UNIT 5: AUTOMOBILE ELECTRICAL &

ELECTRONIC SYSTEM

Electrical and electronic is the branch of

engg and technology that deals with
electrical circuit that involve active
electrical components such as sensors,
vacuum tubes, diodes, transistors and
integrated circuits and associated passive
interconnection technologies.
BASIC ELECTRICAL ELECTRONICS PRINCIPLES:

1. Voltage (V): The electrical potential difference between two points,

measured in volts (V).

2. Current (I): The flow of electric charge, measured in amperes (A).

3. Resistance (R): The opposition to current flow, measured in ohms (Ω)

4. Electricity: It is a fundamental form of energy observation in a positive

and negative forms, that occurs naturally ( as a lighting) or is produced (as
in a generator) and that is expressed in terms of movement and
interaction of electrons.
BASIC ELECTRICAL ELECTRONICS PRINCIPLES:
5. Magnetism: Magnetism is a force exerted by magnets, which attract
or repel certain materials, mainly iron, nickel, and cobalt. It originates
from the movement of electric charges, particularly electrons.

6. Electromagnetism: Electromagnetism is the branch of physics that

deals with the relationship between electricity and magnetism. It
explains how electric currents create magnetic fields and how changing
magnetic fields can induce electric currents.

7. Electromagnetic induction: Electromagnetic induction is the

process of generating an electric current in a conductor by changing the
magnetic field around it. This principle was discovered by Michael
Faraday in 1831. A moving or changing magnetic field induces voltage
(Electromotive Force, EMF) in a conductor.
BASIC ELECTRICAL ELECTRONICS PRINCIPLES:

8. Rectification: Rectification is the process of converting

Alternating Current (AC) into Direct Current (DC). It is commonly
used in power supplies to convert AC from the mains into DC for
electronic devices.
Basic electrical electronics components used in
Automobiles:
1. Transistor: A transistor is a semiconductor
device used to amplify or switch electronic
signals. It is the fundamental building block of
modern electronics, found in everything from
computers to mobile phones.

2. Resistor: A resistor is a passive electronic

component that restricts or limits the flow of electric
current in a circuit. It is one of the fundamental
components used in electronics.
Basic electrical electronics components used in
Automobiles:

3. Rectifier: A rectifier is an electronic circuit that

converts alternating current (AC) into direct current
(DC). It is widely used in power supplies to provide
stable DC voltage for electronic devices.

4. Diode: A diode is a semiconductor device that

allows current to flow in one direction only. It acts as
an electrical check valve, blocking reverse current.
Basic electrical electronics components used in
Automobiles:

3. Amplifier: An amplifier is an electronic circuit that increases the

strength of a weak signal (voltage, current, or power) without
changing its original characteristics. It is widely used in audio
systems, radio transmission, and communication circuits.
Battery:
A battery is an electrochemical device that stores energy and provides
direct current (DC) electricity. It is widely used in electronics, vehicles, and
power backup systems.

Function of battery:
• Starting the Engine (Ignition System)
• Powering Electrical Components.
• Stabilizing Voltage (Voltage Regulation).
• Charging & Energy Storage.
Types of Automobile Batteries:

1. Lead-Acid Batteries: Traditional 12V batteries used in most vehicles.

Uses lead plates and sulfuric acid for chemical reactions.

1. Lithium-Ion (Li-Ion) Battery:

a. Lightweight & high energy density.
b. Used in hybrid and electric vehicles (EVs).
c. Faster charging, longer lifespan, and no maintenance.
d. More expensive than lead-acid batteries.
Lead acid battery:
Lead acid battery:

Main Components:
1. Anode (Negative Plate) – Made of sponge lead (Pb).
2. Cathode (Positive Plate) – Made of lead peroxide (PbO₂).
3. Electrolyte – Dilute sulfuric acid (H₂SO₄) acts as an ion
carrier.
4. Separator – Insulating material (glass fiber, rubber) prevents
short circuits.
5. Battery Container – Made of polypropylene or hard rubber to
hold the plates and electrolyte.
6. Cell Connectors & Terminals – Connects multiple cells and
provides electrical output.
Working of Lead acid battery:
Working of Lead acid battery:
Battery rating :
The Society of Automotive Engineers (SAE) has established standardized
methods to rate automobile lead-acid batteries. These ratings help determine a
battery’s performance under various conditions.

1. Cold Cranking Amps (CCA):

•Measures the battery's ability to start an engine in cold temperatures.
•Defined as the number of amps a 12V battery can deliver at 0°F (-18°C) for 30
seconds while maintaining at least 7.2V.
•Higher CCA is better for cold climates.
•Example: 600 CCA means the battery can supply 600A at 0°F for 30 seconds.
Battery rating :
2. Twenty Hour rate:
The 20-hour rate for a battery, expressed in Ampere-hours (Ah), indicates
the amount of current a battery can deliver at a constant rate for 20 hours
before its voltage drops to a specified level (1.75 volts per cell or 10.5V for
a 12V battery.
A battery's 20-hour rate is calculated by dividing its Ampere-hour (Ah)
capacity by 20. For example, a 100Ah battery at a 20-hour rate can deliver
5 amps continuously for 20 hours (100Ah / 20 = 5A).
Battery rating :

3. Twenty five ampere rate:

•Indicates how long the battery can deliver 25A at 80°F (27°C) before
dropping below 10.5V.
•Higher rate provides better performance in case of alternator failure.

•Example: 120 minutes rate means the battery can provide 25A for 120
minutes.
Battery capacity :
Battery capacity refers to the amount of energy a battery can
store and deliver, typically measured in watt-hours (Wh) or
milliampere-hours (mAh). A higher capacity battery can store
more energy and power devices for a longer time.
Battery testing procedures:
1. Open volt test:
Open circuit voltage (OCV) testing helps determine the state of
charge (SOC) and overall health of a lead-acid battery. This test
is performed without any load connected to the battery.
Battery testing procedures:
OCV (Volts) State of Charge (SOC)

12.7V - 12.8V 100% (Fully Charged)

12.5V - 12.6V ~75% Charged

12.3V - 12.4V ~50% Charged

12.1V - 12.2V ~25% Charged (Needs Charging)

<12.0V Discharged (Recharge Immediately)

<11.8V Severely Discharged (Possible Sulfation)

<10.5V Battery May Be Bad (Cell Failure)

2. Specific
gravity test:
We can measure the
specific gravity using a
hydrometer if you have
flooded lead acid
batteries, ones with
caps on top that you
can remove to get at
the liquid (electrolyte)
inside.
Measurement table:
Depth of
12 Volt battery Specific gravity
Discharge (DOD)
0% 12.70 1.265
10 % 12.58 1.249
20 % 12.46 1.233
30 % 12.36 1.218
40 % 12.28 1.204
50 % 12.20 1.190
60 % 12.12 1.176
discharged 11.90 1.120
Starting system:

The starting system in an automobile is responsible for cranking the

engine to initiate combustion. It converts electrical energy from the battery
into mechanical energy to turn the engine.
Drive used for starting: [Bendix Drive]

A Bendix drive is an engagement mechanism used in starter motors of

internal combustion engines, allowing the pinion gear to automatically
engage or disengage the flywheel ring gear when the starter is powered
or the engine fires, respectively.
Drive used for starting: [Bendix Drive]
Charging system:

The automobile charging system, comprising the alternator, battery,

and voltage regulator, generates electricity to power the vehicle while
running and recharge the battery, ensuring smooth operation of electrical
systems.
Alternator:
Ignition system:

An automobile ignition system generates the spark needed to ignite the

fuel-air mixture in an engine's cylinders, using a battery, ignition coil, and
spark plugs, with different types like conventional, electronic, and
distributorless systems.
❑ Basic Requirements of an Automobile Ignition System:
❖ Must step up the low battery voltage (12V) to 15,000V – 40,000V to create a spark
across the spark plug gap.
❖ The ignition system must provide a precise spark at the right time (before the piston
reaches TDC on the compression stroke).
❖ Should deliver a strong spark under all engine conditions (cold start, high-speed
driving, high load, etc.)
Ignition system:

❑ Basic Requirements of an Automobile Ignition System:

❖ Should use minimal electrical power from the battery while delivering the required
voltage.
❖ Must adjust spark timing automatically based on engine speed and load conditions.
Main Types of Ignition system:

1. Battery ignition system

2. Magneto ignition sytem
3. Electronic ignition system
a. Transistor Assisted Contact system(TAC/TDI)
b. Capacitor Discharge Ignition system (CDI)
Battery Ignition system:
Main parts of Battery ignition system.
1. Battery
2. Ballast resistor
3. Ignition switch
4. Ignition coil
5. Contact breaker
6. Condenser
7. Distributor
8. Spark plug
Battery Ignition system:
Battery Ignition system:
Ignition coil:
Battery Ignition system:
Mechanical Contact breaker:
Battery Ignition system:
Spark plug:
Magneto Ignition system:
Main parts of magneto ignition system:
1. Magneto
2. Ignition coil
3. Switch
4. Contact breaker
5. Condenser
6. Distributor
7. Spark plug
Magneto Ignition system:
Electronic Ignition system:
Transistor Assisted Contact system [TAC System]
Electronic Ignition system:
Electronic Ignition system:
Advantages of TAC System:

1. No moving parts like previous types

2. No maintenance required
3. Spark plug life is increased
4. Combustion efficiency is increased by 90-95 %
5. More output power and more fuel economy
Electronic Ignition system:
Capacitor discharge ignition system [CDI]
Electronic Ignition system:
Capacitor discharge ignition system [CDI]
Colour codes used in wiring system:
Different types of gauges used in Automobile:
1. Speedometer
2. Tachometer
3. Fuel Gauge
4. Temperature Gauge
5. Oil Pressure Gauge
6. Odometer
7. Trip Meter
8. Exhaust Gas Temperature (EGT) Gauge
9. Tire Pressure Monitoring System (TPMS)
Fuel level gauge:

1. AC electric fuel gauge with balanced coil

2. Bimetallic type electric fuel gauge
3. Thermal type electric fuel gauge
4. Thermostatic type electric fuel gauge
1. AC ELECTRIC FUEL GAUGE WITH BALANCED COIL
2. OIL PRESSURE GAUGE:

a) Pressure
expansion type
oil pressure
gauge
2. OIL PRESSURE GAUGE:

b) Balanced coil
type oil pressure
gauge
3. WATER TEMPERATURE GAUGE:
FUNCTION AND LOCATION OF MAJOR SENSORS USED IN
AUTOMOBILE SYSTEM:
1. Engine Sensors:-
a) Mass Air Flow (MAF) Sensor:
•Function: Measures the amount of air entering the engine for the air-fuel mixture.
•Location: Between the air filter and the throttle body.
b) Manifold Absolute Pressure (MAP) Sensor:
•Function: Monitors intake manifold pressure to adjust fuel injection.
•Location: On the intake manifold.
c) Throttle Position Sensor (TPS):
•Function: Detects the throttle valve position to control acceleration.
•Location: On the throttle body.
FUNCTION AND LOCATION OF MAJOR SENSORS USED IN
AUTOMOBILE SYSTEM:
d) Crankshaft Position Sensor:
•Function: Monitors the position and rotational speed of the crankshaft.
•Location: Near the crankshaft, typically on the engine block or transmission bell
housing.
e) Camshaft Position Sensor:
•Function: Helps in timing fuel injection and ignition.
•Location: Near the camshaft, usually in the cylinder head.
f) Coolant Temperature Sensor (ECT):
•Function: Monitors engine coolant temperature to prevent overheating.
•Location: Near the thermostat housing or cylinder head.
FUNCTION AND LOCATION OF MAJOR SENSORS USED IN
AUTOMOBILE SYSTEM:

2. Exhaust and Emission Sensors:-

a) Oxygen (O2) Sensor:
•Function: Measures oxygen levels in exhaust gases for fuel-air mixture adjustment.
•Location: In the exhaust manifold or exhaust pipe (before and after the catalytic
converter).
b) Exhaust Gas Recirculation (EGR) Sensor:
•Function: Regulates the recirculation of exhaust gases to reduce emissions.
•Location: Near the EGR valve on the intake manifold.