47

Table3.1 Development tools in KEIL Software

57

vi

ACRONYMS AND ABBREVIATIONS LCD

Liquid crystal Display

GND

Ground

ASCII

American Standard Code for Information Exchange

LED

Light emitting diode

MOS

Metal oxide semiconductor

GSM

Global System for Mobile

PCB

Printed circuit board

CT

Current transformer

RAM

Random access memory

ROM

Read only memory

AC

Alternating Current

DC

Direct Current

ADC

Analogue to Digital Converter

CPU

Central Processing Unit

CMOS

Complementary metal oxide semiconductor

IC ACS MSB LSB

Integrated circuit Allegro current sensor Most significant bit Least significant bit

ABSTRACT The main intention of this project is to design a microcontroller based system that can be used in Transformer protection. The system checks the operating parameters of the transformer i.e. current and reports the quantity that is flowing through the transformer. The system is designed such that it is able to detect currents above the normal operating level and isolate the Transformer from the distribution line. This isolation process is to ensure that the transformer is safe from any excess current levels that can make it to overheat thus get damaged. It gives a solution to the need to reduce cost of maintenance and ensure that supply of electricity to consumers is not interrupted for long periods taken while repairing or replacing destroyed transformers. In this project as the interfacing instrument between the Transformer and the AT80C51 Microcontroller. The AT80C51 controls all operations that the device does. A relay and a contactor have been used as the switching gears to isolate the transformer from the power system in case a fault occurs. A monochrome LCD has been used to show system current readings and indicate cases of over-current fault. To warn an operator of a fault occurrence, LEDs and a piezoelectric buzzer have been used. All these peripheral devices depend on the microcontroller to make them operate.

1: INTRODUCTION 1.1 BACKGROUND In the design of electrical power transmission and distribution system, there are various factors that need to be considered in the quest to satisfy the needs of electricity consumers. Electrical power systems experience faults at various times due to various reasons. These faults must be foreseen and safety precautions applied to the power system. The power systems engineer must include in his design, safety measures in order to avert any destructive occurrences that the system may undergo at any given time. Power system protection is very essential and necessary for a dependable electrical power supply. It ensures that the system is protected from itself and that the consumer is also safe as he benefits from the electrical power supply. An electrical power system consists of various components such as generators, switches, transmission cables, transformers, capacitor banks among other components. It cannot therefore operate without an effective protective device to keep these components safe and the system stable. Faults in a power system refer to the undesired conditions that occur in the electrical power system. These conditions may include short circuit, over current, overvoltage, high temperatures among others. It is clear that over time, there has been an increase in human population, economic growth and technological advancement. This has continuously made the demand for electrical power to go high because as technology, human population and economy grows; there is an increase in demand for power as many more electrical loads are introduced into the supply line. An increase in load leads to a lot of current drawn from the power line. At times the demand goes above what the power distributor can supply. The consequence of this is that electrical power overload cases ᵠᵠbecome common thus posing danger to power system components. This therefore throws in the

1

need for devices that can monitor the rate of power consumption in accordance with the level that a given system is designed to sustain. Such a device must be designed to cut off consumption if the system oversteps its ability thus being dangerous to users and the components. In this project, we look at the protection of power transformer from various faults that may occur and may be destructive to the component if left undetected. The transformer is a very important component in an electrical power system as distribution of electrical power to consumers is more efficiently effected. Every transformer is designed to comfortably supply a given load. Cases of overload or short circuits can lead to transformer being damaged. To combat such occurrence, an elaborate system that monitors these excesses in supply parameters needs to be built. Such a device controls the flow of electrical power to the load so that the transformer is not overworked. Over current relays and overvoltage relays have been used for a long period of time and have been electromechanically controlled. In this system, a microcontroller is used to monitor cases of electrical faults and communicate to a switch to isolate the transformer from the system.

1.2 PROBLEM STATEMENT Power system protection is a very important consideration in the design of an electrical power system. There is need to protect electrical power components from dangerous faults. This is warranted by the need to increase the life of the components, avoid unnecessary expenditure in frequent replacement of obsolete components and to ensure that there is a continuous supply of power to serve the needs of the ever growing economy. This project therefore seeks to design a microcontroller based system that will intelligently monitor faults and prompt a safety measure to protect the power transformer in case of power overload.

2

1.3 OBJECTIVES The main objective of this project is to design and implement a system that uses microcontroller and other peripheral devices to protect power transformer. To achieve the following must be done. a)

Design and build an over current relay using microcontroller .

b)

Development of the ADC program to convert the analogue sensor output

to equivalent digital form within the microcontroller. c)

Development of the LCD program to display the sensed levels.

d)

Development of warning (audio and visual) and relay control system

program.

1.4 SCOPE WORK The investigation carried out in this project is limited to power transformer protection methods. The extent of the work is to build a device that detects current spikes/overload in the primary and secondary sides of a single phase transformer and isolate it from the power system.

3

1.5 LITERATURE REVIEW Design & Development of A Microcontroller Based Protection Relay To Protect The System Against Over-Voltage, Under-Voltage, Over-Current Faults. [International Journal of Technical Research (IJTR) Vol. 6, Issue 1, Mar-Apr 2017]

1Ashwani, 2Ravi Kumar (2017) In this design & development of a microcontroller based digitally controlled system to implement a multifunctional numerical relay for the purpose of single phase online fault detection to protect the electrical equipments against over-voltage, over-current and under-voltage faults. The developed system is highly responsive, highly rugged, configurable, economical and user friendly. Hardware prototype with NXP P89V51RD2 as core controller is built to validate the operation. Protection of power transformer by using PIC microcontroller Fault Detection System [International Journal of Current Trends in Engineering & Research (IJCTER) e-ISSN 2455–1392 Volume 2 Issue 4, April 2016 pp. 337 – 341 Scientific Journal Impact Factor : 3.468] Ashok J. Naiknaware1, Sagar M. Jadhav 2, Suhas B. Jadhav3 (2016) This paper describe the design and implementation of an “Automatic method of protecting transformer as an PIC microcontroller based protection technique”. The aim of this paper is to provide an alternative, effective, efficient and more reliable method of protecting fault from power transformer which may arose as a result of overload, high temperature or a high input voltage. Generally, fault may occur in transformers due to the stated reasons. To safeguard the damage of the transformer with the aid and help of microcontroller we monitor and control the entire circuitry.

4

Transformer Protection Using Microcontroller Based Relay & Monitoring Using GSM Technology [International Engineering Research Journal (IERJ) Volume 2 Issue 2 Page 813-817, 2016, ISSN 2395-1621]

1Kajal Salunkhe, 2Sana Shaikh, 3B. S. Kunure (2016) To protect transformer against different types of faults, various methods are used like differential protection, microprocessor based relay etc. In this paper, overload and overheating protection is established for protection of transformer. Microcontroller based relay is used for protection of transformer. Simulation circuit is designed in proteus software and programming is done in keil software. In this research, hardware and software of microcontroller based relay has been explained and designed. Differential Protection for Power Transformer Using Relay [International Journal of Trend in Research and Development, Volume 3(1), ISSN: 2394-9333 www.ijtrd.com]

Ihedioha Ahmed C. (2016) MATLAB / SIMULINK platform were used to analyze differential protection relay for a large power transformer. The basic approach is to protect the power transformer against internal faults and prevent interruption due to other operating conditions. The trip time for power transformer relay was seen at 0.05 sec. The obtained result illustrate that the proposed differential relay represents an appropriate action. The proposed relay was able to discriminate between inrush, fault and no-fault conditions. DESIGN OF DIGITAL DIFFERENTIAL RELAY FOR PROTECTION OF POWER TRANSFORMER [International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982 Volume-3, Issue-8, Aug.-2015] 1PRAVIN S. GULHANE, 2CH. MALLA REDDY (2015) For protecting costliest and vital equipment such as transformer, digital schemes have been proposed by several authors in recent past. Efforts are put by all concerned with fast, accurate, flexible, reliable and easy to understand scheme of protection. With the advent of soft computing methods condition monitoring with protection has become on line objective.

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Digital Differential Protection of Power Transformer [International Journal of Digital Application & Contemporary research Website: www.ijdacr.com (Volume 2, Issue 10, May 2014) IJDACR ISSN: 2319-4863] 1Gitanjali Kashyap , 2 Dharmendra Kumar Singh (2014)

This paper presents

design a transformation based technique for protection of transformer. It improves and enhances the sensitivity of the operation of the digital differential relay that protects Power Transformers by discriminating between inrush current and fault current. The proposed method has been simulated with MATLAB/SIMULINK with different test of operations. Analysis of Modern Digital Differential Protection for Power Transformer [International Journal of Interdisciplinary Research and Innovations ISSN 2348-1226 (online)Vol. 2, Issue 1, pp: (46-53), Month: January-March 2014] 1 Nikhil Paliwal , 2Dr. A. Trivedi The analysis of digital differential protection for three phase power transformers. Power transformer is the key element in electrical power system. Proper protection is needed for economical and safe operation of electrical power system. Power transformer protective relay should block the tripping during external fault or magnetising inrush and speedily operate the tripping during internal faults. The foremost objective of this paper is to analyse digital differential protection during internal and external fault and to operate the relay with proper fault discrimination. PERFORMANCE ANALYSIS OF DIGITAL OVER CURRENT RELAYS UNDER DIFFERENT FAULT CONDITIONS IN RADIAL AND PARALLEL FEEDERS [MATTER: International Journal of Science and Technology ISSN 2454-5880] 1K. Naga Sujatha, 2 R. DurgaRao, 3 V.B. Shalini (2017)

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The performance of the proposed relay and over current relay has been tested under various case studies. By adding a directional element in directional over current relay the limitation of over current relay can be mitigated and its performance can be improved and they can be employed for protecting ring or loop networks. It is shown that the proposed model offer effective means for explaining the functionality of over current relay under various fault conditions and it has good advantage in terms of the sensitivity and wide range controlling. The proposed model analyzes the performance of a digital over current relay in radial distribution feeder.

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2: COMPONENTS USED 2.1 MICROCONTROLLER: A microcontroller is an integrated chip with minimum required devices. The microcontroller includes a CPU: ALU, PC,SP and registers, RAM, ROM, I/O ports, and timers like a standard computer, but because they are designed to execute only a single specific task to control a single system, they are much smaller and simplified so that they can include all the functions required on a single chip.

Figure 2.1: Microcontroller Block Diagram.

Most microcontrollers will also combine other devices such as: 

A Timer module to allow the microcontroller to perform tasks for certain time periods.



A serial I/O port to allow data to flow between the microcontroller and other devices such as a PC or another microcontroller.



An ADC to allow the microcontroller to accept analogue input data for processing.

8

2.1.1 MICROCONTROLLER Vs MICROPROCESSOR: 1. A microcontroller is meant to be more self-contained and independent, and functions as a tiny, dedicated computer than microprocessor. 2. The microcontroller may function as a computer with addition of external digital parts; the microprocessor must have many additional parts to be operational. 3. Most microprocessors have many operational codes (opcodes) for moving data from external memory to the CPU; microcontrollers may have one or two. 4. Microcontrollers are designed by using CMOS (complementary metal oxide semiconductor) technology, an efficient fabrication technique that uses less power and is more immune to power spikes than other techniques. 5. Microcontrollers are designed by using CMOS (complementary metal oxide semiconductor) technology, an efficient fabrication technique that uses less power and is more immune to power spikes than other techniques.

2.1.2 ADVANTAGES OF MICROCONTROLLERS: Their powerful, cleverly chosen electronics is able to control a variety of processes and devices (industrial automatics, voltage, temperature, engines, etc) independently or by means of I/O instruments such as switches, buttons, sensors, LCD screens, relays etc.

2.1.3 TYPES OF 8051 MICROCONTROLLER: The 8051 has the widest range of variants of any embedded controller on the market. The smallest device is the Atmel 89c1051, a 20 Pin FLASH variant with 2 timers, UART, 20mA. The fastest parts are from Dallas, with performance close to 10 MIPS! The most powerful chip is the Intel Technologies 80C517A, with 32 Bit ALU, 2 UARTS, 2K RAM, PLCC84 package, 8 x 16 Bit PWMs, and other features.

9

2.1.4 AMONG THE MAJOR MANUFACTURERS ARE: AMD

Enhanced 8051 parts (no longer producing 80x51 parts

Atmel

FLASH and semi-custom parts

Cygnal

Fastest8051 with Flash with 12-bit 1LSB A/D. 20MH internal clock

Dallas

Fast variant. Also battery backed

Intel ISSI

8051 through 80C51GB / 80C51Sl. They invented the 8051 IS80C51/31 runs up to 40MHz

Matra

80C154, low voltage static variants

OKI

80C154, mask parts

Hilips

87C748 Signetics.

Infineon

SMC

80C501 through 80C517A, and a wide variety of CAN devices . COM20051 with ARCNET token bus network engine

SSI

80x52, 2 x HDLC variant for MODEM us

thru 89c588,mostly old legacy 8051

10

Figure 2.2 Micro controller Architectural Block Diagram:

2.3 Atmel At89c51 Pin out and Description: The smallest current device is the ATMEL 89c51, a 40 Pin FLASH variant with 2 timers, UART, 500mA. ATMEL was the first with standard FLASH, and with more program cycles than other custom FLASH. These parts compete with OTP and MASK product on price, but eliminate inventory problems and the hidden costs of OTP development.

11

2.3.1 Why we go for AT89C51? The

AT89C51

is

a

low

power,

high

performance

CMOS

8-bit

microcontroller with 4Kbytes of Flash programmable and erasable read only memory (PEROM). This device is compatible with the industry standard 8051 instruction set and pin. The on-chip Flash allows the program memory to be quickly reprogrammed using a non volatile memory programmer such as the PG302 (with the ADT87 adapter). By combining an industry standard 8-bit CPU with Flash on a monolithic chip, the 8951 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications.

2.3.2 Features of AT89C51: 1. It is a 8-bit microcontroller. 2. It has a flash memory of 4KB for storing the program. 3. It has RAM of 128 bytes. 4. It has 32 I/O ports. -Port 0 (pin 39 to pin 32). -Port 1 (pin 1 to pin 8). -Port 2 (pin 21 to pin 28). -Port 3 (pin 10 to pin 17). 5. It has four register banks. 6. It has two 16-bit timers. -Timer 0 -Timer 1 7. It has full duplex asynchronous serial port. 8. It can support up to 64KB of external memory with the help of PC and DPTR. 9. It has 16-bit address bus. 10. Six interrupts with two priority level -2 general purpose interrupts (INT0, INT1).

12

-4 pre programmed interrupt ( Timer0,Timer1,Serial interrupt, Reset interrupt). 11.Wide range of frequency of operation (0 to 24 MHz). 12.It will operate on 5V dc supply. 13.It can support maximum of 500mA of current. In addition, the 8051 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power Down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.

2.3.3 PINOUTDIAGRAM:

Figure 2.3: Microcontroller Pin Diagram

13

1–8: Port 1: Each of these pins can be used as either input or output. Also, pins 1 and 2 (P1.0 and P1.1) have special functions associated with Timer 2. 9: Reset Signal: High logical state on this input halts the MCU and clears all the registers. Bringing this pin back to logical state zero starts the program anew as if the power had just been turned on. In another words, positive voltage impulse on this pin resets the MCU. Depending on the device's purpose and environs, this pin is usually connected to the push-button, reset-upon-start circuit or a brown out reset circuit. The image shows one simple circuit for safe reset upon starting the controller. It is utilized in situations when power fails to reach its optimal voltage.

Figure 2.4 : Reset Circuit However, each pin of Port 3 has an alternative function: 10-17: Port 3: As with Port 1, each of these pins can be used as universal input or output. However, each pin of Port 3 has an alternative function: Pin 10: RXD - Serial input for asynchronous communication or serial output for synchronous communication

14

Pin 11: TXD - Serial output for asynchronous communication or clock output for

synchronous communication

Pin 12: INT0 - Input for interrupt 0 Pin 13: INT1 - Input for interrupt 1 Pin 14: T0 - Clock input of counter 0 Pin 15: T1 - Clock input of counter 1 Pin 16: WR - Signal for writing to external (add-on) RAM memory Pin 17: RD - Signal for reading from external RAM memory 18-19: X2 and X1: Input and output of internal oscillator. Quartz crystal controlling the frequency commonly connects to these pins. Capacitances within the oscillator mechanism (see the image) are not critical and are normally about 30pF. New MCUs work at frequencies from 0Hz to 50MHz+.

Figure 2.5 : Clock Circuit.

20: GND: Ground 21- 28: Port 2: If external memory is not present, pins of Port 2 act as universal input/output. If external memory is present, then these pins serve as the location of the higher address byte, i.e. addresses A8 – A15. It is important to note that in cases when not all the 8 bits are used for addressing the memory (i.e. memory is smaller than 64kB), the rest of the unused bits are not available as input/output.

15

29: PSEN: MCU activates this bit (brings to low state) upon each reading of byte (instruction) from program memory. If external ROM is used for storing the program, PSEN is directly connected to its control pins. 30: ALE: Before each reading of the external memory, MCU sends the lower byte of the address register (addresses A0 – A7) to port P0 and activates the output ALE. External register (74HCT373

or 74HCT375 circuits are common),

memorizes the state of port P0 upon receiving a signal from ALE pin, and uses it as part of the address for memory chip. During the second part of the mechanical MCU cycle, signal on ALE is off, and port P0 is used as Data Bus. In this way, by adding only one cheap integrated circuit, data from port can be multiplexed and the port simultaneously used for transferring both addresses and data. 31: EA: Bringing this pin to the logical state zero designates the ports P2 and P3 for transferring addresses regardless of the presence of the internal memory. This means that even if there is a program loaded in the MCU it will not be executed, but the one from the external ROM will be used instead. Conversely, bringing the pin to the high logical state causes the controller to use both memories, first the internal, and then the external (if present). 32-39: Port 0: Similar to Port 2, pins of Port 0 can be used as universal input/output, if external memory is not used. If external memory is used, P0 behaves as address output (A0 – A7) when ALE pin is at high logical level, or as data output (Data Bus) when ALE pin is at low logical level. 40: VCC: Power +5V INPUT – OUTPUT (I/O) PORTS: Every MCU from 8051 family has 4 I/O ports of 8 bits each. This provides the user with 32 I/O lines for connecting MCU to the environs. Port 0: Port 0 has two fold role: if external memory is used, it contains the lower address byte (A0-A7), otherwise all bits of the port are either input or output. Another

16

feature of this port comes to play when it has been designated as output. Port 0 lacks the "pull up" resistor (resistor with +5V on one end). Therefore, to get one (5V) on the output, external "pull up" resistor needs to be added for connecting the pin to the positive pole.

Port 1: This is "true" I/O port, devoid of dual function characteristic for Port 0. Having the "pull up" resistor, Port 1 is fully compatible with TTL circuits. Port 2: When using external memory, this port contains the higher address byte (addresses A8–A15). Otherwise, it can be used as universal I/O port. Port 3: Beside its role as universal I/O port, each pin of Port 3 has an alternate function. In order to use one of these functions, the pin in question has to be designated as input, i.e. the appropriate bit of register P3 needs to be set. From a hardware standpoint, Port 3 is similar to Port 0.

2.3.4 Memory in 8051 Microcontroller: The 8051 has three very general types of memory. The memory types are illustrated in the following figure: On-Chip Memory, External Code Memory, and External RAM. 8051 Compat Micro

EXTERNAL RAM

INTERNAL RAM

SPRs INTERNAL CODE

EXTERNAL CODE Figure 2.6 : Memory Block Diagram.

17

On-Chip Memory refers to any memory (Code, RAM, or other) that physically exists on the microcontroller itself. External Code Memory is code (or program) memory that resides off-chip. This is often in the form of an external EPROM. External RAM is RAM memory that resides off-chip. This is often in the form of standard static RAM or flash RAM. During the runtime, microcontroller uses two different types of memory: one for holding the program being executed (ROM memory), and the other for temporary storage of data and auxiliary variables (RAM memory).

2.3.5 ROM memory: In this MCU contain 4 kilobytes of the flash memory on the chip. It is of EEPROM. We can use 12v to program MCU. This option is cost-effective only for large series. The main purpose of ROM is to store the programs to be executed.

2.3.6 RAM memory:

RAM is used for storing temporary data and auxiliary results generated during the runtime. Apart from that, RAM comprises a number of registers: hardware counters and timers, I/O ports, buffer for serial connection, etc. With older versions, RAM spanned 256 locations, while new models feature additional 128 registers. First 256 memory locations form the basis of RAM (addresses 0 – FFh) of every 8051 MCU. Locations that are available to the user span addresses from 0 to 7Fh, i.e. first 128 registers, and this part of RAM is split into several blocks as can be seen in the following figure.

18

Figure 2.7: Ram Memory.

The main purpose of RAM is to provide synchronization between ROM and CPU so as to increase the speed of microcontroller.

2.3.7 Bit Memory: The 8051, being a communications-oriented microcontroller, gives the user the ability to access a number of bit variables. These variables may be either 1 or 0. There are 128 bit variables available to the user, numbered 00h through 7Fh.

2.3.8 Special Function Register (SFR) Memory: Special Function Registers (SFRs) are areas of memory that control specific functionality of the 8051 processor. It may appear that SFR is part of Internal Memory. However, when using this method of memory access (its called direct address), any instruction that has an address of 00h through 7Fh refers to an Internal RAM memory address; any instruction with an address of 80h through FFh refers to an SFR control register.

19

Register Banks: General Purpose registers: The 8051 uses 8 "R" registers which are used in many of its instructions. These "R" registers are numbered from 0 through 7 (R0, R1, R2, R3, R4, R5, R6, and R7). These registers are generally used to assist in manipulating values and moving data from one memory location to another.

2.3.9 SFR Registers (Special Function Registers): SFR registers can be seen as a sort of control panel for managing and monitoring the microcontroller.

.

Figure 2.8: Special Function Registers 20

2.3.10 TIMERS: The 8051 comes equipped with two timers, both of which may be controlled, set, read, and configured individually. The 8051 timers have three general functions: 1) Keeping time and/or calculating the amount of time between events, 2) Counting the events themselves, or 3) Generating baud rates for the serial port. USING TIMERS TO MEASURE TIME: Obviously, one of the primary uses of timers is to measure time. When a timer is used to measure time it is also called an "interval timer" since it is measuring the time of the interval between two events. . Timer SFRs: The 8051 has two timers which each function essentially the same way. One timer is TIMER0 and the other is TIMER1. The two timers share two SFRs (TMOD and TCON) which control the timers, and each timer also has two SFRs dedicated solely to itself (TH0/TL0 and TH1/TL1). An SFR has a numeric address. It is often useful to know the numeric address that corresponds to an SFR name. When you enter the name of an SFR into an assembler, it internally converts it to a number. THE TMOD SFR (Timer Mode): The TMOD SFR is used to control the mode of operation of both timers. Each bit of the SFR gives the microcontroller specific information concerning how to run a timer. The high four bits (bits 4 through 7) relate to Timer 1 whereas the low four bits (bits 0 through 3) perform the exact same functions, but for timer 0. Obviously, one of the primary uses of timers is to measure time. When a timer is used to measure time it is also called an "interval timer" since it is measuring the time of the interval between two events Timer SFRs: The 8051 has two timers which each function essentially the same way. One timer is TIMER0 and the other is TIMER1. The two timers share two SFRs (TMOD and TCON) which control the timers, and each timer also has two SFRs

dedicated

solely

to

itself 21

(TH0/TL0

and

TH1/TL1).

An SFR has a numeric address. It is often useful to know the numeric address that corresponds to an SFR name. When you enter the name of an SFR into an assembler, it internally converts it to a number. THE TMOD SFR (Timer Mode): The TMOD SFR is used to control the mode of operation of both timers. Each bit of the SFR gives the microcontroller specific information concerning how to run a timer. The high four bits (bits 4 through 7) relate to Timer 1 whereas the low four bits (bits 0 through 3) perform the exact same functions, but for timer 0. The individual bits of TMOD have the following functions: Bit Name

Explanation of Function

Timer

7

GATE1 When this bit is set the timer will only 1 run when INT1 (P3.3) is high. When this bit is clear the timer will run regardless of the state of INT1.

6

C/T1

When this bit is set the timer will 1 count events on T1 (P3.5). When this bit is clear the timer will be incremented every machine cycle.

5

T1M1

Timer mode bit (see below)

1

4

T1M0

Timer mode bit (see below)

1

3

GATE0 When this bit is set the timer will only 0 run when INT0 (P3.2) is high. When this bit is clear the timer will run regardless of the state of INT0.

2

C/T0

When this bit is set the timer will 0 count events on T0 (P3.4). When this bit is clear the timer will be incremented every machine cycle.

1

T0M1

Timer mode bit (see below)

0

0

T0M0

Timer mode bit (see below)

0

22

The Four bits (two for each timer) are used to specify a mode of operation. modes of operation are: TxM1 0 0 1 1

TxM0 0 1 0 1

Timer Mode 0 1 2 3

Description of Mode 13-bit Timer. 16-bit Timer 8-bit auto-reload Split timer mode

The TCON SFR: There is one more SFR that controls the two timers and provides valuable information about them. The TCON SFR has the following structure:

TCON (88h) SFR: Bit Name Bit Address 7 TF1 8Fh 6

TR1

8Eh

5

TF0

8Dh

4

TR0

8Ch

Explanation of Function

Timer

Timer 1 Overflow. This bit is set by the microcontroller when Timer 1 overflows. Timer 1 Run. When this bit is set Timer 1 is turned on. When this bit is clear Timer 1 is off. Timer 0 Overflow. This bit is set by the microcontroller when Timer 0 overflows. Timer 0 Run. When this bit is set Timer 0 is turned on. When this bit is clear Timer 0 is off.

1 1 0 0

Only four bits of SFR are used for timers, the remaining four are used for interrupts.

23

2.3.11 11.0592MHZ CRYSTAL This is a 11.0592MHZ Crystal. This is a low cost crystal oscillator with oscillation frequency of 11.0592Mhz. Crystal are normally required to provide clock pulses to your microcontroller or other IC's which require external clock source. An oscillator crystal has two electrically conductive plates, with a slice or tuning fork of quartz crystal sandwiched between them. The crystal oscillator circuit sustains oscillation by taking a voltage signal from the quartz resonator, amplifying it, and feeding it back to the resonator. Quartz has the further advantage that its elastic constants and its size change in such a way that the frequency dependence on temperature can be very low. Features: •

Crystal Case Type: Metal Can

•

Crystal Mounting Type: Through Hole

•

Frequency: 11.0592 MHz

•

Frequency Stability: ± 50ppm

•

Frequency Tolerance: ± 30ppm

•

Load Capacitance: 10 pF

•

No. of Pins: 2

•

Operating Temperature Max: 70 °C

•

Operating Temperature Min: -10 °C

•

Operating Temperature Range: -10°C to +70°C

2.4 Liquid Crystal Display: Liquid crystal display is a type of screen display often used in digital watches, calculators and computers. The LCD display makes use of two layers of polarising material having solution of liquid crystal between them [15]. When an electric current passes through the liquid crystal, it causes them to align and

24

cause light not to pass through them. Each crystal acts like a shutter to either allow or not allow light to pass through. The principle is illustrated in figure 2-9

Figure2.9: The structure of an LCD Monochrome LCDs produce either dark or blue images while colour LCDs use passive matrix or thin film transistor to display many colours. In this project, a monochrome LCD is used because the aim of LCD usage is basically to display numerical figures and characters. LCDs consume little power thus they can be powered using battery. This project makes use of HD44780 LCD. It is a 16x2 line LCD with 8-bit wide data bus (D0-D7). It has three power pins (pins1-3), and three control pins (pins 4-5). The LCD can be operated either in 4-bit or 8-bit interface. 8bit interface makes use of all the pins while 4-bit mode uses only 4 data lines plus the other remaining pins. In this project, 8-bit mode is used.

25

Figure 2.10: LCD pin arrangement

Pin number 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Symbol Function VSS Ground Power supply VCC (+5V) Adjusting VEE contrast RS Register select R/W Read/Write E Enable pin Data line zero DB0 (LSB) DB1 Data line 1 DB2 Data line 2 DB3 Data line 3 DB4 Data line 4 DB5 Data line 5 DB6 Data line 6 DB7 Data line 7 (MSB)

TABLE LCD pins description

ENABLE PIN: This pin is key in the operation of the LCD. Data can only be latched into the LCD when high to low signal is passed into this pin. There should be at least 450ns delay between clearing and setting this pin, because of the higher frequency of the microcontroller relative to the LCD. When: E = 0 LCD cannot be accessed E=1 LCD can be accessed

26

R/W: informs the LCD whether the information is supposed to be read or written on the LCD .When: R/W = 0

Data is written to LCD

R/W = 1

Data is read from LCD

RS: helps the LCD to identify whether the information is data or command. When: RS = 0: command RS = 1: data D0-D7: these are the data pins, information is sent/received via these pins. TABLE : LCD Instructions Code(hex) 1 2 4 5 6 7 8 A C E F 10 14 18 1C 80 C0 38

Command to LCD instruction register Clear display screen Return home Shift cursor to left Shift display right Shift cursor to right Shift display left Display off, Cursor off Display off, Cursor on Display on, Cursor off Display on, Cursor blinking Display on, Cursor blinking Shift Cursor position to left Shift Cursor position to right Shift the entire display to the left Shift the entire display the right Force cursor to beginning of first line Force cursor to beginning of second line 2 lines and 5x7 matrix

27

Instruction

Code DB7 0 0 0

DB6 0 0 0

DB5 0 0 0

DB4 0 0 0

DB3 0 0 0

DB2 0 0 1

DB1 0 1 I/D

Clear display Cursor home Entry mode Display ON/OFF & cursor 0 0 0 0 1 D C Cursor/display shift 0 0 0 1 S/C R/L * Function set 0 0 1 DL N F * Set CGRAM address 0 1 A A A A A Set display address 1 A A A A A A I/D: 1 = Increment, 0 = Decrement S: 1 = Display shift ON, 0 = OFF D: 1 = Display ON, 0 = OFF C: 1 = Cursor ON, 0 = OFF 1 = Right Shift, 0 = Left B: 1 = Cursor blink ON, 0 = OFF R/L: shift S/C 1 = Display shift, 0 = Move 1 = 8-bit interface, 0 = : cursor DL: 4 bit 1 = 5x10 dots, 0 = N: 1 = two lines, 0 = 1 line F: 5x7 dots

DB0 1 * S B * * A A

TABLE : HD44780 instruction set Carrying out any operation on the LCD requires that instructions be sent via the data lines. This means that the RS pin has to be set low. The instructions in the tables above are used to write information to the LCD. The LCD can be used in either of the following configurations, 8-bit configuration: all the eight data pins are used (D0 – D7) 4-bit configuration: only four of the data lines are used (D4 – D7) There are two more pins (anode and cathode) that enable data written when it is dark to be seen.

2.5: Relay: A relay is an electrically operated switch. It uses electromagnetic force to close or open contact. The relay employed in this project can be operated as normally closed or normally open. For this system, the normally closed mode was used. The relay circuit is illustrated in figure 2-25. The relay was used to de-energize the contactor coil in case of a fault thus isolating the transformer from the system.

28

OP AMP LM358

2.6 ABOUT LM358 LM358 is also one of the types of operational amplifier. LM358 consists of two independent, high-gain, frequency-compensated operational amplifiers designed to operate from a single supply over a wide range of voltages. This module can also be used for testing an LDR, a phototransistor and a photodiode. You just need to replace an LDR with phototransistor or photodiode, the circuit simply works. You can try this project using 741 IC also. Photodiode and LM358:- Remove LDR and insert a photodiode, it works instantly. Depending upon the light level of your room, you might have to adjust the variable resistor to adjust sensitivity of the circuit. Figure 2.11 op amp

29

2.7 Comparator ADC MCP3202 MCP3202 The

MCP3202

12-bit

Analog-to-Digital

Converter

(ADC)

combines

high

performance and low power consumption in a small package, making it ideal for embedded

control

applications.

The

MCP3202

features

a

successive

approximation register (SAR) architecture and an industry-standard serial interface, allowing 12-bit ADC capability to be added to any microcontroller. The MCP3202

features

100k

samples/second,

2

input

channels,

low

power

consumption (5nA typical standby, 550 µA max. active), and is available in 8-pin PDIP, SOIC and TSSOP packages. Applications for the MCP3202 include data acquisition, instrumentation and measurement, multi-channel data loggers, industrial PCs, motor control, robotics, industrial automation, smart sensors, portable instrumentation and home medical appliance

Figure2.12: ADC MCP3202 Features: 

12-bit resolution



Dual single-ended inputs



SPI interface



±1 LSB DNL



±1 LSB INL



100 ksps sample



-40 to +85°C temperature range



AEC-Q100 Grade 3 30

Parameter Name

Value

Max Sample Rate (k samples/sec)

100

Max. INL ± (LSB)

1

Max. Supply Current (µA)

550

Input Type

Single-ended

# of Input Channels

2

Resolution (bits)

12

Interface

SPI

Temp Range (°C)

-40 to +85°C

Input Voltage Range (V)

2.7 to 5.5

2.8 Relay Driver IC A Relay driver IC is an electro-magnetic switch that will be used whenever we want to use a low voltage circuit to switch a light bulb ON and OFF which is connected to 220V mains supply. The required current to run the relay coil is more than can be supplied by various integrated circuits like Op-Amp, etc. Relays have unique properties and are replaced with solid state switches that are strong than solid-state devices. High current capacities, capability to stand ESD and drive circuit isolation are the unique properties of Relays. There are various ways to drive relays.Some of the Relay Driver ICs are as below. 

High side toggle switch driver



Low side toggle switch driver



Bipolar NPN transistor driver



N-Channel MOSFET driver and



Darlington transistor driver



ULN2003 driver

31

Relay Driver IC Circuit Relays are components that permit a low-power circuit to control signals or to switch high current ON and OFF which should be electrically isolated from controlling circuit. The Required Components 

Zener Diode



6-9V Relay



9V Battery or DC Power Supply



2N2222 Transistor



1K Ohm Resistor



Second Input Voltage Source

2.9 Relay Driver IC Circuit In order to drive the relay, we use transistor and only less power can be possibly used to get the relay driven. Since, transistor is an amplifier so the base lead receives sufficient current to make more current flow from Emitter of Transistor to Collector. If the base once gets power that is sufficient, then the transistor conduct from Emitter to Collector and power the relay.

32

The Transistor’s emitter-to-collector channel will be opened even though no input current or voltage is applied to Base lead of Transistor. Therefore, blocking current flows through relay coil. The emitter-to-collector channel will be opened and allows current to flow through relay’s coil if enough current or voltage is applied as input to the base lead. AC or DC Current can be used to power the relay and circuit. Relays are electromagnetic devices which allow low-power circuit to switch a high current ON and OFF switching devices with the help of an armature that is moved by an electromagnet. Driver Circuit is used to boost or amplify signals from micro-controllers to control power switches in semi-conductor devices. Driver circuits take functions that include isolating the control circuit and the power circuit, detecting malfunctions, storing and reporting failures to the control system, serving as a precaution against failure, analyzing sensor signals and creating auxiliary voltages. 2.10 Driver Circuits A typical digital logic output pin supplies only tens of MA of current. External devices such as high-power LEDs, motors, speakers, light bulbs, buzzers, solenoids and relays can require hundreds of MA and they need same voltages. In order to control small devices. Which use DC, a transistor-based driver circuit is used to amplify current to the required levels. If the voltage and current levels are in perfect range, the transistor acts like a high-current switch controlled by the lower current digital logic signal.

33

A discrete BJT is used at times in place of MOSFET transistor especially on older or low voltage circuits as shown below.

Figure 2.14 Driver Circuit Basic Driver Circuit using a BJT Transistor PNP, NPN, or MOS transistors are also be used. Transistor provides current gain. The resistor used on the base of the transistor is 1K ohm. On inductive loads (i.e., motors, solenoids, relays), a diode is often connected backwards across the load to suppress the voltage spikes (back EMF) generated when turning devices OFF. Inductor V = L* di/dt A negative voltage spike is produced when turning the device OFF. A diode is also connected across the transistor instead of the load sometimes in order to protect the transistor. The 2N3904 shown below is a small discrete BJT transistor is used for a driver circuit that required less than 200MA. In this circuit with BJTs, Vcc – higher voltage supply than the logic power supply and 6 or 12V DC is required for motors or relays. The load is directly connected to battery power and cannot passed through the voltage regulator in battery operated devices. Many devices such as motors have more inflow current spike when they are first turned ON. Be cautious on maximum current ratings.

34

Advantages of Low Side Driver More interface options are available which includes popular ULN2003 driver. 

Easy to interface to low voltage logic circuitry.



Fewer components are used.



Less expensive NPN drive transistors.



Relay power reduces load on voltage regulator.



It uses more commonly obtained NPN drive transistors.



It is easier to interface relay.



It is economic.

The ULN2003 has internal clamp diodes. While these work OK in non-critical applications and it leads to rise of glitches. Clamp Diode The clamp, free-wheeling or commutation diode provides a path for the inductive discharge current to flow when the driver switch is opened. If not provided, it will generate an arc in the switch—while the arc will not generally damage a switch contact, it will cause contact degradation over time—and yes, it will destroy transistors—been there, done that. The diode requirements are noncritical and a 1N4148 signal diode will generally work OK in low power applications. Avoid emitter follower drivers. If the relay is switched to OFF in 4007 diode eliminates back e.m.f and safe guards the transistor. ON status of the relay is indicated by LED. DC Relay Driver IC Circuit Let us see construction of relay driver circuit for relays that are operated from DC power. In order to drive a DC relay, DC voltage is needed in required quantity to rate a relay and a zener diode. Voltage is required for the relay to operate and to open or close its switch in a circuit. Relays exist with a voltage rating. This is known as relay’s datasheet to rate its coil voltage. For the function of relay, it must receive this voltage at its coil terminals.

35

Thus, if a relay has a rated voltage of 9VDC, it should get 9 volts of DC voltage for its working. In order to eliminate voltage spikes from a relay circuit, a diode is required for its proper functioning. The coil of a relay acts an Inductor.

FIG 2.15DC Relay Driver IC Circuit 2.11 DC Relay Driver Circuit The inductors are electronic components which withstand changes in current and also the inductors are coils of wires wrapped around a conductive core. Voltage spikes damages all components in a circuit and also damages relay’s switch contacts. To prevent these voltage spikes, a diode is kept reverse biased in parallel with the relay which acts as a transient (spike) suppressor eliminates voltage spikes by going into conduction before voltage is formed across the coil. A transient suppressor suppresses these spikes. A diode conducts reverse bias current if voltage reaches a certain threshold. The diode functions to shunt excess power to ground, and the diodes conduct if the voltage reaches breakdown voltage. The Required Components 

DC Relay



Zener Diode



DC Voltage Source or a DC power supply.

The zener diode is placed reverse biased in parallel to the relay.

36

The Relay used in the above is rated for 9Volts. In this a 9V DC Voltage source feeds the resistor. A Zener diode reverse biased is placed in order to suppress the transients caused by opening and closing the relay. This shunts all excess power to ground if it reaches a particular threshold. This is the process to operate a relay. Driving the loads which were connected to the output taking required power the relay will be closed. AC Relay Driver IC Circuit This AC Relay driver IC circuit is a relay that runs with AC power and cannot be run with DC power. In order to run an AC relay, enough AC voltage is required tp rate the relay and transient suppressor. In AC relay circuit we cannot use a diode to remove voltage spikes. This diode conducts an alternate half-cycle with AC power. We use an RC series network by placing across coil in parallel to form a working transient voltage suppressor with an AC circuit. Capacitor absorbs charge which comes excessively and resistor helps to control overflow.Components required to form the circuit is as follows FIG 2.16 AC Relay Driver IC Circuit

2.12 AC Relay Driver Circuit 

AC Relay



100 Ohm Resistor



0.05 Micro Farad Capacitor



AC Voltage Source

NOTE: AC voltage source may come out from plug that is inserted into US wall outlet.

37

Be careful with AC Power that comes out directly from wall outlet as it causes Shock. Consult a Professional before taking power from plug into wall outlet. When we use a relay with rated voltage 110VAC, we should feed it with 110V from an AC power source. To suppress voltage spikes, resistor and capacitor connected in series acts as transient voltage suppressor.

2.13 Relay Driver IC ULN2003 The relay driver uln2003 ic is a high voltage and current darlington array ic, it comprises of 7-open collector darlington pairs with common emitters. A pair of darlington is an arrangement of two bipolar transistors. This IC belongs to the family of ULN200x ICs and various types of this family interface to various logic families. This ULN2003 IC is for 5V TTL and CMOS logic devices. These ICs are used as relay drivers as well as to drive a wide range of loads, line drivers, display drivers etc. This IC is also normally used while driving Stepper Motors. The pairs of darlington in ULN2003 is esteemed at 500mA and can withstand peak current of 600mA.In the pin layout, the i/ps & o/ps are provided reverse to each other. Each driver also has a suppression diode to dissipate voltage spikes while driving inductive loads

Figure 2.17: Relay Driver IC ULN2003

38

2. 14:Buzzer Piezo buzzers are one of the most common buzzers available around, they got their name from the piezoelectric material used as the active element. These buzzers are usually driven at a relatively higher voltage but low current, consumes a little power, but still capable of producing very high sound. The Piezo element must be a three terminal one, like in the picture.

Figure 2.18 Buzzer The blue wire is connected to feedback (F) terminal, red wire to the main (M) terminal and the black wire to the piezo element’s ground(G) plate. The inductor coil’s value and shape is not crucial. You can use any coil from 1mH to 10mHor more, or even no measured value at all. I used a 40 turn coil on a small ferrite toroid in the final design. Circuit diagram and construction Lets have a look at the circuit diagram,

Note the piezoelectric element’s pinout, M is the main terminal, F is the feedback terminal and G is the ground plate.

39

The circuit is fairly simple, you can use a little piece of strip board to make it. As this piezo buzzer circuit uses very few components, so it also could be constructed by soldering the components to each other. My sample prototype, I opted for soldering the components to each other.

Buzzer construction notes The wires connecting the buzzer’s Main and feedback terminal MUST be very flexible and thin, else the buzzer won’t work The piezo element produces a very little displacement, possibly in range of few micro meters only. The flex force ain’t that powerful to overcome the pressure from connecting wires. Did you notice the two copper coils in the above picture ? I used them to minimise the pressure from connecting wires, but it was pretty impractical. So later removed those and and soldered two thin and very flexible wires, that just worked. I also replaced the 5mH coil with a 50 turn coil on a ferrite toroid. Now all components fits nicely inside the buzzer’s housing.

40

My sample prototype, I opted for soldering the components to each other When A voltage is applied to the electrodes of the piezo element, they produces flex in either way. This flex force bends the ground plate up and down.

The exact opposite thing happens too, when a a piezoelectric element is subjected to varying pressure, it produces voltage. As you’ve seen before, self drive piezo buzzers are constructed with an extra electrically isolated feedback electrode. The voltage created by the flex force is available in the feedback terminal. The piezo buzzer is placed in a resonant cavity, there is a hole in the opposite side of the resonant cavity from where the buzzing sound comes out. The driver circuit and piezo buzzer co-operates soon between themselves and they starts oscillating on the resonant frequency of the piezo buzzer. So that’s it, construction of a simple piezo buzzer circuit, I could write more about it’s operating principle, but that’s not necessary here.

41

2.15 Energy meter Energy meter or watt-hour meter or is an electrical instrument that measures the amount of electrical energy used by the consumers. Utilities is one of the electrical departments, which install these instruments at every place like homes, industries, organizations, commercial buildings to charge for the electricity consumption by loads such as lights, fans, refrigerator

Figure 2.19 Energy meter The basic unit of power is watts and it is measured by using a watt meter. One thousand watts make one kilowatt. If one uses one kilowatt in one hour duration, one unit of energy gets consumed. So

energy meters measure the

rapid voltage and currents, calculate their product and give instantaneous power. This power is integrated over a time interval, which gives the energy utilized over that time period. Two Basic Types of Watt-Hour Meter The energy meters are classified into two basic categories, such as: 

Electromechanical Type Induction Meter



Electronic Energy Meter Watt hour meters are classified into two types by taking the following factors into considerations:



Types of displays analog or digital electric meter.



Types of metering points: secondary transmission, grid, local and primary distribution.



End applications like commercial, industrial and domestic purpose



Technical aspects like single phases, three phases, High Tension (HT), Low Tension (LT) and accuracy class materials.

The electricity supply connection may be either single phase or three phase depending on the supply utilized by the domestic or commercial installations. 42

Particularly in this article we are going to study about the working principles of single-phase electromechanical induction type watt- hour meter and also about three-phase electronic watt hour meter from the explanation of two basic energy meters as described below . Single Phase Electromechanical Induction Watt Hour Meter It is a well-known and most common type of age-old watt-hour meter. It comprises a rotating aluminium disc placed on a spindle between two electromagnets. The rotation speed of the disc is proportional to the power, and this power is integrated by the use of gear trains and counter mechanism. It is made of two silicon steel laminated electromagnets: shunt and series magnets. Series magnet carries a coil which is of a few turns of thickness wire connected in series with the line; whereas the shunt magnet carries a coil with numerous turns of thin wire connected across the supply. Braking magnet is a kind of permanent magnet that applies the force opposite to the normal disc rotation to move that disc a balanced position and to stop the disc while power gets off.

Fig 2.20 Single Phase Electromechanical Induction Energy meter Series magnet produces a flux which is proportional to the flowing current, and shunt magnet produces a flux proportional to the voltage. These two fluxes lag at 90 degrees due to inductive nature. The interface of these two fields produces eddy current in the disk, utilizing a force, which is proportional to the product of instantaneous voltage, current and the phase-angle between them. A braking magnet is placed over one side of the disc, which produces a break torque on the disc by a constant field provided by using a permanent magnet. 43

Whenever the braking and driving torques become equal, the speed of the disc becomes steady. A Shaft or vertical spindle of the aluminium disc is associated with the gear arrangement that records a number proportional to the revolutions of the disc. This gear arrangement sets the number in a series of dials and indicates energy consumed over a time. This type of energy meter is simple in construction and the accuracy is somewhat less due to creeping and other external fields. A foremost problem with these types of energy meters is their proneness to tampering, which necessitates an electrical-energy-monitoring system. These series and shunt type meters are widely used in domestic and industrial applications. Electronic energy meters are accurate, precise and reliable type of measuring instruments when compared to electromechanical induction type meters. When connected

to

loads,

they

consume

less

power

and

start

measuring

instantaneous. So, electronic type of three phase energy meter is explained below with its working principle.

44

CHAPTER 3: DESIGN AND IMPLEMENTATION The ultimate objective of this project is to design an automatic over current relay that uses microcontroller to read transformer currents and automatically isolate the transformer from the power system in case of a fault. This design is therefore based on the microcontroller as the main control element in the system. The design of this system has been divided into the following sections. 1. Hardware design 2. Software design 3. PCB design

3.1 HARDWARE DESIGN 3.1.1 POWER SUPPLY Any invention of latest technology cannot be activated without the source of power. So in this fast moving world we deliberately need a proper power source which will be apt for a particular requirement. All the electronic components starting from diode to is only work with a DC supply ranging from 5V to 12V.We are utilizing for the same, the cheapest and commonly available energy source of 230V-50Hz and stepping down, rectifying, filtering and regulating the voltage.

Bridge Rectifier

1

7812

12v 2 1

7805

3

1000 uf

230V/12 AC step-down transformer

Figure3.1 power supply circuit

45

2

5v

3

330 uf

100 uf

Transformer: A bridge rectifier coupled with a step down transformer is used for our design. The voltage rating of transformer used is 0-12V and the current rating is 500mA. When AC voltage of 230V is applied across the primary winding an output AC voltage of 12V is obtained. One alteration of input causes the top of transformer to be positive and the bottom negative. The next alteration will temporarily cause the reverse. Rectifier: In the power supply unit, rectification is normally achieved using a solid state diode. Diode has the property that will let the electron flow easily at one direction at proper biasing condition. Bridge rectifiers of 4 diodes are used to achieve Bridge wave rectification. Two diodes will conduct during the negative cycle and the other two will conduct during the positive half cycle. Filtering unit: Filter circuit which is usually a capacitor acts as a surge arrester always follows the rectifier unit. This capacitor is also called as a decoupling capacitor or a bypass capacitor, is used not only to short the ripple with frequency to ground but also leave the frequency of the DC to appear at the output. Regulators: The voltage regulators play an important role in any power supply unit. The primary purpose of a regulator is to aid the rectifier and filter circuit in providing a constant DC voltage to the device. Power supplies without regulators have an inherent problem of changing DC voltage values due to variations in the load or due to fluctuations in the AC line voltage. With a regulator connected to DC output, the voltage can be maintained within a close tolerant region of the desired output. IC 7805 and 7812 regulators are used in this project for providing a DC voltage of +5V and +12V respectively.

46

3.2 HARDWARE: The AT8051 microcontroller has been used as the main device in the development of this system. Based on the number of input/output pins and the other functional features it was selected for use in this project. The 20 pins of the microcontroller have been distributed for use as follows TABLE3.1 Microcontroller Pin Usage

Pin function

Number of pins

Power pin(VDD)

Pin names

1

RA3

pin

1

RA0

LEDS

2

Buzzer control

1

Relay control

1

LCD

3

LCD data lines

8

Reset pin

1

Sensor input

RC0- RC7

3.2.1 Interfacing LCD to the microcontroller: The

LM016L

LCD

display

device

has

been

employed

in

the

system

implementation. The LCD operates as a medium for communicating the amount

47

of current flowing in the electric conductor at any given time. The logical process that avails the readings takes place within the microcontroller using a program and displayed on the LCD. The LCD operates in 8-bit mode, so 8 pins from the microcontroller have been connected to the 8 data pins on the LCD. Since PORTC of the AT80C51 is 8-bit wide, it is used for this purpose. So, RC0- RC7 pins of microcontroller have been connected to D0-D7 of the LCD as illustrated in figure 3-1.

Figure3.2 Microcontroller-LCD interface The register select (RS) pin has been connected to pin 12 (RB5) on the microcontroller. Enable pin has been connected to RA1 potentiometer of 10KΩ has been used to vary the brightness contrast of the LED

48

3.2.2 Warning devices and relay control LEDs In order to indicate the state of the power line, two Light emitting diodes have been used. One LED emits red light and the other one green light. The green LED is set to blink when the current flowing through the power system is at a normal level. The red LED should blink at an interval of half a second whenever the current build up approaches the overload level through to the point when the relay gets energized. This acts as a visual warning when a fault occurs. The green LED has been connected to the pin RB4 (pin 13) via a current limiting resistor (220Ω) to ground. The red LED has been connected to pin RA5 (pin 2) also through a current limiting resistor (220Ω) to ground. The microcontroller pins can give a maximum of 5.3V. LEDs typically have a forward voltage drop ranging between 1.8V and 3.3V subject to the LED colour. The value for red LED is about 1.8V. The forward voltage drop is a function of the LED colour frequency. For the LED to light, it needs around 20mA of current. The calculation below justifies the resistor values chosen for the design of this system. According to Ohms law, resistance is a function of voltage and current, as shown in the equation below

175Ω is not a standard resistor value, so a value close to it can be chosen. In order to ensure that the current sourced is as little as possible, the 220Ω resistor has been chosen such that the maximum current sourced becomes.

49

The below figure illustrates the connection of LEDs to the microcontroller via current limiting resistors

Figure3.3 Microcontroller-LED connection Audio Alert In order to provide an audio warning in case of a transformer overload, a piezoelectric buzzer has been used. The buzzer rating is between 2V-5V with a current rating of approximately 9mA. In order to achieve the 9mA rating, a resistor of value R= 5V/9mA = 550Ω is required. A standard 560Ω resistor has been used. In order to allow for varied range of buzzers to be used, a Darlington transistor is used as a switch. It is connected to pin RB6 of the microcontroller. The microcontroller produces 5V that drives the transistor thus allowing current flow in the transistor. The buzzer is connected between the transistor VDD and the collector. It goes on whenever the microcontroller pin controlling it is set to high. This results due to an instance of a fault

50

occurring in the system which is unsuitable for the transformer. This piezoelectric buzzer serves to give a warning to users to cease overloading the transformer or for a mitigation process to be conducted. Relay/Relay driver An electromagnetic relay has been employed as a switch to isolate the transformer from the power system in case a fault occurs. The rating of the relay used is in the model system is 5V. Due to the fact that the relay might draw a current of higher value than what the microcontroller can sink or source, a Darlington transistor is used as a switch to run it. It is connected between the transistor VDD and the Darlington transistor collector. When fault current is detected, the RB6 pin of the microcontroller is set high. This produces current that drives the Darlington transistor. The transistor in turn completes the relay coil circuit. The relay is energized through the principle of electromagnetic induction. It in turn de-energizes the contactor to isolate the transformer from the system. The relay is used alongside a contactor because; a power transformer uses high currents that the 5V relay cannot sustain. The relay sends signals to the contactor which in turn disconnects the circuit and isolates the transformer from the power system. The process is illustrated in the figure 3.4 below.

Figure3.4 Microcontroller-relay interface

51

3.2.3 The Oscillator The function of an oscillator in a microcontroller is to generate a clock signal. The clock signals are important because they help the parts of the microcontroller to function together. The clock makes it easier to know when the different parts of the microcontroller are going to change state. It is important to know how long a given operation takes to accomplish. An internal oscillator has been used in this design instead of an external crystal oscillator. It is selected in the program. 3.3 PCB design After the circuit is successfully tested on the breadboard, it is transferred to a PCB. The process for designing the PCB is as follows 3.3.1 PCB design using Software. Earlier, testing on broad board was done and the working process of the circuit was properly tested, problems were troubleshot and rectified. After the bread board testing here comes the Printed Circuited Board design (PCB). Dip trace software was used to place the components, which are joined together with multiple of tracks that gives out the physical and electrical connections. This software was used due its neat layout and accurate PCB layout is always the main priority section of the design

Figure 3.5 Complete circuit PCB design The PCB layout schematics were printed on a transparent paper, where the layouts were printed with a laser printer. Pressing iron was used to iron the

52

transparent paper on the PCB board systematically for about 10 minutes. The copper clods were allowed to cool off and the transparent paper was removed from the PCB board to expose the transferred image. A permanent marker was used to replace the missing tracks before retching. Etching chemical (HCL acid) was poured into a squared shaped container and the PCB board was placed inside. After that the board was cleaned with Tina chemical in order to remove the unwanted copper and

makes the board ready for drilling.

3.3.2 Soldering After the drilling process, there comes the soldering process. Soldering attentions need to be taken into consideration when laying out the board. Hand soldering is the traditional method basically used for prototypes and small production stuffs. Major impacts when laying out the board include suitable access for the iron, and thermal relief for pads. 3.3.3 Electrical Testing and Troubleshooting After soldering, finished PCB has to go through comprehensive checks for electrical continuity test and shorts that might occur at time of soldering. This is achieved by using the multi meter continuity check mode. It checks that the continuity of the tracks if matches each other; if not a troubleshooting session has to take place in order to trace and rectify the problem.

3.4 SOFTWARE DESCRIPTION AND CODING Introduction: The software coding required to perform the control operations of AT80C52 micro controller developed was coded with the help of Keil Cx51 Complier package. Keil Cx51 Complier compiles the program written and checks for errors in the program. Then, the compiler generates a filename.hex file that can be burnt in EPROM of 80C51 Microcontroller. Finally the error free compiled filename.hex file was burnt into the CPU memory with the help of Keil Programmer. 3.5 SOFTWARE USED: 3.6 TOOLS USED:

Embedded C or Assembly Language. Keil uv2 IDE.

53

3.7 Definition of Embedded System Any sort of device which includes a programmable computer, but itself is not intended to be a general-purpose computer” – Wayne Wolf Embedded Device Technology is a transformational technology – a technology that is revolutionizing the way we function. Embedded Systems can be seen everywhere from Wrist Watches, Washing Machines, Microwave Ovens and Mobile Telephones to Automobiles, Aircrafts and Nuclear Power Plants. Embedded Systems are the brains behind 90% of all electronic devices worldwide. The explosion of Embedded System Technology is expected to happen across product categories like office products, consumer products,

industrial

instrumentation,

automation

vending

products,

machines,

automobiles,

vehicles,

medical

communications

infrastructure, etc. An Embedded System is a combination of hardware and software designed to control the additional hardware attached to the system. The software system is completely encapsulated by the hardware that it controls. Embedded system means the processor is embedded into that application or it is meant for that specific application. Thus printer, keyboard, and video game player etc. are all examples of devices performing specific application. In an Embedded System, there is only one application software that is typically burned into ROM. An Embedded System is time-constrained and often resource-constrained. The brain of an Embedded System is the processor. It may be a general-purpose microprocessor like Intel x86 family or a microcontroller like 8051 family. An embedded product uses a microprocessor or microcontroller to do one specific task only. A microcontroller is a specific kind of microprocessor whose primary job is to control the hardware it is attached to. A microcontroller has more pins dedicated to carrying I/O signals as compared to microprocessor. A Microcontroller has built-in memory and peripherals (single-chip computer). Whereas a microprocessor has memory and supporting peripherals externally connected.

54

3.8.1 Introduction to Keil Cx51 Complier: The Cx51 Complier package may be used on all 8051 family processors and is executable under the Windows 32-bit command line prompt. The C programming language is a general-purpose programming language that provides code efficiency, elements of structured programming and a rich set of operators. C is not a big language and is not designed for a particular area of application. It is generally combined with its absence of restrictions, makes C a convenient and effective programming solution for a wide variety of software tasks. Many applications can be solved more easily and efficiently with C than with any other specialized languages. The Cx51 optimising C complier is a complete implementation of the American National Standards Institutes (ANSI) standard for the C language. Cx51 is not a universal C complier adapted for the 8051 target. It is a ground-up implementation dedicated to generating extremely fast and compact code for the 8051 microcontroller. Cx51 provides the flexibility of programming in C and the code efficiency and speed of assembly language The C language on its own is not capable of performing operations (such as input and output) that would normally require intervention from the operating systems. Because these functions are separate from the language itself, C is specially suited for producing code and portable across a wide number of platforms. Since Cx51 is a cross complier Some code of the C programming language and standard libraries are altered or enhanced as the peculiarities of an embedded processor. 3.8.2 Support for all 8051 Variants: 8051

family

is

one

of

the

fastest

growing

Microcontroller

Architectures. More than one device variants from various Silicon vendors are today available. New extended 8051 devices like the Philips 80C51MX architecture are dedicated for large application with several Mbytes code and data space. For optimum support of these different 8051 variants, Keil provides the several development tools that are listed in the Table 1 below. A new output file format (OFM2) allows direct support of upto 16MB code and data space. The cx51 complier is a variant of the C51 complier that is

55

designed for the new Philips 80C51MX architecture. The Cx51 complier is available in different packages. The table 1 below refers to the entire line of the 8051 development tools. Table3.1: Development tools in Keil Software

3.8.3 Compiling with the Cx51 Compiler: The directives below allow compiling of the Cx51 compiler. Control directives can be divided into three groups: Source controls, Object controls and Listing controls. Source controls define macros on the command line and determine the name of the file to be complied. Object controls affect the form and content of the generated object module (*.obj). These directives allow specifying the optimising level or including debugging formation in the object file. Listing controls govern various aspects of the listing file (*.LST), in particular its format and specific content.

56

3.8.4 Running Cx51 from the Command Prompt: To invoke the C51 or Cx51 compiler, enter C51 or Cx51 at the command prompt. On the command line, the name of the C source file to be compiled as well as other necessary control directives required to compile the source file must be included. The format for the Cx51 command line is: C51 sourcefile_directives..._ Cx51 sourcefile_directives.... _ OR C51 @commandfile Cx51 @commandfile Where: Source file is the name of the source program you want to compile. Directives are the directives we want to use to control the function of the command. Command file is the name of a command input file that may contain source file and directives. A command file is used, when the Cx51 invocation line gets complex and exceeds the limits of the windows command prompt. The Cx51 complier displays the following information upon successful compilation: C51 COMPLIER V6.10 C51 COMPILATION COMPLETE 0 WARNING (S), 0 ERROR (S) 0 ERROR LEVEL After the compilation, the number of errors and warnings detected is the output to the screen. The Cx51 complier then sets the ERRORLEVEL to indicate the status of compilation. As shown below:

57

ERRORLEVEL

MEANING

0

No errors or warnings

1

Warnings only

2

Errors and possible warnings

3

Fatal errors

3.8.5 Cx51 Output Files: The Cx51 complier generates a number of output files during compilation. By default each of these output files shares the same filename as the source file. However, each has a different file extension. The following lists the files and gives a brief description of each: File Filename LST: Files with this extension are listing files that contain the formatted source text along with any errors detected by the compiler. Listing files may optionally contain the symbols used and the assembly code generated. Filename OBJ: Files with this extension are object modules that contain reloadable object code. The Lx51 Linker/Locator may link object modules to an absolute object module. Filename I: Files with this extension contain the source text as expanded by the preprocessor. All macros are expanded and all comments are deleted in this listing. filename.SRC: Files with this extension are assembly source files generated from your C source code. These files can be assembled with the A51 assembler.

58

3.8.6 Debugging: When micro-Vision2 IDH and the micro-Vision2 Debugger is being used, complete debug information is obtained when Options for Target Output - Debug information is obtained. For command line tools the following rules apply. By default, the C51 complier uses the Intel Object Format (OFM2) for object files and generates complete symbol information. All Intel compatible emulators may be used for program debugging. The DEBG directive embeds debugging information in the object file. In addition, the OBJECTEXTEND directive embeds additional variable type information in the object file that allows type specific display of variables and structures when using certain emulators. The Cx51 complier uses the OFM2 object file format. The Cx51 complier also uses the OFM2 format when the directive OFM2 is active. The OFM2 format requires the extended Lx51 linker/locator and cannot be used with the BL51 linker/locator.

3.8.7 Complier Limits: The Cx51 complier embodies some known limitations that are listed below. For the most part, there are no limits with respect to components of the C language. If there is enough address space, several thousand symbols could be defined. A maximum of 19 levels of indirection (access modifiers) to any standard data type are supported. This includes array descriptors, indirection operators and function descriptors. Names may be up to 256 characters long. The C language provides for case sensitivity in regard to function and variable names. However, for compatibility reasons all names in the object file appear in capital letters. It is therefore irrelevant if an external object name within the source program is written in capital or small letters. The maximum number of case statements in a switch block is not fixed. Limits are imposed only by the available memory size and the maximum size of the individual functions. 59

The maximum number of nested calls in an invocation parameter list is 10. This value is independent of pre-processor files or whether not an object file is to be generated. The maximum depth of directives for conditional compilation is 20. This is a pre-processor limitation. Instruction blocks ({...}) may be nested up to 15 levels deep. Macros may be nested up to 8 levels deep. A maximum of 32 parameters may be passed into a macro or function call. The maximum length of a line or a macro definition is 2000 characters. Even after a macro expansion the result may not exceed 2000 characters.

3.9 ABOUT KEIL: Keil Software provides you with software development tools for the 8051 family of microprocessors. With the Keil tools, you can generate embedded applications for multitude of 8051 derivatives. Throughout this project we refer to these tools as the 8051 development tools. However, they support all derivatives and variants of the 8051microcontrollerFamily. The Keil Software 8051 development tools listed below are the programs used to compile your C code, assemble your assembler source files, link your program together, create HEX files, and debug your target program. μVision2 for Windows™ Integrated Development Environment: combines project. 

Management, Source Code Editing, and Program Debugging in one powerful environment.



C51 ANSI Optimizing C Cross Compiler: creates relocatable object modules from your C source code,



A51 Macro Assembler: creates re locatable object modules from your 8051 assembler source code,

60



BL51 Linker/Locator: combines reloadable object modules created by the compiler and assembler into the final absolute object module,



LIB51 Library Manager: combines object modules into a library which may be used by the linker,



OH51 Object-HEX Converter: creates Intel HEX files from absolute object modules,



RTX-51 real-time operating system: simplifies the design of complex, time critical software projects.

They are designed for the professional software developer, but any level of programmer can use them to get the most out of the 8051 hardware.

3.10 GETTING STARTED AND CREATING APPLICATIONS: 3.10.1 EVALUATION KITS AND PRODUCTION KITS: Keil Software provides two types of kits in which our tools are delivered. The EK51 Evaluation Kit includes evaluation versions of our 8051 tools along With this user’s guide. The tools in the evaluation kit let you generate these applications up to 2 Kbytes in size. You may use this kit to evaluate for the effectiveness of our 8051 tools and to generate small target applications. The 8051 Production Kits discussed in “Product Overview” topic section, include the unlimited versions of our 8051 tools along with this user’s guide and the full manual set. The production kits also include 1 year of free technical support and product updates

3.10.2 TYPES OF USERS: This manual addresses three types of users: 1) Evaluation users 2) New users and 3) Experienced users.

61

3.10.3 EVALUATION USERS: Evaluation users are those users who have not yet purchased the software but have requested the evaluation package to get a better feel for what the tools do and how they perform. The evaluation package includes evaluation tools that are limited to 2 Kbytes along with several sample programs that provide real-world applications created for the 8051 microcontroller family. Even if you are only an evaluation user, take the time to read this manual. It explains how to install the software, provides you with an overview of the development tools, and introduces the sample programs.

3.11 NEW USERS: New users are those users who are purchasing 8051 development tools for the first time. The included software provides you with the latest development tool technology, manuals, and sample programs. If you are new to the 8051 or the tools, take the time to review the sample programs described in this manual. they provide a quick tutorial and help new or inexperienced users quickly get started.

3.12 EXPERIENCED USERS: Experienced users are those users who have previously used the Keil 8051 development tools and is now upgrading to the latest version. The software included with a product upgrade contains the latest development tools and sample programs.

3.13 DEVELOPMENT TOOLS: This chapter discusses the features and advantages of the 8051 development tools available from Keil Software. We have designed our tools to help you quickly and successfully complete your job. They are easy to use and are guaranteed to help you achieve your design goals.

62

These development tools are meant for easy user under standing and easy endurance of user. These are an integrated part of this IDE (INTEGRATED DEVELOPMENT ENVIRONMENT)

3.14 Micro VISION2 INTEGRATED DEVELOPMENT ENVIRONMENT: Micro Vision2 is a standard Windows application. μVision2 is integrated software development platform that combines a robust editor, project manager, and make facility. Micro Vision2 supports all of the Keil tools for the 8051 including the C compiler, macro assembler, linker/locator, and object-HEX converter. Micro Vision2 

Helps

expedite

the

development

process

of

your

embedded

applications by providing the following: 

Full-featured source code editor,



Device Database for pre-configuring the development tool setting,



Project manager for creating and maintaining your projects,



Integrated make facility for assembling, compiling, and linking your embedded applications,



Dialogs for all development tool settings,



True integrated source-level Debugger with high-speed CPU and peripheral simulator.

Advanced GDI interface for software debugging in the target hardware and for connection to Monitor-51.

3.15 ABOUT THE ENVIRONMENT: The μVision2 screen provides you with a menu bar for command entry, a tool bar where you can rapidly select command buttons, and windows for source Files, dialog boxes, and information displays. Micro Vision2 lets you simultaneously open and view multiple source files.

63

3.16 MENU COMMANDS, TOOLBARS AND SHORTCUTS: The menu bar provides you with menus for editor operations, project maintenance, development tool option settings, program debugging, window Selection and manipulation, and on-line help. With the toolbar buttons you can rapidly execute operations. The commands can be reached also with configurable keyboard shortcuts. The following tables give you an overview of the μVision2 commands and the default shortcuts.

3.17 C51 OPTIMIZING C CROSS COMPILER: For 8051 microcontroller applications, the Keil C51 Cross Compiler offers a way to program in C which truly matches assembly programming in terms of code efficiency and speed. The Keil C51 is not a universal C compiler adapted for the 8051. It is a dedicated C compiler that generates extremely fast and compact code. The Keil C51 Compiler implements the ANSI standard for the C language. Use of a high-level language such as C has many advantages over assembly language programming: The µVision IDE from Keil, combines project management, make facilities, source code editing, program debugging, and complete simulation in one powerful environment. µVision helps you get programs working faster than ever while providing an easy-to-use development platform. The editor and debugger are integrated into a single application and provide a seamless embedded project development environment.

64

3.18 Micro vision Provides Unique Features Like: 

The Device Database which automatically sets the assembler, compiler, and linker options for the chip you select. This prevents you from wasting your time configuring the tools and helps you get started writing code faster.



A robust Project manager which lets you create several different configurations of your target from a single project file. Only the Keil µVision IDE allows you to create an output file for simulating, an output file for debugging with an emulator, and an output file for programming an EPROM--all from the same Project file.



An integrated make facility with automatic dependency generation. You don't have to figure out which header files and include files are used by which source files. The Keil compilers and assemblers do that automatically.



Interactive error correction. As you project compiles, errors and warnings appear in an output window. You may make corrections to the files in your project while µVision continues to compile in the background. Line numbers associated with each error or warning are automatically resynchronized when you make changes to the source.

The Keil 8051 Development Tools are designed to solve the complex problems facing embedded software developers. When starting a new project, simply select the microcontroller you use from the Device Database and the µVision IDE sets all compiler, assembler, linker, and memory options for you. Numerous example programs are included to help you get started with the most popular embedded 8051 devices. The Keil µVision Debugger accurately simulates on-chip peripherals (I²C, CAN, UART, SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM Modules) of your 8051 device. Simulation helps you understand hardware configurations and avoids time wasted on setup problems.

65

Additionally, with simulation, you can write and test applications before target hardware is available. When you are ready to begin testing your software application with target hardware, use the MON51, MON390, MONADI, or FlashMON51 Target Monitors, the ISD51 In-System Debugger, or the ULINK USB-JTAG Adapter to download and test program code on your target system.

3.19 ADVANTAGES: 

Knowledge of the processor instruction set is not required, rudimentary knowledge of the memory structure of the 8051 CPU is desirable (but not Necessary).



Details like register allocation and addressing of the various memory types and data types are managed by the compiler.



Programs get a formal structure and can be divided into separate functions. This leads to better program structure.



The ability to combine variable selection with specific operations improves program readability.



Keywords and operational functions can be used that more nearly resemble the human thought process.



Programming and program test time is drastically reduced which increases your efficiency. The C run-time library contains many standard routines such as: formatted output, numeric conversions and floating point arithmetic.



Existing program parts can be more easily included into new programs,

because

of

the

comfortable

modular

program

construction techniques. 

The language C is a very portable language (based on the ANSI standard) that enjoys wide popular support, and can be easily obtained for most systems. This means that existing program investments can be quickly adapted to other processors as needed.

66

3.20 PROGRAMMING THE CHIP: The

chip

can

be

programmed

using

INTELLIGENT

UNIVERSAL

PROGRAMMER from Advantech, which connects to PC’s parallel port. The LabTool-48UXP features a 48-pin universal pin driver and an expandable TTL pin driver, an on-board processor lets it handle todays (and tomorrows) complicated DIP-type silicon PLDs, microprocessors and high density memory chips. The LabTool-48XP is developed for both laboratory and mass-production applications. It supports over 7000 different devices, including PAL, GAL, CPLD, EPLD, PEEL, MAX, MACH, PLSI, microprocessors, EPROM, series EPROM, PROM and Flash memory. The LabTool-48XP performs device insertion and contact checks before it programs each device. It can detect poor pin contact and incorrect insertion, thus saving expensive chip damage due to operator error. Many EPROM and Flash memories have a built-in device and manufacturer ID. The LabTool-48XP can read this information, making it useful when working with second hand chips and devices that have had their part number removed.

Figure 3.20.1 Intelligent Universal Programmer

67

3.20.2 FEATURES OF IUP: 

High Speed USB port interface.



Supports 5V, 3.3V & 1.8V Devices



Less that 2 seconds per M bit Programming speed



No adapter required for DIL devices up to 48-pin.



48-pin universal pin driver and current limit



Device insertion / continuity check



Supports Windows 95/98, Windows 2000, Windows XP & NT



3 years hardware warranty.



FREE software updates via the web.



Serialization for Memory and Micro's



Memory buffer H / L byte swap



Project file save and load function



User Selectable verify VCC with one or two-pass verify voltage



Automatic file format detection and conversion



Pin swapping table provided for all adapters



Universal adapters, for example one 44 pin PLCC adapter will

program 44 pin memory and micro devices.

3.20.3 Universal pin driver--True universal programming The MOSFET logic controls the programmer's pin switches, so each pin can supply Vcc, Vpp or ground. Pins can also be configured for TTL high/low levels with pull-high/pull-low, high-speed clock and tri-state. This advanced pin design lets you program any DIP device up to 48 pins without an adapter. It also ensures support for the full range of silicon technologies on the market--today and tomorrow.

3.20.4 Unbeatable programming speed The LabTool-48's on-board intelligence reduces system overhead to a minimum.

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The LabTool-48XP can program an 32-Mbit FLASH device in less than 60 seconds. The LabTool-48UXP is very quick, making it much more productive with today's high-density, multi-megabit memory devices. The LabTool-48UXP is much faster than its competitors, making it much more productive with today's high density, multi-megabit memory devices.

3.20.5 Device insertion and contact checks--No mistakes! The LabTool-48UXP performs device insertion and contact checks before it programs each device. It can detect poor pin contact and devices inserted upside down or in the wrong position. This function protects your pocketbook by preventing expensive chip damage due to operator error.

3.20.6 EPROM and Flash memory ID detection Many EPROM’s and Flash memories have a burnt-in device ID and manufacturer ID. The LabTool-48UXP can read the device's ID to determine its vendor and product number. This feature is especially useful with second-user chips and devices that have had their part number accidentally (or intentionally!) removed.

3.21 AUTO-SENSING AND SELF-PROGRAMMING To meet mass-production requirements the LabTool-48UXP has implemented new patented technology in both its hardware and software. After entering the Mass-production Mode, the production line operator inserts a device into the ZIF socket. An LED on the LabTool-48UXP will indicate if the device is programmed successfully and the operator simply removes it and replaces it with a new one. No formal training is necessary adding flexibility and saving time and money. In addition, the LabTool-48's auto-sensing feature ensures the device has been inserted correctly and then automatically programs the device. Furthermore, in the massproduction mode the system keyboard is automatically disabled preventing the operator from making any inadvertent mistakes.

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3.22 Memory buffer auto Increment If your memory devices need individual serial numbers, the LabTool48UXP has an Auto Increment function, This simply increments the serial numbers in the buffer each time a new device is inserted. This saves time and money. The LabTool-48UXP has everything you need in one package: 48-pin driver, socket and complete device support library. You don't need to order separate device libraries. The LabTool-48UXP is much faster than its competitors, making it much more productive with today's high density, multi-megabit memory devices.

3.20.5 Device insertion and contact checks--No mistakes! The LabTool-48UXP performs device insertion and contact checks before it programs each device. It can detect poor pin contact and devices inserted upside down or in the wrong position. This function protects your pocketbook by preventing expensive chip damage due to operator error.

3.20.6 EPROM and Flash memory ID detection Many EPROM’s and Flash memories have a burnt-in device ID and manufacturer ID. The LabTool-48UXP can read the device's ID to determine its vendor and product number. This feature is especially useful with second-user chips and devices that have had their part number accidentally (or intentionally!) removed.

3.21 AUTO-SENSING AND SELF-PROGRAMMING To meet mass-production requirements the LabTool-48UXP has implemented new patented technology in both its hardware and software. After entering the Mass-production Mode, the production line operator inserts a device into the ZIF socket. An LED on the LabTool-48UXP will indicate if the device is programmed successfully and the operator simply removes it and replaces it with a new one. No formal training is necessary adding flexibility and saving time and money. In addition, the LabTool-48's

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auto-sensing feature ensures the device has been inserted correctly and then automatically programs the device. Furthermore, in the massproduction mode the system keyboard is automatically disabled preventing the operator from making any inadvertent mistakes.

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APENDIX A: CIRCUIT DESIGN

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APENDIX B: ASSEMBLY LANGUAGE #include #define lcd_data P2 sbit lcd_rs = P2^0; sbit lcd_en = P2^1; sbit mtr = P0^4; sbit alarm = P3^7; sbit cs = P1^0; //ADC temp sbit din = P1^1; sbit dout = P1^2; sbit clk = P1^3; sbit SEN1 = P0^3; sbit SEN2 = P0^2; sbit RELAY1 = P0^0; sbit RELAY2 = P0^1; unsigned convert(unsigned int); unsigned converts(unsigned int); unsigned convert1(unsigned int); unsigned convert2(unsigned int); unsigned char rcg,pastnumber[11],count=0,rcva='x'; unsigned char rcv1,rcv2; unsigned long int curnt=0,cnt=0,cnt1=0;settemp; void Edelay(unsigned int); void delay(unsigned int v) { unsigned int i,j; for(i=0;i<=v;i++) for(j=0;j<=275;j++); } void MSDelay(unsigned int value) { unsigned int x,y; for(x=0;x<1275;x++) for(y=0;y
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din=1; clock();//start bit din=1; clock();//mode select bit if(sel==1)din=1; else{din=0;} clock();//D2 /* if(sel==1)din=1; else{din=0;} clock();//D1 if(sel==1)din=1; else{din=0;} */ clock();//D0 clock();//sampling time } unsigned int read_mcp3202() { unsigned char ii=0; unsigned int read_i; clk=0; delay(1); clk=1;//for null charecter read_i=0; delay(1); for(ii=0;ii<12;ii++) { clk=0; delay(1); if(dout==1){read_i++;} read_i=read_i<<1; clk=1; delay(1); } return read_i; } void lcdcmd(unsigned char value) // LCD COMMAND { lcd_data=value&(0xf0); //send msb 4 bits lcd_rs=0; //select command register lcd_en=1; //enable the lcd to execute command delay(3); lcd_en=0; lcd_data=((value<<4)&(0xf0)); //send lsb 4 bits lcd_rs=0; //select command register lcd_en=1; //enable the lcd to execute command delay(3);

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lcd_en=0; } void lcd_init(void) { lcdcmd(0x02); lcdcmd(0x02); lcdcmd(0x28); //intialise the lcd in 4 bit mode*/ lcdcmd(0x28); //intialise the lcd in 4 bit mode*/ lcdcmd(0x0e); lcdcmd(0x06); lcdcmd(0x01);

//cursor blinking //move the cursor to right side //clear the lcd

} void lcddata(unsigned char value) { lcd_data=value&(0xf0); //send msb 4 bits lcd_rs=1; //select data register lcd_en=1; //enable the lcd to execute data delay(3); lcd_en=0; lcd_data=((value<<4)&(0xf0)); //send lsb 4 bits lcd_rs=1; //select data register lcd_en=1; //enable the lcd to execute data delay(3); lcd_en=0; delay(3); } void msgdisplay(unsigned char b[]) // send string to lcd { unsigned char s,count=0; for(s=0;b[s]!='\0';s++) { count++; if(s==16) lcdcmd(0xc0); if(s==32) { lcdcmd(1); count=0; } lcddata(b[s]); } } void main(void)

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{ unsigned int amt=1,var=0,temp=0; mtr=1;cnt=0; //relay1=relay2=0; RELAY1=RELAY2=0; alarm=1; lcd_init(); msgdisplay("TRANSFORMER PROTECTION SYSTEM"); //83 delay(700); lcdcmd(0x80); msgdisplay("I:"); lcdcmd(0x8A); msgdisplay("T:");

//0x88 //0xc2,3,4

RELAY2=1; while(1) { cnt1++; if(cnt1==10000) { cnt++; cnt1=0; } if(mtr == 0) { while(mtr == 0);//lcdcmd(0x80); // msgdisplay("I:"); lcdcmd(0x82); curnt=((10000/cnt)); // curnt=(curnt-320); convert(curnt); cnt=0; if(curnt >=1000) cnt=0; delay(50); cs=1; delay(10); cs=0; delay(10); powerup(0); //lcdcmd(0x88);

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temp = (read_mcp3202()); //delay(100); lcdcmd(0x8C);convert2(temp); if(temp >= 40) { alarm=0; RELAY1=1; delay(400); // lcdcmd(1); // msgdisplay("V:230V"); //0xc2 lcdcmd(0xC0); msgdisplay("TEMP INCREASES"); delay(500); alarm=1; } if(temp <40) { RELAY1=0; delay(400); lcdcmd(0xC0); msgdisplay(" "); delay(200); } if(SEN1==0&&SEN2==0) { lcdcmd(0xC0); msgdisplay(" "); RELAY2=1; delay(400); } if(SEN1==1) { alarm=0; RELAY2=0; delay(400); // lcdcmd(1); // msgdisplay("V:230V"); //0xc2 lcdcmd(0xc0); msgdisplay("OVER VOLTAGE"); delay(400); alarm=1; } if(SEN2==1) { alarm=0; RELAY2=0; delay(400); lcdcmd(0xC0); msgdisplay("UNDER VOLTAGE"); delay(400);

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alarm=1; } } } } unsigned convert(unsigned int value) { unsigned int a,b,c,d,e,f,g,h; a=value/10000; b=value%10000; c=b/1000; d=b%1000; e=d/100; f=d%100; g=f/10; h=f%10; a=a|0x30; c=c|0x30; e=e|0x30; g=g|0x30; h=h|0x30; lcddata(a); lcddata(c); lcddata('.'); lcddata(e); lcddata(g);lcddata(h);lcddata('A');//lcddata(' ');lcddata(' '); return 1; } unsigned convert2(unsigned int value) { unsigned char a,b,c,d; a=value/100; b=value%100; c=b/10; d=b%10; a=a|0x30; c=c|0x30; d=d|0x30; lcddata(a); lcddata(c); lcddata(d); return 1; }

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4. RESULT AND DISCUSSIONS

In order to verify the performance of the proposed microcontroller based transformer protection system, a hardware prototype was implemented with a microcontroller AT80C51 with a 16MHz crystal oscillator. During this test, a Variable Resistance was used for varying the input voltage of the transformer in order to create the over voltage fault. Bulbs were used as loads to create the over current fault. Voltage and current sensing circuits were designed for sensing the transformer voltage and current. The validity of this project prototype is verified through this test system. 4.1 Transformer current analysis

Transformer current analysis 1.6

Normal current 1.2A

Overcurrent 1.4A

1.4

Current rises to 1.2A

1.2 1 Current(A)

0.8 0.6

Series1

Current goes to zero

0.4 0.2 0 -0.2

0

20

40

60

Time(mS)

Figure 4.1 Transformer current analyses As in figure 4.1 when no over current detected by the microcontroller through the sensor, the microcontroller energizes the over current relay on. If loads are added to the secondary side of the transformer, the secondary current rises. Therefore the load is proportional to the secondary current. If the load connected does not exceed the rated current of the transformer which 1.2A, the relay continues to be on. But as soon as the load current

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exceeds the transformer rated current, the microcontroller sends a trip signal to the over current relay and the relay goes off., thereby protecting the transformer from burning due to overloading. When the over current is rectified, the relay goes on and continues to allow the flow of electric current through the load. 4.2 Transformer voltage analysis: when no overvoltage detected by the microcontroller through the voltage sensing circuit, the microcontroller energize the overvoltage relay on which allows the flow of electric current and voltage through the transformer primary. When the input AC voltage is varied through the Variable resistance above the rated voltage of the transformer which is 230VAC, the microcontroller detects an overvoltage condition through the voltage sensing circuit, therefore it sends a trip signal the overvoltage relay, and the relay cuts off the primary of the transformer from the input AC voltage thereby saving the transformer from damaging due overvoltage. As soon as the micro controller detects normal voltage, it sends back a switch on signal to relay thereby allowing the flow of electric current and voltage through the through transformer primary. A microcontroller based real time multifunctional digital relay has been implemented for the protection against certain abnormalities in line and is highly reactive and responds in real time. The proposed system is implemented and tested for the desired functionalities. The voltage and current high and low thresholds can be set to define the range of safe operation for the transmission line. The user can rely on this system as it ensures the complete protection of the line against these faults by switching a relay accordingly. All the calculations and decision making is carried out by a high performance eight bit microcontroller. The system was well tested and calibrated to get the optimum results. for the switching of a protection relay to protect transmission line against the over-current, over-voltage, under-voltage faults, over temperature.

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5. CONCLUSION AND FUTURE SCOPE 5.1 Conclusion: In this project, the transformer protection using a microcontroller is proposed. For transformer voltage and current sensing, a current sensing circuit and voltage sensing circuits were designed and the results have been verified with

proteus simulation. Hardware with an

microcontroller was

implemented to verify the proposed technique and the performance of the real time hardware was compared with the proteus computer simulation. Through the transformer current analysis , we can see that the current of the transformer rises as load increases, whenever the load current goes above the transformer rated current, the microcontroller detects an over current and it sends a trip signal to over current relay thereby protecting the transformer from burning. As the load current goes below the rated current of the transformer, the microcontroller detects normal there by sending an on signal to the over current relay. Moreover, through the transformer voltage analysis in figure 5.2, we can see that the voltage of the transformer rises as the input voltage of the transformer is increased through varying an autotransformer. Whenever the input voltage goes above the transformer rated voltage (230VAC), the microcontroller detects an overvoltage and it sends a trip signal to over voltage relay thereby protecting the transformer from burning. The results indicate that the microcontroller based transformer protection achieves numerous advantages over the existing systems in use: 1) fast response, 2) better isolation, 3) accurate detection of the fault. Finally, the practical results matched with the simulation perfectly, therefore the aim and objectives of the project were all achieved successfully and project is said to be industrious and fully automated with no manual interface required.

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5.2 Future Recommendations Any work and investigation on transformer protection is very advantageous and challenging. Based on the present time, it can be observed that the world’s population is increasing rapidly. Therefore demands on electricity will be high and these will lead to demands of highly sophisticated protection devices, which will be incorporated in transformer protection schemes. Based on the work done in this project which protecting transformer using microcontroller, some improvements need to be made in the future work. It was noticed that use of current sensor prevent the protection from high performance application because the current sensor needs some amount of time to sense the load current and transfer the signal to the microcontroller ADC. Correspondingly, a current transformer can be used instead of current sensor, switching semiconductor device such as thyristor can be used instead

of

relay,

highly

advanced

microcontroller

such

as

16bit

microcontroller or a digital signal processor can be used for high speed analogue to digital (ADC) conversion of the transformer voltage and current.

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REFERENCE Books [1]Badri ram and D N Vishwakarma (1995) power system protection and switch gear New delhi: Tata Mc Graw hill. [2]Frank D. Petruzella (2010) Electric motors and control systems 1st ed. New york:McGraw-Hill [3]J.Lewis Blackburn , Thomas J. Domin (2006). Protective Relaying Principles and Applications . 3rd ed. United States of America: CRC press [4]Leonard L. Grigsby (2007). The Electric Power Engineering Handbook. 2nd ed. United States of America: CRC press. [5]P. M. Anderson (1998). Power system protection. New York: John Wiley & Sons, Inc.P.673. [6]Smarajit Ghosh, (2007). Electrric Machines 1st Edn. India: Dorling Kindersley Journals [1]Ali Reza Fereidunian, Mansooreh Zangiabadi, Majid Sanaye-Pasand, Gholam Pournaghi, (2003) ‘Digital Differential Relays For Transformer Protection Using Walsh Series And Least Squares Estimators’. CIRED (International Conference on Electricity), pp. 1-6. [2]Atthapol Ngaopitakkul and Anantawak kunakorn (2006), ‘Internal Fault Classification in Transformer Windings using Combination of Discrete Wavelet Transforms and Back-propagation Neural Networks’ International journal of control, automation and systems, 4(3), pp. 365-371. [3]Mazouz A. Salahar Abdallah R. Al-zyoud (2010), ‘Modelling of transformer differential protection using programmable logic controllers’ European journal of scientific research, 41(3), pp. 452-459. [4]Pankaj Bhambri, Chandni Jindal, Sagar Bathla (2007), ‘Future Wireless Technology-ZIGBEE’ Proceedings of national conference on challenges, pp. 154-156. [5]R. A. LARNER and K. R. GRUESEN, (1959). Fuse Protection or HighVoltage Power Transformers, pp.864-873.

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[6]S.M Bashi, N. Mariun and A.rafa (2007). ‘Power Transformer protection using microcontroller based relay’, Journal of applied science, 7(12), pp.1602-1607. [7]V.Galdi, L.lppolito, A.piccolo and A.Vaccaro (2000) ‘Neural diagnostic system for transformer thermal overload protection’ Electric Power Applications, IEE Proceedings, 147 (5), pp. 415 - 421. [8]V.Thiyagarajan & T.G. Palanivel, (J2010) ‘An efficient monitoring of substations using microcontroller based monitoring system’ International Journal of Research and Reviews in Applied Sciences, 4 (1), pp.63-68.

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