Relais Module 5v Low

// Canonical beginner example for a 5V low-level trigger relay module
// Wiring:
// Arduino 5V  -> Relay VCC
// Arduino GND -> Relay GND
// Arduino D7  -> Relay IN

const int relayPin = 7;

void setup() {
  pinMode(relayPin, OUTPUT);

  // Low-level trigger relay modules are often OFF when the input is HIGH
  // and ON when the input is LOW.
  digitalWrite(relayPin, HIGH);

  Serial.begin(9600);
  Serial.println("Relay module example started.");
  Serial.println("Relay will switch ON and OFF every 2 seconds.");
}

void loop() {
  Serial.println("Relay ON");
  digitalWrite(relayPin, LOW);   // active-low: energize relay
  delay(2000);

  Serial.println("Relay OFF");
  digitalWrite(relayPin, HIGH);  // de-energize relay
  delay(2000);
}