ABSTRACT

This work is on a smart continuity tester using LM749 used for test and repair jobs. The device provides a simple test for localizing faults in multicore cables. Open circuits are more likely at connector ends. By identifying the faulty end, the continuity tester allows you to open and repair the correct cable end. This action avoids the risk of damaging a good connector by opening it up. This approach is also useful for testing an installed cable with ends at different locations.

The schematic illustrates a circuit for a continuity tester that injects a signal on one cable wire and then looks for the absence of capacitive coupling on the other wires. One end of a bad cable typically shows good continuity, while the other end typically has one or more connector pins with no continuity. Because a short in the cable appears as a good connection, the operator can easily confirm that the tester is operating correctly by simply shorting its test leads together.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PROBLEM STATEMENT
• AIM OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• SCOPE OF THE PROJECT
• RESEARCH QUESTION
• METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF THE STUDY
• PURPOSE CONTINUITY TESTING
• ELECTRICAL CONDUCTIVITY
• REVIEW OF ELECTRICITY

CHAPTER THREE

METHODOLOGY

• SYSTEM BLOCK DIAGRAM
• TOOLS REQUIRED
• CIRCUIT DIAGRAM
• CIRCUIT DESCRIPTION
• SYSTEM OPERATION
• DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

4.0      TEST AND RESULT ANALYSIS

• CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
• CASING AND PACKAGING
• ASSEMBLING OF SECTIONS
• TESTING OF SYSTEM OPERATION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

A continuity tester is device used determining if an electrical path can be established between two points. That is, if an electrical circuit can be made. They are also device which is used for identifying the correct continuity of a particular conductor in question. Or in other words the device may be used for tracing faults or breaks in a particular conductor or a wire. The circuit under test is completely de-energized prior to connecting the apparatus (Dean et al., 2010)

The tester consists of an indicator in series with a source of electrical power – normally a battery, terminating in two test leads. If a complete circuit is established between the test-leads, the indicator is activated (Dean et al., 2010).

The indicator may be an electric light or a buzzer. This led to the term “buzzing out a circuit” (which means to test for continuity) Audible continuity buzzers or beepers are built into some models of multimeter, and the continuity setting is normally shared with the ohmmeter setting.

A popular design has the tester combined with a standard flashlight. A phone connector or jack plug in the rear of the unit permits a set of test leads to be plugged in effecting a quick conversion between the two applications.

For situations where continuity testing must be done on high resistance circuits, or where delicate conductors and sensitive components that might be damaged by excessive current are present, a low voltage, low current device must be used. These typically use a dual op-amp and watch batteries to drive an LED as an indicator. These testers can be exquisitely sensitive; for example they will indicate if the test points are taken by both hands.

There are times when a simple continuity test fails to reveal the problem. For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a standard tester to respond.

In these applications a latching continuity tester is used. A more complex device, it detects intermittent opens and shorts as well as steady-state conditions. These devices contain a fast acting electronic switch forming a gated astable oscillator which detects and locks (latches) the indicator on an intermittent condition with a duration of less than a millisecond.

1.2                                                  PROBLEM STATEMENT

It is very difficult to identify a broken conductor in a circuit. A continuity tester is useful in determining the damaged components or broken conductors in a circuit. It can also help in determining if the soldering is good, if the resistance is too high for flow of current or if the electrical wire is broken between two points.

• AIM AND OBJECTIVE OF THE STUDY

The purpose of the electrical continuity testing is to verify and document effective electrical conductance. The main aim of this work is to build a portable device used to determine the presence of electrical path that can be established in between two points of an electrical circuit. The objectives of the study to determine:

1. If a fuse is good or blown.
2. If conductors are open or shorted.

• If switches are operating properly.

1. If circuit paths are clear (accomplished by circuit or conductor tracing).
2. To study the application and configuration of an LM749 dual comparator.

1.4                                           SIGNIFICANCE OF THE STUDY

This study will serve as a means of studying the application of an LM749 which is a dual amplifier. This serve shall serve as a means of troubleshooting your circuit and find faults in it. The basic idea is that the device consists of two probes which when come on contact make a buzzing sound. While troubleshooting a circuit the probes are touched to the two contacts which needs to be tested, if they are connected the continuity sensor makes a buzzing sound.

1.5                                          APPLICATION OF THE PROJECT

This device typically used to construct and test electric circuits. By this device we checked the polarity of any electrical and electronics circuit which is essential for designing any required important system. This tester also helps to check the continuity of the wire of our house wearing system.

1.6                                                BENEFITS OF THE STUDY

• it will save the user’s time.
• Fewer human resources are required.
• Reliability: It is more reliable and quicker way when running boring repetitive standardized tests which cannot be skipped.
• It not only checks for continuity but also for shorts.

1.7                                                   SCOPE OF THE STUDY

The scope of this work covers building a smart continuity tester consists of a battery in housing, with a test probe connected to one end of the battery housing and a test wire with an alligator clip connected to the other end using LM749 as the heart of the circuit. It is used with the current turned off to determine whether a particular electrical component is carrying electricity and to pinpoint the cause of a problem.

1.8                                    RESEARCH QUESTION

1. What is conductor continuity test?
2. How do you check the continuity of a protective conductor?

• How do I test a wire for continuity?

1. What is the continuity tester operating principle?

1.9                                                        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. Design of the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out. The construction of this project includes the placing of components on Vero boards, soldering and connection of components,

• Finally, the whole device was cased and final test was carried out.

1.10                                                      PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.