Apltcl024 Sgd l 01 Electrical Fundamental

s l a t n e m a d n u F l a c e i d i r u t G c t n e e d l u t E S

Caterpillar Service Technician Module APLTCL024 ELECTRICAL FUNDAMENTALS

Published by Asia Pacific Learning 1 Caterpillar Drive Tullamarine Victoria Australia 3043 Version 3.2, 2003

Copyright © 2003 Caterpillar of Australia Pty Ltd Melbourne, Australia. All rights reserved. Reproduction of any part of this work without the permission of the copyright owner is unlawful. Requests for permission or further information must be addressed to the Manager, Asia Pacific Learning, Australia.

This subject materials is issued by Caterpillar of Australia Pty Ltd on the understanding that:

1.

Caterpillar Caterpillar of Austral Australia ia Pty Ltd, Ltd, its offici officials, als, author author(s), (s), or any any other persons persons involve involved d in the preparation of this publication expressly disclaim all or any contractual, tortious, or other form of liability to any person (purchaser of this publication or not) in respect of the publication and any consequence arising from its use, including any omission made by any person in reliance upon the whole or any part of the contents of this publication.

2.

Caterpillar Caterpillar of Austra Australia lia Pty Pty Ltd express expressly ly disclaims disclaims all and any liabil liability ity to any any person person in respect of anything and of the consequences of anything done or omitted to be done by any such person in reliance, whether whole or partial, upon the whole or any part of the contents of this subject material.

Acknowledgements A special thanks to the Caterpillar Family for their contribution in reviewing the curricula for this t his program, in particular: 

Caterpillar engineers and instructors



Dealer engineers and instructors



Caterpillar Institutes.

MODULE I NTRODUCTION Module Title Electrical Fundamentals Fundamentals..

Module Description This module covers the knowledge and skills of Electrical Fundamentals. Upon satisfactory completion of this module students will be able to competently service and repair basic electrical circuits.

Pre-Requisites The following must be completed prior to delivery of this module: 

Occupational Health & Safety Procedures



Workplace Tools.

Learning & Development Delivery of this facilitated module requires access to the Electrical Fundamentals Activity Workbook, a relevant workplace or simulated workplace environment and equipment to develop/practice the skills.

Suggested References 

Electrical Schematic for 988B



SMHS7531 Special Instruction - Use of 6V3000 Sure Seal Repair Kit



SEHS9615 Special Instruction - Servicing DT Connectors

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SEHS9065 Special Instruction - Use of CE/VE Connector Tools Tools



RENR 2140 9509 Electrical Schematic.

Resource 

9U7330 Digital Multimeter



Electrical test bench



Video SEVN3197 - Basic Wire Maintenance



6V3000 Sure Seal Repair Kit



IU5805 Deutsch Crimp Tool



IU5804 Deutsch Crimp Tool



Special Instruction SEHS8038 Use of VE Connector Tool Group



Special Instruction SMHS7531 Use of 6V3000 Sure-Seal Repair Kit



Special Instruction SEHS9615 Servicing DT Connectors



4C3806 Deutsch Connector Kit



9U7246 Deutsch DT Connector Kit



Special Instruction SEHS9065 Use of CE/VE Connector Tools



8T5319 Removal Tool Gp



4C4075 Crimp Tool Gp



IU5804 Crimp tool Gp



Deutsch Rectangular Connectors (ARC) (QTY).

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© Caterpillar of Australia Pty Ltd

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ELECTRICAL FUNDAMENTALS

MODULE INTRODUCTION

Assessment Methods Classroom and Workshop To demonstrate satisfactory completion of this module, students must show that they are competent in all lear ning outcomes. Consequently, Consequently, activities and assessments will measure all the necessary module requirements. For this module, students are required to participate in classroom and practical workshop activities and satisfactorily complete the following: 

Activity Workbook

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Knowledge Assessments

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Practical Activities.

Workplace To demonstrate competence in this module students are required to satisfactorily complete the Workplace Assessment(s).

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ELECTRICAL F UNDAMENTALS

KNOWLEDGE AND SKILLS ASSESSMENT Explain how electricity works and describe electrical fundamentals.

Assessment Criteria 1.1 Define Define fundament fundamental al electrica electricall terminolog terminology: y: 1.1. 1.1.1 1 Mat Matter ter and and e ele leme ment nts s 1.1.2 Atoms 1.1 1.1.2. .2.1 Ne Neut utro ron n 1 .1 .1. 2. 2.2 Proto n 1.1. 1.1.2. 2.3 3 Elect lectro ron n 1.1.3 Explain Explain positiv positively ely charged charged and and negative negatively ly charged charged atoms atoms 1.1. 1.1.4 4 Elec Electri trica call energ energy y 1.1.5 Define charges charges a and nd electrostat electrostatic ic field 1.2 Explai Explain n elect electrica ricall terms: terms: 1.2.1 1.2 .1 Pote otenti ntial al diffe differen rence ce 1.2 1.2.1. .1.1 Volta oltage ge 1.2.1. 1.2 .1.2 2 Co Coun unte terr EMF EMF (back (back EMF EMF)) 1.2. 1.2.2 2 Co Coul ulom omb b 1.2. 1.2.3 3 Cu Curr rren entt 1.2.3. 1.2 .3.1 1 Con Conve venti ntional onal vers versus us Electr Electron on flow flow 1.2. 1.2.4 4 Re Resi sist stan ance ce 1.2.4. 1.2 .4.1 1 Physi Physical cal dime dimensi nsion on of mate material rials s 1.2.4. 1.2 .4.2 2 Mea Measur sureme ement nt of resist resistanc ance e 1 .2 .2. 4. 4.3 Length 1. 2. 2.4 .4 .4 Width 1.2.4. 1.2 .4.5 5 Tem empe pera ratur ture e 1.2.5 Farad 1.2.6 Her tz tz 1.3 Explai Explain n electri electrical cal circ circuit uits s 1.3. 1.3.1 1 Inter Interco conn nnec ecti ting ng path 1.3.2 1.3 .2 Kircho Kirchoff’ ff’s s Law Law of of curre current nt 1.3.3 1.3 .3 Kircho Kirchoff’ ff’s s Law Law of volta voltage ge 1.3. 1.3.4 4 Ohm’ Ohm’s s Law Law 1.3. 1.3.5 5 Co Cond nduc ucto tors rs 1.3.5. 1.3 .5.1 1 Con Conduc ductiv tivity ity of diff differin ering g material materials s 1.3. 1.3.6 6 Insu Insula lato tors rs 1.3.6. 1.3 .6.1 1 Insula Insulatin ting g effect effect of differin differing g materials materials 1.3. 1.3.7 7 Semi Semico cond nduc ucto tors rs

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K NOWLEDGE AND S KILLS A SSESSMENT


1.4 Describe the construction of different types of magnets 1.4.1 Natural 1.4.2 Artificial 1.4.3 Electromagnets 1.5 Explain magnetic terminology 1.5.1 Poles 1.5.2 Magnetic fields 1.5.3 Lines of force 1.5.4 Magnetic flux 1.5.5 Magnetic force 1.6 Explain electromagnetic induction 1.6.1 Basic concepts 1.6.2 Strength of induction 1.6.2.1 Strength of magnetic field 1.6.2.2 Speed and motion 1.6.2.3 Number of conductors 1.6.3 Voltage induction 1.6.3.1 Generated voltage 1.6.3.2 Self-induction 1.6.3.3 Mutual induction. Identify and explain the function of basic electrical components.

Assessment Criteria 2.1 Identify and explain the function of basic electrical components: 2.1.1 Wire 2.1.1.1 Solid 2.1.1.2 Fusible links 2.1.1.3 Stranded 2.1.1.4 Twisted/shielded cable 2.1.1.5 Wire gauge 2.2 Wiring harness 2.2.1 Connectors 2.2.1.1 Purpose 2.2.1.2 General Service 2.2.1.3 Plating 2.2.1.4 Contaminants 2.2.1.5 Vehicular Environmental (VE) connectors 2.2.1.6 Sure-seal connectors 2.2.1.7 Deutsch Connectors 2.2.1.8 Caterpillar Environmental Connectors (CE)

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2.2.2 Terminals 2. 2.2.1 Slide 2. 2.2.2 Bullet 2.2.2.3 Crimp and soldered 2.2.2.4 Install a solderless connection 2.2.3 Switches 2.2.3.1 Single pole, single throw 2.2.3.2 Single pole, double throw 2.2.3.3 Double pole, single throw 2.2.3.4 Double pole, double throw 2.2.3.5 Common Switches – Toggle – Rotary – Rocker – Push -on – Pressure – Magnetic – Key star t – Limit – Cut-out 2.2.4 Circuit protectors 2 .2. 4.1 Fuses – Blade – Car tridge – Ceramic – In-line 2.2.4.2 Fusible link 2.2.4.3 Circuit breakers – Cycling – Non-cycling 2.2.5 Relays 2.2.6 Solenoids 2.2.7 Resistors 2.2.7.1 Fixed resistors 2.2.7.2 Wattage 2. 2.7 .3 Rating 2.2.7.4 Variable resistors 2.2.7.5 Thermistors 2.2.7.6 Failed resistors 2.2.8 Capacitor 2.2.8.1 Energy storage 2.2.8.2 Smoothing 2.2.8.3 Suppression 2.2.8.4 Capacitor measurement

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2.2.9 Lamps 2.2.9.1 Types of bulbs – Common – Festoon – Panel – Sealed beams – Prefocus bulbs – Quartz halogen bulbs – Precautions fitting quartz halogen bulbs 2.2.9.2 Bulb wattage 2.2.9.3 Candlepower 2.2.10 Instruments 2.2.10.1 Mechanical 2.2.10.2 Magnetic operation 2.2.10.3 Thermal operation 2.2.10.4 Digital electronic 2.2.10.5 Indicators and warning lights. Describe the operation of a basic electrical circuit.

Assessment Criteria 3.1 Describe the construction of a basic electrical circuit 3.1.1 Power source 3.1.2 Protection device (fuse or circuit breaker) 3.1.3 Load 3.1.4 Control device (switch) 3.1.5 Conductors 3.2 Explain the general rules of Ohm’s Law 3.2.1 Ohm’s Law equation 3.2.2 Ohm’s Law solving circle 3.2.2.1 Voltage unknown 3.2.2.2 Resistance unknown 3.2.2.3 Current unknown 3.3 Define metric prefixes used in electrical circuits 3.3.1 Base units 3.3.1.1 Volts 3.3.1.2 Ohms 3.3.1.3 Amperes 3.3.2 Prefixes 3.3.2.1 Mega 3.3.2.2 Kilo 3. 3.2.3 Milli 3. 3.2 .4 Micro

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3.4 Calculate power in a circuit using Watt’s Law 3.4.1 What is power 3.4.2 Calculate power 3.5 Explain basic circuit theory 3.5.1 Series circuit 3.5.1.1 Applying Ohm’s Law 3.5.2 Parallel circuit 3.5.2.1 Applying Ohm’s Law 3.5.3 Series-parallel circuit 3.5.3.1 Applying Ohm’s Law. Interpret basic electrical schematics.

Assessment Criteria 4.1 Identify component symbols in an electrical schematic 4.1.1 Battery 4.1.2 Gr ound 4.1.3 Wire 4.1.4 Connectors 4.1.5 Switches 4.1.5.1 Connect/disconnect 4.1.5.2 Toggle 4.1.5.3 Temperature 4.1.5.4 Pressure 4.1.6 Circuit protection 4 .1. 6.1 Fuses 4.1.6.2 Fusible links 4.1.6.3 Circuit breakers 4.1.7 Relays 4.1.8 Solenoids 4.1.9 Transistor 4.1.10 Resistors 4.1.11 Rheostat 4.1.12 Potentiometer 4.1.13 Alternator 4.1.14 Starter 4.1.15 Motor 4.1.16 Lamps 4.1.17 Gauges

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4.2 Identify electrical schematic features 4.2.1 Colour codes for circuit identification 4.2.2 Colour abbreviation codes 4.2.3 Symbol description 4.2.4 Wiring harness information 4.2.5 Schematic notes and conditions 4.2.6 Grid design for component location 4.2.7 Component part numbers 4.2.8 Dashed coloured lines 4.2.9 Heavy double dashed lines 4.2.10 Thin black dashed line 4.2.11 Machine electrical schematics for old and new format 4.2.12 Features on the back of the schematic. Identify electrical measurements using a Digital Multimeter.

Assessment Criteria 5.1 Identify the main parts of a Digital Multimeter 5.1.1 Liquid crystal display 5.1.2 Push buttons 5.1.3 Rotary switch 5.1.4 Meter lead inputs 5.1.5 Overload display indicator 5.2 Measure AC/DC Voltage using a Digital Multimeter 5.2.1 Voltmeter must always be connected in parallel 5.2.2 Circuit is on 5.2.3 Position of leads in the multimeter 5.2.4 Rotary switch 5.2.5 Position of leads in the circuit 5.3 Measure voltage drop using a Digital Multimeter 5.3.1 Source voltage 5.3.2 Closed switch contacts 5.3.3 Circuit under power 5.4 Measure AC/DC Current using a Digital Multimeter 5.4.1 Voltmeter must always be connected in series 5.4.2 Burden voltage 5.4.3 Rotary switch 5.4.4 Position of leads in the multimeter 5.4.4.1 Initial placement to determine current output 5.4.4.2 Buffer 5.4.5 Create an open circuit 5.4.6 Position of leads in the circuit 5.4.7 Apply power to circuit

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5.5 Measure resistance using a Digital Multimeter 5.5.1 Turn off circuit power 5.5.2 Discharge all capacitors 5.5.3 Isolate the circuit 5.5.4 Test lead resistance 5.5.5 Position of leads in multimeter 5.5.6 Rotary switch 5.5.7 Position of leads in the circuit or on component. Identify faults in an electrical circuit.

Assessment Criteria 6.1 Identify various faults that may occur in an electrical circuit 6.1.1 Open circuit 6.1.2 Short circuit 6.1.3 Grounded circuit 6.1.4 High resistance 6.1.5 Intermittent condition. Identify soldering techniques on electrical equipment.

Assessment Criteria 7.1 Identify personal safety precautions when soldering. 7.2 Explain the properties of solder 7.2.1 Types 7.2.2 Wetting action 7.2.3 Flux 7.3 Identify types of soldering irons used to solder electrical components 7.3.1 Controlling heat 7.3.2 Thermal mass 7.3.3 Surface condition 7.3.4 Thermal linkage 7.4 Identify the requirements for applying solder 7.4.1 Applying solder 7.4.2 Post solder cleaning 7.4.3 Resoldering 7.4.4 Quality of work 7.5 Identify the need for wire preparation when soldering electrical connections 7.5.1 Stripping away insulation 7.5.2 Nicks, breaks and cuts 7.5.3 Discolouration 7.5.4 Tinning.

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Perform electrical measurements using a digital multimeter and repair faults to an electrical circuit.

Assessment Criteria 8.1 State and follow the safety precautions that must be observed to prevent personal injury or damage to equipment 8.2 Identify and state the purpose of the parts of a digital multimeter 8.2.1 Liquid crystal display (LCD) 8.2.2 Push buttons 8.2.3 Rotary switch 8.2.4 Test lead jacks 8.3 Explain how to read the scales and connect the leads to a digital multimeter 8.3.1 For measuring AC/DC voltage 8.3.2 For measuring voltage drop 8.3.3 For measuring direct current 8.3.4 For measuring resistance 8.4 Connect a multimeter to an operating electrical circuit, measure electrical values and determine repair action 8.4.1 AC/DC voltage 8.4.2 Voltage drop 8.4.3 Direct current 8.4.4 Resistance 8.4.5 Open circuit 8.4.6 Short circuit 8.4.7 Faulty ground 8.5 Conduct minor repairs on an electrical circuit 8.5.1 Fuse replacement 8.5.2 Bulb replacement 8.5.3 Terminal and wire repairs 8.5.4 Open, short circuits and faulty ground 8.6 Facilitators are to ensure that the tasks are completed 8.6.1 Without causing damage to components or equipment 8.6.2 Using appropriate tooling, techniques and materials 8.6.3 According to industry/enterprise guidelines, procedures and policies 8.6.4 Using and interpreting correct information from the manufacturer’s specifications.

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TOPIC 1: Electrical Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Electrical Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Electrical Circuits and Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Magnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Magnetic Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Electromagnetic Induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

TOPIC 2: Electrical Components . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Terminals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Install a Solderless Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Circuit Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Lamp Bulbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

TOPIC 3: Electrical Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Basic Circuit Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Metric Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Basic Circuit Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

TOPIC 4: Electrical Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

TOPIC 5: Digital Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Introduction to Digital Multimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

TOPIC 6: Circuit Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Circuit Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

TOPIC 7: Soldering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Properties of Solder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Procedure Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

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TABLE OF CONTENTS

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TOPIC 1 Electrical Fundamentals FUNDAMENTALS Electricity

Figure 1

What is electricity? It is said that flashlights, electric drills, motors, etc. are generally recognised as “electric”. However, computers and televisions are often referred to as “electronic”. What is the difference? Anything that works with electricity is electric, including both flashlights and electric drills, but not all electric components are electronic. The term electronic refers to semiconductor devices known as “electron devices”. Electron devices are named as such because they depend on the flow of electrons for their operation. To better understand electricity, it is necessary to have a basic knowledge of the fundamental atomic structure of matter. Matter is anything that has mass and occupies space. It can take several forms, or states, such as the three common forms; being solid, liquid and gas. This module will provide a basic understanding of the theoretical principles needed before studying and working with electrical circuits and components.

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Matter and Elements Matter is anything that takes up space and, when subjected to gravity, has weight. Matter consists of extremely tiny particles grouped together to form atoms. There are approximately 100 different naturally occurring atoms called elements. An element is defined as a substance that cannot be decomposed any further by chemical action. Examples of natural elements are copper, lead, iron, gold and silver. Other elements (approximately 14) have been produced in the laboratory. Elements can only be changed by an atomic or nuclear reaction. However, they can be combined to make the countless number of compounds which we experience every day. The atom is the smallest particle of an element that still has the same characteristics as the element. Atom is the Greek word meaning a particle too small to be subdivided.

Atoms Although an atom cannot be seen, its hypothetical structure fits experimental evidence that can be measured very accurately. The size and electric charge of the invisible particles in an atom are indicated by how much they are deflected by known forces. The present “solar system” model, with the sun at its centre and the planets rotating around it was proposed by Niels Bohr in 1913 and known as the “Atomic Model”.

Figure 2 - Atom

The centre of an atom (Figure 2) is called the nucleus and is composed of particles called protons and neutrons. Orbiting around every nucleus are small particles called electrons, which are much smaller in mass than either the proton or neutron. Normally, an atom has an equal number of protons and electrons. The number of protons or electrons indicates the “atomic number”. The “atomic weight” of an element is the total of protons and neu trons.

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Figure 3 - Neutron, Proton, Electron.

Figure 3 shows the structure of two of the simpler atoms: 



Hydrogen contains 1 proton in its nucleus balanced by 1 electron in its orbit or shell. The atomic number for a hydrogen atom is 1 and its atomic weight is 1 (1 proton). Helium has 2 protons in its nucleus balanced by 2 electrons in orbit. The atomic number for helium is 2 and its atomic weight would be 4 (2 protons + 2 neutrons).

Scientists have discovered many particles in an atom, but for the purpose of explaining basic electricity, just three need discussion: electrons, protons and neutrons. An atom of copper is to be used as an example.

Figure 4 - Copper Atom

The nucleus of the atom is not much bigger than an electron, so their size cannot really be determined. In the copper atom (Figure 4), the nucleus contains 29 protons (+) and 35 neutrons and has 29 electrons (-) orbiting the nucleus. The atomic number of the copper atom is 29 and the atomic weight is 64.

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Electron Flow

Figure 5

If a length of copper wire is connected to a positive and negative source, such as a battery (Figure 5), an electron (-) is forced out of orbit and attracted to the positive (+) end of the battery. The atom is now positively (+) charged because it now has a deficiency of electrons (-). It in turn attracts an electron from its neighbour. The neighbour in turn receives an electron from the next atom, and so on until the last copper atom receives an electron from the negative end of the battery. The result of this chain reaction is that the electrons move through the battery from the negative end to the positive end of the battery. The flow of electrons continues as long as the positive and negative charges from the battery are maintained at each end of the wire.

Electrical Energy There are two types of forces at work in every atom. Under normal circumstances, these two forces are in balance. The protons and electrons exert forces on one another, over and above gravitational or centrifugal forces. It has been determined that besides mass, electrons and protons carry an electric charge, and these additional forces are attr ibuted to the electr ic charge that they carry. However, there is a difference in the forces. Between masses, the gravitational force is always one of “attraction” while the electrical forces both “attract” and “repel”. Protons and electrons attract one another, while protons exert forces of repulsion on other protons, and electrons exert repulsion on other electrons.

Figure 6 - Force between charges

Thus, It appears to be two kinds of electrical charge. Protons are said to be positive (+) and the electrons are said to be negative (-). The neutron as the name implies, is neutral in charge. The directional quality of the electricity, based on the type of charge, is called “polarity”. This leads to the basic law of electrostatics which states: “LIKE charges repel each other and UNLIKE charges attract each other” (Figure 6).

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Charges and Electrostatics

Figure 7 - Electrostatic field between two charged bodies

The attraction or repulsion of electrically charged bodies is due to an invisible force called an electrostatic field, which surrounds the charged body. Figure 7 shows the force between charged particles as imaginary electrostatic lines from the positive charge to the negative charge. The conventional method of representing the lines of force is for the arrowheads to point from the positive charge toward the negative charge.

Figure 8 - Electrostatic field between two negatively charged particles

When two like charges are placed near each other, the lines of force repel each other as shown in Figure 8.

ELECTRICAL TERMS Potential Difference Because of the force of its electrostatic field, an electric charge has the ability to move another charge by attraction or repulsion. The ability to attract or repel is called its “potential”. When one charge is different from the other, there must be a difference in potential between them. The sum difference of potential of all charges in the electrostatic field is referred to as electromotive force (EMF). The basic unit of potential difference is the “Volt” (E) named in honour of Alessandro Volta, an Italian scientist and the inventor of the “Voltaic Pile”, the first battery cell. The symbol for potential is V, indicating the ability to do the work of forcing electrons to move. Because the Volt unit is used, potential difference is called “voltage”. There are many ways to produce voltage, including friction, solar, chemical, and electromagnetic induction. The attraction of paper to a comb that has been rubbed with a wool cloth is an example of voltage produced by friction. A photocell, such as on a calculator, would be an example of producing voltage from solar energy.

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Counter EMF Magnetic lines of force radiate out from a wire in concentric circles. This process is caused by the current flowing in the wire, producing a magnetic field. In a straight wire these lines of force have little effect since they do not cross any other conductor. If the wire is formed into a coil, the lines of force self-induct back into the wire (selfinduction). This induced voltage is called back EMF or counter EMF. This is summed up by the following law known as Lenz’s law: The polarity of the induced EMF is opposite to and opposes the change that create it.

Coulomb A need existed to develop a unit of measurement for electrical charge. A French scientist named Charles Coulomb investigated the law of forces between charged bodies and adopted a unit of measurement called the “Coulomb”. Written in scientific notation, one Coulomb = 6.28 x 10 18 electrons or protons. Stated in simpler terms, in a copper conductor, one ampere is an electric current of 6.28 billion electrons passing a certain point in the conductor in one second (motion).

Current

Figure 9 - Current Flow

In electrostatic theories, as discussed earlier, the concern was mainly the forces between the charges. Another theory that needs explaining is that of “motion” in a conductor. The motion of charges in a conductor is defined as an electric current (Figure 9). An electrostatic field will affect an electron in the same manner as any negatively charged body. It is repelled by a negative charge and attracted by a positive charge. The drift of electrons or movement constitutes an electric current. The magnitude or intensity of current is measured in “Amperes”. The unit symbol is “I”. An ampere is a measure of the rate at which a charge is moved through a conductor. One ampere is a coulomb of charge moving past a point in one second.

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Conventional Versus Electron Flow

Figure 10 - Electron and Conventional Current

There are two ways to describe an electric current flowing through a conductor. Prior to the use of “atomic theory” to explain the composition of matter, scientists defined current as the motion of positive charges in a conductor from a point of positive polarity to a point of negative polarity. This conclusion is still widely held in some engineering standards and textbooks. Some examples of positive charges in motion are applications of current in liquids, gases and semi conductors. This theory of current flow has been termed “conventional current” (Figure 10). With the application of atomic theory, it was determined that current flow through a conductor was based on the flow of electrons (-) or negative charge. Therefore, electron current is in the opposite direction of conventional current and is termed “electron current” (Figure 10). Either theory can be used, but the more popular “conventional” theory describing current as flowing from a positive (+) charge to a negative (-) charge will be used in this module.

Resistance George Simon Ohm discovered that for a fixed voltage, the amount of current flowing through a material depends on the type and physical dimensions of the material. All materials present some “resistance” to the flow of electrons. If the opposition is small, the material is a conductor, if the opposition is large, it is an insulator. The Ohm is the unit of electrical resistance and the Greek letter omega ( Ω) is its symbol. A material has a resistance of one Ohm if a potential of one Volt results in a current of one Ampere. Electrical resistance is present in every electrical circuit, components, wires and connections. As resistance opposes current flow, it changes electrical energy into other forms of energy, such as heat, light or motion. The resistance of a conductor is determined by four factors:

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Figure 11 - Atomic Structure

1.

Atomic structure (free electrons). The more free electrons a material has, the less resistance it offers to current flow (Figure 11).

Figure 12 - Resistance

2.

Length. The longer a conductor of the same width, the higher the resistance. If a length of wire is doubled (Figure 12) the greater the resistance between the two ends.

Figure 13

3.

Width (cross sectional area). The larger the cross sectional area of a conductor, the lower the resistance (a bigger diameter pipe allows for more water to flow). Halving the cross section (Figure 13), doubles the resistance for any given length.

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Figure 14

4.

Temperature. For most materials, the higher the temperature, the higher the resistance. The chart shown in Figure 14 shows the resistance increasing as the temperature rises.

Farad The ability of a capacitor to store electrons is known as capacitance. Capacitance is measures in farads (named after Michael Faraday, the discoverer of the principle). One farad in the ability to store 6.28 billion electrons at a 1-Volt charge differential. Most capacitors have much less capacitance than this, so they are rated in picofarads (trillionths of a farad) and microfarads (millionths of a farad). 1 farad = 1F 1 microfarad = 1µF = 0.000001F 1 picofarad = 1ρF = 0.000000000001F.

Hertz Alternators produce alternating current which cycles between positive & negative. The number of cycles per second is called frequency and is measured in Her tz.

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ELECTRICAL CIRCUITS AND LAWS

Figure 15

An electrical circuit is a path, or group of interconnecting paths, capable of carrying electrical current. It is a closed path (closed circuit) that contains a voltage source or sources. There are two basic types of electrical circuits, series and parallel (Figure 15). The basic series and parallel circuits may be combined to form more complex circuits, but these combined circuits may be simplified and analysed as the two basic types.

Laws It is important to understand the laws needed to analyse and diagnose electrical circuits. They are Kirchoff’s Laws and Ohm’s Law. Gustav Kirchoff developed two laws for analysing circuits. They are stated as: 1.

Kirchoff’s Current Law (KCL) states that the algebraic sum of the currents at any junction in an electrical circuit is equal to zero. Simply stated, all the curr ent that enters a junction is equal to all the current that leaves the junction. None is lost.

2.

Kirchoff’s Voltage Law (KVL) states that the algebraic sum of the electromotive forces and voltage drops around any closed electr ical loop is zero. Simply stated, at a particular point in a closed circuit and going around that circuit, adding all the individual differences in potential, until the starting point was reached, there would be no extra voltage, and none would be left unaccounted for. George Simon Ohm discovered the relationship between three electrical parameters - voltage, current and resistance as follows: The current in an electrical circuit is directly proportional to the voltage and inversely proportional to the resistance.

The relationship can be summarised by a single mathematical equation: 

Electromotive Force Resis tan ce

Current = ----------------------------------------------------------------

or stated in electrical units: 

Volts Amperes = -----------------

Ohms

When using mathematical equations to express electrical relationships, single letters are used to represent them. Resistance is represented by the letter R or the Omega symbol ( Ω ), voltage is represented by the letter E (electromotive force) and current is represented by the letter I (intensity of charge). OHMS law is covered in more detail in Topic 3, Electrical Circuits.

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Electrical Conductors In electrical applications, electrons travel along a path called a conductor or wire. They move by travelling from atom to atom. Some materials make it easier for electrons to travel and they are called “good conductors”. Examples of good conductors are silver, copper, gold, chromium, aluminium and tungsten. A material is said to be a good conductor if it has many free electrons. The amount of electrical pressure or voltage it takes to move electrons through a material depends on how free its electrons are. Although silver is the best conductor it is also expensive. Gold is also a good conductor, and will not corrode like copper but again, is too expensive. Aluminium is less expensive and lighter, but not as good as a conductor as copper. Conductor

Conductivity (to copper)

Silver

1.064

Copper

1.000

Gold

0.707

Aluminium

0.659

Zinc

0.288

Brass

0.243

Iron

0.178

Tin

0.018 Table 1 - Conductivity Chart

The conductivity of a material deter mines how good a conductor that material is. Table 1 shows some of the common conductors and their relative conductivity to copper.

Electrical Insulators Other materials make it difficult for electrons to travel and they are called “insulators”. A good insulator keeps the electrons tightly bound in orbit. Examples of insulators are rubber, wood, plastics, and ceramics. However, it is possible to make an electric current flow through all materials. If the applied voltage is high enough, even the best insulators will break down and allow current flow. Rubber

Plastics

Mica

Glass

Wax or Paraffin

Fibreglass

Porcelain

Dry Wood

Bakelite

Air Table 2 - Common Insulators

Table 2 lists some of the more common insulators. There is another item that should be considered when discussing insulators. Dirt and moisture may serve to conduct electricity around an insulator. If an insulator is dirty or there is moisture present, it could cause a problem. The insulator itself is not breaking down, but the dirt or moisture can provide a path for electrons to flow. It is therefore important to keep the insulators and contacts clean.

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Semi-conductors Materials which are neither good conductors nor good insulators are known as semiconductors. Example of these materials (elements) are Germanium & Silicon. Semiconductors will normally act as inductors, however, they will conduct under certain conditions, such as when an electrical current is applied to them. These materials are the basis for electronic devices discussed in the electronic module.

MAGNETISM

Figure 16 - Magnet

Magnetism is another form of force that causes electron flow or current. A basic understanding of magnetism is also necessary to study electricity. Magnetism provides a link between mechanical energy and electricity. By the use of magnetism, an alternator converts some of the mechanical power developed by an engine to electromotive force (EMF). Conversely, magnetism allows a starter motor to convert electrical energy from a battery into mechanical energy for cranking the engine. Most electrical equipment depends directly or indirectly upon magnetism. Although there are a few electrical devices that do not use magnetism, the majority of our systems, as known today, would not exist. There are three basic types of magnets: 

Natural



Artificial Magnets (Figure 16)



Electromagnets.

Natural Magnets The Chinese discovered magnets about 2637 BC. The magnets used in the primitive compasses are called “lodestones”, and they were crude pieces of iron ore known as magnetite. Since magnetite has magnetic properties in its natural state, lodestones are classified as “natural” magnets.

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Artificial Magnets Artificial Magnets are man-made magnets and are typically produced in the form of metal bars that have been subjected to very strong magnetic fields.

Electromagnets A Danish scientist, named Oersted, discovered a relation between magnetism and electric current. He discovered that an electric current flowing through a conductor produced a magnetic field around the conductor. From this, electromagnets can be used in various applications where switching the flow of electricity ‘on’ or ‘off’ will produce a magnetic field.

MAGNETIC TERMINOLOGY Poles and Fields

Figure 17 - Field Force around a magnet

Every magnet has two points opposite each other that most readily attract pieces of iron. These points are called the “poles” of the magnet: the north pole and the south pole. Just as electric charges repel each other and opposite charges attract each other, like magnetic poles repel each other and unlike poles attract each other. A magnet clearly attracts a bit of iron because of forces that exists around the magnet. This force is called “magnetic field”. Although it is invisible to the naked eye, sprinkling small iron filings on a sheet of glass or paper over a bar magnet can show its force lines. In Figure 17 a piece of glass is placed over a magnet and iron filing are sprinkled on the glass. When the glass cover is gently tapped the filings will move into a definite pattern which shows the field force around the magnet. The field seems to be made up of lines of force that appear to leave the magnet at the north pole, travel through the air around the magnet, and continue through the magnet to the south pole to form a closed loop of force. The stronger the magnet the greater the lines of force and the larger the area covered by the magnetic field.

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Lines of Force

Figure 18 - Lines of Force

To better visualise the magnetic field without iron filings, the field is shown as lines of force in Figure 18. The direction of the lines outside the magnet shows the path a north pole would follow in the field, repelled away from the north pole of the magnet and attracted to its south pole. Inside the magnet, which is the generator for the magnetic field, the lines are from north pole to south pole.

Lines of Magnetic Flux The entire group of magnetic field lines, which can be considered to flow outward from the north pole of a magnet, is called magnetic flux. The flux density is the number of magnetic field lines per unit of a section perpendicular to the direction of flux. The unit is lines per square centimetre in the metric system or lines per square inch in the English system. One line per square centimetre is called a gauss.

Magnetic Force

Figure 19 - Lines of small magnetic circles

Magnetic lines of force pass through all materials; there is no known insulator against magnetism. However, flux lines pass more easily through materials that can be magnetised than through those that cannot. Materials that do not readily pass flux lines are said to have “high magnetic reluctance”. Air has high reluctance; iron has low reluctance. An electric current flowing through a wire creates magnetic lines of force around the wire. Figure 19 shows lines of small magnetic circles forming around the wire. Because such flux lines are circular, the magnetic field has no nor th or south pole.

Figure 20 - Circular Fields

However, if the wire is wound onto a coil, individual circular fields merge. The result is a unified magnetic field with north and south poles as shown in Figure 20.

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As long as current flows through the wire, it behaves just like a bar magnet. The electromagnetic field remains as long as current flows through the wire. However, the field produced on a straight wire does not have enough magnetism to do work. To strengthen the electromagnetic field, the wire can be formed into a coil. The magnetic strength of an electromagnet is proportional to the number of turns of wire in the coil and the current flowing through the wire. If the coils are wound around a metal core, e.g. iron, the magnetic force strengthens considerably. Types of electromagnets typically used in mobile machines are relays and solenoids. Both operate on the electromagnetic principle, but function differently.

ELECTROMAGNETIC INDUCTION

Figure 21 - Electromagnetic Induction

The effect of creating a magnetic field with current has an opposite condition. It is also possible to create current with a magnetic field by ‘inducing’ a voltage in the conductor. This process is known as “electromagnetic induction” (Figure 21). This occurs when the flux lines of a magnetic field cut across a wire (or any conductor). When there is relative motion between the wire and the magnetic field (whether the magnetic field moves or the wire moves), a voltage is induced in the conductor. The induced voltage causes a current to flow. When the motion stops, the current stops. If a wire is passed through a magnetic field, such as a wire moving across the magnetic fields of a horseshoe magnet, voltage is induced. If the wire is wound into a coil, the voltage induced strengthens. This method is the operating principle used in speed sensors, generators, and alter nators. In some cases the wire is stationary and the magnet moves. In other cases, the magnet is stationary and the field windings (wires) move. Movement in the opposite direction causes current to flow in the opposite direction. Therefore, back and forth motion produces Alternating Current (AC). In practical applications, multiple conductors are wound into a coil. This concentrates the effects of electromagnetic induction and makes it possible to generate useful electrical power with a relatively compact device. In a generator, the coil moves and the magnetic field is stationary. In an alternator, the magnetic field is rotated inside a stationary coil.

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The strength of an induced voltage depends on several factors: 

The strength of the magnetic field



The speed of the relative motion between the field and the coil



The numbers of conductors in the coil.

There are three ways in which a voltage can be induced by electromagnetic induction: 

Generated Voltage



Self-Induction



Mutual Induction.

Generated Voltage

Figure 22 - DC Generator

A simple Direct Current (DC) generator in Figure 22 shows a moving conductor passing a stationary magnetic field to produce voltage and current. A single loop of wire is rotating between the nor th and south poles of a magnetic f ield.

Self-Induction

Figure 23 - Self-Induction

Self-induction occurs in a wire when the current flowing through the wire changes. Current flowing through the wire creates a magnetic field that builds up and collapses as the current changes up and down. A voltage is thereby induced in the core. Figure 23 shows self-induction in a coil.

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Mutual Induction

Figure 24 - Mutual Induction

Mutual induction occurs when the changing current in one coil induces a voltage in an adjacent coil. A transformer is an example of mutual induction. Figure 24 shows two inductors that are relatively close to each other. When AC current flows through coil L1 a magnetic field cuts through coil L2 inducing a voltage and producing current flow in coil L2.

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TOPIC 2 Electrical Components WIRE Types of Wire

Figure 25

Wires are the conductors for electrical circuits. Wires are also called leads. Most wires are stranded (made up of several smaller wires that are wrapped together and covered by a common insulating sheath) (Figure 25). There are many types o f wires found in automotive applications, including: 

Copper. The most common type. Copper wires can be single, however are usually stranded.



Fusible Links. There are circuit protection devices that are made of a smaller wire than the rest of the circuit their purpose is to protect against overload.



Twisted/Shielded Cable. A pair of small gauge wires, nor mally stranded, insulated against Radio Frequencies Interference/Electro Magnetic Interference, used for computer communication signals, electronic control modules and other electronic components.

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Wire Gauge In the USA, electrical and electronic circuits are engineered with specific size and length conductors to provide paths for current flow. The size of a wire deter mines how much current it can carry. Wire sizes can be rated in two different ways: 



according to American Wire Gage (AWG) size (usually referred to as simply the “gauge” of the wire) by metric size. AWG No

Ø (inch)

Ø (mm)

Ø (mm2)

Resistance (Ohm/m)

4/0 = 0000

0.460

11.7

107

0.000161

3/0 = 000

0.410

10.4

85.0

0.000203

2/0 = 00

0.365

9.26

67.4

0.000256

1/0 = 0

0.325

8.25

53.5

0.000323

1

0.289

7.35

42.4

0.000407

2

0.258

6.54

33.6

0.000513

3

0.229

5.83

26.7

0.000647

4

0.204

5.19

21.1

0.000815

5

0.182

4.62

16.8

0.00103

6

0.162

4.11

13.3

0.00130

7

0.144

3.66

10.5

0.00163

8

0.128

3.26

8.36

0.00206

9

0.114

2.91

6.63

0.00260

10

0.102

2.59

5.26

0.00328

Table 3 - AWG to Metric Conversion Chart

When repairing or replacing machine wiring it is necessary to use the correct size and length conductors. The chart above illustrates the typical resistances for various size conductors.

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m o d t ) c e n s e d e p R n r r m . u x e C A a m M *

7

1 1

2 1

3 1

5 1

0 2

4 2

2 3

9 5

7 8

e c 0 @ n 0 s C a 0 e o t 1 r 5 s / i t s Ω e 2 e ( m R

0 5

6 3

1 2

8 1

3 . 2 1

3 . 7

4 . 4

2 . 3

5 7 . 1

1 . 1

e z ) t d i s r a S 2 e r d c m a n i r m e a t e ( N t S M

5 3 . 0

5 . 0

5 7 . 0

1

5 0 1

5 . 2

4

6

0 1

6 1

e @ c t n f ) a 0 F t o s 0 7 i 7 s 0 1 / e Ω R (

5 . 6 1

4 . 0 1

-

1 5 0 6

9 0 . 4

8 5 . 2

2 6 . 1

2 0 . 1

4 6 . 0

4 . 0

) s l i n s o m s i t r a o l r c e u C S c r i c (

2 4 6

0 2 0 , 1

-

0 2 6 , 1

0 8 5 , 2

0 1 1 , 4

0 3 5 , 6

0 0 4 , 0 1

0 0 5 , 6 1

0 0 3 , 6 2

s n o ) h s i t c o r c n I e C S (

5 0 0 0 . 0

8 0 0 0 . 0

-

7 2 1 0 0 . 0

3 0 2 0 0 . 0

3 2 3 0 0 . 0

7 1 8 0 0 . 0

7 1 8 0 0 . 0

6 9 2 1 0 . 0

3 0 2 0 . 0

2 2

0 2

-

8 1

6 1

4 1

2 1

0 1

8

6

e n g ) a u c a G i r G W e ( m e r A A i W

. t n e i b m a e v o b a e s i r e r u t a r e p m e t m u m i x a m ) C o 0 2 ( F o 6 3 n o d e s a B *

Table 4

Table 4 therefore assumes a maximum ambient temperature of 150oF (65oC). NOTE: Regard PVC insulated wire as a 185 oF (85 oC) product. When using the AWG, remember that smaller gauge numbers denote larger wire sizes, and larger gauge numbers denote smaller sizes.

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Wiring Harness Many wires are bound together in groups with one or more common connectors on each end. These groups are called wire harnesses. Note that a harness may contain wires from different circuits and systems. An example would be the harness that plugs into the headlight switch assembly, which contains wires for parking lights, tail-lights, and low and high-beam headlights, among others.

Figure 26

Some harness wires are enclosed in plastic or non-conductive fibre conduit (Figure 26). These conduits are split lengthwise to allow easy access to the harness wires. Other harness wires are wrapped in tape. Clips (plastic) and clamps (metal) attach harnesses to the machine. Caterpillar electrical schematics provide wire harness locations to help you easily locate a specific harness on a machine. The features of Caterpillar electrical schematics will be covered later.

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CONNECTORS

Figure 27

The purpose of a connector is to pass current from one wire to another (Figure 27). In order to accomplish this, the connector must have two mating halves (plug or receptacle). One half houses a pin and the other half houses a socket. When the two halves are joined, current is allowed to pass. Connecters are used to make component disassembly easier.

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General Service Comments With the increased use of electronic systems in automotive applications, servicing connectors has become a critical task. With increased usage comes an increase in maintenance on the wiring, connectors, pins and sockets. Another important factor contributing to increased repair is the harsh environment in which the connectors operate. Connectors must operate in extremes of heat, cold, dirt, dust, moisture and chemicals.

Figure 28 - Connectors

Pins and sockets have resistance and offer some opposition to current flow. Since the surface of the pins and sockets are not smooth (contain peaks and valleys) a condition known as asperity (roughness of surface) exists. When the mating halves are connected, approximately one percent of the surfaces actually contact each other (Figure 28). The electrons are forced to converge at the peaks, thereby creating a resistance between the contact halves. Although this process seems rather insignificant to the operation of an electronic control, a resistance across the connector could create a malfunction in electronic controls.

Plating In order to achieve a minimum resistance in the pins and contacts, there needs to be concern with the finish, pressure and metal used in construction of the pins and contacts. Tin is soft enough to allow for “film wiping” but it has a relatively high resistance. Copper has a low resistance but is hard. In striving for minimum resistance and the reduction of asper ity, low resistance copper contacts are often plated with tin. Film wiping occurs when pins and contacts are plated with tin and when they are mated together they have a tendency to “wipe” together and actually smooth out some of the peaks and valleys created by the asperity condition. Other metals, such as gold and silver are excellent plating materials, but are too costly to use.

Contaminants Contaminants are another factor that contribute to resistance in connectors. Some harsh conditions that employ chemicals, etc. can cause malfunctions due to increased resistance. Technicians need to be aware that connectors can and do cause many diagnostic problems. It may be necessary to measure the resistance between connector halves when diagnosing electrical control malfunctions. Also, technicians need to be aware that disconnecting and reconnecting connectors during the troubleshooting process can give misleading diagnostic information.

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Several types of connectors are used throughout the electrical and electronic systems on automotive machines. Each type differs in the manner in which they are serviced or repaired. The following types of connectors will be discussed in detail: 

Vehicular Environmental (VE) Connectors



Sure-Seal Connectors



Deutsch Connectors (HD10, DT, CE and DRC Series).

VE Connectors

Figure 29

The VE connector (Figure 29) was used primarily on earlier Caterpillar machine electrical harnesses where high temperatures, larger number of contacts or higher current carrying capacities were needed. The connector required a special metal release tool for removing the contacts that could damage the connector lock mechanism, if the tool was turned during release of the retaining clip. Do not use these metal release tools for any other type of electrical connector. After crimping a wire to the contact it is recommended that the contact be soldered to provide for a good electrical contact. Use only rosin core solder on any electrical connection. Specific information relating to the process required for installing VE connector contacts (pins and sockets) is contained in Special Instruction: Use of VE Connector Tool Group (Form SEHS8038). This type of connector is no longer used on current product, but may still require servicing by a field/shop technician.

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Sure-Seal Connectors

Figure 30

Sure-Seal connectors are used extensively on Caterpillar machines (Figure 30). These connector housings have provisions for accurate mating between the two halves, but instead of using guide keys or key ways, the connector bodies are moulded such that they will mate correctly. Sure-Seal Connectors are limited to a capacity of 10 contacts (pins and sockets). Part numbers for spare plug and receptacle housings and contacts are contained in Special Instruction: Use of 6V3000 Sure-Seal Repair Kit (Form SMHS7531). Use special tool (6V3001) for crimping contacts and stripping wires. Sure-Seal Connectors require the use of a special tool 6V3008 for installing contacts. Use denatured alcohol as a lubricant when installing contacts. Special tooling is not required for removing pin contacts. Any holes in the housings not used for contact assemblies should be filled with a 9G3695 Sealing Plug. The sealing plug will help prevent moisture from entering the housings.

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Deutsch Heavy Duty (HD10) Series Connectors

Figure 31

The HD10 connector (see Figure 31) is a thermoplastic cylindrical connector utilizing crimp type contacts that are quickly and easily removed. The thermoplastic shells are available in non-threaded and threaded configurations using insert arrangements of 3, 5, 6 and 9 contacts. The contact size is No 16 and accepts No 14, No 16 and No 18 AWG wire. The HD10 uses crimp type, solid copper alloy contacts (size No 16) that feature an ability to carry continuous high operating current loads without overheating. The contacts are crimp terminated using a Deutsch Crimp tool, Caterpillar part number 1U5805. Deutsch termination procedures recommend NO SOLDERING after properly crimped contacts are completed. The procedure for preparing a wire and crimping a contact is the same for all Deutsch connectors and is explained in Special Instruction: Servicing DT Connectors (SEHS9615). The removal procedure differs from connector to connector and will be explained in each section. Kit for Deutsch connector repair is 4C3806.

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Deutsch Transportation (DT) Series Connectors

Figure 32

The DT connector (Figure 32) is a thermoplastic connector utilizing crimp type contacts that are quickly and easily removed and require no special tooling. The thermoplastic housings are available in configurations using insert arrangements of 2, 3, 4, 6, 8 and 12 contacts. The contact size is No 16 and accepts No 14, No 16 and No 18 AWG wire. The DT uses crimp type, solid copper alloy contacts (size No 16) that feature an ability to carry continuous high operating current loads without overheating, or stamped and formed contacts (less costly). The contacts are crimp terminated using a Deutsch Crimp Tool, Caterpillar par t number 1U5804. The DT connector differs from other Deutsch connectors in both appearance and construction. The DT is either rectangular or triangular shaped and contains serviceable plug wedges, receptacle wedges and silicone seals. The recommended cleaning solvent for all Deutsch contacts is denatured alcohol. For a more detailed explanation on servicing the DT connector, consult Special Instruction: Servicing DT Connectors (SEHS9615). Kit for servicing DT connectors is Caterpillar part No 9U7246.

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Caterpillar Environmental Connectors (CE)

Figure 33

The CE connector is a special application connector (Figure 33). The CE Series connector can accommodate between 7 and 37 contacts, with the 37 contact connector being used on various electronic control modules. The CE connector uses two different crimping tools. The crimping tool for No 4 - No 10 size contacts is a 4C4075 Hand Crimp Tool Assembly, and the tool for No 12 - No 18 contacts is the same tool as used on the HD and DT Series connectors (1U5804). Reference SEHS9065 8T5319 Removal Tool GP 4C4075 Crimp tool GP 1U5804 Crimp Tool GP.

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Deutsch Rectangular Connector (DRC)

Figure 34

The DRC connector (Figure 34) features a rectangular thermoplastic housing and is completely environmentally sealed. The DRC is best suited to be compatible with external and internal electronic control modules. The connector is designed with a higher number of terminals. The insert arrangements available are: 24, 40 and 70 contact terminations. The contact size is No 16 and accepts No 16 and No 18 AWG wire. The connector uses crimp type, copper alloy contacts (size No 16) that feature an ability to carry continuous high operating current loads without overheating or stamped and formed contacts (less costly). The contacts are crimp terminated using a Deutsch Crimp Tool, Caterpillar par t number 1U5805. The connector contains a “clocking” key for correct orientation and is properly secured by a stainless steel jackscrew. A 4mm (5/32in) HEX wrench is required to mate the connector halves. The recommended torque for tightening the jackscrew is 25in pounds. NOTE: The DRC uses the same installation and removal procedures as the HD10 series.

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TERMINALS

Figure 35 Examples of wire terminals (a) slide-type crimp terminals (b) bullet connector

(c) crimp and soldered terminals.

There are a number of different types of terminals used. Some terminals, are shown in Figure 35. Most terminals, whether they are original or a replacement, are crimped or swaged to the copper wire of the conductor, but some can be soldered.

Figure 36 - Terminal Crimp Tool Set

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INSTALL A SOLDERLESS CONNECTION When stripping an electrical wire and joining a solderless connector, the following points are to be considered.

Safety Check 





Never use a sharp blade or knife to remove insulation. A sharp blade may cut through the wire completely or may cause personal injury. Wire stripping pliers have sharp edges and require a tight grip. Be careful not to trap your skin between the jaws. When removing the insulation from wire, push away rather than towards the body.

Points to Note 















Electrical wire used in automotive wiring harnesses is covered by an insulating layer of plastic. When electrical wire is joined to other wires or connected to a terminal, the insulation needs to be removed. Wire stripping tools come in various configurations. They all perform the same task. The type of tool used will depend on the amount and type of electrical wire to be repaired. Solderless terminals require a clean, tight connection, so ensure the wire and the connection are clean before fitting any terminals. Use connections that match the size of the wire. Do not use side cutters, pliers or a knife to strip the wire. Using these tools will damage some of the wire strands and may break the wire inside the insulation. To keep the wires together after stripping them, give them a slight twist. Do not twist the wire too much, otherwise a risk of poor wire-to-terminal connection may occur. Use the correct crimpling tool for the connection. Using the wrong type o f tool will cause the connection to have a poor grip on the wire.

1. Select the Terminal

Figure 37

There are different types and sizes of wire terminals, but the procedure for installing all of them is the same. This is a bullet type of crimp terminal (Figure 37).

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Figure 38

Make sure that the correct size of terminal for the wire is selected and that the ter minal has the correct volt/amp rating for the job it will perform (Figure 38).

2. Strip the Wire

Figure 39

Remove an appropriate amount of the protective insulation from the wire (Figure 39). Always use a proper stripping tool that is in good condition.

3. Always Use a Proper Stripping Tool

Figure 40

The purpose of a wire stripping tool is to allow for the removal of insulation from around the copper core of a cable without damaging the cable or causing personal injury (Figure 40).

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Figure 41

Using side cutters or pliers (Figure 41) can also be dangerous; they are also less effective because they often cut away some of the strands of wire.

Figure 42

This is known as ringing the wire (Figure 42), which effectively reduces the current carrying capacity of the wire.

4. Select the Correct Gauge Hole

Figure 43

Using the correct tool is much safer and more effective. Wire Strippers can remove the insulation from different gauges of cable; select the hole in the stripper that is closest to the diameter of the core in the cable to be stripped. On the wire strippers in Figure 43 above, the size of the wire stripping orifices are indicated on the tool.

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5. Cut the Insulation

Figure 44

Place the cable in the hole and close the jaws firmly around it to cut the insulation. If you have selected the right gauge the wire stripper will cut through the insulation but not through the copper core (Figure 44).

Figure 45

Only remove as much insulation as is necessary to do the job. Too little bare wire may not achieve a good connection and too much may expose the wire for potential short circuit with other circuits or to ground. Removing more than 1.2 centimetres (half an inch) of insulation at a time can also stretch and damage the core (Figure 45).

6. Remove the Insulation

Figure 46

Some strippers automatically cut and remove the insulation. Others just make the cut and hold the cable tightly (Figure 46). When using this type of stripper, pull firmly on the wire to remove the insulation.

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Figure 47

To keep the strands together, give them a light twist (Figure 47).

7. Place the terminal on the wire

Figure 48

There will be a better connection if the strands are not twisted together tightly before placing them through the terminal (Figure 48). When crimped, this gives the terminal more surface contact area with the wire. However, it can be difficult to insert the wires into the terminal if they are all just loose strands...

Figure 49

... so twist them together just enough to help insert them cleanly. Place the bullet or terminal onto the wire (Figure 49).

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8. Alternative Terminal Types

Figure 50

Some types of crimp terminals do not have an insulation component fixed to them. These come in two parts and the insulator is supplied as a separate component (Figure 50). In these cases, always make sure that the ‘core’ of the wire to be crimped...

Figure 51

... extends through the ‘core wings’ in the terminal (Figure 51).

9. Select the Crimping Anvil

Figure 52

Use a proper crimping tool for pin or core crimping. DO NOT use pliers. They have a tendency to cut through the connection and can give trouble during service. Select the proper anvil on the crimping tool for the connector or terminal selected. These are usually colour-coded so it is easy to match the terminal with the right size anvil.

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10. Crimping

Figure 53

Crimp the ‘core’ section first. Use firm pressure so that a good electrical contact will be made, but not excessive force as this can bend the pin or terminal (Figure 53). Then crimp the insulation wings or section. This crimp is on the wire insulation to hold the cable in place, not for electrical contact, so there is no need to crimp this section quite as hard.

Figure 54

Give a gentle tug on the finished job to ensure that the connection will hold i n s er vi ce ( Fi gu re 5 4) .

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SWITCHES

Figure 55

A switch (Figure 55) is a device used to complete or interrupt a current path. Typically, switches are placed between two conductors (or wires). There are many different types of switches, such as Single-Pole Single-Throw (SPST), Single-Pole Double Throw (SPDT), Double-Pole Single-Throw (DPST) and Double-Pole Double-Throw (DPDT).

Figure 56

There are also many ways of actuating switches, the switches shown in Figure 56 are mechanically operated by moving the switch lever or toggle. Sometimes, switches are linked so that they always open and close at the same time. In schematics, this is shown by connecting linked switches with a dashed line (DPST and DPDT in Figure 56). Other mechanically operated switches are limit switches and pressure switches. The switch contacts are closed or opened by an external means, such as a lever actuating a limit switch or pressure actuated.

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Some of the more common switches used on Cater pillar machines are: 

Toggle

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Rotary

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Rocker

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Push-On

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Pressure

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Magnetic

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Key Start

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Limit

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Cutout.

Some switches are more complex than others. Caterpillar machines use magnetic switches for measuring speed signals or electronic switches that contain internal electronic components, such as transistors to turn remote signals on or off. An example of a more complex switch used on Caterpillar machines is the key start switch.

Figure 57

Figure 57 shows the internal schematic of the Key Start Switch. This type of switch controls several different functions, such as an accessory position (ACC), Run position (RUN), a start position (START) and an off position (OFF). This type of switch can control other components and/or deliver power to several components at the same time.

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CIRCUIT PROTECTORS

Figure 58

Fuses and fusible links are circuit protectors. If there is excess current in a circuit, it causes heat. The heat, not the current, causes the circuit protector to open before the wiring can be damaged. This has the same effect as turning a switch OFF. Note that circuit protectors (Figure 58) are designed to protect the wiring, not necessarily other components. Fuses and circuit breakers can help diagnose circuit problems. If a circuit protector opens rep eatedly, there is probably a more serious electrical problem that needs to be repaired.

Fuses

Figure 59

Fuses are the most common circuit protectors (Figure 59). A fuse is made of a thin metal strip or wire inside a holder made of glass or plastic. When the current flow becomes higher than the fuse rating, the metal melts and the circuit opens. A fuse must be replaced after it opens. Fuses are rated according to the amperage they can carry before opening. Plastic fuse holders are moulded in different colours to denote fuse ratings and fuse ratings are also moulded or stamped on to the top of the fuse. APLTCL024


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A fusible link is a short section of insulated wire that’s thinner than the wire in the circuit it protects. Excess current causes the wire inside the link to melt. Like fuses, fusible links must be replaced after they’re blown. Fusible links are commonly used on the ignition lead from the positive terminal of the battery. An indication that a fusible link is blown is conducted by pulling on its two ends. If it stretches like a rubber band, the wire must have melted and the link is no longer good. (The insulation of a fusible link is thicker than regular wire insulation so that it can contain the melted link after it blows.) NOTE:

When replacing a fusible link, never use a length longer tha n 225mm (about 9″). Long wires tend to hold the heat better and may not break at the required specification.

Circuit Breakers A circuit breaker is similar to a fuse, however, high current will cause the breaker to “trip” thereby opening the circuit. The breaker may be manually reset after the overcurrent condition has been eliminated. Some circuit breakers are automatically reset. They are called “cycling” circuit breakers. Circuit breakers are built into several Caterpillar components, such as the headlight switch.

Figure 60

A thermal circuit breaker with a reset button is shown in Figure 60. This has a bimetal blade which carries the current when the contacts are closed. However, if an overload occurs, the heat from the excess current will cause the bimetal blade to bend and open the contacts to break the circuit. The spring toggle, which normally helps to keep the contacts closed, will keep the contacts open and the circuit broken even though the bimetal blade will try to straighten as it cools. The points will only close when the button is pressed to reset the circuit breaker. These circuit breakers are also referred to as ‘non-cycling’ circuit breakers.

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Figure 61

A cycling circuit breaker contains a strip made of two different metals. Current higher than the circuit breaker rating makes the two metals change shape unevenly. The str ip bends, and a set of contacts is opened to stop current flow. When the metal cools, it returns to its normal shape, closing the contacts. Current flow can resume (Figure 61). Automatically resetting circuit breakers are also called “cycling” because they cycle open and closed until the current retur ns to a normal level.

Figure 62

A Positive Temperature Coefficient (PTC) is a special type of circuit breaker called a thermistor (or thermal resistor). PTCs are made from a conductive polymer. In its normal state, the material is in the form of a dense cr ystal, with many carbon particles packed together. The carbon particles provide conductive pathways for current flow. When the material is heated, the polymer expands, pulling the carbon chains apart. In this expanded state, there are few pathways for current. A schematic symbol for a PTC is shown in Figure 62. A PTC is a solid state device; it has no moving parts. When tripped, the device remains in the “open circuit” state as long as voltage remains applied to the circuit. It resets only when voltage is r emoved and the polymer cools.

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Apltcl024 Sgd l 01 Electrical Fundamental

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