Design And Construction Of A Microcontroller Based Capacitance Meter

ABSTRACT

Capacitors are one of the most common passive electrical components that are extensively used in all kinds of electronic circuits. In this project, we will discuss a technique of building a digital capacitance meter using a PIC microcontroller. This project can measure capacitance values from 1 nF to 99 nF, with a resolution of 1 nF. The technique is based on measuring the time elapsed when a capacitor is charged to a known voltage through a series resistor. The microcontroller used in this project is AT89s52 microcontroller.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• SCOPE OF THE PROJECT
• LIMITATION OF THE PROJECT
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• REVIEW OF CAPACITANCE
• REVIEW OF CAPACITORS
• MICROCONTROLLER UNIT
• SYSTEM POWER SUPPLY

CHAPTER THREE

SYSTEM DESIGN

• SYSTEM BLOCK DIAGRAM
• DESCRIPTION OF SYSTEM BLOCK
• SYSTEM CIRCUIT
• CIRCUIT DESCRIPTION
• SYSTEM OPERATION
• SYSTEM FLOW CHAT

CHAPTER FOUR

TEST AND RESULT ANALYSIS

• INSTALLATION OF THE COMPLET DESIGN
• CONSTRUCTION PROCEDURE AND TESTING
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION
• RESULT

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

A capacitor is a device that stores an electrical charge or energy on its plates. These plates (a positive and a negative plate) are placed very close together with an insulator (dielectric) in between to prevent the plates from touching each other. A capacitor can carry a voltage equal to the battery or input voltage. Usually a capacitor has more than two plates depending on the capacitance or dielectric type. The capacitance value of a capacitor can be measured by utilizing one of its basic properties. The process is a bit complicated when compared to measuring of a resistance value because the capacitor is a reactive. Capacitance measurement with standardized and easy to read output has been for many years the primary goal of numerous research and development efforts. As such are considered the solutions with frequency output [1-4]. Their typical disadvantages are (1) relatively slow sensor readout speed (only a few conversions per second); (2) dependence of the readout time on the value of the measurands [4]. Another trend is the direct conversion of capacitance into digital code, in which the measured capacitance makes part of the analog-to-digital converter [5-7]. In general people use to measure the capacitance value by comparing its value with the known value of another capacitor using complicated LCR Bridge. There are different bridge techniques [8-13] for measuring the capacitance, but the Schering bridge technique may, perhaps, be considered to be one of the most sensitive technique for this measurement. The measurement errors due to the stray capacitances with this bridge technique may be minimized by using the Wagner-earth technique with screened bridge components and lead wires. One disadvantage of this technique may be the requirement for several repetitions of bridge balance and Wagner-earth balance for each observation. Moreover, there are other techniques proposed by various investigators to minimize the error due to the effect of stray capacitances. A modified approach of the balancing technique of the AC Wheatstone bridge network has been reported by Takagishi [14], whereas Morioli et al. [15] and Holmberg [16] have proposed self-balancing techniques to achieve highly accurate measurements. Kolle et.al. [17] Suggested a synchronous modulation and demodulation technique for the precision measurement of the capacitance of a capacitive transducer. Yang et. Al. [18] suggested an electrical capacitance tomography (ECT) technique for measurement of the change of capacitance of a multi-electrode capacitive transducer. Various other attempts have been made to measure small capacitance of a transducer very accurately such as Capacitance to DC voltage converter technique [19], Charge transfer technique [20-21] and circuit theory based technique [22] etc. In the present study, we adopted the basic principle of charging and discharging of the capacitor an arrangement. Nowadays, the popularity of microcontroller is increasing, due to the fact that they are being used in all types of instruments and in embedded environments. In the present study, the technique utilizes charging and discharging for determination of capacitance using the microcontroller as a tool, while most of the conventional techniques measure the capacitance using bridge methods.

1.2                                                  PROBLEM STATEMENT

There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible to identify them by size due to the different forms of construction. So you have to be able to read and interpret the codes on the body. But if the numbers are missing or microscopic in size, you have a problem. The only solution is to have a piece of test equipment to identify them for you.

A microcontroller based capacitance meter measures capacitance. Depending on the sophistication of the meter, it may display the capacitance only, or it may also measure a number of other parameters such as leakage, equivalent series resistance (ESR), and inductance.

This device reads the value of a capacitor and displays it on an analogue meter.

1.2                                             OBJECTIVE OF THE PROJECT

The objective of this project is construct an electronic testing equipment used to measure capacitance of capacitors. It focuses on building a digital capacitance meter using a AT89s52.

1.3                                         SIGNIFICANCE OF THE PROJECT

There has always been a problem identifying capacitors, due to the enormous variety in size, shape and coding. Most of the time it is impossible to identify them by size due to the different forms of construction. So you have to be able to read and interpret the codes on the body. But if the numbers are missing or microscopic in size, you have a problem. The only solution is to have a piece of test equipment- capacitance meter, to identify them for you.

1.4                                                 SCOPE OF THE PROJECT

This project is capable of measuring all but the largest capacitors used in circuits. As well, the markings of capacitors from salvaged equipment often rub off. By being able to measure these unmarked components, this project will prove useful to the constructor, vintage radio enthusiast or antenna experimenter.

1.5                                              PURPOSE OF THE PROJECT

The purpose of this work is to design a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors. Depending on the sophistication of the meter, it displays the capacitance of capacitors only

1.6                                              PROBLEM OF THE PROJECT

1. it digitally display capacitance of capacitors using a AT89s52 microcontroller.
2. This project can measure capacitance values from 1 nF to 99 ?F, with a resolution of 1 nF

1.7                                      APPLICATIONS OF THE PROJECT

1. Capacitance Meter can be used to measure capacitance of unknown capacitors.
2. Using PIC microcontroller for Capacitance Meter makes it easy to implement the project and with slight modifications, the circuit can be made for a wide range of capacitors.

1.8                                         METHODOLOGY

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. programming of a AT89s52microcontroller
2. Design and calculation for the changeover was carried out.
3. Studying of various component used in circuit.

• Construct a digital changeover circuit.
• Finally, the whole device was cased and final test was carried out.

1.8                          PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to the study. In this chapter, the background, significance, objective, purpose, scope, application, limitation and problem of the study were discussed.

Chapter two is on literature review of this study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.