HC SR-04 and servo problem.

Hey guys, I’m new to the forum and to Arduino.
I have cobbled to gethe r this sketch. The idea is to have to ultrasonic sensors pointing in different directions both driving a servo. One driving the servo to one side the other sensor driving the servo to the other side. When both sensors are in range the servo will be driven to the middle.
The problem I’m having is I can only get the left sensor to work. When the right servo doesn’t seem to be putting out a reading. It prints 0 to the serial port.
Please help.
Here is the code I’m using.

]//* This sketch is trying to read from to HC-SR04 sensors and drive a servo . One sensor drives
//the servo from0-80 deg the other from 100-10 deg.

Servo myservo;

#define trigPin 13
#define echoPin 12
#define echoPinr 7 //defining pins

void setup()

Serial.begin (9600);
pinMode (trigPin, OUTPUT);
pinMode (echoPin, INPUT);
pinMode (echoPinr, INPUT);

void loop()
int val; // declared the int “val”
int valr; // declared the int “valr”
int duration, distance; // declared the int “duration and distance”
int durationr, distancer; // declared the int “durationr and distancer”
digitalWrite(trigPin, HIGH); // turn on signal to ultrasonic sensor

digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);
distance = (duration/2) / 29.1;
val = map(distance, 10, 50, 80, 0); // Getting the value from the sensor
durationr = pulseIn(echoPinr, HIGH);
distancer = (durationr/2) / 29.1;

valr = map(distancer, 10, 50, 100, 180);

if (val <10 >100 && valr <10 >100) //If both sensors in range servo goes to middle
myservo.write (90);

else if (val >10 <100) //If this sensor in range, write val to servo

else if (valr >10 <100) //If this sensor in range, write valr to servo

else myservo.write(90); //if both sensors out of range then servo write to pos 90

Serial.print(“Left” );
Serial.print(distance); //Prints the distance of the left sensor

Serial.print(“Right” );
Serial.print(distancer); //Prints the distance of the right sensor



if (val <10 >100 && valr <10 >100)


You appear to be trying to trigger two sensors using one pin. After triggering both sensors, you wait for the echo from the first one, and time how long it took to get. Then, you seem to think that because you weren't listening, the other ping hasn't gone out yet.

Wrong. The ping has gone out, been reflected, and died out before you get around to listening.

Welcome to these forums. Please read and follow the instructions contained in the sticky post, the first post on this forum's opening page. - Scotty

Hey, I am getting back into Arduino myself and my first time on the forums. I built a sonar with your sensor with a plan off instructables. I had some hiccups along the way but here is a link to the issue I am having currently.


This will have links for my code, the original sonar sketch and the processing code for the sonar as well. Its a pretty fun project. Something that helped me when I was wiring was having a basic sketch handy to make sure your HC SR04 is working first before having it drive the servo.