How to Use Two Color LED: Examples, Pinouts, and Specs

A Two Color LED is a light-emitting diode capable of emitting two distinct colors of light. This is typically achieved by incorporating two separate LED chips within a single package or by altering the polarity of the current flowing through the LED. These LEDs are widely used in applications where status indication or multi-state signaling is required, such as in electronic devices, control panels, and DIY projects.

• Status indicators (e.g., power on/off, error states)
• Multi-state signaling in control systems
• Visual feedback in user interfaces
• DIY electronics and hobby projects
• Automotive dashboards and displays

• Forward Voltage (per LED chip): 1.8V to 3.3V (varies by color)
• Forward Current (per LED chip): 20mA (typical)
• Colors: Commonly red and green, but other combinations are available
• Polarity Control: Color changes based on the direction of current flow
• Package Type: 2-pin or 3-pin configurations
• Viewing Angle: 20° to 60° (varies by model)
• Operating Temperature Range: -40°C to +85°C

1. Determine the LED Type: Identify whether the Two Color LED is a 2-pin or 3-pin type.
2. Connect the LED:
   • For a 2-pin LED, connect the pins to a DC power source with a current-limiting resistor (typically 220Ω to 1kΩ). Reverse the polarity to switch between colors.
   • For a 3-pin LED, connect the common pin to the appropriate voltage (ground for common cathode or Vcc for common anode). Use separate current-limiting resistors for each anode pin.
3. Control the LED:
   • Use a microcontroller (e.g., Arduino) or a manual switch to control the current flow and select the desired color.

• Always use a current-limiting resistor to prevent damage to the LED.
• Verify the forward voltage and current ratings for each color before connecting the LED.
• For 2-pin LEDs, ensure the power supply polarity is correct to avoid malfunction.
• For 3-pin LEDs, ensure the common pin is correctly connected to ground or Vcc based on the LED type.
• Avoid exceeding the maximum forward current to prolong the LED's lifespan.

// Example code to control a 2-pin Two Color LED with an Arduino UNO
// Connect one pin of the LED to pin 9 and the other to pin 10 via 220Ω resistors.

const int ledPin1 = 9; // Pin connected to one side of the LED
const int ledPin2 = 10; // Pin connected to the other side of the LED

void setup() {
  pinMode(ledPin1, OUTPUT); // Set pin 9 as an output
  pinMode(ledPin2, OUTPUT); // Set pin 10 as an output
}

void loop() {
  digitalWrite(ledPin1, HIGH); // Turn on the first color
  digitalWrite(ledPin2, LOW);  // Ensure the second color is off
  delay(1000); // Wait for 1 second

  digitalWrite(ledPin1, LOW);  // Turn off the first color
  digitalWrite(ledPin2, HIGH); // Turn on the second color
  delay(1000); // Wait for 1 second
}

1. LED Does Not Light Up:

   • Check the polarity of the connections. Reverse the connections if using a 2-pin LED.
   • Ensure the current-limiting resistor is not too large, which could prevent sufficient current flow.
   • Verify the power supply voltage matches the LED's forward voltage requirements.

2. LED Flickers or is Dim:

   • Check for loose connections or poor soldering.
   • Ensure the power supply provides a stable voltage and current.

3. One Color Does Not Work:

   • Verify the connections for the non-working color.
   • Test the LED with a multimeter to check if one of the LED chips is damaged.

4. LED Overheats:

   • Ensure the current-limiting resistor is appropriately sized to limit the current to 20mA or less.
   • Avoid prolonged operation at maximum current.

Q: Can I use a Two Color LED without a resistor?
A: No, a current-limiting resistor is essential to prevent excessive current, which can damage the LED.

Q: How do I identify the common pin on a 3-pin Two Color LED?
A: Use a multimeter in diode mode to test the connections. The common pin will show continuity with both anodes (or cathodes) depending on the LED type.

Q: Can I control a Two Color LED with PWM?
A: Yes, you can use PWM (Pulse Width Modulation) to control the brightness of each color independently, especially with a 3-pin LED.

Q: What happens if I reverse the polarity of a 2-pin Two Color LED?
A: The LED will emit the second color, as the current flows through the other LED chip.