#define trigPin 10 #define echoPin 9 #define trigPin2 3 #define echoPin2 4 #define led 8 #define led2 2 #define buzzer1 7 void setup(){ Serial.begin (9600); pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); pinMode(led, OUTPUT); pinMode(trigPin2, OUTPUT); pinMode(echoPin2, INPUT); pinMode(led2, OUTPUT); pinMode(buzzer1, OUTPUT); } void loop(){ long duration1, distance1; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW); duration1 = pulseIn(echoPin, HIGH); distance1 = (duration1/2) / 29.1; if (distance1 < 10){ digitalWrite(buzzer1, HIGH); digitalWrite(led,HIGH); delay(2000); digitalWrite(buzzer1, LOW); } else { digitalWrite(led,LOW); } Serial.print(distance1); Serial.println(" cm"); delay(500); // you don't actually need the serial print. Either way it works with or without the serial print long duration2, distance2; digitalWrite(trigPin2, LOW); delayMicroseconds(2); digitalWrite(trigPin2, HIGH); delayMicroseconds(10); digitalWrite(trigPin2, LOW); duration2 = pulseIn(echoPin2, HIGH); distance2 = (duration2/2) / 29.1; if (distance2 < 10){ digitalWrite(buzzer1, HIGH); digitalWrite(led2,HIGH); delay(2000); digitalWrite(buzzer1, LOW); } else { digitalWrite(led2,LOW); } Serial.print(distance2); Serial.println(" cm"); delay(500); }