Automotive Electronics Chapter 8 Lesson 3

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

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

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

Diode Operation

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

Transistor versus Relay Relay operation

Transistor versus Relay Transistor operation

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

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

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

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

Instrument Panel Printed Circuit

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

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

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

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 0.16072 380 OOO 0.4096 10.4038 0.0618 0.2027 328 OO 0.3648 9.26592 0.0779 0.25551 283 0.3249 8.25246 0.0983 0.32242 245 1 0.2893 7.34822 0.1239 0.40639 211 2 0.2576 6.54304 0.1563 0.51266 181 3 0.2294 5.82676 0.197 0.64616 158 4 0.2043 5.18922 0.2485 0.81508 135 5 0.1819 4.62026 0.3133 1.02762 118 6 0.162 4.1148 0.3951 1.29593 101 7 0.1443 3.66522 0.4982 1.6341 89 8 0.1285 3.2639 0.6282 2.0605 73 9 0.1144 2.90576 0.7921 2.59809 64 10 0.1019 2.58826 0.9989 3.27639 55 11 0.0907 2.30378 1.26 4.1328 47 12 0.0808 2.05232 1.588 5.20864 41 13 0.072 1.8288 2.003 6.56984 35 14 0.0641 1.62814 2.525 8.282 32 15 0.0571 1.45034 3.184 10.4435 28 16 0.0508 1.29032 4.016 13.1725 22 17 0.0453 1.15062 5.064 16.6099 19 18 0.0403 1.02362 6.385 20.9428 0.0359 0.91186 8.051 26.4073 20 0.032 0.8128 10.15 33.292

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

Wire Color-Coding

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

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

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

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

Workbook Exercise Answer questions 12 – 35 Page 99 - 105