Here is how you can use an RGB LED as a rainbow party light continuously travelling through the visible spectrum. What you will need is:

-1 or many RGB LEDs

-1 Arduino UNO board; it can be other Arduino brand boards

-a breadboard

-5 jumper wires, three of which are color coded for the LEDs colors

-three 330 ohm resistors

-9v battery to power the Arduino when not plugged into the computer

Let's get started!

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Step 1: Creating the Circuit

Using the 330-ohm resistors, the RGB LED, breadboard, jumpers, and the Arduino chip place the components as shown in the picture. Each resistor goes to one of the anodes, the positive color control leads. The longest lead, the cathode, goes to the ground terminal on the Arduino does not need resistors. Each wire is color coded. Red for red color, green for green, blue for blue, and black for ground. Red is linked to pin 9, green is linked to pin 10, and blue is linked to pin 11 on the Arduino chip. Next is the programming.

Step 2: Coding

The code is made so the LED shows red, green, blue, yellow, cyan, and magenta with each color lasting one second. After the primary/secondary cycle is complete the LED will phase through the visible spectrum along with mixed colors. After coding is complete upload the code to the Arduino.

RGB_LED.txt
Download

Step 3: Display

If done correctly, the RGB LED should go through the primary colors, secondary colors, then a spectrum. You can hide the circuitry behind or in an object with only the RGB LED exposed to make the LED look like a well made, non-messy, or scrambled light display. You can put a foggy white diffuser such as tape over the LED to mix and spread the light better. You can use a 9V battery with the 9V plug-in for the Arduino to have a portable power source.

Options to hide the circuitry with exposed LED:

-In a cabinet or box with a small hole for the LED which is what I chose

-In a foggy acrylic box

-In the wall or ceiling if you can

You can also use many RGB LEDs to have a bigger, better light display for more crowd pleasing. Enjoy.