Digital Rain Cloud

This is a very simple project that turns a Rainbow Cube Kit from Seeedstudio, into a digital rain cloud. It features a relaxing rain animation which is ruined by a not-so-relaxing yet somewhat realistic lightning effect. The animation has a very random pattern, and is quite satisfying to watch. The strategically placed cotton wool on the top of the cube makes all the difference to the project, and is sure to impress all of your friends. Luckily, I have done all of the hard work for you. You will find the full source code for the animation sequence below. You just have to provide the Rainbow Cube Kit and the cotton wool. Have fun !!

Parts Required

  1. Rainbow Cube Kit (Assembled) – 4x4x4 RGB LED cube
  2. Cotton Wool
  3. Mini USB cable – to connect Rainbow Cube Kit to Computer

More information about the Rainbow Cube Kit can be found here:

Arduino IDE

The Rainbow Cube Kit comes pre-configured with its own animation sequence.
We will over-write this sequence with the Digital Rain Cloud sketch below, and use the Arduino IDE to re-program the Rainbow Cube Kit. While there are many Arduino IDE alternatives out there, I would recommend that you use the official Arduino IDE for this project.
I used the official Arduino IDE app (v1.8.5) for Windows 10.
Make sure to get the most up-to-date version for your operating system here.

Arduino IDE Setup (Libraries)

You will need to install a couple of libraries into your Arduino IDE before you upload the sketch to the Rainbow Cube Kit.

Download the Rainowduino-v3 library

The Rainowduino-v3 library by unwiredben can be found here:

Install the Rainbowduino-v3 library using the Arduino IDE:

Sketch > Include Library > Add .ZIP library
Then select the downloaded Rainowduino-v3 library ZIP file.

The FastLED library can also be installed via the IDE:

Sketch > Include Library > Manage Libraries : then search for FastLED
Select the latest version, and then select INSTALL.
I used version 3.2.0 – but the latest version should also work.

Arduino Code

Upload the following sketch to the Rainbow Cube via the mini USB cable.

* Project: ArduinoBasics Digital Raincloud
* Author: Scott C
* Date created: 06 November 2018
* Arduino IDE version: 1.8.5
* Operating System: Windows 10 Pro
* Tutorial Link: https//arduinobasics.blogspot.com/
* Description:
* A simple program written for the Rainbowduino 4x4x4 RGB LED cube (by Seeedstudio),
* that creates a digital raincloud effect, lightning and all. Add a bit of cotton wool to the top of the
* cube and the project really comes alive.
* Acknowledgements:
* My son suggested putting cotton wool on the top. This simple suggestion made all the difference.
* The Seeedstudio Rainbowduino WIKI page is a great place to get started with this cube.
* http://wiki.seeedstudio.com/Rainbowduino_v3.0/
* ————————————————————————-
* The Rainowduino-v3 library by unwiredben was used in this project.
* The Rainbowduino-v3 library can be found here: https://github.com/unwiredben/Rainbowduino-v3
* The FastLED library was used for the random8() function.
* The FastLED library can be installed via the IDE:
* Sketch > Include Library > Manage Libraries : then search for FastLED
* Select the latest version, and then select INSTALL.
* I used version 3.2.0
============================================================================ */
#include <FastLED.h>
#include <Rainbowduino.h>
/* ————————————————————————–
* xPos,yPos = allows us to select a specific LED position in a layer.
* randomLED = is used to select the random LED from which rain falls
* cRed, cGreen, cBlue = allows slight variations in colour of the raindrops.
* topR, topG, topB = restores the colours of the top layer after the lightning effect
* rainChance = affects the frequency/amount of rainfall
* rainSpeed = the speed at which the rain falls. Recommend you set this between 2-5.
* lightningChance = affect the frequency of lightning
unsigned char xPos[16] = {0,1,2,3,0,1,2,3,0,1,2,3,0,1,2,3};
unsigned char yPos[16] = {0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3};
int randomLED = 0;
int cRed[4][16];
int cGreen[4][16];
int cBlue[4][16];
int topR[16];
int topG[16];
int topB[16];
int rainChance;
int rainSpeed = 5;
int lightningChance;
* Initialise the Rainbowduino 4x4x4 RGB LED cube and the colour arrays
void setup() {
for(int i=0; i<4; i++){
for(int j=0; j<16; j++){
cRed[i][j] = 0;
cGreen[i][j] = 0;
cBlue[i][j] = 0;
* Randomise the chance of a lightning strike with every loop. Probability = 5%
* Randomise the chance of a rain drop. Probability = 40%
* Randomise the LED from which the rain drop falls from
* Randomise the colour of the raindrop, with a bias towards blue colours
* Record the colour of the raindrop into the topR, topG, and topB arrays.
* Then update the display to start the raindrop animation.
void loop() {
rainChance = random8(100);
randomLED = random8(16);
topR[randomLED] = cRed[3][randomLED];
topG[randomLED] = cGreen[3][randomLED];
topB[randomLED] = cBlue[3][randomLED];
* updateDisplay:
* This function is responsible for the raindrop animation.
* Illuminate the randomLED
* Move the raindrop down to the next level with every cycle
* Gradually fade the LEDs on every cycle, and prevent the values from dropping below zero
* Update the LED brightness and rain drop animation sequence on the lower levels of the cube.
* The delay at the end, will determine the speed of the raindrop animation (larger values are slower)
void updateDisplay(){
for(int i=0; i<4; i++){
for(int j=0; j<16; j++){
// Illuminate the randomLED on the top layer
Rb.setPixelZXY(3,xPos[j],yPos[j], topR[j],topG[j],topB[j]);
// Move the raindrop down to the next level
cRed[i-1][j] = cRed[i][j];
cGreen[i-1][j] = cGreen[i][j];
cBlue[i-1][j] = cBlue[i][j];
// Gradually fade the LEDs – Please note: the top layer is not affected
cRed[i][j] = 0;
cGreen[i][j] = 0;
cBlue[i][j] = 0;
// Update the LED brightness and rain drop animation sequence on the lower levels.
//Set the speed of the raindrop animation sequence
* lightning:
* The LEDs will be set to flash a random number of times (0 to 19 times)
* But the flash may or may not always occur.
* If the flash does occur, then there is a 50% chance that any particular LED will join in.
* The LED will illuminate to full brightness WHITE (255,255,255)
* They will stay illuminated for 20 to 70 milliseconds
* and then return back to their normal colour for 0 to 20 milliseconds until the next flash.
* We do not want the rain animation to stop when the lightning is flashing, so we need to update
* the raindrop sequence from time to time. I did this randomly to eliminate any PERCEIVED delay from the
* lightning sequence.
* The lightning sequence and pattern is very RANDOM, which makes it very realistic.
void lightning(){
int chance = random8(20);
for(int k=0; k<chance; k++){
for(int j=0; j<16; j++){
chance = random8(100);
for(int j=0; j<16; j++){
chance = random8(100);

view rawDigital_Rain_Cloud.ino hosted with ❤ by GitHub

Final Touches

Once the code is uploaded, you will see a very random LED sequence. The top layer represents the clouds, and the 3 layers beneath represent the rain. Add a bit of cotton wool to cover the LEDs on the top layer and watch the light show begin.


While this may seem like a simple project, it actually took a little time to get the effect that I wanted. The cotton wool really brought the project to life, and if you don’t like the lightning, you can always delete that section in the program. If you would like to try some other animations on your LED cube, then feel free to look at the example folder on my GitHub page:
Enjoy your new digital Rain cloud – I would love to see your versions.

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