Mobile maintenance: Module 3-Electronics Basics

MMC Module 3 Electronics Basics Training Manual

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1 MMC [Module Three]

TRAINING MANUAL Electronics Basics

Table of Contents

3.1 Electronics Definition: .................................................................................................. 2

3.2 OHMs Law:................................................................................................................. 2

3.3 Series/Parallel Circuits: ................................................................................................ 4

3.4 Identifying Electronic Components & Circuit Symbols: .................................................. 5

3.5 Details of various Components used inside mobile phones: .......................................... 5

3.6 Testing of various components: ................................................................................. 12

3.7 Using of DC supply:.................................................................................................... 12



3.1 Electronics Definition:

Electronics is the branch of science that deals with the study of flow and control of electrons

(electricity). This control of electrons is accomplished by devices that resist, carry, select, steer,

switch, store, manipulate, and exploit the electron.

Electronics may defined as the art of knowledge that make such impossible things work. Things

such as (Televisions, AM/FM Radios, Computers and of course the mobile phones, etc.). We

are surrounded by electronics.

Learning how things work can be fun. With this skill, you can build things, make better use of it

and repair it.

Inside any electronic device, what is happening can be described as some kind of source

delivering power to some kind of load. A source is where the energy comes from. A load is what

does the work. When power is delivered to a load, the load produces sound, heat,

light, pictures or anything else that can be produced electronically.

3.2 OHMs Law:

Voltage, Current and Resistance:

An electric circuit is formed when a conductive path is created to allow free electrons to

continuously move. This continuous movement of free electrons through the conductors of

a circuit is called a current, and it is often referred to in terms of "flow," just like the flow of

a liquid through a hollow pipe.

The force motivating electrons to "flow" in a circuit is called voltage. Voltage is a specific

measure of potential energy that is always relative between two points. When we speak of

a certain amount of voltage being present in a circuit, we are referring to the measurement

of how much potential energy exists to move electrons from one particular point in that

circuit to another particular point. Without reference to two particular points, the term

"voltage" has no meaning.

Free electrons tend to move through conductors with some degree of friction, or opposition

to motion. This opposition to motion is more properly called resistance.



The amount of current in a circuit depends on the amount of voltage available to motivate

the electrons, and also the amount of resistance in the circuit to oppose electron flow. Just

like voltage, resistance is a quantity relative between two points. For this reason, the

quantities of voltage and resistance are often stated as being "between" or "across" two

points in a circuit.

Mathematical Relationship:

Standard units of measurement for electrical current, voltage, and resistance.

Georg Simon Ohm has discovered in his 1827 paper the relationship between V, I, R:

In this algebraic expression, voltage (E) is equal to current (I) multiplied by resistance (R).

= R

=

=

How it work?

Let's see how these equations might work to help us analyze simple circuits:

Example:

I =

=

12

3= 4



3.3 Series/Parallel Circuits:

Series Circuit: With simple series circuits, all components are connected end-to-end to form only one path

for electrons to flow through the circuit.

Series Circuits Rules:

1- Voltage drops add to equal total voltage.

2- All components share the same (equal) current.

3- Total Resistance is bigger than the biggest resistor.

Rtotal =R1 + R2 + R3

Parallel Circuit: With simple parallel circuits, all components are connected between the same two sets of

electrically common points, creating multiple paths for electrons to flow from one end of the

battery to the other.

Parallel Circuit Rules:

1- All components share the same (equal) voltage.

2- Branch currents add to equal total current.

3- Total resistance is smaller than the smallest resistor.

= 1

(1

1 +1

2 +1

3)



3.4 Identifying Electronic Components & Circuit

Symbols:

Identifying Electronic Components is very important when fixing mobile phone problems. Circuit

symbols are used in circuit diagrams that show how a circuit is connected together. The actual

layout of the components is usually quite different from the circuit diagram. Here is a standard

guide for Electronic circuit symbols.

Symbols.doc

3.5 Details of various Components used inside mobile

phones:

Resistor:

Mobile phones use SMD resistor or Surface Mont chip resistor. SMD resistor appears

black from the top with some blue color, the color at the bottom is white.

SMD resistor coding:

Note that SMD resistor could be printed value or unmarked value due to small size. If

its a printed value SMD resistor you can read its value as following:

However, if its unmarked value SMD resistor we have to use multimeter to measure it.

Points to remember:

A resistor never gets short.



Resistor can be open.

Mostly resistors without code are used in mobile phones.

Different types of SMD resistors:

1. Network resistor: Combination of more than one resistor groups is called

network resistor. They are made in a single package.

2. Chip Jumper (Zero Ohm) type resistor: This type of chip resistor is used as

jumper in mobile phones.

3. Thermistor-Type Resistor: The rating of this type of resistor depends on

temperature. It is black in colour from all sides. These resistors are of two types

NTC Thermistor (Negative Temperature Co-efficient type Thermistor) and PTC

Thermistor (Positive Temperature (Co-efficient type Thermistor).

4. LDR (Light Dependent Resistor): This resistance is dependent upon light.

Resistance of a LDR may be several mega Ohms in dark, but is reduced to few

Ohms under light.

Capacitor:

There is two common types of capacitors, Ceramic Capacitors as a Non-polarized one

and Electrolytic Tantalum capacitor as a Polarized capacitor.

SMD Ceramic Capacitors (Non-polarized):

It is a type of capacitor in which ceramic is used as dielectric matter. Non-polarized caps

are typically used in low voltage situations, both AC and DC. Polarity is not critical.

Measured in Pico farads typically.

SMD ceramic capacitor coding:

SMD ceramic capacitors are sometimes marked with a code, consisting of one or two

letters and a digit. The first letter if present is a manufacturer code (i.e. K for Kemet,

etc.); the second letter the mantissa and the digit the exponent (multiplier) of the

capacitance in pF. For example S3 is a 4.7nF (4.7 x 10 pf) capactitor from an unknown

manufacturer, while KA2 is a 100 pF (1.0 x 10 pF) capacitor from Kemet.

Letter Mantissa Letter Mantissa Letter Mantissa Letter Mantissa

A 1.0 J 2.2 S 4.7 a 2.5

B 1.1 K 2.4 T 5.1 b 3.5

C 1.2 L 2.7 U 5.6 d 4.0

D 1.3 M 3.0 V 6.2 e 4.5



E 1.5 N 3.3 W 6.8 f 5.0

F 1.6 P 3.6 X 7.5 m 6.0

G 1.8 Q 3.9 Y 8.2 n 7.0

H 2.0 R 4.3 Z 9.1 t 8.0

y 9.0

SMD Tantalum capacitor (Polarized): Polarized capacitors are typically used in large voltage situations, such as DC

line filtering to reduce noise after rectification from an AC source. Mainly measured in

microfarads.

SMD Tantalum capacitor coding:

SMD electrolytic capacitors are often marked with their capacitance and working

voltage, e.g. 10 6V is 10 F 6V . Sometimes a code is used instead, which normally

consists of a letter and 3 digits. The letter indicates the working voltage and the 3 digits

(2 digits and multiplier) give the capacitance in pF.

For example, a capacitor marked A475 is a 4.7 F, 10V unit.

475 = 47 x 105 pF = 4.7 x 106 pF = 4.7 F

Diode:

In electronics, a diode is a two-terminal electronic component that conducts electric

current in only one direction (called the diode's forward direction), while blocking

Letter Voltage

E 2.5

G 4

J 6.3

A 10

C 16

D 20

E 25

V 35

H 50



current in the opposite direction (the reverse direction). The most common kind of

diode in modern circuit design is the semiconductor diode.

Diode operation:

The following picture shows how the diode operates on both forward and reverse bias

also the voltage measurement on its terminals on both cases.

SMD diode:

The notched pin is the cathode (-ve terminal). To know the characteristics of any diode,

use its code to get the datasheet.

Zener Diode:

This is a special type of diode made with silicon, which is used to keep the output supply

stable. Zener diodes are used to stabilize voltage. Zener diode is represented by Z.

Zener diode is recognized by its Zener Volt or break down volt like 3.0VZ, 3.9VZ, 5.1VZ,

6.2VZ etc.

Varacter diode:

This is a variable capacitance diode, which functions on the principle of variable

capacitor. These diodes function within a defined range of capacity. Varacter diodes are

available in the values ranging from 1 to 500 pf and 10 to 100 V. These are used in the

signal transmission circuits.

Tunnel Diode:



These diodes are used for processing the properties of negative resistance and are used

for switching at microwave frequency level.

LED (Light Emitting Diode):

These diodes produce light after receiving forward biasing. They are used to enlighten

the display or keypad in mobile cell phone.

Photodiodes:

These diodes are sensitive to the light. It can be used in solar cells, Optical

communications, etc.

Transistor:

The transistor is the fundamental building block of modern electronic devices, and its

presence is ubiquitous in modern electronic systems. A transistor is a semiconductor

device used to amplify and switch electronic signals. Its made up of semiconductor

material like silicon or germanium. There are two types of surface mount transistors:

NPN type, PNP type. There are three terminals of a transistor: Emitter (E), Collector (C),

and Base (B). These terms refer to the internal operation of a transistor but they are

not much help in understanding how a transistor is used, so just treat them as labels!

Points to remember:

Indicating Character: Q or V, TR.

Function: Switching, Amplification, Regulating Voltage.

Unit: Transistors are identified according to the code.

SMD Transistor:

To know the transistor features using the TR code get its data sheet like this:

s8050_galaxy.pdf



For further information about transistors:

Visit http://goo.gl/UCkdxv

Fuse:

A fuse is a sacrificial over current protection device that melts when too much current

flows through the circuit. Short circuit, overload or device failure is often the reason

for excessive current.

It is simply a short circuit wire when its working and in case of over current, it melts

and turns to open circuit.

Coils and Inductor:

SMD Chip Coil is made by twisting any conductor wire on a bad conductor base. The

base on which the coil is formed is called core. When these coils do not have any base,

they are called air core coil. Coil is also known as inductor. A coil always resists any

variation in flow of current. If any variable supply is given to any coil, the voltage of

opposite polarity is generated in the coil. This property of a coil is known as inductance.

Hence, a coil is also called inductor. Coil is indicated by the alphabet L and the unit of

coil is hanery.

The main function of a Coil is to STOP AC and PASS DC. Smaller inductor/capacitor

combinations provide tuned circuits used in radio reception and broadcasting, for

instance.



Transformer:

A SMD Transformer is made from coils. There are a minimum of 2 coils in any SMD

transformer. One coil is called primary coil and the other is called secondary coil. SMD

transformer in a mobile cell phone is used in receiving and transmitting section of

mobile phones. Transformers made of ferrite core are used in mobile cell phones. It

produces a very high quality flux density. This is the reason why it can be used for high

frequencies with minimum loss.

Principle of SMD transformer:

A magnetic field is generated around the coil when current flows through a coil. When

AC supply is given to a coil, the intensity of magnetic field keeps on varying between

minimum to maximum because in AC positive and negative half cycle are produced

alternately. If another coil is placed within the magnetic field of the first coil, voltage

is generated in the second coil also. The component made on this principle is called

transformer. Two coils are placed near each other where one coil in neutralized by

placing the magnetic field of the other coil. Mostly both the coils are encircled one

below the other. The conductor wires used in the coils are insulated with fine

insulating material to prevent short circuit.

The main function of a Transformer is increase or decrease AC voltage and The Unit of

Transformer is Volt Ampere. There are two types of transformer:

1. Step up transformer:

On a step-up transformer, there are more turns on the secondary coil

than the primary coil. The induced voltage across the secondary coil is

greater than the applied voltage across the primary coil or in other

words, the voltage has been stepped-up.

2. Step Down transformer:



A step down transformer has less turns on the secondary coil that the

primary coil. The induced voltage across the secondary coil is less the

applied voltage across the primary coil or in other words, the voltage

is stepped-down.

Filters:

Filters are electronic circuits which perform signal processing functions, specifically to

remove unwanted frequency components from the signal, to enhance wanted ones,

or both. There are generally four different types of filters used get the desired

frequency.

1. Low-Pass filter:

A low-pass filter allows only a specific frequency to pass and stops or

rejects all frequencies above the low-tuned frequency.

2. High-Pass filter:

A high-pass filter stops or rejects all lower frequencies below the set

frequency and passes the higher frequencies.

3. Band-Pass filter:

This type of filter passes only a specific band of frequencies and stops

higher and lower bands.

4. Band-Stop filter:

This type of filter stops a particular band but allows passing high or

low bands.

]

3.6 Testing of various components:

LAB

3.7 Using of DC supply:

LAB

3.1 Electronics Definition:3.2 OHMs Law:3.3 Series/Parallel Circuits:3.4 Identifying Electronic Components & Circuit Symbols:3.5 Details of various Components used inside mobile phones:3.6 Testing of various components:3.7 Using of DC supply:

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Mobile maintenance: Module 3-Electronics Basics