Arduino/C2/Pulse-Width-Modulation/English-timed
From Script | Spoken-Tutorial
| 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 0 volts and 5 Volts |
| 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. |
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| 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. |
