const int buzPIN = 5;
const int hijPIN = 3;
const int merPIN = 4;
const int trgPIN = 11;
const int echPIN = 10;

void setup(){

    Serial.begin(9600);

    pinMode(buzPIN, OUTPUT);
    pinMode(hijPIN, OUTPUT);
    pinMode(merPIN, OUTPUT);

    pinMode(echPIN, INPUT);
    pinMode(trgPIN, OUTPUT);
}   

void loop(){

    digitalWrite(trgPIN, HIGH);
    delayMicroseconds(10);
    digitalWrite(trgPIN, LOW);

    int pulsa = pulseIn(echPIN, HIGH);
    float jarakCm   = pulsa/58;
    float jarakInc  = pulsa/148;

    Serial.print("jarak obj: ");
    Serial.print(jarakCm);
    Serial.println(" cm");

    if( jarakCm < 15){
        digitalWrite(hijPIN, LOW);
        digitalWrite(merPIN, HIGH);
        digitalWrite(buzPIN, HIGH);
    }
    else{
        digitalWrite(hijPIN, HIGH);
        digitalWrite(merPIN, LOW);
        digitalWrite(buzPIN, LOW);
    }

    delay(1000);
}