1 BEET ( Basic Electricals & Electronics ) - Self Study module.pdf

BASIC ELECTRICAL & ELECTRONICS
SELF STUDY LEARNING COURSE

Course Content
FAMCO
 Introduction
 Safety precautions
 Basic of Electricals - Ohm`s law, Voltage drop, Watt`s law.
 Battery, Alternator & Starter Motor Function & working
 Different type of circuits & symbols
 Wiring diagram, reading and understanding
 Electric Components
 Measuring instruments
 Circuits Fault-tracing
 Basics Of Electronics
 Electrical Terms

Course Objectives
FAMCO
Upon completion of this course the attendees will be able to:
 Know the concepts voltage, current, and resistance as well as
have insight into Ohm`s and Watt`s law.
 Understanding the function of basic components used in electrical
systems.
 Identify the parts of a complete circuit.
 Usage of Digital Multi meter (DMM).
 Describe the characteristics of an open, a short-to-ground, and a
short-to-voltage.
 Be able to use correct measuring technique and be able to perform
troubleshooting as well as handle troubleshooting equipment.
 Have an understanding of a wiring diagram and be able to read it.
 Understand Basics of electronics & Electrical terms

Introduction
Today's Trucks & Buses have many functions that demand various
electrical components and systems in order to work.
To fault-trace and repair these components and systems it is important
to understand the basics of electricity.
The driver and passengers can control many of these functions
electrically. This helps to increase safety and comfort.

Safety Precautions
Take off your watch and jewelry when
working with electrical systems.
Even small voltages may generate
powerful currents. High risk of injury in
case of contact between a voltage
source and the skin via a metal object.
For example, if current passes through
a ring it gets hot very quickly, which
may cause serious burn injuries

Safety Precautions
How Human are affected by current
through the heart :
- 0,5 mA : No noticeable impact on
humans
- 15 mA : Muscle cramp – hand holding
`live` object cannot be opened
- 30 mA : irregular heart beat and
increased blood pressure
- 80 mA : In case of exposure for more
than 0.5 – 1 second = immediate death

Structure of an Atom
An atom is like a tiny solar system, the center part is called as nucleus made up of
tiny particles called as protons and neutrons. The nucleus is surrounded by clouds of
tiny particles are called as electrons

Neutron
The neutron and protons make up the central nucleus of an atom ,and the neutrons
are neutral charge.

Proton
The proton contains A positive electrical charge

Free electrons
The closer an electron is to the nucleus, the stronger it is bound to the nucleus. The
further an electron is from the nucleus ,the less it is bound to the nucleus. Therefore
,electrons in an outer-most orbit are easiest electrons to dislodge from their orbit,
these are called free electrons.

Transfer of free electrons
Free electrons may be pulled from one atom to another. Causing an overlap. This
overlap allows the free electrons to hop from atom to atom ,temporarily rotating about
each nucleus's free electrons bounce from the orbit of one atom to the orbit of
another atom ,they dislodge other free electrons, thus creating a continuous chain
reaction ,it is the transfer of these free electrons ,from atom to atom ,that creates
electricity.

Electrons
Orbiting the nucleus are electrons ,which contain a negative charge, opposite
electrical charges attract ,therefore the positive charge of the proton holds the
electron in its orbit. The movement of electrons from one atom to another atoms
make up electricity

Electrical System
Main Functions of Electrical System in Vehicle
Power Generation
Electric Power is generated by Alternator when Engine runs at Specific
Speed.
Storage
Battery is a source of electric current. It supplies electric current when
engine is not running and it gets charged when engine is running.
Transportation
It transmits & controls the power flow to the consumers through Wiring
harness, Fuses, Relays and Switches.
Consumers
Electrical aggregates( like Starter Motor, head lights, Horn etc) which
consume electricity for functioning. Vehicle electrical system works on
12/24 volt DC.

Types of Current
ALTERNATING CURRENT – AC
used for Domestic purpose
DIRECT CURRENT – DC
Used for Automobiles
 In Automobile we need to store the energy for starting / other use so we need
DC Current
 AC current can not be stored so not possible to use in Automobile

Alternating Current (AC)
Electrons keep switching directions, sometimes going "forwards"
and then going "backwards."

Direct Current (DC)
The electrons flow steadily in a single direction, or “forward.

Functions of Current
When current passes through a conductor it performs heat,
lighting and magnetism.

Types of Materials
Materials can be categorized as conductors, semiconductors and insulators.
Conductors
Conductors are materials that have very low resistance. They can therefore
carry electric currents.
Most of the conductors used in electronics are metals like silver, copper,
gold, Aluminum, iron, steel, brass, bronze, mercury, graphite, dirty water.
Insulators
Materials with high resistance are called as insulators; they won’t allow the
current to flow
E.g. glass, rubber, oil, asphalt, fiberglass, porcelain & ceramic.
quartz,(dry) cotton,(dry) paper,(dry) wood, plastic,air,diamond,Pure water.

Semiconductors;
A semiconductor will carry electric current, but not as easily as a normal
conductor. All the transistors, diodes, integrated circuits, etc. used in
modern electronics are built using a range of semiconductors.
E.g. Silicon and Germanium.
Types of Materials

Current: The Flow of electrons in a circuit.
Measured in Amperes
Unit- Amps
Symbol - A
Elements of Electricity
Current, Voltage and Resistance

Measured in – voltage
Unit – Volt
Symbol – V or E
Voltage
Electrical pressure is created by the difference in the number of electrons
between two points, The amount of attraction between the two points is
measured in units known as voltage, Voltage is sometimes referred to as
“potential” because whenever there is a difference in the number of
electrons between two points ,there is a potential for electricity move,
voltage is also referred to as electro-motive force (EMF).

Resistance
Resistance restricts the flow of electron, The unit of measurement for the
amount of restriction is known as ohms
Symbol- Ω
Unit - Ohm

OHMS LAW
In an Electrical Circuit Current (I) is
directly proportional to voltage (V) and
inversely proportional to Resistance (R)
Voltage (V)= I X R
Current ( I ) =V/ R
Resistance (R)= V/I

Ohms law calculation
Current- I

OHM’S LAW RELATIONSHIP
OHM’S LAW APPLIED TO SIMPLE CIRCUITS

Relation between Current Voltage and Resistance

Power is the rate at which work is done in a circuit i.e. many electrical
devices(bulb, motor) are rated by how much electrical power they consume
,rather than by how much power they produce , power consumption
expressed in watts
P= I X V
Watts = Amps X Volts
If 5A of current is applied in one second using a voltage of 12 V, the
electrical
Device (bulb) performs 60W of work. The lamp is dissipating
(releasing) 60 watts of power, most likely in the form of both light and heat.
5 x 12 = 60 Watts
To calculate the fuse rating for a 60W bulb, divide the wattage by the
voltage (12V)
I (Amps) = P (Watts) 60 ÷ V (Voltage) 12
I (Amps) = 5 Amps
A 5 amp fuse would be required
Power

Factors that creates resistance to the flow of Electrons

Storage- Battery
A device which stores current through chemical reaction is called as Battery
Provide Electrical energy to the Vehicle electrical system
Supply power to the starter and ignition system to crank the engine.
Supply extra power when the vehicle load exceed the supply from the alternator.
Acts as a voltage stabilizer in the electrical system.
Vent plug
Battery Terminal
Terminal Clamp
Battery

Need of Battery in a Vehicle
 Starting
 Lighting
 Ignition
AMPERE HOUR
Battery Capacity is expressed in Ampere- hour the electric charge
transferred through a specified circuit by a current of one ampere in
one hour.

Battery Internal Construction:

Cell
+ + +
+ + +
+ + +
- - -
- - -
- - -
POSITIVE
PLATE
NEGATIVE
PLATE
ELECTROLYTE
ENERGY CONVERTER
CHEMICAL ELECTRICAL

Positive Plate = Lead dioxide (PbO2)
Negative Plate = Spongy Lead (Pb)
Electrolyte = Dilute Sulphuric Acid (H2SO4)
Separator = PVC
Container = Hard rubber or PVC
Battery Components

 Leaving Idle
 Neglecting topping up, in case of dry out
 Impure Water
 Over Charge
 Under Charge
 Damage/Wrong fitment
Factors affecting battery life

Electrolyte
Electrolyte
A mixture of concentrated H2so4 and Distilled water

Hydrometer Specific Gravity Checking
Checking Battery Specific Gravity Using Hydro Meter
Specific Gravity Value :-
1.270-1.240 (Yellow Region)– Fully Charged
1.240-1.200 (Blue Region) – 70% Charged
1.200- and below (Red Region) – Needs Recharge

 Secure the battery firmly on the cradle.
 Ensure the cable terminals tightly fitted on the battery posts.
 Do not hammer down terminals onto posts.
 Keep the battery top clean and dry.
 Clean the terminals and the posts regularly to avoid corrosion.
 Apply Petroleum jelly / Vaseline on the terminals and posts.
never apply grease.
 Top up only with distilled water and maintain the level corresponding to the
maximum level, never add Acid.
 Keep vent plugs tightly closed.
 Ensure the fan belt tension.
Maintenance Tips for Battery

Dos and don’ts
 While disconnecting battery cable first remove the negative cable.
 While topping always fill distilled water.
 While charging vent plugs should be removed.
 Never attempt to interchange the polarity while connecting to the vehicle.
 Never apply grease on battery terminals (apply only petroleum Jelly to
avoid flux formation).
 While carrying welding job on the vehicle, be sure the negative
cable should be disconnected.
 Keep all electrical switches in off while installing the battery.

Rusted battery bracket & Grease applied on terminals

Alternator
A device which converts Mechanical energy in to electrical energy
Power
Generation
Rectification
Regulation
Functions Of Alternator

B+
L
E
AC Blower
Accessories
Head lights
Horn
+
-
Ignition coil
Battery
Alternator
Alternator Basic Application
In an automobile the electrical power is generated by the Alternator.
The generated power is used to operate various accessories in an Automobile

Charging Circuit
B is out-put and supplies current to the battery
IG is ignition input, it turns on the alternator/regulator assembly.
S is used by the regulator to monitor charging voltage at the battery.
L is the wire that regulator uses to ground the charge warning lamp.

Structure of Charging System & Electricity Generating System

Alternator
 Power is generated by Alternator in the vehicle .
 Alternator is driven by the engine through a belt.
 An Alternator is a machine that converts mechanical energy to Electrical
energy.
 The Alternator output is used to charge the battery.
 The capacity of the Alternator for a vehicle is decided based on the total
electrical loads of the vehicle.

Alternator consists of :
 Rectifier- Rectifies the AC and converts to DC
 Regulator- Regulates the alternator output voltage to a maximum of
14.5 Volts.
 Rotor & Rotor winding -They work as an Electro Magnet. They are
rotating parts of Alternator, which produce magnetic field.
 Stator winding- It consists of three windings connected in “Y”,
Junction. It is a stationery part which is mounted inside around
Alternator body.
 Slip rings-The rotor winding is connected with slip rings.
 Carbon brushes -Two carbon brushes are connected with slip rings
which pass the current in the rotor winding to produce magnetic
field.
Alternator

Principle of operation – Alternator
 Initial excitation of Rotor field from battery through regulator
creates magnetic flux in the Rotor.
 Rotor rotation produces rotating magnetic flux.
 A.C. output induced in Stator winding.
 Rectification by Positive & Negative main diodes for battery
charging.
 Output controlled by the in-built Regulator.
 Rectification by Auxiliary diodes for field excitation. of Rotor field.

9 Diode Alternator Wiring Full
1. Rotor winding
2. Stator Winding
3. Diode Main Positive
4. Diode Main
Negative
5. Diode Auxiliary
(Field)
6. Voltage Regulator
7. Built – in Fuse
8. Battery
9. Fusible link
10.Ign. Start Switch
11.Warning Lamp

Diode Rectifier
 The Diode Rectifier Bridge is responsible for the conversion or rectification of AC
voltage to DC voltage.
 Six or eight diodes are used to rectify the AC stator voltage to DC voltage
 Half of these diodes are use on the positive side and the other half are on the
negative side.

ALTERNATOR DO’S AND DONT’S
Observe correct Polarity when
refitting vehicle Battery, or slave
Battery to aid starting. Always
Battery (-) to earth.
DO’s Don'ts
Don’t run the Alternator without
the Battery in the system
Use Multi meter or test lamp to
check continuity of wiring.
Don’t flash the Alternator output
leads to check output.
Keep the Engine off when you
disconnect or reconnect wiring
during electrical service.
Don’t disconnect Battery cable or
charging system wiring while the
Engine is running
Isolate Alternator while carrying
out electric welding on the
vehicle.
Don’t use high voltage instrument
like Meggar on Alternator or
wiring for insulation check.
Use special tester for checking
electronic Regulator and
Multimeter for Diodes
Don’t run Alternator integral with
Vacuum pump without oil for
more than a minute.

Factors Affecting Alternator Life
Alternator
 Loose and excess fan belt tension.
 Fused warning lamp bulb.
 Discharged Battery.
 Loose Battery positive wire & warning lamp socket connection.
 Carrying out welding operation w/o disconnecting battery connection.
Note
By strictly adhering the above points the damages to the alternator can
be avoided result in increased product life.

Starter Motor
A device which converts electrical energy in to mechanical energy

Starter Motor Function
 A Starter motor is a machine that converts electrical energy to
mechanical energy.
 The Starter output is used to crank the engine.
 The Starter motor gets supply from the battery.
 When the Starter solenoid switch getting energized, the pinion
engages with the flywheel ring gear and rotates the same.
 The starter performance depends on the battery charge status
and the voltage drop in the starting circuit.

Starter Motor – Exploded view

Factors Affecting Starter Motor Life
Starter Motor
 Discharged Battery (Battery specific gravity should be
1.250 in all cells).
 Poorly Soldered battery terminals.
 Excess cable length result in increased voltage drop.
 Loose battery terminals and starter cables.
 Oxidized terminals and posts. (Clean them regularly and apply
petroleum jelly).
 Prolonged cranking of engine.
 Faulty Ignition Switch.
Note
By strictly adhering the above points the damages to the Starter can
be avoided result in increased product life.

Wiper Motor
1. Cable Assembly with
socket
1
2
2. Rotary Link
3
3. Motor

Maintenance Tips for Wiper Motor
 Ensure all electrical connections are in good condition.
 Always keep the wind screen clean.
 Do not operate the wiper on dry wind screen.
 Check the free movement of wiper links at regular intervals.
 Worn out or perished blades should be replaced immediately.

Fuse & Fusible Link
A Fuse is a type of over Current protection device. It is connected between
the Battery terminal & load terminal.

What is different between Fuse & Fusible Link ?
 Fuse is provided for Individual Circuits ,where ever fusible link is provided
for entire circuit.
 The capacity of fuse is lesser than fusible link.
 Incase of over flow of current ,fuse can protect an individual circuit while
fusible link protects entire circuits.

Switch lever Type
A switch which is used to control the circuit

Relay
Relay Applications:A relay is an electromagnetic switch

Relay Construction
 A relay is an electromagnetic switch that opens and closes under the control of
another electrical circuit in the original form.
 The switch is operated by an electromagnet to open or to close one or many sets
of contact.
 Using relays in vehicle can reduce the total size of wiring
 To make design of switch simpler
 Relay is a sealed unit can avoid internal switch Arching.

Relay
Relays are control devices that turn current on or off or use a small current
to control a large current as illustrated here voltage travels down circuit A
and magnetism closes the contact points ,voltage then travels down circuit
B and turns the lights on.

Relay Types
Normally open
Normally closed
Double Thro

5 point Relay Working
A relay uses a movable arm to complete a circuit whenever there is a power at
terminal 86 and a ground at terminal 85. A typical relay only requires about 1/10
ampere through the relay coil. The movable arm then closes the contacts (30 to 87)
and can relay 30 amperes or more.
A cross-sectional view of a typical four-terminal relay. Current flowing through the
coil (terminals 86 and 85) causes the movable arm (called the armature) to be drawn
toward the coil magnet. The contact points complete the electrical circuit connected
to terminals 30 and 87.

Application of relay in a electrical circuit

KEY TERMS
• Complete circuit
• Continuity
• Ground
• High resistance
• Load
• Ohm’s law
• Open circuit
• Closed Circuit
• Power source
• Protection
• Return path (ground)
• Shorted
• Short-to-ground
• Short-to-voltage

Battery and Ground Symbol
The symbol for a battery. The positive plate of a battery
is represented by the longer line and the negative plate by the shorter
line.
The voltage of the battery is usually stated next to the symbol.
Represents earth ground. The ground symbol on the right represents a
chassis ground

Circuit Definition
A circuit is a complete path that electrons travel from a power source (such as a battery)
through a load such as a light bulb and back to the power source.
It is called a circuit because the current must start and finish at the same place (power
source).
For any electrical circuit to work at all, it must be continuous from the battery (power), through
all the wires and components, and back to the battery (ground).
A circuit that is continuous throughout is said to have continuity.
All complete circuits must have a power source, a power path, protection (fuse), an electrical
load (light bulb in this case), and a return path back to the power source.
Every complete circuit contains the following parts.
A power source.
Protection from harmful overloads.
An insulated path for the current to flow through from the power source to the
resistance.
The electrical load or resistance which converts electrical energy into heat, light, or
motion.
A ground (return) path for the electrical current from the load back to the power source
so that there is a complete circuit.
Switches and controls that turn the circuit on and off

Basic Circuit
A group of electrical component build a simple circuit
1.A battery –power source
2. Fuse- circuit protection device
3. Switch - A controlling Device
4. Resistance – Which consumes current and do work
5. Wires – which is used to connect the circuit .

Parts of complete circuit
GROUND: The return path back to the battery can be any electrical conductor,
such as a copper wire or the metal frame or body of the vehicle.
An electrical switch opens the circuit and no current flows. The switch could also be
on the return (ground) path wire.

Series and Parallel circuit
SERIES CIRCUIT PARALLEL CIRCUIT

Compound Circuit
A third type of circuit involves the dual use of series and parallel connections in a
circuit; such circuits are referred to as compound circuits or combination circuits.
The circuit depicted at the right is an example of the use of both series and parallel
connections within the same circuit. In this case, light bulbs A and B are connected
by parallel connections and light bulbs C and D are connected by series
connections. This is an example of a combination circuit.

Electrical Wiring Diagram
• A system out line to find out how the circuit is supposed
to operate.
• Electrical wiring is shown as straight lines and with a few
numbers and/or letters to indicate the following:
– Wire size
– Wire Color
– Terminals
– Wire Connections
– Connectors
– Grounds

The alphanumeric characters in the highlighted area show the wiring colour.
The wiring colours also include striped colours. These are expressed as L-Y
with the first letter standing for the wire base colour and the second letter
standing for the stripe colour.
Electrical Wiring Color codes

Horn circuit
Transportations- wiring harness
A circuit is complete Path for an electric Current from the source, through Electrical or
electronic components such as resister, capacitor etc and to the power source.

Digital Multimeter Analog Multimeter
Multi meter is a combination of meters which is used to measure the elements of
Electricity.
Ammeter: An Ammeter measures the amount of current in the circuit
Volt Meter; A Volt meter is useful to determine the amount of voltage in a circuit
Ohm Meter ; An ohm meter measures the amount of resistance in between two points

Ammeter- Current measuring instrument
Ammeter is a device used to measure the amount of current flow in a circuit.
It has the measuring range from Zero to a Maximum Value that the Instrument
can measure. Ammeter is connected always in series in an electrical
circuit.

Volt Meter-Voltage measuring Instrument
Volt Meter is a measuring device used to measure the voltage,
Which has a needle that start from 0 (zero) and ends at the maximum
value of voltage. Volt Meter is to be connected always In Parallel in a
circuit.

Digital Multimeter (DMM) - Components
What can you Check up With
Multi meter ?
*AC Voltage
*DC Voltage
*DC Current
*Resistance
*Continuity

Electrical Terms & Conversion
Ω - Ohm
m - milli = 1/1000
µ - micro = 1/1000000
K - Kilo = 1000
M - Mega or Meg = 1000000

You should follow these safety guidelines.
 Never operate a multimeter unless the battery cover is in place and fully
closed.
 Never connect a source of voltage with the function switch in the OHM
(Ω) position or the DIODE position.
 Don’t replace the battery or fuse unless the test leads have been
disconnected and the power is OFF.
 When making current measurements, make certain the multimeter is
connected in series with the load.
 Never connect the meter in parallel to measure current. To do so can
result in blowing the overload protection fuse or damaging the device
being tested.
Multimeter Operation

Measuring Voltage
While Measuring Voltage in a circuit the Volt meter should be
connected in parallel to the circuit.
Voltage = 12 V

Measuring open circuit Voltage
While Measuring Voltage the volt
meter should be connected parallel
in a live circuit.

Measuring Voltage drop in a circuit

Measuring Current
While Measuring
Current the Ammeter
should be connected in
series.ie Break the
circuit and connect the
Ammeter series to the
Circuit.

Measuring Resistance
While measuring resistance the
battery power should be disconnected

FAMCO
Open circuit
An open-circuit means that there is a break somewhere in the circuit. The current
cannot flow through the circuit. As a result components in the open circuit do not
function. This can be due to a broken cable, loose connection a faulty
component.

Open circuit upstream of a component
 First measure the battery voltage. The voltmeter shows 12 V, which is correct.
 Measure the voltage drop across the electrical load. In this case it is 0 V, but it should be 12 V.
 The next step is to begin tracing the fault in the circuit.
 Move the negative test probe to a suitable earth, in this case the battery's negative terminal.
 The reading here is 0 V, but it should be 12 V. This indicates that the fault is upstream of the
light bulb.
 Continue to locate the fault by measuring the circuit before the light bulb. The voltage after the
switch is 12 V, which is correct. This means that the circuit is open somewhere between the
switch and the light bulb. Check the wire and its connections.

High resistance
High resistance means that the resistance somewhere in the circuit has increased and
current has decreased in that part of the circuit. As a result the components in the
circuit de not receive enough power and may cease to function. This could be due to a
damaged cable, a corroded connection or a component which has been damaged.

Short to Voltage
If a wire (conductor) or component is shorted to voltage, it is commonly called
shorted.
A short-to-voltage is where the power side of one circuit is electrically
connected to the power side of another circuit
Circuit - Faults

Short to Ground
A short-to-ground is a type of short circuit that occurs when the current bypasses part
of the normal circuit and flows directly to ground.

General Safety Precautions ,Rules for Electricity and
Electronics
• Do not pull the wiring harness while unplugging connectors, to disconnect
the lockable connecter press the lock in the direction shown by the arrow
• To connect a lockable connecter, mate the pair until it snaps
• Don’t alter the wires cross section this may reduce capacity or short
circuit,
• While connecting or disconnecting connectors or electrical devices make
sure the ignition switch is in off position.

Basic Electronics
Electronics Definition
• The branch of physics and technology concerned with the design of circuits using
transistors and microchips. In other words it’s the study of semiconductors.

Diode
It is a two layer PN junction device .it conduct electric current in one
direction(is called forward biased condition) and to block the current in
opposite direction ( is called reversed biased condition) it is used to convert
AC supply to DC supply in Alternator.
Main function of diode is to rectify electric current to flow it always in only one
direction. But it is also used in many other functions so that main functions may be
summarized as follows: -
Usage as electric current rectifier to change the alternating current to the direct current
in electric supply facilities
Use as detector to take out signal from radio frequency
Usage in switching to control electric current ON/OFF
Prevention of backward current flow
Usage in protective circuit

Testing Diode
While checking the ohm meter shows (0 Ω) from anode to
cathode ,when reversed it should show infinity (∞ ) or (OL)

Zener Diodes
Zener diodes are used to maintain a fixed voltage. They are designed to
'breakdown' in a reliable and non-destructive way so that they can be used
in reverse to maintain a fixed voltage across their terminals.
Application
Used in charging circuit inside the voltage regulator for Alternator
Zener diode breakdown voltage of circuit is below 12 V.

Function
LEDs emit light when an electric current passes through them in other
words its work same as a diode.
Testing an LED
Never connect an LED directly to a battery or power supply!
It will be destroyed almost instantly because too much current will pass
through and burn it out.
LEDs must have a resistor in series to limit the current to a safe value, for
quick testing purposes a 1kΩ resistor is suitable for most LEDs if your
supply voltage is 12V or less.
Light Emitting Diode

Function
Capacitors store electric charge temporarily. They are used with resistors in
timing circuits because it takes time for a capacitor to fill with charge. They
are used to smooth varying DC supplies by acting as a reservoir of charge.
They are also used in filter circuits because capacitors easily pass AC
(changing) signals but they block DC (constant) signals.
Capacitance
This is a measure of a capacitor's ability to store charge. A large capacitance
means that more charge can be stored. Capacitance is measured in farads,
symbol F. However 1F is very large, so prefixes are used to show the smaller
values.
Capacitors

Capacitor
Can Type -Capacitor
Ceramic- Capacitor Mica - Capacitor
A temporary current storing device.

Transistors
Transistors amplify current, for example they
can be used to amplify the small output current
from a logic IC so that it can operate a lamp, relay
or other high current device. In many circuits a
resistor is used to convert the changing current to
a changing voltage, so the transistor is being
used to amplify voltage.
A transistor may be used as a switch (either fully
on with maximum current, or fully off with no
current).
Function

A transistor can be used as a switch and signal amplifier. It is an electronic device with three
contacts: the emitter (E), base (B) and collector (C). A very small current on the transistor's base
can control a much larger current flowing through a passage between collector and emitter. The
above drawing shows the concept behind an NPN transistor using a water analogy If there is no
water flowing down the base channel, the gate between the collector and the emitter channel is
closed, no water can flow from the collector to the emitter. If there is water flowing down the base
channel it lifts the gate that normally blocks the collector/emitter channel. Once this gate is open,
water flows from the collector to the emitter.
Transistor

Types of transistor
There are two types of standard transistors, NPN and PNP, with different
circuit symbols. The letters refer to the layers of semiconductor material used
to make the transistor. Most transistors used today are NPN because this is
the easiest type to make from silicon. If you are new to electronics it is best to
start by learning how to use NPN transistors.
The leads are labeled base (B), collector (C) and emitter (E).
Transistor Circuit Symbol

In PNP-type transistors, when a positive voltage is applied to the emitter
and negative voltage to the collector, almost no current flows from the
collector to the emitter. However, if the emitter voltage is raised slightly
higher than the base voltage, and a small amount of current flows from the
emitter to the base, a large amount of current flows from the emitter to the
collector.
Transistor Working

In NPN-type transistors, almost no current flows when a positive voltage is
applied to the collector and a negative voltage to the emitter. When a small
amount of current flows from the base to the emitter, a large amount of
current flows from the collector to the emitter Ω µ.
Transistor Working
Note :Transistors resemble switching devices. The transistor is turned on, allowing
collector-to-emitter current to flow when there’s base current, and turned off when no
base current exists.

Variable resistors may be used as a rheostat with two connections (the wiper
and just one end of the track) or as a potentiometer with all three connections
in use.
Variable resistors used as potentiometers have all three terminals
connected.
This arrangement is normally used to vary voltage, for example to set the
switching point of a circuit with a sensor, or control the volume (loudness) in
an amplifier circuit. If the terminals at the ends of the track are connected
across the power supply then the wiper terminal will provide a voltage which
can be varied from Zero up to the maximum of the supply.
Application
Used in Accelerator pedal sensor
Potentiometer symbol
Potentiometer
Variable Resistor

Integrated Circuits are usually called ICs or chips. They are complex circuits
which have been etched onto tiny chips of semiconductor (silicon). The chip is
packaged in a plastic holder with pins spaced on a 0.1" (2.54mm) grid which
will fit the holes on strip board and breadboards. Very fine wires inside the
package link the chip to the pins.
Integrated Circuits (Chips)
Type of I.C
Classification by Scale of Integration
SSI (Small Scale Integrated Circuit) : Less than 100 elements
MSI (Medium Scale Integrated Circuit) : 100 to 1,000 elements
LSI (Large Scale Integrated Circuit) : 1,000 to 100,000 elements
VLSI (Very Large Scale Integrated Circuit) : 100,000 or more elements

Automotive Computers
Automotive computers are solid state controllers that combine integrated
circuits and other devices in to single unit,
Examples:
ECU – Engine Control Unit
BCU – Body Control Unit
Automotive computers performs three task
 Receive input signals
 Perform calculations
 Send output signals based on the calculations of input signals, and store
 information
 The brain of a small computer is Microprocessor .It does the calculations
and makes the decision
 A microprocessor cannot store information.
 One of the elements needed for a brain (Microprocessor) to function is a
memory.

The memories are as follows
ROMs – Read only Memories used for permanent data storage, while
building ECU, the programs that control the microprocessor are stored in
ROM. The computer cannot write- in any new information nor can it change
anything that is already written in the ROM chip.
RAMs – Random Access Memories can be both written into and read from.
Rams are often used for temporary storage.
There are two types of RAM memories: A nonvolatile RAM and Volatile RAM
A Nonvolatile RAM will hold its information even when the power is
removed.
A Volatile RAM will be erased when the power is disconnected.
Another Common computer memory is the (PROM) programmable read
only memory like the ROM, the PROM can be read from, but not written to,
by the computer. However the PROM is different from the ROM because it
can be programmed new information from external sources.

In an Automotive computer system E –PROMS Erasable Programmable
Read only Memories are used, which are electrically programmable and
electrically erasable. This allows the PROM to be updated by using special
Electronic Equipment’s.

The following terms are often found in material related to electrical repairs.
Your job as a technician will be much easier if you know and understand
these terms. For ease of reference, they’re listed in alphabetical order.
AC. Abbreviation for “alternating current,” which is electricity that reverses
direction and polarity while flowing through a circuit. Examples: 230 volts AC
in a household reverses direction and polarity 50 times per second (50 Hz).
Alternator. An AC “generator” that uses magnetic induction to produce
electricity. A revolving magnet and stationary stator windings are used. The
current produced is AC.
Amperes. Commonly called “amps,” which are electrical units of current
flow through a circuit (similar to gallons per minute of water through a hose).
Amp hour. Discharge rate of battery in amperes times hours.
Electrical Terms

Armature. A group of rotating conductors which pass through a magnetic
field. The current produced is usually DC after passing through a commutator
device.
Battery. A chemical device used to store electrical power. Within the battery, a
chemical reaction takes place which produces a voltage potential between the
positive and negative terminals.
Bench test. Isolated component inspection.
Capacitor (condenser). A component which, in a discharge state, has a
deficiency of electrons and will absorb a small amount of current and hold it
until discharged again.
Circuit. Composed of three items: a power supply, load, and completed path.
Circuit breaker. Heat-activated switch that interrupts current when
overloaded. A circuit breaker can be reset and replaces the function of a fuse.
Coil. A conductor looped into a coil-type configuration which, when current is
passed through, will produce a magnetic field.
Electrical Terms

Conductor. A wire or material (such as a frame) which will allow current to
flow through it with very little resistance.
Continuity. Having a continuous electrical path.
Current. The flow of electrons in a circuit.
DC. Abbreviation for “direct current,” which means that the current will only
flow in one direction—from positive to negative (conventional theory).
Dielectric. Non-conductor or insulator.
Diode. A semiconductor often used in a rectifier on motorcycles. A diode has
the characteristic of allowing current to pass through in only one direction.
Thus it’s used to change AC to DC current.
Dynamic. Spinning or rotating in motion. Refers to making a test when the
component is in use.
Electricity. The flow of electrons through a conductor.
Electron. The revolving part or moving portion of an atom. The electrons
moving from atom to atom is electrical current.
Electrical Terms

.Electrolyte. The sulphuric acid and distilled water solution that batteries are
filled with at setup.
Electromagnet. A coil of wire which is wound around a soft iron core which
acts as a magnet when current is passed through it
Electromotive force (EMF). The pressure of electrons in a circuit (also
known as voltage). Created by difference in potential between positive and
negative terminals of power supply. Also called pushing force of electricity.
Electrolysis. The movement of electrons through an electrolyte solution. A
battery charges and discharges through electrolysis. Electroplating
(chroming) is an example where electrolysis is used to move and deposit
metals from one electrode to another. In cooling systems, contaminated (tap
water) coolant becomes an electrolyte, allowing electrolysis and the
deposition of metal oxide scale on cooling system components.
Free electron. An electron in an atom’s outer orbit, which is held only loosely
within the atom. Free electrons can move between atoms.
Electrical Terms

Field coil. The field coil is an electromagnet. The flux lines may be used for
generating electricity, for electric motor operation, or for operating a
solenoid/relay.
Fuse. A short metal strip that’s protected by a glass or plastic case which is
designed to melt when current exceeds the rated value.
Flux lines. All the magnetic lines of force from a magnet.
Ground. A common conductor used to complete electrical circuits (negative
side). The ground portion of motorcycle electrical systems is often the frame.
Insulator. Doesn’t conduct current.
Lines of force. Refers to a magnetic field whose lines run from its North
Pole to its South Pole. (Also see flux lines.)
Load. Anything that uses electrical power such as a bulb, coil, or spark plug.
Magnetic induction. When a conductor is moved through a magnetic field,
electricity will be “induced” into the conductor when the flux field cuts through
the conductor.
Electrical Terms

No-load test. A dynamic test with the component insulated or disconnected
from its main system.
NPN. A transistor in which the emitter and collector layers are N-type and the
base layer is P-type (Negative, Positive, Negative).
Pole. The North “Pole” or South “Pole” of a magnet. Also refers to the lugs
(iron cores) of a stator around which the AC generator’s wires are wound.
Polarity. In magnets, polarity is north and south; in electricity, polarity is
positive and negative.
PNP. Transistor in which the emitter and collector layers are P-type and the
base layer is N-type (Positive, Negative, Positive).
Rectifier. (See diode.) Changes AC to DC. Usually a group of 4 or 6 diodes
comprises a “bridge rectifier.”
Regulator. Used to limit the output of a generator or alternator.
Resistance. The opposition offered to the flow of current in a circuit.
Rotor. The revolving magnets or electromagnets which form the magnetic
field in an alternator or ignition signal generator.
Electrical Terms

Reluctance. “Resistance” to magnetism.
Reflector. Magnetic field interrupter used as a signal generator in ignition
systems.
Silicon. A material used in the construction of semiconductors. Because of its
characteristics, the material allows current flow only under certain prescribed
conditions.
Sine wave. A graphic depiction of the form of alternating current usually
taken from an oscilloscope.
SCR. An abbreviation for silicon-controlled rectifier, which is an electronically
controlled switch. (See thyristor.)
Stator. A stationary conductor (usually several coils of wire). When magnetic
flux cuts the stator windings, a voltage potential is induced in the windings.
Switch. A device which opens or closes an electrical circuit.
Schematic. A wiring diagram showing the components and circuitry in detail.
Electrical Terms

Thermo-switch. A bimetallic switch which, when heated, opens or closes a
circuit current flow in the reverse direction when the breakdown voltage is
reached.
Thermistor. An electronically controlled switch when signaled at the gate and
closes after current flow falls.
Unloaded. See no-load test.
Valence electrons. Outer most orbiting electrons in an atom.
Voltage. Electromotive force.
Watt. The unit of electric power; W= E _ I (Wattage = Voltage _ Current).
Wire gauge. Wire diameter. Usually specified by an AWG (American Wire
Gauge) number. The smaller the number, the larger the wire diameter.
Wiring diagram. Similar to a schematic, but less in detail. A wiring diagram
usually shows components in block form rather than illustrating their internal
circuitry.
Zener diode. Similar to a standard diode, but allows current flow in the
reverse direction when the breakdown voltage is reached.
Electrical Terms

FAMCO
Thank You
Aftermarket – Competence Development Team

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