In This Lesson<\/h3>\n\n\n\n- Components Needed<\/a><\/li>
- Connection and Circuit<\/a><\/li>
- Code:<\/a>
- Method 1: Basic Color Control Using analogWrite()<\/a><\/li>
- Method 2: For Loop Color Transition (All Pins)<\/a><\/li>
- How this code works<\/a><\/li><\/ul><\/li>
- Understanding Color Mixing<\/a>
- RGB Color Matrix:<\/a><\/li><\/ul><\/li>
- Advanced Techniques<\/a><\/li>
- Troubleshooting<\/a><\/li>
- Going Even Further<\/a><\/li><\/ul><\/div>\n\n\n\n
Components Needed<\/h2>\n\n\n\n\n- Arduino Uno<\/strong> (or compatible board)<\/li>\n\n\n\n
- Common cathode RGB LED<\/strong> (Key specification for correct wiring)<\/li>\n\n\n\n
- 3\u00d7 220\u03a9 (or greater) resistors<\/strong> (Current-limiting for each color channel)<\/li>\n\n\n\n
- Breadboard and jumper wires<\/strong> (For prototyping)<\/li>\n\n\n\n
- USB cable<\/strong> (For power and programming)<\/li>\n<\/ul>\n\n\n\n
Connection and Circuit <\/h2>\n\n\n\n
For a common cathod<\/strong> RGB LED<\/p>\n\n\n\n\n- Longest LED leg (common cathode)<\/strong> \u2192 Arduino GND
Or
Longest LED leg (common anode)<\/strong> \u2192 Arduino 5V<\/li>\n\n\n\n- Red anode<\/strong> \u2192 Digital Pin 9 (with 330\u03a9 resistor)<\/li>\n\n\n\n
- Green anode<\/strong> \u2192 Digital Pin 10 (with 330\u03a9 resistor)<\/li>\n\n\n\n
- Blue anode<\/strong> \u2192 Digital Pin 11 (with 330\u03a9 resistor)<\/li>\n<\/ol>\n\n\n\n
WARNING<\/mark>: Always verify your RGB LED type (common cathode vs. anode) before wiring!<\/strong><\/em><\/p>\n\n\n\n![\"RGB](\"https:\/\/samerli.com\/en\/lessons\/..\/..\/wp-uploads\/2025\/05\/RGB-circuit-common-cathod.png\")
Common cathode connection<\/strong><\/figcaption><\/figure>\n\n\n\nCode:<\/h2>\n\n\n\n
The codes below work for common cathode mode, and will work upside down<\/strong> for common anode (subtract the below numbers from 255 for common anode)<\/em>.<\/p>\n\n\n\nMethod 1: Basic Color Control Using analogWrite()<\/h3>\n\n\n\nvoid setup() {
pinMode(9, OUTPUT); \/\/ Red
pinMode(10, OUTPUT); \/\/ Green
pinMode(11, OUTPUT); \/\/ Blue
}
void loop() {
\/\/ Purple (Red + Blue)
analogWrite(9, 255); \/\/ Red full
analogWrite(10, 0); \/\/ Green off
analogWrite(11, 150); \/\/ Blue mid
delay(1000);
\/\/ Teal (Green + Blue)
analogWrite(9, 0); \/\/ Red off
analogWrite(10, 100); \/\/ Green mid
analogWrite(11, 255); \/\/ Blue full
delay(1000);
\/\/ White (All colors) AND No light if common anode
analogWrite(9, 255);
analogWrite(10, 255);
analogWrite(11, 255);
delay(1000);
}<\/pre>\n\n\n\nMethod 2: For Loop Color Transition (All Pins)<\/h3>\n\n\n\nint redPin = 9;
int greenPin = 10;
int bluePin = 11;
void setup() {
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
void loop() {
\/\/ Rainbow cycle through all colors
for(int i=0; i<=255; i++) {
analogWrite(redPin, 255-i); \/\/ Red fades out
analogWrite(greenPin, i); \/\/ Green fades in
analogWrite(bluePin, 0); \/\/ Blue off
delay(10);
}
for(int i=0; i<=255; i++) {
analogWrite(greenPin, 255-i); \/\/ Green fades out
analogWrite(bluePin, i); \/\/ Blue fades in
analogWrite(redPin, 0); \/\/ Red off
delay(10);
}
for(int i=0; i<=255; i++) {
analogWrite(bluePin, 255-i); \/\/ Blue fades out
analogWrite(redPin, i); \/\/ Red fades in
analogWrite(greenPin, 0); \/\/ Green off
delay(10);
}
}<\/pre>\n\n\n\nHow this code works<\/h3>\n\n\n\n
For loops are used to repeat a piece of code for a number of time. They have this format<\/p>\n\n\n\n
for(int i=minNo<\/mark>; i<maxNo<\/mark>; i++<\/mark>){\n \/\/put the code you want to repeat here\n \/\/you can have more than one line\n}<\/code><\/pre>\n\n\n\nThis creates a counting variable<\/strong> called i<\/em>, set it equal to a number minNo<\/mark><\/em>, and checks if i <\/em>is less than maxNo<\/em>. If i<maxNo<\/mark><\/em> is true, it will run the codes between the curly brackets, then perform i++<\/mark><\/em>, which simply adds 1 to i<\/em> before it checks the i<maxNo <\/em>condition again, and keeps going until i<maxNo<\/em><\/strong><\/mark> becomes false and the loop breaks<\/strong>.<\/p>\n\n\n\nThe analogWrite<\/code> function in Arduino is used to simulate analog output using a technique called PWM (Pulse Width Modulation). Even though Arduino doesn\u2019t have true analog output, analogWrite(pin, value)<\/code> quickly turns the pin on and off to create an average voltage between 0 and 5 volts. The value<\/code> can be any number from 0 (always off) to 255 (always on), and values in between control how long the pin stays on versus off in each cycle. This is useful for dimming LEDs or controlling motor speeds smoothly.<\/p>\n\n\n\nUnderstanding Color Mixing<\/h2>\n\n\n\nRGB Color Matrix:<\/h3>\n\n\n\nRed<\/th> Green<\/th> Blue<\/th> Result Color<\/th><\/tr><\/thead> 255<\/td> 0<\/td> 0<\/td> Bright Red<\/td><\/tr> 0<\/td> 255<\/td> 0<\/td> Bright Green<\/td><\/tr> 0<\/td> 0<\/td> 255<\/td> Bright Blue<\/td><\/tr> 255<\/td> 255<\/td> 0<\/td> Yellow<\/td><\/tr> 255<\/td> 0<\/td> 255<\/td> Magenta<\/td><\/tr> 0<\/td> 255<\/td> 255<\/td> Cyan<\/td><\/tr> 255<\/td> 255<\/td> 255<\/td> White<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nAdvanced Techniques<\/h2>\n\n\n\n\n- Color Palette Generator<\/strong><\/li>\n<\/ol>\n\n\n\n
\/\/ write this function at the end of your code
void setColor(int r, int g, int b) {
analogWrite(redPin, r);
analogWrite(greenPin, g);
analogWrite(bluePin, b);
}
\/\/ Usage, inside loop:
setColor(255, 50, 0); \/\/ Orange<\/pre>\n\n\n\n\n- Serial Color Control<\/strong> (Add to setup:
Serial.begin(9600);<\/code>)<\/li>\n<\/ol>\n\n\n\nif(Serial.available() >= 3) {\n int r = Serial.parseInt();\n int g = Serial.parseInt();\n int b = Serial.parseInt();\n setColor(r,g,b);\n}<\/pre>\n\n\n\nTroubleshooting<\/h2>\n\n\n\n\n- Only one color works<\/strong>: Check all three PWM pins are connected<\/li>\n\n\n\n
- Colors appear dim<\/strong>: Verify resistor values (330\u03a9 recommended)<\/li>\n\n\n\n
- Unexpected colors<\/strong>: Confirm common cathode vs. anode wiring<\/li>\n<\/ul>\n\n\n\n
Going Even Further<\/h2>\n\n\n\n
- Components Needed<\/a><\/li>
- Connection and Circuit<\/a><\/li>
- Code:<\/a>
- Method 1: Basic Color Control Using analogWrite()<\/a><\/li>
- Method 2: For Loop Color Transition (All Pins)<\/a><\/li>
- How this code works<\/a><\/li><\/ul><\/li>
- Understanding Color Mixing<\/a>
- RGB Color Matrix:<\/a><\/li><\/ul><\/li>
- Advanced Techniques<\/a><\/li>
- Troubleshooting<\/a><\/li>
- Going Even Further<\/a><\/li><\/ul><\/div>\n\n\n\n
Components Needed<\/h2>\n\n\n\n
- \n
- Arduino Uno<\/strong> (or compatible board)<\/li>\n\n\n\n
- Common cathode RGB LED<\/strong> (Key specification for correct wiring)<\/li>\n\n\n\n
- 3\u00d7 220\u03a9 (or greater) resistors<\/strong> (Current-limiting for each color channel)<\/li>\n\n\n\n
- Breadboard and jumper wires<\/strong> (For prototyping)<\/li>\n\n\n\n
- USB cable<\/strong> (For power and programming)<\/li>\n<\/ul>\n\n\n\n
Connection and Circuit <\/h2>\n\n\n\n
For a common cathod<\/strong> RGB LED<\/p>\n\n\n\n
- \n
- Longest LED leg (common cathode)<\/strong> \u2192 Arduino GND
Or
Longest LED leg (common anode)<\/strong> \u2192 Arduino 5V<\/li>\n\n\n\n- Red anode<\/strong> \u2192 Digital Pin 9 (with 330\u03a9 resistor)<\/li>\n\n\n\n
- Green anode<\/strong> \u2192 Digital Pin 10 (with 330\u03a9 resistor)<\/li>\n\n\n\n
- Blue anode<\/strong> \u2192 Digital Pin 11 (with 330\u03a9 resistor)<\/li>\n<\/ol>\n\n\n\n
WARNING<\/mark>: Always verify your RGB LED type (common cathode vs. anode) before wiring!<\/strong><\/em><\/p>\n\n\n\n
Common cathode connection<\/strong><\/figcaption><\/figure>\n\n\n\n Code:<\/h2>\n\n\n\n
The codes below work for common cathode mode, and will work upside down<\/strong> for common anode (subtract the below numbers from 255 for common anode)<\/em>.<\/p>\n\n\n\n
Method 1: Basic Color Control Using analogWrite()<\/h3>\n\n\n\n
void setup() {
pinMode(9, OUTPUT); \/\/ Red
pinMode(10, OUTPUT); \/\/ Green
pinMode(11, OUTPUT); \/\/ Blue
}
void loop() {
\/\/ Purple (Red + Blue)
analogWrite(9, 255); \/\/ Red full
analogWrite(10, 0); \/\/ Green off
analogWrite(11, 150); \/\/ Blue mid
delay(1000);
\/\/ Teal (Green + Blue)
analogWrite(9, 0); \/\/ Red off
analogWrite(10, 100); \/\/ Green mid
analogWrite(11, 255); \/\/ Blue full
delay(1000);
\/\/ White (All colors) AND No light if common anode
analogWrite(9, 255);
analogWrite(10, 255);
analogWrite(11, 255);
delay(1000);
}<\/pre>\n\n\n\nMethod 2: For Loop Color Transition (All Pins)<\/h3>\n\n\n\n
int redPin = 9;
int greenPin = 10;
int bluePin = 11;
void setup() {
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
void loop() {
\/\/ Rainbow cycle through all colors
for(int i=0; i<=255; i++) {
analogWrite(redPin, 255-i); \/\/ Red fades out
analogWrite(greenPin, i); \/\/ Green fades in
analogWrite(bluePin, 0); \/\/ Blue off
delay(10);
}
for(int i=0; i<=255; i++) {
analogWrite(greenPin, 255-i); \/\/ Green fades out
analogWrite(bluePin, i); \/\/ Blue fades in
analogWrite(redPin, 0); \/\/ Red off
delay(10);
}
for(int i=0; i<=255; i++) {
analogWrite(bluePin, 255-i); \/\/ Blue fades out
analogWrite(redPin, i); \/\/ Red fades in
analogWrite(greenPin, 0); \/\/ Green off
delay(10);
}
}<\/pre>\n\n\n\nHow this code works<\/h3>\n\n\n\n
For loops are used to repeat a piece of code for a number of time. They have this format<\/p>\n\n\n\n
for(int i=minNo<\/mark>; i<maxNo<\/mark>; i++<\/mark>){\n \/\/put the code you want to repeat here\n \/\/you can have more than one line\n}<\/code><\/pre>\n\n\n\nThis creates a counting variable<\/strong> called i<\/em>, set it equal to a number minNo<\/mark><\/em>, and checks if i <\/em>is less than maxNo<\/em>. If i<maxNo<\/mark><\/em> is true, it will run the codes between the curly brackets, then perform i++<\/mark><\/em>, which simply adds 1 to i<\/em> before it checks the i<maxNo <\/em>condition again, and keeps going until i<maxNo<\/em><\/strong><\/mark> becomes false and the loop breaks<\/strong>.<\/p>\n\n\n\n
The
analogWrite<\/code> function in Arduino is used to simulate analog output using a technique called PWM (Pulse Width Modulation). Even though Arduino doesn\u2019t have true analog output,analogWrite(pin, value)<\/code> quickly turns the pin on and off to create an average voltage between 0 and 5 volts. Thevalue<\/code> can be any number from 0 (always off) to 255 (always on), and values in between control how long the pin stays on versus off in each cycle. This is useful for dimming LEDs or controlling motor speeds smoothly.<\/p>\n\n\n\nUnderstanding Color Mixing<\/h2>\n\n\n\n
RGB Color Matrix:<\/h3>\n\n\n\n
Red<\/th> Green<\/th> Blue<\/th> Result Color<\/th><\/tr><\/thead> 255<\/td> 0<\/td> 0<\/td> Bright Red<\/td><\/tr> 0<\/td> 255<\/td> 0<\/td> Bright Green<\/td><\/tr> 0<\/td> 0<\/td> 255<\/td> Bright Blue<\/td><\/tr> 255<\/td> 255<\/td> 0<\/td> Yellow<\/td><\/tr> 255<\/td> 0<\/td> 255<\/td> Magenta<\/td><\/tr> 0<\/td> 255<\/td> 255<\/td> Cyan<\/td><\/tr> 255<\/td> 255<\/td> 255<\/td> White<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Advanced Techniques<\/h2>\n\n\n\n
- \n
- Color Palette Generator<\/strong><\/li>\n<\/ol>\n\n\n\n
\/\/ write this function at the end of your code
void setColor(int r, int g, int b) {
analogWrite(redPin, r);
analogWrite(greenPin, g);
analogWrite(bluePin, b);
}
\/\/ Usage, inside loop:
setColor(255, 50, 0); \/\/ Orange<\/pre>\n\n\n\n- \n
- Serial Color Control<\/strong> (Add to setup:
Serial.begin(9600);<\/code>)<\/li>\n<\/ol>\n\n\n\nif(Serial.available() >= 3) {\n int r = Serial.parseInt();\n int g = Serial.parseInt();\n int b = Serial.parseInt();\n setColor(r,g,b);\n}<\/pre>\n\n\n\nTroubleshooting<\/h2>\n\n\n\n
- \n
- Only one color works<\/strong>: Check all three PWM pins are connected<\/li>\n\n\n\n
- Colors appear dim<\/strong>: Verify resistor values (330\u03a9 recommended)<\/li>\n\n\n\n
- Unexpected colors<\/strong>: Confirm common cathode vs. anode wiring<\/li>\n<\/ul>\n\n\n\n
Going Even Further<\/h2>\n\n\n\n
- Colors appear dim<\/strong>: Verify resistor values (330\u03a9 recommended)<\/li>\n\n\n\n
- Only one color works<\/strong>: Check all three PWM pins are connected<\/li>\n\n\n\n
- Serial Color Control<\/strong> (Add to setup:
- Red anode<\/strong> \u2192 Digital Pin 9 (with 330\u03a9 resistor)<\/li>\n\n\n\n
- Common cathode RGB LED<\/strong> (Key specification for correct wiring)<\/li>\n\n\n\n
- Advanced Techniques<\/a><\/li>
- Method 2: For Loop Color Transition (All Pins)<\/a><\/li>
- Connection and Circuit<\/a><\/li>