How to Use LED: Examples, Pinouts, and Specs

A Light Emitting Diode (LED) is a semiconductor device that emits light when an electric current flows through it. LEDs are highly efficient, long-lasting, and require low power to operate. They are widely used in various applications such as indicator lights, digital displays, lighting, signage, and as components in electronic devices.

• Indicator lights on electronic devices
• Backlighting for LCD screens
• Traffic signals and automotive lighting
• General illumination and decorative lighting
• Flashlights and headlamps
• Electronic signs and billboards

• Forward Voltage (Vf): Typically ranges from 1.8V to 3.3V for standard LEDs
• Forward Current (If): Recommended operating current, usually around 10mA to 20mA
• Luminous Intensity: Measured in millicandela (mcd), indicating the light output
• Wavelength/Color: The color of the light emitted, measured in nanometers (nm) for monochromatic LEDs
• Viewing Angle: The angle over which the LED is visibly luminous

1. Identify the Anode and Cathode: The longer lead is typically the anode (+), and the shorter lead is the cathode (-).
2. Current Limiting Resistor: Always use a current limiting resistor in series with the LED to prevent it from drawing excessive current.
3. Calculating Resistor Value: Use Ohm's law to calculate the resistor value: R = (Vsource - Vf) / If, where Vsource is the supply voltage.
4. Polarity: Ensure correct polarity by connecting the anode to the positive voltage and the cathode to the negative or ground.

• Do not exceed the maximum forward current and voltage ratings.
• Use a resistor with an adequate power rating to avoid overheating.
• Consider using a breadboard for prototyping to easily test LED circuits.
• When using multiple LEDs, connect them with individual resistors to ensure equal brightness.

// Define the LED pin
const int ledPin = 13;

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

void loop() {
  // Turn the LED on
  digitalWrite(ledPin, HIGH);
  delay(1000); // Wait for 1 second
  // Turn the LED off
  digitalWrite(ledPin, LOW);
  delay(1000); // Wait for 1 second
}

• LED not lighting up: Check the polarity of the LED and ensure the current limiting resistor is correctly calculated and installed.
• Dim LED: The current limiting resistor may be too high, or the supply voltage is too low.
• LED burned out: The current may have exceeded the maximum rating, or the polarity was reversed.

• Double-check the polarity of the LED before powering the circuit.
• Verify the supply voltage and ensure it matches the calculated requirements.
• Use a multimeter to check the continuity of the LED and the resistor.

Q: Can I connect an LED directly to a battery? A: No, you should always use a current limiting resistor to prevent damage to the LED.

Q: How do I choose the right resistor for my LED? A: Calculate the resistor value using Ohm's law, considering the supply voltage and the LED's forward voltage and current.

Q: Can I use one resistor for multiple LEDs? A: It's best to use individual resistors for each LED to ensure they all receive the correct current.

Q: What happens if I reverse the polarity of the LED? A: The LED will not light up if the polarity is reversed, and prolonged reverse voltage may damage the LED.