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

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

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

Cybernetics

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

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)

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

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

There are several reasons that computers are being used in modern vehicles

Computers can provide several advantages

Computer Advantages Fewer moving parts to wear and go out

of calibration Reduced fuel consumption Lower emissions Increased engine power Reduced vehicle weight

Computer Advantages

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

Field of study dealing with the ways a computer uses on-off signals to produce

“artificial intelligence”

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

Binary Numbering System

To use the binary system, a computer turns switches (transistors) on or off

Off represents zero On represents one

Binary Numbering System

Binary Numbering System

Binary numbers can be converted into decimal (base ten) numbers

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

Gating Circuits Gate

electronic circuit that produces a specific output voltage for given input voltages

Common gate types: NOT AND NAND OR NOR

NOT Gate

AND Gate

NAND Gate

OR Gate

NOR Gate

Truth Table

Shows what the output of a gate will be with

different inputs

“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

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

Electronic circuits that have been reduced in size and etched on the surface of tiny

semiconductor chips

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

Integrated Circuit

Wire leads connect the chip to the metal pins.

The pins plug into or are soldered to other parts of the circuit.

Integrated Circuit

A digital IC uses logic gates.

An analog IC increases output strength or alters output.

IC Construction

The circuit has been photographically reduced in size, etched on a silicon chip, and placed in a

protective plastic case

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

Digital Signal

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

Digital Signal

A digital waveform as seen onan oscilloscope

Analog Signal

Gradually changes in strength like the output from a dimming switch

Analog Signal

An analog waveform as seen onan oscilloscope

Scoping a Magnetic Sensor

Electrical Waveforms

Signal Frequency

How fast a signal changes over time High-frequency signal

short pulse width

Low-frequency signal long pulse width

Signal Frequency

Measured in cycles per second (hertz)

Signal Amplitude

Voltage level present in the waveform

Duty Cycle

Percentage of on-time comparedto total cycle time

There are three stages of computer system operation: input processing and storage output

Inputs and Outputs

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

Computer System Block

DiagramFig 18

Most vehicle sensors, or transducers, change a physical condition into an electrical signal

Transduce: to change from one form to another

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

Sensor Locations

Sensor Locations

Some of the sensors located on the engine and transaxle

Sensor Classifications

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

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)

Active Sensor

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

Passive Sensor

Types of Sensors

Variable Resistor Sensor

Changes its resistance with a change in condition temperature, pressure, etc.

Throttle position and temperature sensors are variable resistance sensors

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

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

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

Hall-Effect Sensor

Uses a semiconductor chip that reacts to magnetic fields

Optical Sensor

A reverse-biased photodiode conducts

current when exposed to light

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

Optical Sensor

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

Piezoelectric Sensor

Solar Sensor

Converts sunlight directly into an electrical signal

Made of a semiconductor material that converts photons into direct current

Solar Sensor

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

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

Sensor Types Oxygen sensors

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

Sensor Types Throttle position sensor (TP)

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

Sensor Types Camshaft position sensor (CMP)

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

Sensor Types Transaxle/transmission sensor

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

Sensor Types Oil level sensor

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

Sensor Types Vehicle speed sensor (VSS)

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

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

The term computer refers to any electronic circuit configuration that can

use multiple inputs to determine outputs

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)

Computer Names

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

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

Computer Types

Engine control module controls engine management functions

Anti-lock brake module controls anti-lock brake operation

Instrumentation module operates the digital dash display

Computer Types

Ignition 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

Computer Types

Computer Types Air bag 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.

Computer Locations

Computers may be located almost anywhere on the vehicle

Computer Construction

Computers are composed of printed circuit boards, integrated circuits, capacitors, resistors, transistors,

and other electronic components

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

Parts of a Computer

Parts of a Computer

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)

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

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

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

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

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

Computer Data Flow

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

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

RAM

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

removed

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

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

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

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

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

Output Drivers

Control current flow through the actuators

When energized by the computer, drivers ground the actuator circuits, providing actuator operation

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

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

Multiple Sensor Inputs

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

Devices that allow the computer to do work and alter the operation of other components

Actuators may be found anywhere on the modern automobile

ActuatorClassifications

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

ActuatorClassifications

Actuator Operation

When the computer turns on an actuator, it normally provides the device with a ground circuit

Current can then operate the actuator

Actuator Operation

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.

Solenoid Operation(Automatic Door Locks)

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

Relay Operation

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

Servo Motor Operation

Specific coils can be energized to attract and stop the armature

Specific Actuators Common actuators used on modern

vehicles include: Fuel injector

solenoid valve that controls fuel flow

Fuel pump electric motor-driven pump

Specific Actuators Idle air solenoid

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

Canister purge solenoids 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

Specific Actuators

Specific Actuators Ignition coil

changes low voltage into high voltage, which operates the spark plugs

Ignition module uses computer signals to control the

operation of the ignition coils