A Red LED (Light Emitting Diode) is a semiconductor device that emits red light when an electric current flows through it. It is one of the most commonly used LEDs due to its simplicity, low power consumption, and versatility. Red LEDs are widely used in electronic circuits as indicators, status lights, and in displays.
Below are the typical specifications for a standard 5mm Red LED. Note that values may vary slightly depending on the manufacturer.
Parameter | Value |
---|---|
Forward Voltage (Vf) | 1.8V to 2.2V |
Forward Current (If) | 20mA (typical) |
Maximum Current (Imax) | 30mA |
Wavelength | 620nm to 645nm (red light) |
Viewing Angle | 20° to 30° |
Reverse Voltage (Vr) | 5V (maximum) |
Power Dissipation | 60mW (maximum) |
Package Size | 5mm (standard) |
A Red LED has two pins: the anode (positive) and the cathode (negative). The table below describes the pin configuration:
Pin Name | Description | Identification Method |
---|---|---|
Anode | Positive terminal; connects to the positive side | Longer leg of the LED |
Cathode | Negative terminal; connects to ground | Shorter leg or flat edge on case |
Determine the Resistor Value: To prevent damage, always use a current-limiting resistor in series with the LED. Calculate the resistor value using Ohm's Law: [ R = \frac{V_{supply} - V_f}{I_f} ]
For example, with a 5V supply and a forward voltage of 2V: [ R = \frac{5V - 2V}{0.02A} = 150\Omega ]
Connect the LED:
Power the Circuit: Apply the appropriate voltage to the circuit. The LED will emit red light.
Below is an example of how to connect and control a Red LED using an Arduino UNO:
// Red LED Blink Example
// This code blinks a Red LED connected to pin 9 of the Arduino UNO.
const int ledPin = 9; // Define the pin connected to the LED
void setup() {
pinMode(ledPin, OUTPUT); // Set the LED pin as an output
}
void loop() {
digitalWrite(ledPin, HIGH); // Turn the LED on
delay(1000); // Wait for 1 second
digitalWrite(ledPin, LOW); // Turn the LED off
delay(1000); // Wait for 1 second
}
LED Does Not Light Up:
Cause: Incorrect polarity.
Solution: Ensure the anode is connected to the positive side and the cathode to ground.
Cause: No current-limiting resistor or incorrect resistor value.
Solution: Use a resistor with the correct value (e.g., 150Ω for a 5V supply).
LED is Dim:
LED Burns Out:
LED Flickers:
Q: Can I connect a Red LED directly to a 3.3V or 5V power supply?
A: No, you must use a current-limiting resistor to prevent excessive current from damaging the LED.
Q: How do I know the polarity of the LED?
A: The longer leg is the anode (positive), and the shorter leg is the cathode (negative). Alternatively, look for the flat edge on the LED case, which marks the cathode.
Q: Can I use a Red LED with a PWM signal?
A: Yes, Red LEDs can be dimmed or controlled using a PWM (Pulse Width Modulation) signal from a microcontroller like an Arduino.
Q: What happens if I exceed the maximum current rating?
A: Exceeding the maximum current rating can cause the LED to overheat and fail permanently.
By following these guidelines, you can effectively use a Red LED in your electronic projects!