Arduino: RGB Gradient

Posted on April 11, 2020 by Administrator Posted in Arduino, C++, Computer Hardware, Computer Science, Physical Computing

In this challenge we will use the Arduino board to control a RGB LED to create a gradient light effect where the LED will fade from red to purple, to blue, to purple and back to red.

You do not need to have access to an Arduino board. Instead you can use the online Arduino simulator from Tinkercad to recreate the electronic circuit and add the code provided below.

Open Tinkercad in new window

RGB Colour Codes

Did you know that every colour on the screen can be represented using an RGB code (Red, Green, Blue) code. This code consists of three numbers between 0 and 255, indicating how much red, green and blue are used to recreate the colour.

For instance the RGB code for:

Red is (255,0,0)
Green is (0,255,0)
Blue is (0,0,255)
Yellow is (255,255,0)
Orange is (255,165,0)

Check the following RGB Color picker to see how RGB codes work:

Electric Circuit

An RGB LED is a 3-in-1 LED. It consists of a RED LED, a Green LED and a Blue LED all within the same component. It has 3 cathodes (+ pins) that can take different amperages. It has 1 common anode (- pin).

This is how we will connect our RGB LED to our Arduino board.

The purpose of the resistors is to limit the amperage in the circuit and hence protect the LED from receiving a too strong current (which could damage the LED). The resistors we use here are 100 ohms (Brown Black Brown rings).

C/C++ Code

// Arduino - RGB Gradient - www.101computing.net/arduino-rgb-gradient
int redOut = 13;
int greenOut = 11;
int blueOut = 12;

void setup() {
  pinMode(redOut, OUTPUT);
  pinMode(greenOut, OUTPUT);
  pinMode(blueOut, OUTPUT);
}

void setRGB(int red, int green, int blue)
 {
    analogWrite(redOut, red);
  	analogWrite(greenOut, green);
  	analogWrite(blueOut, blue);
}

void loop() {
  int red = 255;
  int green = 0;
  int blue = 0;
  for (int i = 0; i <= 255; i++) {
    blue = i;
	setRGB(red,green,blue);
    delay(20);
  } 
  for (int i = 0; i <= 255; i++) {
    blue = 255 - i;
	setRGB(red,green,blue);
    delay(20);
  } 
  
}