Arduino/C2/Pulse-Width-Modulation/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Pulse Width Modulation.
00:06	In this tutorial we will learn about: PWM i.e Pulse Width modulation
00:13	PWM Duty Cycle
00:16	PWM Frequency L293D Motor Driver IC
00:24	To follow this tutorial, you should have basic knowledge of: Electronics and C or C++ programming language
00:35	To record this tutorial, I am using Arduino Uno board
00:40	Ubuntu Linux 16.04 OS Arduino IDE
00:46	We will also require some external components such as: Breadboard
00:53	10K Ohm Potentiometer LED
00:58	220 ohm Resistor
01:01	Jumper Wires Push Button
01:05	DC Motor
01:08	and L293D Motor Driver IC
01:14	PWM signal is a square wave signal which has a high frequency i.e 1KHz.
01:22	PWM is a technique by which the width of the pulse is varied.
01:28	It is done while keeping the frequency of wave constant.
01:33	PWM signal consists of two main properties that define its behaviour.
01:40	They are Duty Cycle and Frequency.
01:44	It is the percentage of time, a digital signal is on, over a period of time.
01:50	Duty cycle can be varied from 0% to 100%..
01:55	The formula to calculate the percentage of duty cycle is shown here.
02:01	tON is equal to the duration of time when signal is high.
02:06	tOFF is equal to the duration of time when signal is low.
02:11	Time Period is tON + tOFF. i.e. It is equal to the sum of on time and off time of PWM signal.
02:24	Frequency determines how fast the PWM completes a cycle.
02:29	i.e. How fast it switches from HIGH to LOW states.
02:34	We will perform one simple experiment by varying duty cycle.
02:39	This will control the brightness of LED.
02:43	Arduino Uno has 6 PWM channels.
02:48	Pins 3, 5, 6, 9, 10, 11 on Arduino Uno are PWM channels.
02:58	PWM channels are denoted by tilde sign.
03:02	Let us see the circuit connection now.
03:05	Connect anode leg of the LED to pin 9 of Arduino through 220 ohm resistor.
03:13	Connect cathode leg of the LED to ground.
03:17	This is the live setup of the connection.
03:20	Do the connection as shown in the image.
03:23	Let us open the Arduino IDE. We will write a program to change the brightness of LED using PWM pin.
03:32	Type the code as shown.
03:35	We have assigned the PWM pin 9 to the variable LED_Pin.
03:42	We have initialized duty_cycle_value as 1 for an LED to turn ON.
03:51	Inside void setup, we will write pinMode function.
03:56	We have declared pin 9 of the Arduino as OUTPUT.
04:01	Inside void loop function we will write this code. Let me explain the code.
04:08	While loop executes the code till the duty_cycle_value is below 255.
04:17	analogWrite() function is used to generate PWM signal.
04:22	We are passing two parameters. i.e PWM pin number and the duty cycle value.
04:30	The duty cycle value must be between 0 to 255 i.e between 0voltz and 5Voltz
04:40	We will keep a delay of 3000 millisecond i.e. 3 seconds
04:46	Click on the compile button to verify your program.
04:51	A pop up window will appear to save the current program.
04:55	Let us save the program as LED_Brightness and click on the Save button.
05:03	Now click on upload button to upload the current program on Arduino board.
05:09	We can see the brightness of LED increasing gradually.
05:15	Next, we will do an experiment to control the speed and direction of a DC motor.
05:22	This is the pinout diagram of L293D motor driver IC.
05:28	The speed of the motor is controlled by EN 1 and EN 2 of the IC.
05:36	The direction of the motor is controlled by IN1, IN2, IN3, IN4 of the IC.
05:45	We can control 2 motors at a time using this IC.
05:50	In our experiment, we will connect only one DC motor.
05:55	Let us see the circuit connection now.
05:58	Pin 1, pin 8 and pin 16 of driver IC are connected to 5V.
06:05	Pin 4 and pin 5 of driver IC are connected to ground.
06:11	Pin 2 and pin 7 of driver IC are connected to pin 11 and pin 10 of Arduino.
06:20	2 push buttons are connected to pin 12 and pin 13 of Arduino.
06:27	These push buttons are used to control the direction of DC motor.
06:33	10Kohm potentiometer is connected to control the speed of the DC motor.
06:39	Middle pin of potentiometer is connected to analog pin A0.
06:45	Pin 3 and pin 6 of driver IC are connected to DC motor.
06:51	Do the connection as shown in the image.
06:55	This is the live setup of the connection, as shown in the image.
07:00	I have fixed a wheel on the shaft of the motor.
07:04	This will help to see the rotation and varying speed of motor clearly.
07:10	Now we will write a program for this circuit to work.
07:14	Let’s switch to Arduino IDE.
07:18	Type the code as shown here. We have initialized the connection between Arduino and driver IC.
07:28	Potentiometer pin is connected to analog pin A0.
07:33	fwdbuttonPin is the variable for push button connected to pin 13 of Arduino.
07:40	bckbuttonPin is the variable for push button connected to pin 12 of Arduino.
07:47	ICpin2 and ICpin7 are the variables which indicate pin 2 and pin 7 of the IC.
07:57	They are connected to pin 11 and pin 10 of Arduino respectively.
08:04	First we make sure that the potentiometer, motor and push buttons are in LOW state. For that we have initialised it to 0.
08:15	In the void setup function, we will write this code.
08:20	pinMode function defines the pins as INPUT or OUTPUT.
08:25	fwdbuttonPin and bckbuttonPin are set to INPUT_PULLUP mode.
08:32	In this mode we are using Arduino’s internal pull-up resistors.
08:38	To know about the INPUT_PULLUP mode, refer to the manual.
08:44	Click on the Help menu in the Arduino IDE. Then click on Reference.
08:50	This opens an offline page in your browser. Scroll down.
08:55	Click on INPUT_PULLUP.
09:00	Switch back to Arduino IDE.
09:03	ICpin2 and ICpin7 are set to OUTPUT mode to drive the motor.
09:10	Next we will write the code in void loop function.
09:14	analogRead command will read the analog value from the potentiometer.
09:20	This value will be given to analog pin A0.
09:24	Depending upon the potentiometer value, the speed of the motor will vary.
09:30	map command will convert the analog value to digital.
09:35	fwdbuttonState and bckbuttonState will fetch the signal if push button is pressed.
09:43	The IF command checks, if the push button connected to pin 12 or pin 13 is pressed.
09:50	This enables the motor to rotate in a clockwise or anti-clockwise direction.
09:56	Suppose we don’t press any of the two buttons.
10:00	Then the else command ensures the motor is in OFF condition.
10:05	This code is available in the Code file link of this tutorial You can download and use it.
10:13	Click on the compile button to verify the program.
10:17	Let us save the program as PWM_Motor and click on the Save button.
10:25	Now click on upload button to upload the current program on Arduino.
10:31	Now we will see the output of the above program.
10:35	I’ll press the push button connected to pin 13.
10:39	We can see the motor rotating in the clockwise direction.
10:43	Now I will release the push button.
10:47	The motor will stop rotating and it will be in OFF state.
10:52	Now again, I’ll press the push button connected to pin 12.
10:57	We can see the motor is rotating in anti-clockwise direction.
11:02	We can change the speed of motor by adjusting the potentiometer connected to A0.
11:14	This brings us to the end of this tutorial. Let us summarize.
11:20	In this tutorial, we learnt about Pulse Width modulation
11:26	PWM Duty Cycle
11:29	PWM Frequency and How to control speed and direction of DC motor.
11:38	As an assignment: Connect a Buzzer instead of LED in the above circuit connection.
11:45	Upload the same program and check the output.
11:49	You would hear a noise with different frequencies.
11:53	Here is the output of the assignment.
12:01	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
12:09	The Spoken Tutorial Project Team conducts workshops and gives certificates. For more details, please write to us.
12:19	Please post your timed queries in this forum.
12:23	Spoken Tutorial project is funded by MHRD, Government of India.
12:29	This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay. And this is Saurabh signing off. Thanks for joining.

Contributors and Content Editors

PoojaMoolya