View source for Arduino/C2/Pulse-Width-Modulation/English


{| style="border-spacing:0;"
| style="border-top:1.5pt solid #000000;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| '''Visual Cue'''
| style="border:1.5pt solid #000000;padding:0.176cm;"| '''Narration'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 1:
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Welcome to the '''Spoken Tutorial''' on '''Pulse Width Modulation.'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 2:

Learning Objectives
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| In this tutorial we will learn about:

* '''PWM i.e Pulse Width modulation'''
* '''PWM Duty Cycle'''
* '''PWM Frequency'''
* '''L293D Motor Driver IC'''

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| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 3:

Pre-requisites
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| To follow this tutorial, you should have basic knowledge of:

* '''Electronics''' and
* '''C or C++''' programming language

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 4:

System Requirements
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| To record this tutorial, I am using

* '''Arduino Uno board'''
* '''Ubuntu Linux 16.04 OS'''
* '''Arduino IDE '''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 5(A):

External Components Required
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| We will also require some external '''components''' such as:

* '''Breadboard'''
* '''10K Ohm Potentiometer'''
* '''LED'''
* '''220 ohm Resistor'''
* '''Jumper Wires'''
* '''Push Button'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 5(B) :

Image '''DC-motor.jpg'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * '''DC Motor'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 5(C) :

Image '''L293D.jpg'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * '''L293D Motor Driver IC'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 6:

Pulse Width Modulation
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * '''PWM signal '''is a square wave signal which has a high frequency i.e (1KHz).
* '''PWM''' is a technique by which the width of the pulse is varied.
* It is done while keeping the frequency of wave constant.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 7:

Pulse Width Modulation
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * PWM signal consists of two main properties that define its behaviour.
* They are '''Duty Cycle''' and '''Frequency.'''

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| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 8:

Image '''duty_cycle.jpg'''

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| It is the percentage of time, a digital signal is on, over a period of time.

Duty cycle can be varied from 0% to 100%..

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| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 9:

Formula - Duty cycle 

Image''' duty_cycle_formula.jpg'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| The Formula to calculate the percentage of duty cycle is shown here.
* '''tON '''is equal to the''' '''duration of time when signal is high.
* '''tOFF '''is equal to the''' '''duration of time when signal is low.
* '''Time Period'''is''' tON + tOFF'''.
* i.e. It is equal to the sum of on time and off time of PWM signal.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 10:

PWM frequency
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * Frequency determines how fast the PWM completes a cycle.
* i.e. How fast it switches from HIGH to LOW states.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 11:

Example - Duty Cycle
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * We will perform one simple experiment by varying duty cycle.
* This will control the brightness of LED. 

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 12:

Image '''Arduino_PWM_pins.png'''

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * '''Arduino Uno''' has 6 '''PWM channels.'''
* Pins '''3,5,6,9,10,11 '''on '''Arduino Uno''' are '''PWM channels.'''
* '''PWM '''channels are denoted by''' tilde '''sign.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| narration
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Let us see the circuit connection now.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 13:

Image '''LED_Connection.png'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * Connect '''anode''' leg of the '''LED''' to '''pin 9 '''of Arduino through 220 ohm resistor.
* Connect '''cathode''' leg of the '''LED''' to ground.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Image Live Setup

'''LED_connection_setup.png'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| This is the '''live setup''' of the connection, as shown in the image.


Do the connection as shown in the image.
|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Open Arduino IDE

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Let us open the''' Arduino IDE'''.

We will write a program to change the brightness of '''LED''' using '''PWM''' pin.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| int LED_Pin = 9;

int duty_cycle_value = 1; 

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Type the code as shown.

We have assigned the '''PWM pin 9''' to the variable '''LED_Pin.'''

We have initialized '''duty_cycle_value''' as 1 for an LED to turn ON.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| void setup()

{

pinMode( LED_Pin, OUTPUT);

}
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Inside void setup, we will write '''pinMode''' function.

We have declared '''pin 9''' of the Arduino as output.


|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Highlight according to narration

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Inside void loop function we will write this code.

Let me explain the code.

'''While''' loop executes the code till the '''duty_cycle_value''' is below 255.

'''analogWrite'''() function is used to generate PWM signal.

We are passing two parameters. i.e PWM pin number and the duty cycle value.

The '''duty cycle''' '''value''' must be between''' 0 '''to '''255 '''i.e between (0v) and (5V)

We will keep a delay of 3000 millisecond i.e. 3 seconds 

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Compile and save the program
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Click on the '''compile button '''to verify your program.

A pop up window will appear to save the current program.

Let us save the program as '''LED_Brightness '''and click on the save button.

Now click on '''upload button''' to upload the current program on '''Arduino'''.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Live Output Video

'''LED_output.mp4'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| We can see, the brightness of '''LED''' increasing gradually.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Next, we will do an experiment to control the speed and direction of a '''DC motor.'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 14:

Image '''L293D_Pinout.png'''

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| This is the pinout diagram of '''L293D motor driver IC.'''

The speed of the motor is controlled by '''EN 1''' and '''EN 2''' of the IC.

The direction of the motor is controlled by '''IN1''', '''IN2''', '''IN3''', '''IN4''' of the IC.

We can control 2 motors at a time using this IC.

In our experiment, we will connect only one DC motor.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Let us see the circuit connection now.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 15:

Image '''Speed-Direction-Control-Connection.png'''

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| * '''Pin 1, Pin 8 and Pin 16 '''of driver IC are connected to''' 5V.'''
* '''Pin 4 '''and''' pin 5 '''of driver IC are connected to ground.
* '''Pin 2 and Pin 7''' of driver IC are connected to''' Pin 11''' and '''Pin 10''' of Arduino.
* 2 push buttons are connected to '''pin12''' and '''pin13''' of arduino.
* These push buttons are used to control the direction of DC motor'''.'''
* '''10Kohm''' potentiometer is connected to control the speed of the DC motor.
* Middle pin of '''potentiometer''' is connected to analog '''pin A0.'''
* '''Pin 3''' and '''Pin 6''' of driver IC are connected to DC motor.
* Do the connection as shown in the image.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 16:

Image Live Setup

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| This is the '''live setup''' of the connection, as shown in the image.

I have fixed a wheel on the shaft of the motor.

This will help to see the rotation and varying speed of motor clearly.

Now we will write a program for this circuit to work

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Switch to Arduino IDE
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Let’s switch to '''Arduino IDE.'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Highlight the code


const int potPin = A0;

const int fwdbuttonPin = 13;

const int bckbuttonPin = 12;

const int ICpin2 = 11;

const int ICpin7 = 10;
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Type the code as shown here.

We have initialized the connection between Arduino and driver IC.

Potentiometer pin is connected to '''analog pin A0'''.

'''fwdbuttonPin '''is the variable for push button connected to pin 13 of Arduino. 

'''bckbuttonPin '''is the variable for push button connected to pin 12 of Arduino. 

'''ICpin2''' and''' ICpin7 '''are the variables which indicates '''Pin 2 and Pin 7''' of IC.

They are connected to''' Pin 11''' and '''Pin 10''' of Arduino respectively.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| int potValue = 0;

int motorValue = 0;

int fwdbuttonState = 0;

int bckbuttonState = 0;
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| First we make sure that the potentiometer, motor and push buttons are in LOW state.

For that we have initialised it to 0.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| void setup()

{

pinMode(fwdbuttonPin, INPUT_PULLUP);

pinMode(bckbuttonPin,INPUT_PULLUP);

pinMode(ICpin2, OUTPUT);

pinMode(ICpin7, OUTPUT);

}
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| In the''' void setup''' function, we will write this code.

pinMode function defines the pins as INPUT or OUTPUT.

'''fwdbuttonPin''' and '''bckbuttonPin''' are set to '''INPUT_PULLUP '''mode. 

In this mode we are using arduino’s internal pull-up resistors.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Show the demo of the manual
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| To know about the '''INPUT_PULLUP''' mode, refer to the manual.

Click on the '''Help menu''' in the '''Arduino IDE.'''

Then click on '''reference.'''

This opens an offline page in your browser. 

Scroll down.

Click on '''INPUT_PULLUP. '''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Switch back to '''Arduino IDE.'''

'''ICpin2 '''and''' ICpin7 '''are set to '''OUTPUT''' mode to drive the motor.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| void loop()


| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Next we will write the code in '''void loop''' function.

'''analogRead''' command will read the analog value from the potentiometer.

This value will be given to analog pin A0.

Depending upon the potentiometer value, the speed of the motor will vary.

'''map''' command will convert the analog value to digital.

'''fwdbuttonState''' and '''bckbuttonState''' will fetch the signal if push button is pressed. 

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| The IF command checks, if the push button connected to pin12 or pin13 is pressed.

This enables the motor to rotate in a clockwise or anti-clockwise direction.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| else

{

digitalWrite(ICpin2, LOW);

digitalWrite(ICpin7, LOW);

}

}


| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Suppose we don’t press any of the two buttons.

Then the else command ensures the motor is in '''OFF''' condition.

This code is available in the code file link of this tutorial

You can download and use it.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Click on the '''compile button'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Click on the '''compile button '''to verify the program.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Compile and save the program
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Let us save the program as '''PWM_Motor''' and click on the save button.

Now click on '''upload button''' to '''upload''' the current program on '''Arduino'''.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Point to the output in the video 

'''DC_motor_output.mp4'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Now we will see the output of the above program.

I’ll press the '''push button''' connected to '''pin13'''.

We can see the motor rotating in the '''clockwise''' direction.

Now I will release the push button.

The motor will stop rotating and it will be in OFF state.

Now again, I’ll press the '''push button''' connected to '''pin12'''.

We can see the motor is rotating in '''anti-clockwise '''direction.

We can change the speed of motor by adjusting the potentiometer connected at A0.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| This brings us to the end of this tutorial. Let us summarize.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 17:

Summary

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| In this tutorial, we learnt about

* '''Pulse Width modulation'''
* '''PWM Duty Cycle'''
* '''PWM Frequency '''and
* How to control speed and direction of '''DC motor.'''

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 18:

Assignment

'''Buzzer_output.mp4'''
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| As an '''assignment''':

* Connect a '''Buzzer''' instead of '''LED''' in the above circuit connection.
* Upload the same program and check the output.
* You would hear a noise with different frequencies.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Here is the output of the assignment .

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 19:

About Spoken Tutorial project

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| The video at the following link summarizes the '''Spoken Tutorial''' project.

Please download and watch it.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 20:

Spoken Tutorial workshops

| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| The''' Spoken Tutorial Project''' Team:

* conducts '''workshops''' and
* gives '''certificates'''.

For more details, please write to us.

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 21:

Forum for specific questions
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| Please post your timed queries in this '''forum'''. 

|-
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| Slide 22:

Acknowledgement
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| '''Spoken Tutorial''' project is funded by '''MHRD, Government of India'''.

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| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:none;padding:0.176cm;"| 
| style="border-top:none;border-bottom:1.5pt solid #000000;border-left:1.5pt solid #000000;border-right:1.5pt solid #000000;padding:0.176cm;"| This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay. 

And this is saurabh''' '''signing off. 

Thanks for joining.

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