How to Use 5 mm RGB LED, Common Cathode (R-B-G Pin Order): Examples, Pinouts, and Specs

The 5 mm RGB LED, Common Cathode, is a versatile light-emitting diode that combines red, blue, and green LEDs into a single package. This component allows users to create a wide range of colors by varying the intensity of each LED. The "common cathode" configuration means that all three LEDs share a single cathode (negative) pin, while the anodes (positive pins) are separate for each color.

• Decorative lighting and displays
• Status indicators
• DIY electronics projects
• Color-mixing experiments
• Arduino and microcontroller-based projects

• Package Size: 5 mm
• Configuration: Common Cathode
• Forward Voltage:
  • Red: 2.0V - 2.4V
  • Green: 3.0V - 3.4V
  • Blue: 3.0V - 3.4V
• Forward Current: 20 mA (per color)
• Maximum Power Dissipation: 75 mW (per color)
• Viewing Angle: 120°
• Pin Order: Red (R), Cathode (Common), Blue (B), Green (G)

1. Connect the Cathode: Connect the cathode pin (pin 2) to the ground (GND) of your circuit.
2. Connect Resistors: Use current-limiting resistors (typically 220Ω to 330Ω) for each color pin (R, B, G) to prevent excessive current from damaging the LEDs.
3. Control the Colors: Apply a voltage to the red, blue, and green pins to light up the respective LEDs. By adjusting the voltage or using pulse-width modulation (PWM), you can control the brightness and mix colors.

Below is an example of how to connect and control the 5 mm RGB LED using an Arduino UNO:

• Connect the cathode pin (pin 2) to the GND pin on the Arduino.
• Connect the red pin (pin 1) to Arduino digital pin 9 through a 220Ω resistor.
• Connect the blue pin (pin 3) to Arduino digital pin 10 through a 220Ω resistor.
• Connect the green pin (pin 4) to Arduino digital pin 11 through a 220Ω resistor.

// Define the RGB LED pins
const int redPin = 9;   // Red LED connected to pin 9
const int bluePin = 10; // Blue LED connected to pin 10
const int greenPin = 11; // Green LED connected to pin 11

void setup() {
  // Set the RGB LED pins as outputs
  pinMode(redPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
  pinMode(greenPin, OUTPUT);
}

void loop() {
  // Turn on the red LED
  analogWrite(redPin, 255);  // Full brightness for red
  analogWrite(bluePin, 0);   // Blue off
  analogWrite(greenPin, 0);  // Green off
  delay(1000);               // Wait for 1 second

  // Turn on the green LED
  analogWrite(redPin, 0);    // Red off
  analogWrite(bluePin, 0);   // Blue off
  analogWrite(greenPin, 255); // Full brightness for green
  delay(1000);               // Wait for 1 second

  // Turn on the blue LED
  analogWrite(redPin, 0);    // Red off
  analogWrite(bluePin, 255); // Full brightness for blue
  analogWrite(greenPin, 0);  // Green off
  delay(1000);               // Wait for 1 second

  // Mix colors (e.g., purple)
  analogWrite(redPin, 128);  // Half brightness for red
  analogWrite(bluePin, 128); // Half brightness for blue
  analogWrite(greenPin, 0);  // Green off
  delay(1000);               // Wait for 1 second
}

• Always use current-limiting resistors to protect the LEDs from overcurrent.
• Avoid exceeding the forward voltage and current ratings for each LED.
• Use PWM to achieve smooth color transitions and brightness control.
• Ensure proper heat dissipation if the LEDs are used at high brightness for extended periods.

1. One or More LEDs Not Lighting Up:

   • Check the connections and ensure the cathode is properly connected to GND.
   • Verify that the current-limiting resistors are correctly installed.
   • Ensure the applied voltage matches the forward voltage requirements.

2. LEDs Are Dim:

   • Check the resistor values; they may be too high.
   • Verify the power supply voltage is sufficient.

3. Incorrect Colors Displayed:

   • Double-check the pin connections to ensure the correct pins are connected to the intended control signals.

4. LEDs Flicker:

   • If using PWM, ensure the frequency is high enough to avoid visible flickering.
   • Check for loose connections or unstable power supply.

Q: Can I use the RGB LED without a microcontroller?
A: Yes, you can use simple switches or potentiometers to control the voltage applied to each pin, allowing manual color mixing.

Q: What happens if I connect the LED without resistors?
A: Without resistors, the LEDs may draw excessive current, leading to overheating and permanent damage.

Q: Can I use this LED with a 3.3V microcontroller?
A: Yes, but ensure the forward voltage of each LED is compatible with the 3.3V logic level, and use appropriate resistors to limit current.

This concludes the documentation for the 5 mm RGB LED, Common Cathode.