int sensorPin = 8;int ledPin = 3;
int sensorValue = 0;unsigned long currentTime = 0;
unsigned long previousTime = 0, previousTime2=0;
void setup() {  // put your setup code here, to run once:
  Serial.begin(115200);  pinMode(sensorPin, INPUT);
  pinMode(ledPin, OUTPUT);}
void ledState(unsigned long &pvT, int interval, int ledValue) {
  if (currentTime - pvT >= interval) {    digitalWrite(ledPin, ledValue);
    pvT = currentTime;  }
}
void loop() {  // put your main code here, to run repeatedly:
  // if someonse is close by, let the LED blink  sensorValue = digitalRead(sensorPin);
    if (sensorValue == LOW) {
    //blinking    currentTime = millis();
    ledState(previousTime, 500, 1);    ledState(previousTime2, 1000, 0);
//    if (currentTime - previousTime >= interval) {
//      digitalWrite(ledPin, HIGH);////      previousTime = currentTime;
//      }//    else {
//      digitalWrite(ledPin, LOW);//      previousTime = currentTime;
//      }  }
  //But if nobody is nearby, let the LED remain off.
  else {
    digitalWrite(ledPin, LOW);    }

}