Attached PIR sensor to Arduino, so it could adjust power 12V ~18W LED lamp sticker-strip under kitchen's cupboards. Just a simple, although interesting project combining electronics, automation and programming.

PIR sensor for LED lighting

int relayPin = 3;
int pirPin = 2;
int ledPin = 13; // just a LED on Arduino board. Not that huge ~18W LED lamp.

long lastDetection = 0; // millis
long DELAY = 3 * 1000; // N seconds (also adjustable at PIR sensor too)

void setup() {
  pinMode(relayPin, OUTPUT);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int pirValue = digitalRead(pirPin);
  if (pirValue == HIGH) {
    lastDetection = millis();
    Serial.println("Moved: " + lastDetection);
  }
  
  if (lastDetection + DELAY > millis()) { 
    digitalWrite(relayPin, LOW); // Switch relay, so it would turn on LED strip
    digitalWrite(ledPin, HIGH); // Also turn on indicator LED added to Arduino board
  } else {
    digitalWrite(relayPin, HIGH); 
    digitalWrite(ledPin, LOW);
  }
}