Mobile Repairing

Itroduction

it's easy to learn about mobile repairing. there is very good scope of regular income. you just need to visit our page regularly and learn about it. the course designed to build up the capacity of self-employment in the field of mobile handset repairing.

 1. Online Mobile Repairing Course Free

2. Learn Mobile Repairing With Modern Tools

3. Students Can Starts Their Own Business

Scope For Students

1. Student Can Start Their Own Business In Mobile Repairing Field.

2. Student Can Work As A Technician In A Mobile Repairing Service Centre.

3. Student Can Find Job in Cell Phone Industry

Course Overview

1.     Introduction and Identification of PCB

2.     Short forms

3.    Basic Electronics

4. Mobile Repairing Tools and Equipment

5.     Fault finding

6.     Identification of tools and their use

7.     Software issues

1. Introduction and identification of PCB  : -  A PCB is a thin board made of fiberglass, composite epoxy, or other laminate material. Conductive pathways are etched or "printed" onto board, connecting different components on the PCB, such as transistors, resistors, and integrated circuits. PCBs are used in both Mobile cell phone and Laptop or desktop.

PCB od mobile phone : -  

The PCB of any mobile phoneor smartphone (Android and iPhone) of any brand namely Nokia, iPhone, Samsung, Motorola, Huawei, Lenovo, LG, Mobicel, Motorola, Oppo, Vivo, Xiaomi, China Mobile Phones etc is divided into several parts mainly : (1) Network Section; and (2) Power Section.

  VIVO Y91 PCB example

What is SMD Components?

SMD are available as both active and passive electronic components. The world of passive surface mounting is somewhat simpler. Monolithic ceramic capacitors, tantalum capacitors, and thick film resistors form the core group of passive SMD. The shapes are generally rectangular and cylindrical.                                                    

Mobile Phone Related Short Forms

1G - First Generation In Mobile Telephony.

2G - Second Generation In Mobile Telephony.

3G - Third Generation In Mobile Telephony.

4G - Fourth Generation In Mobile Telephony.

5G - Fifth Generation In Mobile Telephony.

AC - Alternate Current. 

DC - Direct Current.

BGA - Ball Grid Array.

CDMA - Code Division Multiple Access.

CPU – Central Processing Unit

DCT – Digital Core Technology

GSM – Global System for Mobile Communication

IMEI – International Mobile Equipment Idendity

IC - Integrated Circuit

LED – Light Emitting Diode

PDA – Personal  Digital Assistant

PFO – Power Frequency Oscillator

PCB – Printed Circuit Board

RAM – Random Access Memory

RF – Radio Frequency

ROM – Read Only Memory

RTC – Real Time Clock

RX – Receive

SMD – Surface Mount Device

2. Basic Electronics: - Before learning about mobile repairing we have to know about basic electronics and basic electronic components. There in a mother board we saw lots of components let’s gain some knowledge about those components.

Resistor: - A resistor impedes the flow of electricity through a circuit.  Resistors have a set value. Since voltage, current and resistance are related through Ohm’s law, resistors are a good way to control voltage and current in your circuit.

Color code

Tolerance: Gold = within 5% 

Black: 0 

Brown 1

 Red: 2 

Orange: 3 

Yellow: 4

 Green: 5 

Blue: 6 

Violet: 7

 Gray: 8

 White: 9

Units  

Knowing your units is important Kilo and Mega are common in resistors Milli, micro, nano and Pico can be used in other components

 K (kilo) = 1,000 M (mega) = 1,000,000 M (milli) = 1/1,000 u (micro) = 1/1,000,000 n (nano) = 1/1,000,000,000 (one trillionth) p (pico) = 1 / 1,000,000,000,000 (one quadrillionth)

Variable resistor / Potentiometer: - A potentiometer is a variable resistor. As you manually  turn a dial, the resistance changes.

How a variable resistor works: - As the dial/wiper turns, electricity must go through more or less of the resistive strip. In series, the change in resistance means a change in voltage.

So as you turn the dial/wiper, you get a change in voltage.

Capacitor   : - A capacitor stores electrical energy.  This pool of electrons is available for electronic components to use.

Capacitance is measured in Farads. The small capacitors usually used in electronics are often measured in microfarads and nanofarads.

Some capacitors are polarized.

 Note the different length terminals on one of the capacitors.

Polarity of capacitors

 The shorter terminal goes on the negative side.  The stripe is on the

negative terminal side of the capacitor.  The board is marked for positive or negative.

Diode circuit protection

In a DPDT switch, if polarity is wrong, the motor will run backwards.  In an electronic circuit, if the polarity is wrong, you can fry— your components. A diode in your system will help to prevent problems.

Light emitting diode (LED)

A light emitting diode is a Semiconductor light source. When electricity is passing through the diode, it emits light.

Transistors: - A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. This is our electronic switch 

How a transistor works: - A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. A transistor is composed of semiconductor material with at least three terminals for connection to an external circuit.

Transistors have 3 pins

 For these transistors :

 Collector

 Emitter

base

Terminology

1.  BJT versus FET

2.  Bipolar junction transistor.

Useful as amplifiers. Collector, Emitter, Base

3.  Field-effect transistor.

Useful as motor drivers. Source, Drain, Gate

MOSFET: Metal-oxide-semiconductor FET

4.  NPN (N-channel FET) versus PNP (P-channel FET)

5.  NPN versus PNP is how the semiconductors are layered.

NPN: Not pointing in PNP: Pointing 

Integrated circuit: - An integrated circuit (IC) is a set of transistors that is the controller or ‘brain’ of an electronic circuit. An input is received, an output is sent out. Modern microprocessor ICs can have billions of transistors per square inch!

What an IC can do for us?

Billions of electronically controlled on/off switches (transistors) is how the microprocessor in a digital computer ‘thinks’ and functions. A computer has a wide range of tasks to perform. But other ICs can complete simpler, discrete jobs. For example, an IC can take a voltage input and output commands to a motor.

Terminology: Op-amp: - An operational amplifier (op-amp) is a set of transistors inside the integrated circuit. They often are the components doing the mathematical operations.

H-bridge: - An electronic circuit that enables voltage to be applied across a load in either direction. A DPDT switch also does this, but not electronically.

H-bridge

1.       Need four electronic switches.

2.       Either have 1 and 4 closed. Or 2 and 3 closed.

3.       What happens if both 1 and 2 are closed

4.       The H-bridge allows electricity to flow both ways across the motor, which gives us forward and reverse.

5.       We can use pulse width modulation to control how often the switches are on versus off, which gives us speed control.

 

Varying voltage

A potentiometer/variable resistor allows you to change the voltage input that goes into the integrated circuit.

Integrated circuit can now output variety of pulse widths to the transistors on the H-bridge.

 This combination of potentiometer, integrated circuit and PWM to the H-bridge is the key to speed control.

Why not skip the IC?

There are a couple reasons we don’t use just a potentiometer to control the speed of our motors.  Potentiometers are rarely used to control significant power (more than a watt).  You would still need a way to switch the direction of the motor. Just using a potentiometer can control speed, but not direction.  DPDT switch and potentiometer combinations can lead to problems if you quickly switch from full forward to full reverse. Problems can occur if the polarity of a spinning DC motor gets suddenly switched from forward to reverse.  Current surge  Mechanical stress.

Printed Circuit Board: - Components are attached to a printed circuit board. The ‘front’ side of the board will have printed component information, such as resistor # and resistance, diode type and polarity, etc. Holes go all the way through the board from one side to the other. Through hole

soldering is needed to connect components to the board. 

Conclusion: -

 Hopefully that wasn’t too confusing. The goal was to give you a basic understanding of how some of the electronic components of a motor speed controller work. There are lots of tools to help you with the basics. 

Next  Topic will be mobile repairing tools and equipment's