Controlling R_G_B Led using Microcontroller

November 2, 2009 by admin
Filed under: Microcontrollers, electronics

Hi…

Here is another experiment to share. An RGB led is a electroluminescent device capable of creating any color by some combination of Red, Green and Blue LED. Actually it is a LED with 3 led’s (red, green & blue) inside one package.

RGB led has 4 Legs. The one i have has one leg for Vcc (Positive Supply) and other three terminals corresponding to R, G and B values.

Different color patterns can be generated by controlled PWM Pulses on respective terminals.

From left to right in above picture -> 1. RED 2. Vcc 3. GREEN 4. BLUE

Now lets move onto the main part that is How to control using Microcontroller. I am going to use ATmega8l from AVR family for demo. You can use any controller the concept will remian the same.

And here is the code that generates almost all combination’s of R G B using PWM over three pins of MEga8.

PORTC_0 —-Controlling RED

PORTC_1 —-Controlling GREEN

PORTC_2 —-Controlling BLUE

#include<avr/io.h>
#include<util/delay.h>
#include<compat/deprecated.h>
#include<avr/interrupt.h>
unsigned char r=255,g=0,b=0;

ISR(TIMER0_OVF_vect)
{
  sbi(PORTC,0);
  _delay_ms(255-r);
  cbi(PORTC,0);
  _delay_ms(r); 

   sbi(PORTC,1);
  _delay_ms(255-g);
  cbi(PORTC,1);
  _delay_ms(g);

  sbi(PORTC,2);
  _delay_ms(255-b);
  cbi(PORTC,2);
  _delay_ms(b);   

}

int main(void)
{
  DDRC=0xFF;   // PORTC as output
  PORTC=0xFF;  // Initially all leds off no color
  TCCR0=0x01;  // No prescaling of timer clock
  TIMSK=0x01;  // Timer Overflow interrupt enable
  TCNT0=0;
  sei();   // Global interrupt enable
  while(1==1)    // Infinite loop
  {
    if(r==255 && g==0 && b==0)
    {
        r=r-1;g=g+1;
        if(g==255 && b==0 && r==0)
        {
          g=g-1; b=b+1;
           if(b==255 && r==0 && g==0)
           {
              b=b-1;r=r+1;
           }
         }
    }
  }
  return (0);
}

Tags: RGB LED