Relay Module 5V

// Relay Module 5V - Canonical Beginner Example
// This sketch switches the relay ON and OFF every 2 seconds.
// Wiring:
// Arduino GND -> relay -
// Arduino 5V  -> relay +
// Arduino D7  -> relay S

const int RELAY_PIN = 7;

void setup() {
  pinMode(RELAY_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("Relay module demo starting...");
}

void loop() {
  digitalWrite(RELAY_PIN, HIGH); // Many 5V relay modules are active HIGH
  Serial.println("Relay ON");
  delay(2000);

  digitalWrite(RELAY_PIN, LOW);
  Serial.println("Relay OFF");
  delay(2000);
}