Chapter 06 Bennet
Transcript of 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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Using Electronic Signals (2 of 3)
Analog signals operate
on variable voltage
values.
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Using Electronic Signals (3 of 3)
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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Semiconductors (2 of 4)
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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Semiconductors (3 of 4)
Silicon crystals doped
with boron or some
other trivalent element
will form P-type silicon
crystals.
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Semiconductors (4 of 4)
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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Transistors (2 of 10)
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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Transistors (4 of 10)
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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Transistors (5 of 10)
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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Transistors (6 of 10)
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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Transistors (7 of 10)
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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Transistors (8 of 10)
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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Transistors (9 of 10)
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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Transistors (10 of 10)
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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Photonic Semiconductors (2 of 5)
The optical light
spectrum includes:
Ultraviolet
Visible
Infrared
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Photonic Semiconductors (3 of 5)
The portion of the
electromagnetic
spectrum that is visible
is very narrow.
Photonic
semiconductors
operate in this range.
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Photonic Semiconductors (4 of 5)
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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Photonic Semiconductors (5 of 5)
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.
Potentiometers (2 of 2)
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Potentiometers (2 of 2)
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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Data Processing Cycle (1 of 2)
Data Processing Cycle (2 of 2)
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Data Processing Cycle (2 of 2)
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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