How to Create Rainbow Spectrum with Arduino


In this project, we learn How to Create Rainbow Spectrum with Arduino, Unleash a vibrant burst of colors with the Rainbow Spectrum project using Arduino Nano. In this tutorial, we will guide you through the exciting process of generating a mesmerizing rainbow spectrum using an RGB LED and Arduino programming. By harnessing the power of creative coding and color manipulation, you can craft a captivating visual display that transitions smoothly through the entire color spectrum. Let’s dive into the components required and the step-by-step instructions to bring this dynamic rainbow effect to life.

Hardware Required

You will require the following Hardware Components for How to Create Rainbow Spectrum with Arduino.

Components#Buy From Amazon
Arduino Nano1Buy Now
Potentiometer1Buy Now
9v DC Adapter (Optional)1Buy Now
Resistor 1KΩ3Buy Now
Resistor 100KΩ1Buy Now
Jumper WiresFewBuy Now
Breadboard1Buy Now

Creating the Rainbow Spectrum

Follow these steps to craft the Rainbow Spectrum with Arduino:

  1. Connect the cathode (longest leg) of the RGB LED to the GND rail on the breadboard.
  2. Connect the anode (shortest leg) of the RGB LED to digital pins 6, 5, and 3 on the Arduino Nano through 1KΩ resistors (one resistor per channel).
  3. Connect one end of the potentiometer to the 5V rail and the other end to the GND rail on the breadboard. Connect the wiper (middle pin) of the potentiometer to analog pin A0 on the Arduino Nano.
  4. Connect the 100KΩ resistor from the wiper of the potentiometer to the GND rail on the breadboard.

Circuit Diagram


Installing Arduino IDE Software

First, you will require to Download the updated version of Arduino IDE Software and Install it on your PC or laptop. if you Learn How to install the Arduino step-by-step guide then click on how to install Arduino Button given Blow


//For more Projects:

Created 21 April 2012
By Jason Judge
This example code is in the public domain.
const int ledPinRed = 3; // Red LED connected to analogue out pin
const int ledPinGrn = 5; // Green LED connected to analogue out pin
const int ledPinBlu = 6; // Blue LED connected to analogue out pin

const int modeSwitchPin = 12;

// The Hue potentiometer goes on an analogue pin, taking the pin from
// 0V to 5V.

const int potPinHue = 0;

// Constants to define the ranges.
const int hueRedLow = 0;
const int hueRedHigh = 255;
const int hueBlue = 170;

// The size of the angle of one sector (1/6 of a colour wheel), and of a complete
// cycle of the colour wheel.

const int angleMin = 0;
const int angleSector = 60;
const int angleMax = 360;

const int brightMin = 0;
const int brightMax = 255;

// Work variables.

// The potentiometer value is mapped to the range 0 to 360 (degrees).
int potValueHue;

// The hue is the range 0 (red) to 170 (blue) in rainbow
// mode or 255 (red) in colour wheel mode.
// The brightness ranges from 0 (dark) to 255 (full brightness)

int hue, brightness;

// The saturation is fixed at 255 (full) to remove blead-through of different
// colours.
// It could be linked to another potentiometer if a demonstration of hue
// is desired.
const int saturation = 255;

// The brightess of each LED (0 to 255).

unsigned int r, g, b;

void setup() {
// Still need to set a baud rate, even for USB.

// Set LED pins to output.
pinMode(ledPinRed, OUTPUT);
pinMode(ledPinGrn, OUTPUT);
pinMode(ledPinBlu, OUTPUT);

// Poteniometer analogue pin is an input.
pinMode(potPinHue, INPUT);

// TODO: mode switch in a digital input.
pinMode(modeSwitchPin, INPUT);

void loop() {
// The Hue potentiometer value is mapped to degrees – 0 to 360 – for convenience.
potValueHue = map(analogRead(potPinHue), 0, 1023, 0, 360);

// Control the mode using a physical switch.

if (digitalRead(modeSwitchPin)) {
// Rainbow colour mode (infra-red to ultra-violet – well invisible to invisible ;-).
// The hue ranges from red (0) at 60 degrees to blue (170) at 300 degrees.
hue = constrain(map(potValueHue, angleSector, angleMax – angleSector, hueRedLow, hueBlue), hueRedLow, hueBlue);

// Brightness – fade up 0-60 degrees
brightness = constrain(map(potValueHue, angleMin, angleSector, brightMin, brightMax), brightMin, brightMax);

// Brightness fade down 300-360 degrees
brightness = brightness – constrain(map(potValueHue, angleMax – angleSector, angleMax, brightMin, brightMax), brightMin, brightMax);
} else {
// Colour wheel mode (red to red, wrapped around in a cycle).

hue = map(potValueHue, angleMin, angleMax, hueRedLow, hueRedHigh);

// The brightness is fixed at full for the colour wheel. This could be
// linked to another poteniometer if that is a concept you wish to
// demonstrate.
brightness = 255;

// Do the conversion.
HSBToRGB(hue, saturation, brightness, &r, &g, &b);

analogWrite(ledPinRed, r);
analogWrite(ledPinGrn, g);
analogWrite(ledPinBlu, b);
Serial.print(” bright=”);
Serial.print(” hue=”);
Serial.print(” red=”);
Serial.print(” green=”);
Serial.print(” blue=”);
void HSBToRGB(
unsigned int inHue, unsigned int inSaturation, unsigned int inBrightness,
unsigned int *oR, unsigned int *oG, unsigned int *oB )
if (inSaturation == 0)
// achromatic (grey)
*oR = *oG = *oB = inBrightness;
unsigned int scaledHue = (inHue * 6);
unsigned int sector = scaledHue >> 8; // sector 0 to 5 around the color wheel
unsigned int offsetInSector = scaledHue – (sector << 8); // position within the sector
unsigned int p = (inBrightness * ( 255 – inSaturation )) >> 8;
unsigned int q = (inBrightness * ( 255 – ((inSaturation * offsetInSector) >> 8) )) >> 8;
unsigned int t = (inBrightness * ( 255 – ((inSaturation * ( 255 – offsetInSector )) >> 8) )) >> 8;
switch( sector ) {
case 0:
*oR = inBrightness;
*oG = t;
*oB = p;
case 1:
*oR = q;
*oG = inBrightness;
*oB = p;
case 2:
*oR = p;
*oG = inBrightness;
*oB = t;
case 3:
*oR = p;
*oG = q;
*oB = inBrightness;
case 4:
*oR = t;
*oG = p;
*oB = inBrightness;
default: // case 5:
*oR = inBrightness;
*oG = p;
*oB = q;


  1. Decorative Lighting: Add a captivating visual display to parties, events, or interior spaces with the ever-changing rainbow spectrum.
  2. Mood Lighting: Craft an ambiance that complements different moods or occasions by adjusting the color spectrum speed.
  3. Art Installations: Incorporate the rainbow effect into interactive art installations to engage and captivate viewers.
  4. Display Systems: Create attention-grabbing displays for retail or commercial spaces with dynamic and eye-catching visuals.
  5. Educational Tools: Teach concepts of light, color, and coding by demonstrating the principles of color mixing and gradient transitions.


In this tutorial, we explored how to create a Rainbow Spectrum using an Arduino Nano and an RGB LED. By combining creative coding and color manipulation, you can generate a visually stunning display that seamlessly transitions through the entire color spectrum. We discussed the required components, the circuit connections, and provided a sample Arduino code to bring the rainbow effect to life. Now you have the tools to infuse your projects with a dynamic and mesmerizing visual element that evokes the beauty of a rainbow. Whether for decorative lighting, art installations, or educational purposes, the Rainbow Spectrum opens up a world of captivating possibilities for your creative endeavors.

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