How to Use LED: Two Pin (green): Examples, Pinouts, and Specs

A green LED (Light-Emitting Diode) with two pins is a semiconductor light source that emits green light when an electric current flows through it. LEDs are widely used in various applications due to their low power consumption, long service life, and compact size. Green LEDs, in particular, are often used in electronics to indicate power status, signal messages, or as part of user interfaces.

• Indicator lights on electronic devices
• Backlighting for LCD displays
• Traffic signals and signage
• Decorative and architectural lighting
• Hobbyist projects, including Arduino-based circuits

• Forward Voltage (Vf): Typically 2.0V to 3.4V
• Forward Current (If): Recommended 20mA (max. current without risking damage)
• Luminous Intensity: Varies with current and manufacturer, typically around 20 mcd (millicandela)
• Viewing Angle: Typically between 20° and 30°
• Peak Wavelength: Approximately 520nm to 570nm (green spectrum)

1. Identify the Pins: The longer pin is usually the anode (positive), and the shorter pin is the cathode (negative).
2. Current Limiting Resistor: Always use a current-limiting resistor in series with the LED to prevent it from drawing excessive current. The value of the resistor can be calculated using Ohm's law: R = (V_supply - Vf) / If.
3. Polarity: Connect the anode to the positive voltage supply and the cathode to the negative side (ground) through the current-limiting resistor.
4. Power Supply: Ensure that the power supply voltage is appropriate for the LED. Exceeding the maximum forward voltage can damage the LED.

• Do not exceed the maximum forward current rating.
• Use a resistor with an appropriate power rating to avoid overheating.
• Consider using a PWM (Pulse Width Modulation) signal to control the brightness of the LED.
• When using multiple LEDs, connect each with its own current-limiting resistor to ensure even brightness.

• LED Not Lighting Up: Check the polarity of the connections and ensure the power supply is functioning.
• Dim LED: Confirm that the current-limiting resistor value is correct and that the power supply voltage is adequate.
• LED Burnt Out: The LED may have been subjected to excessive current or voltage. Replace the LED and verify the circuit design.

• Use a multimeter to check for continuity and proper voltage levels in the circuit.
• Ensure that solder joints are secure and free of shorts.
• If using with a microcontroller like Arduino, verify that the output pin is configured correctly in the code.

// Define the LED pin
const int ledPin = 13; // Most Arduino UNOs have an onboard LED on pin 13

void setup() {
  // Set the LED pin as an output
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Turn the LED on (HIGH is the voltage level)
  digitalWrite(ledPin, HIGH);
  // Wait for a second
  delay(1000);
  // Turn the LED off by making the voltage LOW
  digitalWrite(ledPin, LOW);
   // Wait for a second
  delay(1000);
}

Note: The onboard LED on the Arduino UNO is connected with a built-in resistor, so you do not need to add an external current-limiting resistor for pin 13. However, for external LEDs, always include a resistor in the circuit.