1. Automotive Electronics
Chapter 8 Lesson 3

2. Automotive Electronics
In electronic systems, the components are solid state and do not have moving parts
Solid state circuits use semiconductors

3. Semiconductor
Substance capable of acting as both a conductor and an insulator
this enables semiconductor devices to control current without mechanical points
Semiconductor devices include:
diodes
transistors
integrated circuits

4. Diode
An “electronic check valve” that allows current to flow in only one direction
when a diode is forward biased, it acts as a conductor
when a diode is reverse biased, it acts as an insulator

5. Diode Operation

6. Transistor
Allows the control of a high current circuit with a low current circuit
performs the same basic function as a relay
Acts as a remote switch or current amplifier
Operates more quickly than a mechanical device can
Has no moving parts to wear or deteriorate

7. Transistor versus Relay
Relay operation

8. Transistor versus Relay
Transistor operation

9. Transistor Operation
Small base current energizes the semiconductor material, changing it from an insulator to a conductor
Higher current can pass through the collector and emitter terminals

10. Capacitors
Devices used to absorb unwanted electrical pulses, such as voltage fluctuations
Used in various types of electrical and electronic circuits
Connected to the supply wires for the car radio
absorbs alternator or ignition system “noise” that may be heard in the speakers

11. Integrated Circuit (IC)
Contains microscopic diodes, transistors, resistors, and capacitors in a wafer-like chip

12. Printed Circuit
Uses flat conductor strips mounted on an insulating board
Reduces weight and bulk by replacing separate wires

13. Instrument Panel Printed Circuit

14. Amplifier
Electronic circuit designed to use a very small current to control a very large current
Ignition control module is an amplifier
uses small electrical pulses from the distributor to produce strong on/off cycles to operate the ignition coil

15. Automotive Wiring
An automobile uses various types of wiring in its many electrical systems

16. Wire Size Determined by the diameter of the wire’s metal conductor
Stated in a relative numbering system called gauge size
Wires become smaller as gauge numbers increase
When replacing a wire, always use wire of equal size
a smaller wire could overheat

17. AWG gauge
Diameter Inches
Diameter mm
Ohms per 1000 ft
Ohms per km
Maximum amps for chassis wiring
OOOO
0.46
11.684
0.049
380
OOO
0.4096
0.0618
0.2027
328 OO
0.3648
0.0779
283
0.3249
0.0983
245 1
0.2893
0.1239
211 2
0.2576
0.1563
181 3
0.2294
0.197
158 4
0.2043
0.2485
135 5
0.1819
0.3133
118 6
0.162
4.1148
0.3951
101 7
0.1443
0.4982
1.6341 89 8
0.1285
3.2639
0.6282
2.0605 73 9
0.1144
0.7921 64 10
0.1019
0.9989 55 11
0.0907
1.26
4.1328 47 12
0.0808
1.588 41 13
0.072
1.8288
2.003 35 14
0.0641
2.525
8.282 32 15
0.0571
3.184 28 16
0.0508
4.016 22 17
0.0453
5.064 19 18
0.0403
6.385
0.0359
8.051 20
0.032
0.8128
10.15
33.292

18. Primary Wire Carries battery or alternator voltage
Uses thin plastic insulation
The insulation is color-coded for easy troubleshooting

19. Wire Color-Coding

20. Wiring Harness
A group of wires enclosed in a plastic or tape covering that helps protect and organize the wires

21. Secondary Wire
Used in a vehicle’s ignition system for spark plug or coil wires
Extra thick insulation prevents high voltage from short circuiting
Core may be a metal conductor or a carbon-impregnated cord

22. Battery Cable
Extremely large-gauge wire capable of carrying high current from the battery to the starting motor
Current flow is often well over 100 amperes

23. Ground Wires (Straps)
Connect electrical components to the chassis or ground of the car
Insulation may not be used on these wires

24. Workbook Exercise
Answer questions 12 – 35
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