An Arduino program that allows the user to fade the led either by using a potentiometer or a photoresistor. To switch between the two modes a push button must be pressed. The sketch also goes through a completely automated calibration process in the setup() that sets the sensor values automatically.

SensorCalibrate.ino

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

// Pins
const int ledPin =  11;
const int buttonPin = 12;
const int lightPin = A0;
const int potPin = A1;

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

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

// Variables for the potentiometer
int highPotValue = 9999;
int lowPotValue;

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

// Timer for the setup
int setupTimer = 0;

// Option for testing
boolean TEST = false;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(lightPin, INPUT);
  pinMode(potPin, INPUT);
  pinMode(buttonPin, INPUT_PULLUP);
  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("Now rotate the pot from left to right to calibrate");

  // Calibrate the potentiometer
  setupTimer = 0;
  while (setupTimer < 30000) {
    potVar = analogRead(potPin);
    if (highPotValue > potVar) {
      highPotValue = potVar;
    }

    if (lowPotValue < potVar) {
      lowPotValue = potVar;
    }

    // Make the LED Flash a bit faster this time
    if(setupTimer % 500 == 0) {
      switchState = !switchState;
    }

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

  Serial.println("POTENTIOMETER CALIBRATED!");
  Serial.print("Light = ");
  Serial.println(lowPotValue);
  Serial.print("Dark = ");
  Serial.println(highPotValue);

  Serial.println("STARTING THE PROGRAM!");
  delay(500);
}

void loop() {
  lightVar = analogRead(lightPin);
  potVar = analogRead(potPin);
  buttonState = digitalRead(buttonPin);

  // Button code
  if (buttonState == HIGH && pressed == false ) {
    if (switchState == LOW) {
      switchState = HIGH;
    }
    else {
      switchState = LOW;
    }
    pressed = true;
    delay(20);
  }

  if (buttonState == LOW && pressed == true ) {
    pressed = false;
    delay(20);
  }


  if (switchState) {
    // 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;
    }
  } else {
    // Trigger if the potentiometer senses a value higher than
    // half distance between the lowPotValue and the highPotValue
    if (potVar <= lowPotValue + (highPotValue - lowPotValue)/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);

  // If not testing, still allow some delay to occur
  if (TEST) {
    Serial.print("Light:");
    Serial.print(lightVar);
    Serial.print("\tPot: ");
    Serial.print(potVar);
    Serial.print("\tButton: ");
    Serial.print(buttonState);
    Serial.print("\tFade State:");
    Serial.print(fadeUp);
    Serial.print("\tTigger Brightness:");
    Serial.print(light + (dark - light)/2);
    Serial.println("\t");
  } else {
    delay(5);
  }
}