ASE 6 - Electrical Electronic Systemsfaculty.ccbcmd.edu/~smacadof/Books/A6Student... · At the end of this section, the technician will be able to explain basic circuit elements,

ASE 6 - Electrical ElectronicSystems

Module 6Circuit Elements

AcknowledgementsGeneral Motors, the IAGMASEP Association Board of Directors, and RaytheonProfessional Services, GM's training partner for GM's Service Technical College wish tothank all of the people who contributed to the GM ASEP/BSEP curriculum developmentproject 2002-3. This project would not have been possible without the tireless efforts ofmany people. We acknowledge:

• The IAGMASEP Association members for agreeing to tackle this large project tocreate the curriculum for the GM ASEP/BSEP schools.

• The IAGMASEP Curriculum team for leading the members to a single vision andimplementation.

• Direct contributors within Raytheon Professional Services for their support oftranslating 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, & NancyDeSantis.

– For his help on the Electrical curriculum volume, Subject Matter Expert, KenBeish, Jr., for his wealth of knowledge.

Finally, we wish to recognize the individual instructors and staffs of the GM ASEP/BSEPColleges 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 thisvolume, 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

ContentsModule 6 – Circuit ElementsObjective .......................................................................................................... 4

Basic Circuit Elements .................................................................................................... 4Power (Feed) .................................................................................................................. 5Circuit Protectors ............................................................................................................ 5Controls .......................................................................................................................... 8Load ................................................................................................................................ 8Ground ............................................................................................................................ 8Experiment 6-1 ............................................................................................................... 9Exercise 6-1 ...................................................................................................................11

© 2002 General Motors CorporationAll Rights Reserved

ASE 6 - ElectricalElectronic Systems

Module 6 - CircuitElements

6-4

Student WorkbookObjectiveAt the end of this section, the technician will be able to explain basiccircuit elements, including source protection, control, load, and ground.

Basic Circuit ElementsA circuit is a path for electric current. Current flows from one end of acircuit to the other end when the ends are connected to opposite charges(positive and negative). We usually call these ends “power” and “ground”.

Figure 6-1, Basic Circuit Elements

Current flows only in a closed or completed circuit. If there is a breaksomewhere in the circuit, current cannot flow. We usually call a break in acircuit an open.Every automotive circuit contains a source of power, protection, load,controls, and ground. These elements are connected together withconductors.




6-5

Student WorkbookPower (Feed)A 12-volt battery and generator are the most common voltage sources inautomotive circuits. The operation of the generator continuouslyreplenishes the electrical potential of the battery to prevent it fromdischarging.

Circuit ProtectorsTo prevent damage to wires and components, automotive circuits use aprotection device to prevent excess current flow. Fuses, fusible links, andcircuit breakers are circuit protectors. If there is excess current, theseprotectors open before the circuit wiring can be damaged. This has thesame effect as turning a switch to OFF. Circuit protectors are designed toprotect the wiring, not necessarily other components.Excess current causes excess heat. It is the heat – not the current – thatcauses the circuit protector to open.

Figure 6-2, Circuit Protectors




6-6

Student WorkbookFusesThe most common protection device in automotive circuits is a fuse. Afuse is made of a thin metal strip or wire inside a holder made of glass orplastic. When the circuit exceeds a certain amperage, the element insidethe fuse (melts) opens, preventing damage to the circuit. A fuse must bereplaced after it opens.

Figure 6-3, Fuse Rating and Color Chart




6-7

Student WorkbookFusible LinksAnother type of protection device is a fusible link. Fusible links are shotlengths (no longer than 9 inches) of smaller diameter wire (4 gaugessmaller) than the circuit they are protecting. Because they are smaller,they will melt and open the circuit before damage can occur. Fusible linksare also covered with a special non-flammable insulator. Like fuses,fusible links must be replaced after they have opened.

Figure 6-4, Fusible Link

Circuit BreakersCircuit breakers are also protection devices. Automatically resetting circuitbreakers have a set of contacts controlled by an arm made of two differenttypes of metal. These metals expand at different rates. When too muchcurrent flows, the arm becomes overheated and the contacts open. Whenthe metal cools, it returns to its normal shape, closing the contacts.Current flow can resume. Automatically resetting circuit breakers are alsocalled “cycling” because they cycle open and closed until the currentreturns to a normal level.

Figure 6-5, Circuit Breaker




6-8

Student WorkbookControlsControl devices perform many different jobs, such as turning lights on andof, dimming lights, and controlling the speed of motors. These deviceswork by completely stopping current flow or by varying the rate of flow.Typical control devices used to stop current flow include switches, relays,and transistors. Controls used to vary current flow include variableresistors and rheostats.Control devices can be on the positive (before the load) or negative (afterthe load) side of the circuit.

LoadThe load is any device in a circuit that uses electricity to do its job. Theloads in a circuit can include a motor, solenoid, relay, and a light bulb. Allloads offer some resistance to current flow.

GroundGround is used to provide a return path to the negative side of the battery.The groundside of the circuit can include wires, body sheet metal, frame,and drive train components, such as the engine block.

Figure 6-6, Controls




6-9

Student WorkbookExperiment 6-1Experiment Objective: Prove Ohm’s Law on a circuit.Go the Techline terminal and locate a cigar lighter circuit. Assemble asimplified version of that circuit on your project board. Use a simpleswitch as a substitute for the ignition switch.When you have conformed that the circuit works correctly, perform acurrent measurement. Recall that the DVOM must be wired in series withthe circuit in order to measure current.

Current flow in cigar lighter circuit:

With cigar lighter popped out __________.

With cigar lighter pressed in __________.

Use Ohm’s Law to determine the approximate resistance of the cigarlighter element. __________ Ohms.

Disconnect the cigar lighter from the power supply on the project board.Depress the lighter into the socket and measure the resistance of thecigar lighter element. __________ Ohms.Did your predicted resistance match your measured resistance(approximately)? Answer Yes or No __________.




6-10

Student WorkbookWhere in the Techline terminal’s Electronic Service Information (ESI) didyou find the cigar lighter?

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During your diagnosis work at the dealership, when would you find a usefor Ohm’s Law?

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Caution:Do not hold the lighter socket in on the project board.

Damage will result to the project board’s powersource.




6-11

Student WorkbookExercise 6-1Read each question carefully and answer by filling in the blanks.

1. Circuit protectors are designed primarily to protect the __________.a. loadsb. charging systemc. system electronicsd. wiring

2. Circuit protectors open because of excess __________ caused byexcess __________.a. currentb. heatc. currentd. voltage

3. Automatically resetting circuit breakers are also called __________.a. alternating breakersb. controlling breakersc. cyclingd. electronic breakers

4. Control devices can be on __________ side of the circuit.a. the positiveb. the negativec. either the positive or negatived. neither the positive or negative

5. A fuse is made of a __________.a. set of contacts controlled by an arm made of two different metalsb. smaller size wire in a special non-flammable insulatorc. thin metal strip inside of a glass or plasatic holderd. ceramic material encased in a glass or plastic holder




6-12

Student Workbook6. The five basic circuit elements are __________, __________,__________, __________, and __________.

7. A 20-amp fuse is __________in color.a. blueb. greenc. redd. yellow

8. The three circuit protection devices are __________, __________, and__________.

9. The maximum length of a fusible link is __________.a. 5 inchesb. 6 inchesc. 9 inchesd. 12 inches

10.The following are all examples of loads: __________, __________,__________.a. motor, switch, bulbb. bulb, fuse, solenoidc. bulb, motor, solenoidd. circuit breaker, motor, bulb




6-13

Student WorkbookNotes:

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Documents

ASE 6 - Electrical Electronic Systemsfaculty.ccbcmd.edu/~smacadof/Books/A6Student... · At the end of this section, the technician will be able to explain basic circuit elements,