int Sensor = 4; //Input Pin
int LED = 3; // Led pin for Indication
int flg = 0; //Change detection flag
void setup() {
pinMode (Sensor, INPUT); //Define Pin as input
pinMode (LED, OUTPUT); //Led as OUTPUT
}
void loop() {
int val = digitalRead(Sensor); //Read Pin as input
if((val > 0) && (flg==0))
{
digitalWrite(LED, HIGH);
flg = 1;
}
if(val == 0)
{
digitalWrite(LED, LOW);
flg = 0;
} 
delay(100);
}