How to Connect a Relay to Arduino

Materials Needed:

• Arduino (e.g., Arduino Uno)
• Relay Module (typically 5V)
• External Power Source (if needed for your load)
• Jumper Wires
• Load Device (e.g., a lamp or motor)

💡 Wiring Diagram:

1. Relay Module to Arduino:
   • VCC pin on the relay → 5V pin on Arduino (or 3.3V for 3.3V relays).
   • GND pin on the relay → GND pin on Arduino.
   • IN pin on the relay → Digital pin on Arduino (e.g., pin 7).
2. Relay Contacts to Load:
   • COM (Common) pin on the relay → Live wire (L) of the power source.
   • NO (Normally Open) pin on the relay → One terminal of the load device (e.g., light bulb).
   • The other terminal of the load device → Neutral wire (N) of the power source.

📟 Control Code:

int relayPin = 7;  // Pin connected to IN on the relay module

void setup() {
  pinMode(relayPin, OUTPUT);  // Set relay pin as output
}

void loop() {
  digitalWrite(relayPin, HIGH);  // Turn relay ON (close the switch)
  delay(1000);                    // Wait for 1 second
  digitalWrite(relayPin, LOW);   // Turn relay OFF (open the switch)
  delay(1000);                    // Wait for 1 second
}

⚠️ Important Notes:

• Ensure your load power source is appropriate (e.g., 120V AC for a lamp).
• Electromechanical relays may make a clicking sound when activated.
• High-voltage handling requires caution. Always be safe when working with AC circuits.