110V UNIVERSAL BATTERY CHARGING PANEL

USING PIC MICROCONTROLLER

A dissertation submitted to the

Department of Electrical Engineering, University of Moratuwa

in partial fulfillment of the requirements for the

degree of Master of Science

by

SWARNA KUMARA VIJITHANANDA

Supervised by: Dr. J.P Karunadasa

Department of Electrical Engineering

University of Moratuwa, Sri Lanka

December 2006

DECLARATION

The work submitted in this dissertation is the result of my own

investigation, except where otherwise stated.

It has not already been accepted for any degree, and is also not being

concurrently submitted for any other degree.

S.K Vijithananda

Date: \ \ CM

We/I endorse the declaration by the candidate.

CONTENTS Declaration I

Abstract IV

Acknowledgement VI

List of Figures VII

List of Tables IX

CHAPTER 1

1.00 Introduction 1

1.10 Requirement of the Project 1

1.20 Project Benefits 1

1.30 Technical Concept & Techniques 2

1.40 Project Tools & Materials 2

CHAPTER 2

2.00 Structure of the Project 12

2.10 Hardware Circuitry 13

2.11 Design of DC-DC Converter 15

2.12 Testing Circuit with 555 Timer 21

2.13 Converter Switching Amplifier Circuits 26

2.14 Overcurrent & Over/Under Voltage Circuits 30

2.20 Software Programming 34

2.21 Introduction to PIC (16F876A) Microcontroller 34

2.22 Analog to Digital Converter (A/D) Module 37

2.23 Operation in PWM Mode 45

2.24 Assembly Programs for A/D Conversion 49

& PWM operation

2.24 (i) A/D Conversion 49

2.24 (ii) PWM Operation 49

II

CHAPTER 3

3.00 Results and Practical Observation 55

3.10 Waveforms of the DC-DC Converter 55

3.20 Voltage variation of the Panel Output 60

3.30 Project Photos 64

CHAPTER 4

4.00 Practical Limitations Challenges & Difficulties 69

4.10 Technical limitations & Challenges 69

4.20 Financial Difficulties 69

CHAPTER 5

5.00 Conclusion 71

5.10 Conclusion and Remarks 71

5.20 Recommendation for Future Developments 71

References 73

Appendix A Definitions of the terms 74

Appendix B Program Codes 77

III

Abstract

Conventional power electronics and electronic control circuits have been replacing by the

intervention of the microprocessors/microcontrollers in modern industrial applications.

This is mainly because with their applications the whole systems becomes more and more

compact while enhancing the durability. On the other even with the more robust

applications hand more accurate & fine operation could achieve by using such modern

programming devices.

This project was origin from based on an actual requirement of designing 1 lOv battery

charging panel (to energize the batteries in spring charge type breakers)for electrical

engineering division of Jaya Container Terminal(J.C.T) of Sri Lanka Ports Authority. But

this technique would use to not only to charge batteries of spring charge breakers , but

also batteries widely use in VHF communication hand held sets, explosive detectors,

emergency lamps, etc...

Rechargeable batteries are vital to portable electronic equipment such as laptop

computers and cell phones. Fast charging circuits must be carefully designed and

are highly dependent on the particular battery's chemistry. The most popular types

of rechargeable batteries in use today are the Sealed-Lead-Acid (SLA), Nickel-

Cadmium (NiCd), Nickel-Metal-Hydride (NiMH), and Lithium-Ion (Li-Ion). Li-Ion is

fast becoming the chemistry of choice for many portable applications because it

offers a high capacity-to-size (weight) ratio and a low self-discharge characteristic.

Depending on the battery chemistry the charging characteristics of a battery differs to

each other. In this project simply what I have done is allows the particular battery to

follow its charging characteristic curve when they where you could not find in

conventional charging techniques. The charging process is controlled by the software

program microcontroller (PIC 16F876).Since the battery chemistries are different for

different types of batteries, several sets of programs would have to written to the

controller for each battery given by the manufacturer.

IV

There are some theoretical design calculations included for designing of power

electronics modules. (DC-DC converter, square pulse generator, single rail power & dual

rail power supplies,etc...) Calculations have been done based on highly theoretical facts.

Therefore some practical observations are tends to differ from the theoretical approach.

Most of the theories studied in the power electronic lessons of my M.Sc post graduate were

widely used in doing above mentioned designs.

At the beginning the actual target was to built a battery charging panel of 110V,but due to

some limitations of purchasing of high capacity transformer which suit to this application,

the project was limited to 40V panel only. But the concept, approach & the guide line would

be more or less same for the more advanced systems also.

V

Acknowledgement

Thanks are due first to my supervisor, Dr. J.P Karunadasa, for his great insight,

perspectives, guidance and of humor. My sincere thanks go to the JCT Electrical

engineering staff of J.C.T (Jaya Container Terminal) of Sri Lanka Ports Authority for

helping in various ways to clarify things related to my academic works in time with

excellent corporation and guidance. Sincere gratitude is also extended to the people who

serve in the Department of Electrical Engineering office.

I extend sincere gratitude to my superiors, Mr. A.D.T Gunasekara (Chief Electrical

Engineer of Sri Lanka Ports Authority) who made me to be released from my duties to

success this project & Mr.H.A.N.S Fernando (Deputy Chief Electrical Engineer) who

suggested this project concept for this thesis.

Lastly, I should thank many individuals, friends and colleagues who have not been

mentioned here personally in making this educational process success. May be I could

not have made it without your supports.

VI

List of Figures

Figure Page

Figure 1.3.1 Basic Functional Block 3

Figure 1.3.2 Typical Characteristics of Ni-Cd battery 4

Figure 1.3.3 Basic Software Algorithm 6

Figure 1.4.1 Pin Configuration of PIC 16F876A 8

Figure 1.4.2 Demonstration Circuit 10

Figure 1.4.3 PIC Programmer Circuit 10

Figure 2.1.14 Bridge Rectifier 13

Figure 2.1.2 DC-DC Converter Circuit 14

Figure 2.1.3 Single Rail Power Supplies 14

Figure 2.1.4 Dual Rail Power Supplies 14

Figure 2.11 (a) Dimensions of the Core 17

Figure 2.11 (b) Core Loss Curves 19

Figure 2.12 (a) Pin Configuration of 555 Timer 23

Figure 2.12 (b) Pin Data of 555 Timer 25

Figure 2.12 (c) Square Pulse Generator using 555 Timer 26

Figure 2.13 (a) Pin Configuration of TL082 family 27

Figure 2.13 (b) Internal View of TL082 28

Figure 2.13 (c) Frequency & Temperature Characteristics of TL082 28

Figure 2.13 (d) Load & Voltage Characteristics TL082 29

Figure 2.13 (e) Switching Amplifier Circuit 30

Figure 2.14 (a) Figure 2.14-(a) Pin Configuration of TL082 31

Figure 2.14 (b) Typical Characteristics of LM339 (Vcc=15v;Ta =25°) 33

Figure 2.14 (b) Comparator Circuit 33

Figure 2.21 (a) Pin Configuration of PIC16F876A 34

Figure 2.21 (b) Demonstration Circuit 37

Figure 2.22(a) ADCONO Register 38

VII

Figure 2.22(b) ADC0N1 Register 40

Figure 11.2 Analog Input Model 42

Figure 11.3 A/D Conversion TAD Cycle 44

Figure 11.4 A/D Result Justification 45

Figure 2.23(a) CCP Module in PWM Mode 46

Figure 2.23(b) PWM Output 46

Figure 2.23(c) Data of the PIC16F876A 48

Figure 3.0 (a) Voltage across the Primary Winding (Theoretical) 55

Figure 3.0 (b) Voltage across the Primary Winding (Observed) 56

Figure 3.0 (c) Current of the Primary side of the Converter (Theoretical) 56

Figure 3.0 (d) Current of the Secondary side of the Converter (Observed) 57

Figure 3.0 (e) Current through the Secondary Diode 57

Figure 3.0 (f) Duty Cycle 50% 58

Figure 3.0(g) Duty Cycle 35% 58

Figure 3.0 (h) Duty Cycle 10% 59

Figure 3.21(a) Voltmeter reading & desired value vs. time (8 hrs.) 62

Figure 3.21(b) Voltage Error vs. Time (8 hrs.) 63

Figure 3.3 (a) Switching Amplifiers 64

Figure 3.3 (b) Controller Circuit Operate with the main Panel 64

Figure 3.3 (c) Fly-Back Transformer of the Converter 65

Figure 3.3 (d) Overvoltage Comparator Circuit 65

Figure 3.3 (e) Power Transformer Output to the Dual Supply 66

Figure 3.3 (f) Top view of the Panel ' 66

Figure 3.3 (g) 3 Push Buttons Assigned for 3 Battery Types 67

& the Reset Button (left corner)

Figure 3.3 (h) 4 -Bridge Rectifier testing with a Variac 67

Figure 3.3 (i) 3 Sets of Batteries under Charging. 68

Figure Appendix A: (i) Comparator Symbol 75

VIII

List of Tables

Table

Table 1: Operating characteristics of TL082

Table 2: Ratings of the LM339 comparator

Table 3: Analog / Digital channel configuration

Table 11.1: TAD vs. maximum device operating frequency

Table 3.20 Voltmeter reading during eight hours