Lesson 7--Microduino “RGB LED”

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Objective

By now you are familiar with using an LED. Let's take a look at the RGB LED. This new type of LED allows us to display different colors. We can also replicate the breathing light effect from last lesson.

Equipment

Lesson7All.jpg

RGB

RGB LED contains three LEDs: red, green, and blue. By controlling the three LED's brightness, you can create any color you want.

Lesson7-RGB.jpg

Connection Methods

  • Method 1: Connect the longest lead wire (anode) to +5V. The other three pins are connected to a 220Ω resistor and then connected to a Microduino PWM output port. We attach resistors to prevent too much current flow from damaging the LEDs.
  • Method 2: Connect the anode through a 220Ω resistor to Vcc. The other three pins are connected to PWM output ports. Since three LEDs share a single resistor, the brightness will be dimmer.

Experiment Schematic

The following connection uses method 1 and uses D5,D6,D11.

Lesson7-schematic.jpg

Program

int redPin = 11;
int greenPin = 5;
int bluePin = 6;
void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
}
void loop()
{
     setColor(255, 0, 0);  // Red
     delay(1000);
     setColor(0, 255, 0);  // Green
     delay(1000);
     setColor(0, 0, 255);  // Blue
     delay(1000);
     setColor(255, 255, 0);  // Yellow
     delay(1000);  
     setColor(80, 0, 80);  // Purple
     delay(1000);
     setColor(255, 255, 255);// White 
     delay(1000);
     setColor(0, 0, 0);  //Black
     delay(1000);
     for(int i=0;i<255;i+=5)//Red coming on
     {
        setColor(i, 0, 0);  
        delay(30);
     }
     delay(100);
     for(int i=255;i>0;i-=5)//Red coming off
     {
        setColor(i, 0, 0);  
        delay(30);
     }
     delay(100);
     for(int i=0;i<255;i+=5)//Blue coming on
   {
        setColor(0, i, 0); 
        delay(30); 
     }
     delay(100);
     for(int i=255;i>0;i-=5)//Blue coming off
     {
        setColor(0, i, 0);  
        delay(30);
     }
     delay(100);
     for(int i=0;i<255;i+=5)//Green coming on
     {
        setColor(0, 0, i);  
        delay(30);  
     }
     delay(100);
     for(int i=255;i>0;i-=5)//Green coming off
     {
        setColor(0, 0, i);  
        delay(30);
     }
     delay(100);
}
void setColor(int red, int green, int blue)//Color display program
{
     analogWrite(redPin, 255 - red); 
     analogWrite(greenPin, 255 - green);
     analogWrite(bluePin, 255 - blue);  
}

We wrote a setColor() function so that it can be invoked in loop() directly. This makes the program look cleaner and clearer.

The above program only lists a few colors you can make. You can search online for RGB values for any color you want.

Result

The light will go from red, green, blue, yellow, purple, black, and to white. Then, it will behave like a breathing light as in Lesson 6.

Lesson7Result.jpg

Video

http://v.youku.com/v_show/id_XNzEwMDA0Njg0.html