Arduino: Relays

Opens and closes a circuit that’s “air-gapped” from the Arduino, allowing you to open/close circuits of much higher voltages (like 120V). Not sure how how good of an idea that is, considering the quality of these boards.

On the other side, “COM” is the positive “input”. “NO” is “normally open” and “NC” is “normally closed”.

//Opens and closes relay

#define RELAY_PIN 2     // Sets pin connect to relay as D2

void setup() {
  // initialize digital pin 9 as an output.
  pinMode(RELAY_PIN, OUTPUT);
}

void loop() {
  digitalWrite(RELAY_PIN, HIGH);
  delay(1000);
  digitalWrite(RELAY_PIN, LOW);
  delay(1000);
}