Question

Control Brightness of LED Using PWM of Raspberry PI. How does PWM control LED brightness? Can Raspberry Pi do PWM? What is Gpio in Raspberry Pi?

Answer 1

Hardware requirement and connections:

Hardware requirement and connections are same as explained in 

 What is Gpio in Raspberry Pi? 

Turning on and off LED with your Raspberry Pi's GPIO Pins

Python program

import RPi.GPIO as GPIO # Importing RPi library to use the GPIO pins from time import sleep # Importing sleep from time library led_pin = 21 # Initializing the GPIO pin 21 for LED GPIO.setmode(GPIO.BCM) # We are using the BCM pin numbering GPIO.setup(led_pin, GPIO.OUT) # Declaring pin 21 as output pin pwm = GPIO.PWM(led_pin, 100) # Created a PWM object pwm.start(0) # Started PWM with 0% duty cycle while 1: # Loop will run forever           for x in range(100): # This Loop will run 100 times                     pwm.ChangeDutyCycle(x) # Change duty cycle                     sleep(0.01) # Delay of 10mS           for x in range(100,0,-1): # Loop will run 100 times; 100 to 0                     pwm.ChangeDutyCycle(x)                     sleep(0.01) pwm.stop() # Stop the PWM GPIO.cleanup() # Make all the output pins LOW