When using ultrasonic sensors, pulsein always returns 0

Projects General Guidance
1

I am trying to make a radar with to ultrasonic sensors that are at a 30ish degree angle away from each other. If on detects an object, they will turn to try ad face the object. The issue im facing is that one of the sensors always returns 0 when i call the pulsein command. I am certain that both sensors are not broken and that the wiring is fine. I am sure that the issue is not interference since i am running the sensos individually with a half second delay between each use. Any suggestions on how i can get it to work?
Heres the code:

const int trigPinA = 12; // Trigger pin for Sensor A
const int echoPinA = 11; // Echo pin for Sensor A
const int trigPinB = 9;  // Trigger pin for Sensor B
const int echoPinB = 10; // Echo pin for Sensor B

void setup() {
    Serial.begin(9600);
    Serial.println("Ultrasonic Sensors Initialized!");

    pinMode(trigPinA, OUTPUT);
    pinMode(echoPinA, INPUT);

    pinMode(trigPinB, OUTPUT);
    pinMode(echoPinB, INPUT);
}

void loop() {
    // Measure and print distance for Sensor A
    float distanceA = measureDistance(trigPinA, echoPinA);
    Serial.print("Distance A: ");
    Serial.println(distanceA >= 0 ? String(distanceA) + " cm" : "Error");

    // Short delay to avoid interference
    delay(500);

    // Measure and print distance for Sensor B
    float distanceB = measureDistance(trigPinB, echoPinB);
    Serial.print("Distance B: ");
    Serial.println(distanceB >= 0 ? String(distanceB) + " cm" : "Error");

    // Wait before repeating
    delay(500);
}

float measureDistance(int trigPin, int echoPin) {
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    long duration = pulseIn(echoPin, HIGH, 30000); // 30 ms timeout
    if (duration == 0) return -1; // No valid pulse received

    float distance = (duration / 2.0) * 0.0343; // Calculate distance in cm
    return distance;
}
2

Review your connections as your code worked correctly in the wokwi simulator.

3

Which pair? Try moving pin 9 to another pin (my guess about a timer on pin 9).

1 Like
4

I am facing the same issue
My code:

int trig = 3;
int echo = 2;
int pie = 4;

double cm;
int dur;

void setup()
{
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(pie, OUTPUT);
}

void loop()
{
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  
  dur = pulseIn(echo, HIGH);
  
  cm = dur * 0.034 / 2;
  
  if (cm <= 200){
    tone(pie, 262, 500);
  }
  
  Serial.println(cm);
  
  delay(200);
}

It works fine on tinkercad but never real life. I am using an arduino mega

5

Send pictures of the wiring and also try changing the wires

6

@thunder200911133 - you should start your own topic. Not all similar problems have the same cause or solution, and you are distracting from the original poster.

7

@arduinojanuary NO.

8

Wdym. Are you talking about the part where I suggested changing wires.
Clarification- I just meant try replacing the wires with better wires.

Do correct me if I have given wrong suggestions

9

I don't speak Welsh, whatever this is. Do not encourage topic hijacking.

10

Sorry i use it as an abbreviation for What do you mean.
I apologise, I won't do this again

1 Like
11

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