POWER CONTROL USING TRIAC AND ARDUINO

HERE POWER TO THE BULB IS CONTROLLED.MCT2E OPTO-COUPLER USED TO GET THE ZERO CROSSING. MOC3021 OPTO-COUPLER TRIAC IS USED TO FIRE THE TRIAC BT136. THIS PROJECT IS SIMILIAR TO FADING EXAMPLE OF LED IN ARDUINO WHICH IS AN DC VOLTAGE ,BUT HERE FADING IS DONE AC VOLTAGE

OUTPUT WAVEFORM AT ZERO CROSSING  OPTO COUPLER (YELLOW) AND INPUT SINE WAVE

CIRCUIT

PROGRAM

int a,i;
void setup() 
{ 
pinMode(4,INPUT);
pinMode(10,OUTPUT);
}
void loop() 
{
  for(i=0;i<10;i++)
  {
    for(int j=0;j<10;j++)
    { 
    waitfornextzerocrossing ();delay(i);   digitalWrite(10, HIGH); delayMicroseconds(200);   digitalWrite(10, LOW); 
    }
  }
    for(i=9;i>0;i--)
    {
      for(int j=0;j<10;j++)
      { 
      waitfornextzerocrossing ();delay(i);   digitalWrite(10, HIGH); delayMicroseconds(200);   digitalWrite(10, LOW); 
      }
    }
}
void waitfornextzerocrossing (void)
{
  do
    { 
      a =digitalRead(4); 
    }
  while(!a); 
}