To control an RGB LED with an Arduino, connect its red, green, and blue channels to three PWM-capable pins, add a separate current-limiting resistor to each channel, and set the channel values with analogWrite(). First identify whether the LED is common-anode or common-cathode: that determines how its shared lead is wired and whether your code must invert the values.
What you need to know before wiring
An RGB LED contains red, green, and blue elements. Adjusting each channel independently mixes their light into a displayed color. Arduino’s analogWrite() uses pulse-width modulation (PWM) on supported pins; it does not produce a true analog voltage on every pin. PWM pins vary by board. Arduino’s PWM output guide lists pins 3, 5, 6, 9, 10, and 11 for Uno R3 and earlier, Uno R4, Nano, and Mini. Check that guide for other boards and confirm the exact board variant.
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At the default 8-bit resolution, analogWrite() takes values from 0 to 255: 0 is off and 255 is the maximum PWM setting. The Arduino guide notes that resolution can be changed on supported cores, so use this range only when your configuration uses the default 8-bit resolution.
Identify the LED type
Look up the part number or check the component documentation to determine whether the LED is common-anode or common-cathode. The shared lead connects to a different supply point for each type, and the channel values in the sketch behave differently.
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| LED type | Shared lead connection | Channel code |
|---|---|---|
| Common-cathode | Connect the shared cathode to GND. | Write the channel value directly; higher values request more output. |
| Common-anode | Connect the shared anode to the appropriate positive supply for the component and board. | Invert each channel value; at default 8-bit resolution, write 255 - value. |
These are the two common RGB LED arrangements shown in the cited tutorials. Follow the LED and board specifications for the correct supply connection; do not infer the pinout from the LED’s appearance alone.
Wire the LED with current limiting
Use one current-limiting resistor in series with each color channel. Check the LED’s forward voltage and current limits along with the Arduino board’s output constraints before selecting resistor values. Arduino Project Hub’s common-anode example lists a 220-ohm resistor, but that is a parts-list example for that project, not a universal value for every LED and board.
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- Connect the LED’s red, green, and blue leads, each through its own resistor, to three PWM-capable Arduino pins.
- Connect the shared lead to GND for a common-cathode LED, or to the appropriate positive supply for a common-anode LED.
- Check the LED’s pinout and the board’s pin capabilities before powering the circuit.
Set colors in Arduino code
Declare the three channel pins as outputs, then use a function to set all three values together. This example uses PWM pins 9, 10, and 11. Change them if needed to match PWM-capable pins on your board.
const int redPin = 9;
const int greenPin = 10;
const int bluePin = 11;
// Set to true for common-anode; false for common-cathode.
const bool commonAnode = false;
void setup() {
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
void setColor(int red, int green, int blue) {
if (commonAnode) {
red = 255 - red;
green = 255 - green;
blue = 255 - blue;
}
analogWrite(redPin, red);
analogWrite(greenPin, green);
analogWrite(bluePin, blue);
}
void loop() {
setColor(255, 0, 0); // red
delay(1000);
setColor(0, 255, 0); // green
delay(1000);
setColor(0, 0, 255); // blue
delay(1000);
setColor(255, 255, 255); // all channels on
delay(1000);
}For a common-anode LED, set commonAnode to true. Adafruit’s Arduino Lesson 3 RGB LEDs sketch gives the same instruction: “If you are using a Common Anode RGB LED, then you need to change the analog write values so that the color is subtracted from 255, Uncomment the line #define COMMON_ANODE in the sketch!”
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Choose channel values and refine the mix
The three numbers are relative channel controls, not guaranteed color-calibrated measurements. For instance, setColor(255, 0, 0) requests the red channel at its maximum setting and the other two off at default 8-bit resolution. Mixed values can be adjusted by eye, but the cited tutorials do not establish calibrated color matching across different LEDs.
If you want physical controls, three potentiometers can provide one adjustable input per color channel. Read each potentiometer and map its reading to the range supported by your analogWrite() configuration, then pass those three values to setColor(). Keep the LED channel resistors in place; potentiometers do not replace current limiting.
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Common problems to check
- No light: Verify the shared lead connection, LED pinout, resistor path, and that the three selected pins support PWM on your board.
- Colors appear reversed or stay on: Check the LED type and set the common-anode option correctly. Common-anode channels need inverted output values.
- Only some colors respond: Check each channel’s wiring and resistor separately, and confirm the pin numbers in the sketch match the circuit.
- Unexpected brightness or color: Confirm the values and resolution used by the board, and remember that the numeric channel settings are not a universal calibrated color standard.
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