Project 8 RGB LED
Description
RGB LED (Red Green Blue Light Emitting Diode) is a light-emitting diode that can emit light in three basic colors of red, green, and blue, and produce various other colors through different combinations of these three colors.
This project will use a RGB LED to achieve color changes and gradient effects of RGB LED through Arduino programming.
Hardware
1. 328 Plus development board x1
2. RGB LED x1
3. 220 ohm resistor x3
4. Breadboard x1
5. Jumper wires
Working Principle
An RGB LED is basically an LED package that can produce almost any color. It can be used in different applications such as outdoor decoration lighting, stage lighting designs, home decoration lighting, LED matrix display, and more.
RGB LEDs have three internal LEDs (Red, Green, and Blue) that can be combined to produce almost any color output. In order to produce different kinds of colors, we need to set the intensity of each internal LED and combine the three color outputs. In this project, we are going to use PWM to adjust the intensity of the red, green, and blue LEDs individually and the trick here is that our eyes will see the combination of the colors, instead of the individual colors because the LEDs are very close to each other inside.
RGB LED Types and Structure
As mentioned earlier, RGB LEDs have three LEDs inside them and usually, these three internal LEDs share either a common anode or a common cathode especially in a through-hole package. So basically, we can categorize RGB LEDs as either common anode or common cathode type just like in seven segment displays.
When you look at an RGB LED, you’ll see that it has four leads. If you face it so that its longest lead is second from the left, the leads should be in the following order: red, anode or cathode, green, and blue.
Common Anode RGB LED
In a common anode RGB LED, the anode of the internal LEDs are all connected to the external anode lead. To control each color, you need to apply a LOW signal or ground to the red, green, and blue leads and connect the anode lead to the positive terminal of the power supply.
Common Cathode RGB LED
In a common cathode RGB LED, the cathode of the internal LEDs are all connected to the external cathode lead. To control each color, you need to apply a HIGH signal or VCC to the red, green, and blue leads and connect the anode lead to the negative terminal of the power supply.
Specifications
Low Thermal Resistance
No UV rays
Super High flux Output and High luminance
Forward Current for Red, Blue and Green color: 20mA
Forward Voltage
Red: 2v (typical)
Blue: 3.2(typical)
Green: 3.2(typical)
Luminous Intensity
Red: 800 mcd
Blue: 4000 mcd
Green: 900 mcd
Wavelength
Red: 625 nm
Blue: 520 nm
Green: 467.5 nm
Operating Temperature: -25 ℃ to 85 ℃
Storage Temperature: -30 ℃ to 85 ℃
Wiring Diagram
Connect the R pin of the RGB LED to digital pin D9 on the board
Connect the G pin of the RGB LED to digital pin D10 on the board
Connect the B pin of the RGB LED to digital pin D11 on the board
Connect the GND pin of the RGB LED to GND on the board
Sample Code
/*
Keye New RFID Starter Kit
Project 8
RGB LED
Edit By Keyes
*/
int redPin = 9; // red pin
int greenPin = 10; // green pin
int bluePin = 11; // blue pin
void setup() {
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
void loop() {
// red gradient
for (int i = 0; i <= 255; i++) {
analogWrite(redPin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(redPin, i);
delay(10);
}
// green gradient
for (int i = 0; i <= 255; i++) {
analogWrite(greenPin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(greenPin, i);
delay(10);
}
// blue gradient
for (int i = 0; i <= 255; i++) {
analogWrite(bluePin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(bluePin, i);
delay(10);
}
}
Code Explanation
The code defines three integer variables, redPin, greenPin, and bluePin, which are assigned the values 9, 10, and 11, respectively. These numbers represent the corresponding pins on the Arduino board connected to the RGB LED. These pins will be configured in output mode to send analog signals to control the brightness of the LEDs.
int redPin = 9; // Pin connected to the red LED
int greenPin = 10; // Pin connected to the green LED
int bluePin = 11; // Pin connected to the blue LED
In the setup() function, we use the pinMode() function to set each color pin to output (OUTPUT). This is necessary because the Arduino pins are set to input mode by default.
void setup() {
pinMode(redPin, OUTPUT);
pinMode(greenPin, OUTPUT);
pinMode(bluePin, OUTPUT);
}
The loop() function contains the main logic for controlling the RGB LED color gradient. Three separate for loops are used to control the brightness of the red, green, and blue LEDs, respectively. Each loop first increases gradually from 0 to 255 and then decreases gradually back to 0. This process creates a fade-in, fade-out effect from completely off to the brightest and then back to off. The analogWrite() function is used to set the PWM (Pulse Width Modulation) value of a specific pin, which adjusts the brightness of the LED.
void loop() {
// Red fade
for (int i = 0; i <= 255; i++) {
analogWrite(redPin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(redPin, i);
delay(10);
}
// Green fade
for (int i = 0; i <= 255; i++) {
analogWrite(greenPin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(greenPin, i);
delay(10);
}
// Blue fade
for (int i = 0; i <= 255; i++) {
analogWrite(bluePin, i);
delay(10);
}
for (int i = 255; i >= 0; i--) {
analogWrite(bluePin, i);
delay(10);
}
}
Project Result
After uploading the code to the development board, the RGB LED will display a gradient effect of red, green and blue in sequence.
The brightness of each color will gradually increase from 0 to 255, and then gradually decrease to 0.