chapter 06 bennet

8/10/2019 Chapter 06 Bennet

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Chapter 6

Fundamentals of Electronics and

Computers


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Objectives (1 of 4)

Outline some of the developmental history of

electronics.

Describe how an electrical signal can be

used to transmit information.

Define the term pulse width modulation.

Define the principle of operation of N- and P-

type semiconductors.

Outline the operating principles and

applications of diodes.


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Objectives (2 of 4)

Describe the construction and operation of a typical

transistor.

Describe what is meant by the optical spectrum.

Identify some commonly used optical componentsused in electronic circuitry.

Explain what is meant by an integrated circuit and

outline its application in on-board vehicle

electronics.

Define the role of gates in electronic circuits.


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Objectives (3 of 4)

Describe the operating modes of some

common gates used in electrical circuits

including AND, OR, and NOT gates.

Interpret a truth table that defines theoutcomes of gates in an electrical circuit.

Explain why the binary numeric system is

used in computer electronics. Define the role of an electronic control

module in an electronic management system.


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Objectives (4 of 4)

Outline the distinct stages of a computerprocessing cycle.

Describe the data retention media used in

vehicle ECMs. Demonstrate an understanding of input

circuits on a vehicle electronic system.

Troubleshoot a potentiometer-type TPS.

Describe the operating principles of theVORAD collision warning system.


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Using Electronic Signals (1 of 3)

Electronic signals used to manage

information are generally low voltage/low

current circuits.

They may be classified as:

Analog

Digital


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Analog signals operate

on variable voltage

values.


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Digital signals operateon specific voltagevalues.

A digital signalproduces a squarewave pattern.

Digital signals may beclassified as:

Frequency modulated

Pulse width modulated(duty cycled)


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Frequency Modulation

Frequency is the

number of pulses per

second.

It is expressed in hertz(Hz).

Information may be

transmitted by varying

the frequency of thesignal.


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Pulse Width Modulation (1 of 2)

A square wave of fixed

frequency, but varying

duty cycle is achieved

by changing the

percentage of on-time.

This is known as pulse

width modulation

(PWM).


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Pulse Width Modulation (2 of 2)

Electronic noise is an

unwanted pulse or

waveform interference

that can scramble

signals.


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Semiconductors (1 of 4)

Semiconductors have exactly four electrons

in their valence shell.

The ones commonly used are:

Silicon

Germanium


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In crystal form,semiconductor atoms shareelectrons in the outer shellwith adjacent atoms.

Pure silicon or germaniummust be doped before it isuseful.

The type of doping agentused defines the electricalproperties of the crystals

produced.


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Silicon crystals doped

with boron or some

other trivalent element

will form P-type silicon

crystals.


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Silicon crystals doped

with phosphorus or

some other pentavalent

element will form N-

type silicon crystals.


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Diodes (2 of 3)

The positive terminal is

called the anode.

The negative terminal

is called the cathode. In an electrical

schematic showing a

diode, the arrow points

in the direction ofcurrent flow using

conventional theory.


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Diodes (3 of 3)

Types of diodes

Small signal diodes

Power rectifier diodes

Zener diodes

Light-emitting diodes (LEDs)

Photo diodes


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Transistors (1 of 10)

Transistors are three-terminal semiconductor chips

that are used extensively in electronic circuits

primarily for switching and amplification.

Transistors are active circuit elements capable ofamplifying or transforming a signal level.

A transistor consists of two P-N junctions.

A transistor functions in an electronic circuit in much

the same manner that a relay functions in anelectrical circuit.


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The base can beregarded as a switch.

The collector can beregarded as an input.

The emitter is theoutput.

A small base currentcontrols a larger

current through theemitter/collector.


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Bipolar transistors

The base emitter junctions will not conduct

until the forward bias voltage exceeds 0.6V.

Excessive current flow through a transistor willcause it to overheat or fail.

Excessive voltage can destroy the

semiconductor crystal media.

A small base current can be used to control a

much larger collector current.


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Field effect transistors

(FETs) are more

commonly used than

bipolar transistors.

They are cheaper to

manufacture.

They may be divided

into: Junction-type

Metal-oxide


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JFETs

JFET gate resistance is very high, so the

device has almost no effect on external

components connected to the gate. The gate and channel form a diode, and as

long as the input signal reverse biases this

diode, the gate will show high resistance.


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MOSFETs

They have become the most important type of

transistor in microcomputer applications.

Thousands can be photo-infused onto minutesilicon wafers.

They can act both as a switch and as variable

resistors.

They can be switches at very high speeds.


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Thyristors

Thyristors are solid-state switches.

They are only capable of switching.

They fall into two classes depending uponwhether they switch AC or DC current.


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Silicon-controlled rectifiers

are similar to a bipolar

transistor with an additional

layer added.

SCRs will remain on evenwhen the gate current is

removed.

Current will continue to flow

until the anode-cathode

circuit is either opened orreverse biased.


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Darlington pairs

A pair of transistors are connected so that the emitter

of one supplies the base of the other through which a

much larger current flows.

This provides signal amplification.

They are used extensively in computer control

systems and ignition modules.


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Photonic Semiconductors (1 of 5)

Photonic semiconductors emit and detect

light (photons).

A photon is a unit of light energy.

Photons behave like waves.

All visible light is classified as

electromagnetic radiation.


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The optical light

spectrum includes:

Ultraviolet

Visible

Infrared


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The portion of the

electromagnetic

spectrum that is visible

is very narrow.

Photonic

semiconductors

operate in this range.


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The importance of optical components in the

electronic age is increasing.

Data signaling functions will be removed from

hard-wired buses and will be performed usingfiber optics.

Optical components may conduct, refract, or

modify light. The use of optical components in vehicle

technology is increasing.


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Optical components:

Filters

Reflectors

Beam splitters

Lenses

Optical fibers

Solar cells


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Testing Semiconductors (1 of 2)

Diodes should producea low resistance when

forward biased and a

high resistance when

reverse biased.


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Testing Semiconductors (2 of 2)

Test a transistor using aDMM in ohmmeter mode.

There should be continuitybetween the emitter andbase.

There should be continuitybetween the base and thecollector in one directionand high resistance whenthe leads are reversed.

There should be highresistance in either directionbetween the emitter andcollector terminals.


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Integrated Circuits

G d T h T bl


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Gates and Truth Tables

Digital integrated circuits contain thousandsof gates.

Gates are only to be either be open or

closed. Gates may be categorized as:

AND gates

OR gates NOT gates (inverter gates)


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Bi S t B i


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Binary System Basics

The binary system is an arithmetic system with onlytwo digits, 1 and 0.

The binary system is used in computers because it

directly corresponds to the on or off states of

switches.

Digital electronic data is stored in binary code.

Digital signals may be transmitted:

Serial data link Parallel data link

S i l d P ll l D t Li k


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Serial and Parallel Data Links

Mi


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Microprocessors (1 of 2)

A microprocessor is a solid-state chipcontaining many hundred of thousands ofgates per square inch.

The microprocessor is the core of bothpersonal and vehicular computer systems

On-board computers are referred to asECMs.

Truck technicians must have a basicunderstanding of both personal computersand vehicle ECMs.

Mi


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Microprocessors (2 of 2)

Information processingrequires:

Data input

Data processing

Data output

Data Input


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Data Input

Most data input devices are sensors.

Thermistors

Variable capacitance sensor (pressure)

Piezo-resistive sensor

Potentiometers

Hall-effect sensors

Induction pulse generator Switches

Thermistors


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Thermistors

Thermistors preciselymeasure temperature.

If the resistance decreasesas temperature increases, itis an NTC thermistor.

If the resistance increasesas temperature decreases, itis a PTC thermistor.

Coolant temperature,ambient temperature, and

oil temperature aremeasured using thermistors.

Variable Capacitance Sensors


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Variable Capacitance Sensors

These sensors areprovided with areference voltage andreturn a signal voltage

based upon pressure. Oil pressure, boost

pressure, and fuelpressure can bemeasured usingvariable capacitancesensors.

Piezo Resistive Pressure Sensor


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Piezo-Resistive Pressure Sensor

Piezo-resistive sensors are sometimes referred toas wheatstone bridges.

A doped silicon chip is formed in a diaphragmshape with the center much thinner. A set of

sensing resistors are attached around the perimeterand measure the amount of flexing in response topressure.

An electrical signal proportional to pressure is thus

obtained. Manifold pressure may be measured using piezo-

resistive sensors.

Potentiometers (1 f 2)


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Potentiometers (1 of 2)

A potentiometer is a three-wire voltage divider thatvaries its resistance inresponse to mechanicalmovement.

Throttle position iscommonly measured usinga potentiometer.

This sensor may be referredto as the TPS (throttle

position sensor) or APP(accelerator pedal position)sensor.



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Zero accelerator pedal angle: Signal output is0.2 volts.

0.0 volts would indicate anopen circuit.

Maximum accelerator pedalangle:

Signal voltage is4.8 volts. Between zero and full pedal

travel: Actual mechanical position will

produce a signal in proportionto reference voltage.

Loss of potentiometer ground: Signal voltage will equalsupply voltage. This isinterpreted as a short circuit.

Hall-effect Sensors


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Hall-effect Sensors

A digital signal is producedas windows and vanes on a

rotating pulse wheel pass

through a magnetic field.

The pulse wheel

incorporates one narrow

window for relaying position

data.

The frequency and width of

the signal provides the ECMwith shaft speed and

position data.

Induction Pulse Generator


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Induction Pulse Generator

A disc known as a reluctorwith evenly spaced teeth is

rotated through a magnetic

field produced by a

permanent magnet.

As the field alternately

builds and collapses, an AC

voltage is produced.

The voltage changes in

frequency and amplitude inproportion to speed

changes.

Switches


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Switches

Switches produce a digital signal by beingeither open or closed.

Toggle switches and coolant level sensors

are examples of switches used as sensors.

Data Processing Cycle (1 of 2)


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Functions of the ECM Uses a CPU to clock and manage the processing

cycle

Arithmetic logic unit (ALU) performs numericcalculations

Contains in memory banks the data required tomanage the system

Conditions the processor circuit voltage

Manages the reference signal

Converts analog input data into a digital format usingan ADC (analog to digital converter)

Converts digital output to analog voltages required toactuate electrical components

Outputs


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Outputs

The results of data processing are convertedinto action by switching units (drivers) and

actuators.

Examples of actuators are solenoids, relays,lights, and displays.

SAE Hardware and Software Protocols


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SAE Hardware and Software Protocols

SAE J1587 Electronic data exchange protocols used in data exchange

between heavy-duty, electronically managed systems

SAE J1708

Serial communications and hardware compatibility protocols

SAE J1939 The set of standards incorporating both J1587 and J1708

Separate J1939-compatible electronic systems can sharerather than duplicate common hardware using a commonlanguage.

J1939 will be updated by simply adding a suffix.

Multiplexing


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Multiplexing

Multiplexing is used to network multiple

electronically managed systems.

This avoids hardware duplication and

synergizes the operation of the system.

Data Retention


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Data Retention

Random access memory (RAM) Designed not to be overwritten

Read-only memory (ROM)

Sometimes described as a personalitymodule which calibrates the ECM to eachtrucks configuration

Electronically erasable PROM (EEPROM)

Contains customer data options andproprietary data that can be altered using avariety of electronic service tools


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Summary (1 of 8)


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y ( )

Data can be transmitted electronically by means ofelectrical waveforms.

Semiconductors are by definition elementalmaterials with four electrons in their outer shells.

Silicon is the most commonly used semiconductormaterial.

Semiconductors must be doped to provide themwith the electrical properties that can make them

useful as electronic components. After doping, semiconductor crystals may be

classified as having N or P electrical properties.

Summary (2 of 8)


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y ( )

Diodes are two-terminal semiconductors that oftenfunction as a sort of electrical one-way check valve.

Zener diodes are commonly used in vehicle

electronic systems.

They act as a voltage-sensitive switch in a circuit.

Transistors are three-terminal semiconductor chips.

Transistors can be generally grouped into bipolar

and field effect types.

Summary (3 of 8)


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y ( )

Essentially, a transistor is a semiconductorsandwich with the middle layer acting as a control

gate. A small current flow through the base-emitter

will ungate the transistor and permit a much larger

emitter-collector current flow. Many different types of transistors are used in

vehicle electronic circuits, but their roles are

primarily concerned with switching and

amplification.

The optical spectrum includes ultraviolet, visible,

and infrared radiation.

Summary (4 of 8)


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y

Optical components conduct, reflect, refract, ormodify light. Fiber optics are being usedincreasingly in vehicle electronics, as are opticalcomponents.

Integrated circuits consist of resistors, diodes, andtransistors arranged in a circuit on a chip of silicon.

A common integrated circuit chip package used incomputer and vehicle electronic systems is a DIPwith either 14 or 16 terminals.

Many different chips with different functions areoften arranged on a primary circuit board, alsoknown as a motherboard.

Summary (5 of 8)


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y

Gates are switched controls that channel flows of data throughelectronic circuitry.

AND, OR, and NOT gates are three commonly used means ofproducing an outcome based on the switching status ofcomponents in the gate circuit.

The binary numeric system is a two-digit arithmetic system thatis often used in computer electronics because it directlycorresponds to the on or off states of switches and circuits.

A bit is the smallest piece of data that a computer canmanipulate. It has the ability to show one of two states, either onor off.

A byte consists of 8 bits.

Summary (6 of 8)


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A byte of data can represent up to 256 pieces of coded data. Almost all current on-highway trucks use computers to manage

the engine and usually other chassis systems as well.

A truck with multiple ECM-managed systems can network themusing a chassis data bus; this is known as multiplexing.

A vehicle ECM information processing cycle comprises threestages: data input, data processing, and outputs.

RAM or main memory is electronically retained and thereforevolatile.

Summary (7 of 8)


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The master program for system management isusually written to ROM.

PROM data is used to qualify the ROM data to aspecific chassis application.

Some OEMs describe their PROM component as apersonality module.

EEPROM provides an ECM with a read/write/erasememory component.

Multiplexing is the term used to describe a systemwhere two or more ECMs are networked to reduceinput hardware and optimize vehicle operation.


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