Controlling the Brightness of an LED

In this example we will show you how to control the brightness of an LED connected . The RPi.GPIO library has a PWM feature that allows you to control the power to an LED and its brightness, we will use this in this example

 

Schematic

Fairly simple, simply connect an LED like this

pi-pwm-led_schem

 

This is a breadboard layout

pi-pwm-led_bb

Code

Save the following as pwm.py

import RPi.GPIO as GPIO
 
#pin 12 on GPIO header
led_pin = 18
GPIO.setmode(GPIO.BCM)
GPIO.setup(led_pin, GPIO.OUT)
pwm_led = GPIO.PWM(led_pin, 500)
pwm_led.start(100)
 
while True:
	brightness = raw_input("Enter Brightness value (0 to 100):")
	duty_value = int(brightness)
	pwm_led.ChangeDutyCycle(duty_value)

 

Testing

From a terminal run the program by typing in

sudo python pwm.py

You should now see a prompt, type in a value and press enter and observe the effect on the LED