AC Light Control With potensio

/*AC Light Control

 Update by HwThinker
 * added Serial
 *
 Updated by Robert Twomey

 Changed zero-crossing detection to look for RISING edge rather
 than falling.  (originally it was only chopping the negative half
 of the AC wave form).

 Also changed the dim_check() to turn on the Triac, leaving it on
 until the zero_cross_detect() turn's it off.

 Adapted from sketch by Ryan McLaughlin
 http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1230333861/30

 */

#include  <TimerOne.h>          // Avaiable from http://www.arduino.cc/playground/Code/Timer1
int sensorValue = 0;        // value read from the pot
const int analogInPin = A0;
volatile int i=0;               // Variable to use as a counter volatile as it is in an interrupt
volatile boolean zero_cross=0;  // Boolean to store a "switch" to tell us if we have crossed zero
int AC_pin = 3;                // Output to Opto Triac
int dim = 0;                    // Dimming level (0-128)  0 = on, 128 = 0ff
int inc=1;                      // counting up or down, 1=up, -1=down

int freqStep = 75;    // This is the delay-per-brightness step in microseconds.
                      // For 60 Hz it should be 65
// It is calculated based on the frequency of your voltage supply (50Hz or 60Hz)
// and the number of brightness steps you want.
//
// Realize that there are 2 zerocrossing per cycle. This means
// zero crossing happens at 120Hz for a 60Hz supply or 100Hz for a 50Hz supply.

// To calculate freqStep divide the length of one full half-wave of the power
// cycle (in microseconds) by the number of brightness steps.
//
// (120 Hz=8333uS) / 128 brightness steps = 65 uS / brightness step
// (100Hz=10000uS) / 128 steps = 75uS/step

void setup() {                                      // Begin setup
   Serial.begin(9600);
  pinMode(AC_pin, OUTPUT);                          // Set the Triac pin as output
  attachInterrupt(0, zero_cross_detect, RISING);    // Attach an Interupt to Pin 2 (interupt 0) for Zero Cross Detection
  Timer1.initialize(freqStep);                      // Initialize TimerOne library for the freq we need
  Timer1.attachInterrupt(dim_check, freqStep);
  // Use the TimerOne Library to attach an interrupt
  // to the function we use to check to see if it is
  // the right time to fire the triac.  This function
  // will now run every freqStep in microseconds.
}

void zero_cross_detect() {
  zero_cross = true;               // set the boolean to true to tell our dimming function that a zero cross has occured
  i=0;
  digitalWrite(AC_pin, LOW);       // turn off TRIAC (and AC)
}

// Turn on the TRIAC at the appropriate time
void dim_check() {
  if(zero_cross == true) {
    if(i>=dim) {
      digitalWrite(AC_pin, HIGH); // turn on light
      i=0;  // reset time step counter
      zero_cross = false; //reset zero cross detection
    }
    else {
      i++; // increment time step counter
    }
  }
}

void loop() {
//  dim+=inc;
//  if((dim>=128) || (dim<=0))
//    inc*=-1;
  sensorValue = analogRead(analogInPin);
  dim = map(sensorValue, 0, 1023, 0, 128);
  // print the results to the Serial Monitor:
  Serial.print("sensor = ");
  Serial.print(sensorValue);
  Serial.print("\t output = ");
  Serial.println(dim);
  delay(18);
}