Presentation is loading. Please wait.

Presentation is loading. Please wait.

Chapter 17 Computer System Fundamentals.

Similar presentations

Presentation on theme: "Chapter 17 Computer System Fundamentals."— Presentation transcript:

1 Chapter 17 Computer System Fundamentals

2 Contents Cybernetics Computer advantages Digital electronics
Integrated circuits Computer signals Computer system operation Sensors Computers Actuators

3 Computer Complex electronic device that will produce programmed electrical output signals after receiving specific electrical input signals Computers monitor and control all major systems of a modern vehicle

4 Cybernetics Study of how electrical-mechanical devices can duplicate the action of the human body Comparing the human body to a computer system is an easy way to explain this subject

5 Cybernetics

6 The Nervous System Uses chemical-electrical signals to control the body If you touch a sharp needle, nerve cells in your finger “fire” and send a signal through a strand of nerve cells in your hand, up your arm, and into your brain Nerve cells in your finger are comparable to a sensor, or input device, in a computer system

7 The Brain Uses billions of cells interconnected by linking cells called neurons When the brain “thinks”, minute electrical impulses travel from neuron to neuron Cells in the brain can be either charged (on) or not charged (off)

8 The Brain By connecting all the brain cells, the brain can decide what to do in each situation Computers produce logical outputs in a similar fashion

9 The Reflex Action Specific brain cells are activated by the needle prick (pain) signal, and a reflex output is produced The brain sends a signal to your arm to pull back This is similar to the action of an actuator, or output device, in a car’s computer system

10 Computer Advantages There are several reasons that computers are being used in modern vehicles Computers can provide several advantages

11 Computer Advantages Fewer moving parts to wear and go out of calibration Reduced fuel consumption Lower emissions Increased engine power Reduced vehicle weight

12 Computer Advantages On-board diagnostics Increased driver convenience
Improved passenger safety Compensation for component wear

13 Digital Electronics Field of study dealing with the ways a computer uses on-off signals to produce “artificial intelligence”

14 Binary Numbering System
Uses only two numbers, zero and one Key to how computers operate Zero (0) and one (1) can be arranged in different sequences to represent other numbers, letters, words, an input, an output, or a condition

15 Binary Numbering System
To use the binary system, a computer turns switches (transistors) on or off Off represents zero On represents one

16 Binary Numbering System

17 Binary Numbering System
Binary numbers can be converted into decimal (base ten) numbers

18 Binary Language A single zero or a one is called a bit
Four bits make a nibble Eight bits make a byte or word

19 Gating Circuits Gate Common gate types:
electronic circuit that produces a specific output voltage for given input voltages Common gate types: NOT AND NAND OR NOR

20 NOT Gate

21 AND Gate

22 NAND Gate

23 OR Gate

24 NOR Gate

25 Shows what the output of a gate will be with different inputs
Truth Table Shows what the output of a gate will be with different inputs

26 “Thinking” with Gates If an AND gate is compared to two switches wired in series, both switches must be on to activate the starter motor

27 Using Gates Logic gates can be connected together to form super-complex circuits Millions of gates can be interconnected to produce thousands of programmed outputs from numerous inputs This is how a computer works, or thinks

28 Integrated Circuits Electronic circuits that have been reduced in size and etched on the surface of tiny semiconductor chips

29 Integrated Circuit Different semiconductor substances are deposited on a silicon chip and then etched to produce resistors, diodes, and transistors Metal conductors on the top of the chip connect these various electronic components to form the circuit Wire leads allow for input and output connections

30 Integrated Circuit Wire leads connect the chip to the metal pins.
The pins plug into or are soldered to other parts of the circuit.

31 Integrated Circuit A digital IC uses logic gates.
An analog IC increases output strength or alters output.

32 IC Construction The circuit has been photographically reduced in size, etched on a silicon chip, and placed in a protective plastic case

33 Computer Signals Computer signal
voltage variation over short periods of time specific arrangement of pulses or waves used to carry data, or information Computer signals can be digital or analog

34 On-off signal like that is produced by a rapidly flipping switch
Digital Signal On-off signal like that is produced by a rapidly flipping switch

35 A digital waveform as seen on an oscilloscope
Digital Signal A digital waveform as seen on an oscilloscope

36 Gradually changes in strength like the output from a dimming switch
Analog Signal Gradually changes in strength like the output from a dimming switch

37 An analog waveform as seen on an oscilloscope
Analog Signal An analog waveform as seen on an oscilloscope

38 Scoping a Magnetic Sensor

39 Electrical Waveforms

40 Signal Frequency How fast a signal changes over time
High-frequency signal short pulse width Low-frequency signal long pulse width

41 Measured in cycles per second (hertz)
Signal Frequency Measured in cycles per second (hertz)

42 Voltage level present in the waveform
Signal Amplitude Voltage level present in the waveform

43 Percentage of on-time compared to total cycle time
Duty Cycle Percentage of on-time compared to total cycle time

44 Computer System Operation
There are three stages of computer system operation: input processing and storage output

45 Inputs and Outputs

46 Computer System Block Diagram
Service manual drawing that shows how the sensors, the actuators, and the computer interact Useful when trying to find out what types of sensors are used and what conditions are controlled

47 Computer System Block Diagram
Fig 18

48 Sensors Most vehicle sensors, or transducers, change a physical condition into an electrical signal Transduce: to change from one form to another

49 Sensor Locations Sensors can be found almost anywhere on a vehicle:
on the engine on or in the transmission or transaxle in the exhaust system on the wheel hubs on and in the fuel tank on the suspension in the trunk

50 Some of the sensors located on the engine and transaxle
Sensor Locations Some of the sensors located on the engine and transaxle

51 Sensor Classifications
Sensors can be classified into two general categories: active sensors passive sensors

52 Active Sensor Produces its own voltage signal internally
The signal is fed to the computer for analysis Shielded wire may be used to block induced voltage and interference in the signal wire(s)

53 Active Sensor

54 Passive Sensor Variable resistance sensor
Voltage is fed to the sensor from the computer Sensor resistance varies with changes in a condition temperature, pressure, motion, etc. As sensor resistance changes, the voltage signal sent back to the computer changes

55 Passive Sensor

56 Types of Sensors

57 Variable Resistor Sensor
Changes its resistance with a change in condition temperature, pressure, etc. Throttle position and temperature sensors are variable resistance sensors

58 Switching Sensor Opens or closes the sensor circuit to provide an electrical signal Used to detect almost any condition Produces a digital signal Transmission pressure switches are switching sensors

59 Magnetic Sensor Also called a permanent magnet (PM) generator
Uses part movement and induced current to produce a signal Produces an analog signal Used to monitor speed or part rotation Vehicle speed and wheel speed sensors are often magnetic sensors

60 Hall-Effect Sensor Uses a special semiconductor chip to sense part movement and speed Produces a digital signal Applications: crankshaft position sensors camshaft position sensors distributor pickup devices

61 Uses a semiconductor chip that reacts to magnetic fields
Hall-Effect Sensor Uses a semiconductor chip that reacts to magnetic fields

62 A reverse-biased photodiode conducts current when exposed to light
Optical Sensor A reverse-biased photodiode conducts current when exposed to light

63 Optical Sensor Uses light-emitting diodes and photo diodes to produce a digital signal Used to sense part rotation and speed Used in some distributors and as speed sensors mounted outside the speedometer

64 Piezoelectric Sensor Generates voltage from a physical shock or motion
An internal crystal produces a voltage signal proportional to the amount of vibration detected Used to sense abnormal engine vibration caused by engine knock knock sensor

65 Piezoelectric Sensor

66 Solar Sensor Converts sunlight directly into an electrical signal
Made of a semiconductor material that converts photons into direct current

67 Solar Sensor

68 Direction Sensor Detects the polarity of a moving magnet
Signals which direction a part is rotating Used in some computer-controlled steering systems

69 Reference Voltage Applied to a passive sensor by the computer
5 volts on most vehicles The computer steps down battery voltage so that a smooth, constant supply of dc voltage is fed to the sensor The sensor changes its internal resistance to alter the reference voltage

70 Sensor Types Common sensors used in late-model vehicles:
Intake air temperature sensor (IAT) measures the temperature of intake air as it enters the intake manifold Engine coolant temperature sensor (ECT) measures the temperature of engine coolant

71 Sensor Types Oxygen sensors Manifold absolute pressure sensor (MAP)
measure the amount of oxygen in the engine’s exhaust gases Manifold absolute pressure sensor (MAP) measures pressure inside the intake manifold Barometric pressure sensor (BARO) measures the outside air pressure

72 Sensor Types Throttle position sensor (TP) Engine speed sensor
measures the opening angle of the throttle valves to detect driver power demand Engine speed sensor measures engine rpm Crankshaft position sensor (CKP) measures crankshaft position and speed

73 Sensor Types Camshaft position sensor (CMP) Mass airflow sensor (MAF)
measures camshaft position and rotation Mass airflow sensor (MAF) measures the amount of intake air flowing into the engine Knock sensor (KS) detects engine pinging, preignition, or detonation

74 Sensor Types Transaxle/transmission sensor Brake switch
checks transaxle or transmission gear selection Brake switch detects brake pedal application Wheel speed sensor measures wheel rotational speed for anti-lock brake and traction control application

75 Sensor Types Oil level sensor EGR sensor Impact sensors
measures the amount of oil in the engine oil pan EGR sensor measures the position of the exhaust gas recirculation valve pintle Impact sensors detect a collision

76 Sensor Types Vehicle speed sensor (VSS) Fuel tank pressure sensor
measures the vehicle’s road speed Fuel tank pressure sensor measures fuel tank pressure as part of some evaporative emission control systems Battery temperature sensor monitors battery temperature so the computer can adjust charging system output as needed

77 Circuit Sensing Involves using the computer itself to monitor component and circuit operation Computer monitors current flow through various circuits to diagnose: fuel injectors ignition coil action computer operation

78 Computers The term computer refers to any electronic circuit configuration that can use multiple inputs to determine outputs

79 Computer Names Automobile manufacturers have many names for their computers: central processing unit (CPU) electronic control unit (ECU) electronic control module (ECM) engine control module (ECM) (Continued)

80 Computer Names electronic control assembly (ECA)
powertrain control module (PCM) vehicle control module (VCM) microprocessor logic module

81 Computer Types Several types of computers can be used in a car
The most common types are: Vehicle control module coordinates engine, transmission, traction control, and anti-lock brake functions Powertrain control module monitors and controls the engine and transmission

82 Computer Types Engine control module Anti-lock brake module
controls engine management functions Anti-lock brake module controls anti-lock brake operation Instrumentation module operates the digital dash display

83 Computer Types Ignition module Suspension system module
controls ignition functions, such as timing Suspension system module controls ride stiffness or shock absorber action Climate control module controls the operation of the heating, ventilation, and air conditioning systems

84 Computer Types Air bag module High-power module Body module
controls the vehicle’s air bag system High-power module Controls current or processes output signals from a few sensors and the main computer Body module coordinates body functions, such as lighting, radio, driver’s information center, electronic compass, etc.

85 Computers may be located almost anywhere on the vehicle
Computer Locations Computers may be located almost anywhere on the vehicle

86 Computer Construction
Computers are composed of printed circuit boards, integrated circuits, capacitors, resistors, transistors, and other electronic components

87 Parts of a Computer A computer can be divided into 11 basic parts:
voltage regulator amplifiers conditioners buffer microprocessor memory clock output drivers circuit board harness connector computer housing

88 Parts of a Computer

89 Voltage Regulator Provides a reduced voltage for the components in the computer and sensors Provides a smooth dc voltage that does not vary and is free of any spikes (abrupt changes in voltage)

90 Computer Amplifier Strengthens various signals when inside the computer amplifier might increase the voltage signal from the oxygen sensor, which is less than one volt Allows a low voltage signal to be used by the circuits in the computer

91 Input Conditioner Also called a converter or interface
Alters the input signals from some sensors Modifies incoming data so that it can be utilized by the computer Converts analog signals to digital signals

92 Output Conditioner Also called a converter or interface
Changes output signals from digital to analog Allows the operation of actuators Protects the computer processor from high current

93 Buffer Serves as a temporary storage area for data
Protects internal components from improper data controls the rate of data flow Built into the input conditioner

94 Microprocessor Integrated circuit capable of analyzing data and calculating appropriate outputs Uses the binary number system to make decisions, comparisons, or calculations Compares input signals to memory data to decide what the outputs should be for maximum efficiency

95 Computer Data Flow The interaction between the different computers in a vehicle's computer network is referred to as multiplexing

96 Computer Memory Uses gates that are capable of storing data as voltage charges ICs inside the memory chips will hold the data until needed by the microprocessor

97 RAM Random access memory Stores information or data temporarily
Data is erased if battery power is removed

98 ROM Read only memory Stores permanent data that cannot be removed from memory Contains calibration tables and lookup tables for the general vehicle make and model

99 PROM Programmable read only memory
Contains permanent data that is more specific than the data stored in ROM engine and transaxle specifications, vehicle weight, and tire size are specifics found in the PROM May be replaced or reprogrammed to upgrade vehicle operation

100 EPROM Erasable programmable read only memory
Can be changed, usually by the manufacturer using special equipment Used for storing odometer readings on an electronic dash display

101 EEPROM Electrically erasable programmable read only memory
Can be altered by the technician in the field Allows the manufacturer to change operating parameters if a performance or driveability problem is discovered

102 Other Memories Flash erasable programmable read only memory (FEPROM)
similar to EEPROMs in all respects Keep alive memory (KAM) memory chip that allows the computer to have an adaptive strategy stores calibration information that enhances vehicle operation as parts wear

103 Output Drivers Control current flow through the actuators
When energized by the computer, drivers ground the actuator circuits, providing actuator operation

104 Processor-Memory Bus Pathway by which sections of a computer communicate Microprocessor controls this flow of data writes data about vehicle operation into memory and reads data about how the vehicle should operate from memory

105 Multiple Sensor Inputs
Computer system uses inputs from more than one sensor to make most control decisions Fuel injection example: engine coolant temperature sensor signals a cold engine computer would use both speed and temperature signals to increase injector pulse width to enrich the mixture for cold engine operation

106 Multiple Sensor Inputs

107 Computer Network Series of computers that control different systems but work together to improve overall vehicle efficiency Shares wires, input signals, and output signals Computers exchange data from sensors to prevent duplication of parts and to reduce wiring

108 Actuators Devices that allow the computer to do work and alter the operation of other components Actuators may be found anywhere on the modern automobile

109 Actuator Classifications
Actuators can be grouped into the following categories: solenoid relay servo motor display device control module

110 Actuator Classifications

111 Actuator Operation When the computer turns on an actuator, it normally provides the device with a ground circuit Current can then operate the actuator

112 Actuator Operation

113 Solenoid Operation Computer grounds the solenoid circuit
Current flows through the solenoid winding A magnetic field moves the plunger mounted in the solenoid windings Plunger movement is used to operate a device fuel injectors, vacuum valves, door locks, etc.

114 Solenoid Operation (Automatic Door Locks)

115 Relay Operation Computer grounds the relay coil windings
Low current flows through the relay windings Relay coil field will then pull the mechanical contacts closed, allowing high current to flow to the load

116 Relay Operation

117 Servo Motor Operation Computer can ground the motor circuit, turning the motor on and off or reversing motor rotation as needed Some servo motors are simply reversible dc motors these motors turn a threaded mechanism to produce controlled movement of a part

118 Specific coils can be energized to attract and stop the armature
Servo Motor Operation Specific coils can be energized to attract and stop the armature

119 Specific Actuators Common actuators used on modern vehicles include:
Fuel injector solenoid valve that controls fuel flow Fuel pump electric motor-driven pump

120 Specific Actuators Idle air solenoid Idle speed motor EGR solenoids
controls airflow into the engine to control idle speed Idle speed motor reversible dc motor that opens and closes the throttle valve to control idle speed EGR solenoids open and close small ports to control exhaust gas flow back into the engine

121 Specific Actuators Canister purge solenoids Door lock motors
control vacuum flow to draw fuel vapors from the fuel tank into the engine for burning Door lock motors solenoids that move latch mechanisms to lock or unlock the doors Electric seat motors reversible dc motors that move the seat into the desired position

122 Specific Actuators Ignition coil Ignition module
changes low voltage into high voltage, which operates the spark plugs Ignition module uses computer signals to control the operation of the ignition coils

Download ppt "Chapter 17 Computer System Fundamentals."

Similar presentations

Ads by Google