DC 12V adjustable timer delay, time delay relay turn off switch module time relay time switch 0~25sec for smart home, automatic control

// Canonical beginner example for a 12V adjustable timer delay relay module
// Arduino Uno drives the module's IN pin to start the delay timing action.

const int relayTriggerPin = 4;  // Connected to module IN

void setup() {
  pinMode(relayTriggerPin, OUTPUT);
  Serial.begin(9600);

  // Keep the trigger in its inactive state at startup.
  digitalWrite(relayTriggerPin, LOW);

  Serial.println("Timer delay relay demo started.");
  Serial.println("Module is powered from 5V here for documentation example.");
  Serial.println("Pulsing IN to start the delay timing action...");
}

void loop() {
  // Send a short trigger pulse to the module.
  digitalWrite(relayTriggerPin, HIGH);
  Serial.println("IN = HIGH (trigger pulse)");
  delay(200);

  digitalWrite(relayTriggerPin, LOW);
  Serial.println("IN = LOW (waiting for the delay to run)");

  // Wait long enough to observe the module timing behavior.
  delay(5000);
}