Potentiometer + LED brightness by BARRAGAN http://barraganstudio.com

Reads values from a potentiometer connected to the analog input pin 0. The value read from the sensor is proportional to the knob position. The value read is used to dim an LED connected to the PWM output pin 19 On Wiring v1 boards the PWM capable pins are: 29, 30, 31, 35, 36 and 37 On Wiring S board the PWM capable pins are: 4, 5, 6, 7, 19 and 20

int sensorValue;

void setup()
{
  pinMode(19, OUTPUT);
}

void loop()
{
  sensorValue = analogRead(0);  // read analog input pin 0 (value in the range 0-1023)

  // The LED brightness will be proportional to knob position.

  analogWrite(19, sensorValue / 4); // write the value to PWM output pin 37 (value in the range 0-255)

  // if you want the sensorValue of the LED to be inversely proportional to the amount of
  // of light in the environment comment the previous line and use the line below instead:

  //analogWrite(37, 1023 - sensorValue);

  delay(100);  // wait 100ms for next reading
}