Relay

A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.

#define RELAY_PIN D7

void setup() {
  pinMode(RELAY_PIN, OUTPUT);
}
 
void loop() {

    digitalWrite(RELAY_PIN, HIGH);
    delay(3000);
    digitalWrite(RELAY_PIN, LOW);
    delay(3000);

}

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