LilyPad Development Board Activity Guide

Contributors: Gella

2: Basic Color Mixing

Now that you know how to turn LEDs on and off, let's try controlling a colorful LED. The LilyPad Development Board has a tri-color, or RGB (Red Green Blue), LED that can be controlled in your code just like the LED from the last activity. Unlike the LED used in the Blink example, this LED is special - it is actually 3 small LEDs in one package - a red, green, and blue. You can access them in code to a variety of color combinations.

LilyPad Boards Used in This Activity

• LilyPad Arduino Simple
• LilyPad Tri-Color LED

What is an RGB LED?

Inside an RGB LED are three smaller LEDs - a red, green, and blue. Each of these LEDs is connected to a sew tab on the Tri-Color LED, and they are all connected through a common anode (positive) pin. Unlike other RGB LEDs, this configuration means that to light up the LED you need to ground the individual red, green, and blue LEDs instead of sending them power.

New Concepts Introduced in This Activity

Declaring and Using Variables

A variable is a placeholder for values in your code, typically a descriptive word. While we could continue to write the sew tab or pin number we are referencing in our programs, a variable can make it easier to read, update, and share information within your code. Every time you want to create and use a variable, you must declare it - tell the program what type of data it is storing.

Color Mixing

In order to create colors with the RGB LED, you'll have to set each of the LEDs within it individually. The combination of light from the LEDs mixed together creates new colors.

Example Code

To open the code, go to:

File > Examples > LilyPadDevelopmentBoard_ActivityGuide > LPD_02_BasicColorMixing

You can also copy and paste the following code into the Arduino IDE. Hit upload, and see what happens!

language:c
/*
LilyPad Development Board Activity 2: Basic Color Mixing
SparkFun Electronics
https://www.sparkfun.com/products/11262

Create primary and secondary colors on the tri-color (Red/Green/Blue)
LED connected to sew tabs 9, 11, and 10 on the LilyPad Arduino Simple.

Follow the tutorial at:
https://learn.sparkfun.com/tutorials/lilypad-development-board-activity-guide/2-basic-color-mixing

This code is released under the MIT License (http://opensource.org/licenses/MIT)

******************************************************************************/

// The LilyPad Development Board has a tri-color, also known as an RGB 
// (Red / Green / Blue) LED.
// In this activity we'll use digitalWrite to tun the three LEDs on and off
// in various combinations to create eight primary and secondary colors.

// Create integer variables for our LED pins:

// The built-in LED:

int RGB_red = 9;
int RGB_green = 11;
int RGB_blue = 10;


void setup()
{
  // Make all of our LED pins outputs:

  pinMode(RGB_red, OUTPUT);
  pinMode(RGB_green, OUTPUT);
  pinMode(RGB_blue, OUTPUT);

}

void loop()
{

  // This code will step through the six primary and secondary colors, plus white and black.
  // Note: for this particular LED, the wiring shares a common anode (+), which means to
  // turn on the LEDs you will set them LOW instead of HIGH. 
  // Keep this in mind as you prototype with the LED and mix your colors.

  // For each of these colors, we'll turn the necessary RGB LEDs on or off.


  // Black (all LEDs off)

  // RGB LEDs:

  digitalWrite(RGB_red, HIGH);
  digitalWrite(RGB_green, HIGH);
  digitalWrite(RGB_blue, HIGH);
  delay(1000);

  // Red (red LED on)

  digitalWrite(RGB_red, LOW);
  digitalWrite(RGB_green, HIGH);
  digitalWrite(RGB_blue, HIGH);
  delay(1000);

  // Yellow (red and green LEDs on)

  digitalWrite(RGB_red, LOW);
  digitalWrite(RGB_green, LOW);
  digitalWrite(RGB_blue, HIGH);
  delay(1000);

  // Green (green LED on)

  digitalWrite(RGB_red, HIGH);
  digitalWrite(RGB_green, LOW);
  digitalWrite(RGB_blue, HIGH);
  delay(1000);

  // Cyan (blue and green LEDs on)

  digitalWrite(RGB_red, HIGH);
  digitalWrite(RGB_green, LOW);
  digitalWrite(RGB_blue, LOW);
  delay(1000);

  // Blue (blue LED on)

  digitalWrite(RGB_red, HIGH);
  digitalWrite(RGB_green, HIGH);
  digitalWrite(RGB_blue, LOW);
  delay(1000);

  // Magenta (red and blue LEDs on)

  digitalWrite(RGB_red, LOW);
  digitalWrite(RGB_green, HIGH);
  digitalWrite(RGB_blue, LOW);
  delay(1000);

  // White (all LEDs on)

  digitalWrite(RGB_red, LOW);
  digitalWrite(RGB_green, LOW);
  digitalWrite(RGB_blue, LOW);
  delay(1000);
}

What You Should See

After uploading your code, the RGB LED will step through a color sequence beginning with all LEDs off ('black'), red, yellow, green, cyan, blue, magenta, and white. Once the color sequence is complete, the program will loop back to the beginning and repeat the sequence.

Turning on different combinations of three LEDs inside the RGB LED will create new colors. Combining the primary colors of light (red, green, and blue) gives different results than combining pigments in paints or inks. Turning on all three colors will create white - this is called additive color. Take a look a the graphic below to see what colors combine to create primary and secondary colors with light.

Understanding Your Program

Program Overview

1. Turn all of the LEDs off by turning on all the pins associated with their variables.
   Wait 1 second.
2. Display red:
   R: ON, G: OFF, B: OFF
   Wait 1 second.
3. Display yellow:
   R: ON, G: ON, B: OFF
   Wait 1 second.
4. Display green:
   R: OFF, G: ON, B: OFF
   Wait 1 second.
5. Display cyan:
   R: OFF, G: ON, B: ON
   Wait 1 second,
6. Display blue:
   R: OFF, G: OFF, B: ON
   Wait 1 second.
7. Display magenta:
   R: ON, G: OFF, B: ON
   Wait 1 second.
8. Display white:
   R: ON, G: ON, B: ON
   Wait 1 second.
9. Repeat.

Code to Note

Coding Challenges

• Can you create a new color sequence on the tri-color LED using a new order of colors being displayed?

• Try changing the delay to create a faster or slower color sequence.

• Create a variable called delayTime at the top of your code near the other variable declarations. Then replace the 1000 in each delay() function with this variable. This way you can easily set the delay between color steps once at the beginning of your code instead of copying and pasting in each part of the sequence.