RGB LED color mixing in Raspberry Pi

Introduction

RGB LED color mixing lets you create many colors by combining red, green, and blue light. It helps make lights show different colors using just one LED.

You want to make a light that changes colors for decoration.

You want to show different statuses with colors on a device.

You want to learn how colors mix using electronics.

You want to build a simple mood light with a Raspberry Pi.

You want to control colors in a project with buttons or sensors.

Syntax

Raspberry Pi

import RPi.GPIO as GPIO
import time

# Setup pins for red, green, blue
RED_PIN = 17
GREEN_PIN = 27
BLUE_PIN = 22

GPIO.setmode(GPIO.BCM)
GPIO.setup(RED_PIN, GPIO.OUT)
GPIO.setup(GREEN_PIN, GPIO.OUT)
GPIO.setup(BLUE_PIN, GPIO.OUT)

# Create PWM objects for each color
red = GPIO.PWM(RED_PIN, 1000)
green = GPIO.PWM(GREEN_PIN, 1000)
blue = GPIO.PWM(BLUE_PIN, 1000)

# Start PWM with 0 duty cycle (off)
red.start(0)
green.start(0)
blue.start(0)

# Function to set color by duty cycle (0-100)
def set_color(r, g, b):
    red.ChangeDutyCycle(r)
    green.ChangeDutyCycle(g)
    blue.ChangeDutyCycle(b)

Use PWM (Pulse Width Modulation) to control brightness of each color.

Duty cycle 0 means LED off, 100 means fully on.

Examples

This makes the LED show bright red color.

Raspberry Pi

set_color(100, 0, 0)  # Full red, no green, no blue

This makes the LED show bright green color.

Raspberry Pi

set_color(0, 100, 0)  # Full green, no red, no blue

This makes the LED show bright blue color.

Raspberry Pi

set_color(0, 0, 100)  # Full blue, no red, no green

This mixes red and green light to create yellow color.

Raspberry Pi

set_color(50, 50, 0)  # Mix red and green to get yellow

Sample Program

This program cycles through main colors by changing the brightness of red, green, and blue parts of the LED. It prints the color name each time so you know what color is showing.

Raspberry Pi

import RPi.GPIO as GPIO
import time

RED_PIN = 17
GREEN_PIN = 27
BLUE_PIN = 22

GPIO.setmode(GPIO.BCM)
GPIO.setup(RED_PIN, GPIO.OUT)
GPIO.setup(GREEN_PIN, GPIO.OUT)
GPIO.setup(BLUE_PIN, GPIO.OUT)

red = GPIO.PWM(RED_PIN, 1000)
green = GPIO.PWM(GREEN_PIN, 1000)
blue = GPIO.PWM(BLUE_PIN, 1000)

red.start(0)
green.start(0)
blue.start(0)

def set_color(r, g, b):
    red.ChangeDutyCycle(r)
    green.ChangeDutyCycle(g)
    blue.ChangeDutyCycle(b)

try:
    while True:
        set_color(100, 0, 0)  # Red
        print("Red")
        time.sleep(1)
        set_color(0, 100, 0)  # Green
        print("Green")
        time.sleep(1)
        set_color(0, 0, 100)  # Blue
        print("Blue")
        time.sleep(1)
        set_color(50, 50, 0)  # Yellow
        print("Yellow")
        time.sleep(1)
        set_color(0, 50, 50)  # Cyan
        print("Cyan")
        time.sleep(1)
        set_color(50, 0, 50)  # Magenta
        print("Magenta")
        time.sleep(1)
        set_color(100, 100, 100)  # White
        print("White")
        time.sleep(1)
except KeyboardInterrupt:
    pass
finally:
    red.stop()
green.stop()
blue.stop()
GPIO.cleanup()

Important Notes

Make sure to connect the LED pins correctly with resistors to avoid damage.

Use BCM pin numbering mode for clarity and consistency.

Clean up GPIO pins after use to avoid warnings on next run.

Summary

RGB LED color mixing uses red, green, and blue light combined at different brightness levels.

Use PWM to control each color's brightness from 0 (off) to 100 (full).

Mixing colors lets you create many colors with just one RGB LED.