A simpler way of calibrating a light sensor.

SensorCalibrateSimple.ino

// Michael Braverman
// Lab Class
// 29 September 2015

// Pins
const int ledPin =  11;
const int lightPin = A0;

// States and numbers of the sensors and buttons
int lightVar;
boolean pressed = false;
boolean switchState;

// Variables for the photoresistor
int light = 9999;
int dark;

// Variables for fading
boolean fadeUp = true;
int fadeLevel = 0;

// Timer for the setup
int setupTimer = 0;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(lightPin, INPUT);
  Serial.begin(115200);
  Serial.println("-------------------------------------------------");
  Serial.println("Wave your hand over the sensor to calibrate");

  // Calibrate the photoresistor
  while (setupTimer < 20000) {
    lightVar = analogRead(lightPin);
    if (light > lightVar) {
      light = lightVar;
    }

    if (dark < lightVar) {
      dark = lightVar;
    }

    // Make the LED Flash
    if(setupTimer % 1000 == 0) {
      switchState = !switchState;
    }

    digitalWrite(13, switchState);
    setupTimer++;
  }

  Serial.println("LIGHT SENSOR CALIBRATED!");
  Serial.print("Light = ");
  Serial.println(light);
  Serial.print("Dark = ");
  Serial.println(dark);

  Serial.println("STARTING THE PROGRAM!");
}

void loop() {
  lightVar = analogRead(lightPin);

  // Trigger if the light sensor senses a value higher than
  // half distance between the darkest and the ligthest value
  if (lightVar <= light + (dark - light)/2) {
    fadeUp = true;
  } else {
    fadeUp = false;
  }

  // Fading code
  if (fadeUp == true) {
    if (fadeLevel != 255) {
      fadeLevel++;
    }
  } else {
    if (fadeLevel != 0) {
      fadeLevel--;
    }
  }

  // Set the outputs to their according values
  analogWrite(ledPin, fadeLevel);
  digitalWrite(13, switchState);

  delay(5);
}