쿨링팬+초음파센서

int relay=4;

const int trig_pin=11;

const int echo_pin=12;

void setup() {

pinMode(relay, OUTPUT);

pinMode(trig_pin, OUTPUT);

pinMode(echo_pin, INPUT);

Serial.begin(9600);

}

void loop() {

digitalWrite(trig_pin,LOW);

delayMicroseconds(2);

digitalWrite(trig_pin,HIGH);

delayMicroseconds(10);

digitalWrite(trig_pin,LOW);

long duration=pulseIn(echo_pin,HIGH);

long distance=(duration/2)/29.1;

Serial.print(distance);

Serial.println("cm");

if(distance<20){

digitalWrite(relay, HIGH);

delay(500);

}

else{

digitalWrite(relay, LOW);

delay(500);

}

}