/*This program increases luminosity of a LED when ambient luminosity is decreasing. It is necessary
  to regulate the higher and lower value in function of the place where you are meassuring*/
int ldr = 0;  //define a pin for Photo resistor
int led = 11;   //define a pin for LED
int higher = 945;
int lower = 660;

void setup()
{
  Serial.begin(9600);  //Begin serial communcation
  pinMode( led, OUTPUT );
}

void loop()
{
  int value = analogRead(ldr);
  Serial.println(value); //Write the value of the photoresistor to the serial monitor.
  //If the limits are exceeded value is equal to the maximum or minimum
  if (value >= higher) {
    value = higher - 1;
  }
  if (value <= lower) {
    value = lower + 1;
  }
  value = map(value, higher, lower, 0, 255);//Change the range and invert it to
  //increase the intesity of led when resistance
  //of ldr is increasing.
  analogWrite(led, value); .
  delay(20); //short delay for faster response to light.
}