Demonstrates analog input through a potentiometer and a photoreceptor paired to dimming LED lights.

Analog_Input_and_Output.INO

/*
  Analog input, analog output, serial output

  Reads an analog input pin, maps the result to a range from 0 to 255 and uses
  the result to set the pulse width modulation (PWM) of an output pin.
  Also prints the results to the Serial Monitor.

  The circuit:
  - potentiometer connected to analog pin 0.
    Center pin of the potentiometer goes to the analog pin.
    side pins of the potentiometer go to +5V and ground
  - LED connected from digital pin 9 to ground
*/

// These constants won't change. They're used to give names to the pins used:
int analogInPin1 = A0; // Analog input pin that the potentiometer is attached to
int analogInPin2 = A1; // Analog input pin that the photoreceptor is attached to

int ledPin1 = 9; // Digital output pin that uses PWM
int ledPin2 = 10; // Analog output pin that uses PWM

int sensorValue1 = 0;        // value read from the potentometer
int sensorValue2 = 0;        // calue read from the photoreceptor
int outputValue1 = 0;        // value output to ledPin1
int outputValue2 = 0;        // calue output to ledPin2

void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);

  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
}

void loop() {
  // read the analog in value:
  sensorValue1 = analogRead(analogInPin1);
  // map it to the range of the analog out:
  outputValue1 = map(sensorValue1, 0, 1023, 0, 255);
  // change the analog out value:
  analogWrite(ledPin1, outputValue1);

  // read the analog in value:
  sensorValue2 = analogRead(analogInPin2);
  // map it to the range of the analog out:
  outputValue2 = map(sensorValue2, 300, 900, 0, 255);
  // change the analog out value:

  // Turns off ledPin2 if the light level drops below 500
  if (outputValue2 < 0){
    outputValue2 = 0;
  }

  analogWrite(ledPin2, outputValue2);
  
  // print the potentiometer results to the Serial Monitor:
  Serial.print("potentiometer = ");
  Serial.print(sensorValue1);
  Serial.print("\t output = ");
  Serial.println(outputValue1);

  Serial.print("\n");

  // print the photoreceptor results to the Serial Monitor:
  Serial.print("photoreceptor = ");
  Serial.print(sensorValue2);
  Serial.print("\t output = ");
  Serial.println(outputValue2);

  // wait 2 milliseconds before the next loop for the analog-to-digital
  // converter to settle after the last reading:
  delay(5);
}