Arduino AC Dimmer ino

// Original code kindly provided by::
// http://www.youtube.com/watch?v=ztXRjyCQxlE
// backyard amusement
// What follows is a minor tweak.

const int PIN_ZERO_CROSS = 2;  // ZeroCross (ZCR)
const int PIN_TRC = 1;  // Triac (TRC)
const int PIN_LED = 14; // LED on Teensy.

unsigned long timer = 0;
int dimStep = 5;
int dimDir = -1;
int minDimValue = 0; // Min dim value
int maxDimValue = 128; // Max Dim value.
int dimValue = maxDimValue;


void setup()
{
 pinMode(PIN_ZERO_CROSS, INPUT);
 pinMode(PIN_TRC,OUTPUT);
 pinMode(PIN_LED,OUTPUT);
}

void loop()
{
  if(digitalRead(PIN_ZERO_CROSS))
  {
    zeroCross();
  }

  // Fading Test code. Sets dim value betwen 0 and 128 in steps of 5.
  if(micros() - timer > 1500){
      timer = micros();
      dimValue += dimDir;

      if(dimValue >= maxDimValue){
        dimDir = -1;
        dimValue = maxDimValue;
      }
      if(dimValue <= minDimValue){
        dimDir = 1;
        dimValue = minDimValue;
      }
    }
}

  // In the UK i'm on 50hz. That means 50 cycles per second.
  // For each half cycle we need to turn the TRC off when the zeropoint has occurred
  // and on after a delay. The longer the delay the dimmer the light.
  //
  //
  // At the beginning of the cycle (the ZeroCross event) we want to switch the TRC OFF (LOW)
  // After the required delay we want to turn the TRC ON (HIGH) for the remainder of the cycle.
  //
  // Different from the other code examples, which caused flicker, i've done two things.
  // First! i'm not using the interrupt. Based on other peoples suggestions.
  // Second! I've changed the order of setting the low and high pins. This stopped the flickering.
  //
  // Working out the delay.
  // In 1000ms (1second) we have 50 cycles, so 1 cycle = 20ms
  // Every half cycle we will get our ZeroCross event. So 1/2 a cycle = 10ms
  // Every time we get the zeroCross event, we need to wait Nms before turning the TRC on.
  //
  // So how do we determine the amount of time to wait? We take the max wait time of 10ms and divide it
  // by however many levels of light we need. I've used the 128 in the other examples, but you
  // could use 255 for example, if you were converting an rgb value into a light level.
  // delay time = 10000us/255 = 39.21us (microseconds)
  //
  // If your input range is quite arbitrary they you can use the following Arduino method to map it.
  // int dimValue = constrain ( map(myValue, 200, 1024, 0, 128) , 0, 128);
  //
  // Once we have the delay time we then every time the ZeroCross() method is called we just wait that time
  // before setting the TRC pin high.
  //
  // Firing angle calculation
  // 50Hz-> 10ms (1/2 Cycle) → (10000us - 10us) / 128 = 78 (Approx)
  // 60Hz-> 8.33ms (1/2 Cycle) → (8333us - 8.33us) / 128 = 65 (Approx)
void zeroCross()
{
  int dimtime = 0;
  float propTime = 0;
  if(true){
    dimtime = (77*dimValue);
  }
  else{
    dimtime = (65*dimValue);
  }
  digitalWrite(PIN_TRC, LOW);    // triac Off
  delayMicroseconds(dimtime);    // Off cycle
  digitalWrite(PIN_TRC, HIGH);   // triac firing
}