Electronic Systems Module 2
Acknowledgements General Motors, the IAGMASEP Association Board of Directors, and Raytheon Professional Services, GM's training partner for GM's Service Technical College wish to thank all of the people who contributed to the GM ASEP/BSEP curriculum development project 2002-3. This project would not have been possible without the tireless efforts of many people. We acknowledge: The IAGMASEP Association members for agreeing to tackle this large project to create the curriculum for the GM ASEP/BSEP schools. The IAGMASEP Curriculum team for leading the members to a single vision and implementation. Direct contributors within Raytheon Professional Services for their support of translating a good idea into reality. Specifically, we thank: Chris Mason and Vince Williams, for their leadership, guidance, and support. Media and Graphics department under Mary McClain and in particular, Cheryl Squicciarini, Diana Pajewski, Lesley McCowey, Jeremy Pawelek, & Nancy DeSantis. For his help on the Electrical curriculum volume, Subject Matter Expert, Ken Beish, Jr., for his wealth of knowledge. Finally, we wish to recognize the individual instructors and staffs of the GM ASEP/BSEP Colleges for their contribution for reformatting existing General Motors training material, adding critical technical content and the sharing of their expertise in the GM product. Separate committees worked on each of the eight curriculum areas. For the work on this volume, we thank the members of the Electrical committee: Jack Davis, Community College of Baltimore County - Catonsville Jim Halderman, Sinclair Community College Megan Kuehm, Community College of Allegheny County Frank Longbottom, Camden County College Jeff Rehkopf, Florida Community College at Jacksonville Randy Peters, Des Moines Area Community College David Rodriguez, College of Southern Idaho Ed Schauffler, Longview Community College Vince Williams, Raytheon
Contents Module 2 Acknowledgements... 2 Objective... 4 Common Symbols... 5 Ground Symbol... 6 Relay... 7 Generator... 7 Circuit Protection Devices... 8 Circuit Breakers... 8 Fuses... 8 Resistor... 9 Wire and Wire Symbols... 9 Switch...11 Battery... 12 Motor... 12 Light Bulb... 13 Exercise 2-1... 14
Objective At the end of this section, the student will be able to identify common electrical symbols used in service manual schematics NATEF Area VI A5: Use wiring diagram during diagnosis of electrical circuit problems. 2-4
Common Symbols Symbols are used to represent various electrical components. These are referred to as schematic symbols and are used extensively in automotive publications for diagnosing electrical concerns. Although there are many electrical symbols used in circuit diagrams, let s look at some more common GM electrical symbols by building a circuit. At the top of figure 2-1 is the symbol for a battery. A conductor, or wire, leaves the battery and connects to a fuse. Another wire connects the fuse to a splice. Wires branch off from the splice and connect to two switches. One switch has a wire connected to a bulb, the other switch is connected to a motor. Both the bulb and motor are grounded through the chassis. Figue 2-1, Typical Schematic Symbols 2-5
Ground Symbol Because automotive circuits share a common ground, that is, a return path to the battery, a special ground symbol is used to simplify circuit diagrams. Figure 2-2, Ground Symbol Solenoid A solenoid provides a push or pull force. A moveable core is connected to a mechanism. When current flows through the solenoid coil, the core is pulled toward the coil center to operate the mechanism. A solenoid electrical circuit is controlled by a switch or relay. Figure 2-3, Solenoid 2-6
Relay A relay is a switch that is remotely controlled by a manually operated switch. It is usually used where heavy current is required. Current is applied to a relay coil, creating a magnetic field which closes the relay points. The closed points supply electricity to the load in the circuit. Upon the release of the switch, the relay opens the points to break the circuit and the current flows stops. Figure 2-4, Relay Generator The generator symbol shows the major electrical components of the unit. The generator is made with a number separate coils connected to each other. This assemble is called a stator. Alternating north-south magnets on the rotor assembly concentrate the magnetic lines of force from the field windings. The rectifier bridge converts the alternating current produced by the stator to direct current. Figure 2-5, Generator 2-7
Circuit Protection Devices Circuit breakers and fuses are circuit protection devices. They are designed to create an open if a specified amount of amperes is exceeded. Circuit Breakers When a circuit breaker opens a circuit, it can be reset. The symbol for a circuit breaker shows a box with a half-moon inside it. Figure 2-6, Circuit Breaker Fuses When a fuse opens, it cannot be reset as a link inside the body of the fuse melts. The symbol for a fuse shows a box with a squiggly line inside of it. Figure 2-7, Fuse 2-8
Resistor Resistors are used to limit current, divide voltage, and in certain applications, generate heat. There are a variety of resistors classified into two main categories: fixed and variable. Below is an example of a resistor in a wiring schematic. Figure 2-8, Resistor Wire and Wire Symbols Wire is the most common type of conductive material used to connect components. Wire is available in different sizes called gauge size. It is also available in both round and flat types. Below are the symbols used to show different wire routing. This is the symbol for wires that cross, but are not connected. Figure 2-9, Crossing Wires 2-9
This is the symbol for wires that cross and are connected at a splice. Figure 2-10, Wires Connected at a Splice A wavy line means a wire is to be continued somewhere else in the circuit. Typically, these lines are used to show a graphically shortened wire. Figure 2-11, Wavy Line 2-10
An arrow symbol at the end of a wire with a letter inside of it indicates a wire continues as labeled on another page. For example, this wire connects to the generator, but it is shown on another page. The symbol is then repeated on that page. The arrow indicates the direction of current flow. Figure 2-12, Wire Continued on Another Schematic Switch Switches are most commonly used to control a circuit by either allowing or restricting voltage flow. Switches can be mechanical, or electromechanical, or electronic. Switches can be in a multiple of different configurations, such as SPST (single pole, single throw). Figure 2-13, Switch 2-11
Battery A battery provides a source potential (voltage) for an electrical/electronic circuit. Most batteries work by the conversion of a chemical reaction into electricity. Below is a symbol for a battery. Figure 2-14, Battery Motor A motor provides the conversion of electrical potential into a moving mechanical energy. Below is a schematic symbol for a motor. Figure 2-15, Motor 2-12
Light Bulb A light bulb converts electrical energy into a radiant light. The filament resists electrical flow and heats up, causing the filament to glow. This is the light we see. Below is a schematic symbol for a light bulb. Figure 2-16, Light Bulb 2-13
Exercise 2-1 Match the component to the symbol. 1. Battery 2. Fuse 3. Switch 4. Bulb 5. Ground 6. Relay 7. Circuit Breaker 8. Resistor 9. Wire Continued on another schematic 2-14