HC-SR04P (NOT HC-SR04) Ultrasonic Sensor Distance Return Zero

Other Hardware Sensors
1

I having issue when using HC-SR04P (not HC-SR04)

The sensor will always return 0 then the true distance.

Below is the code:

#define echoPin 7
#define trigPin A2

// defines variables
long duration; // variable for the duration of sound wave travel
int distance; // variable for the distance measurement

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}
void loop() {
  // Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  // Calculating the distance
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
  // Displays the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
}

Below is the output:

...
10:46:42.344 -> Distance: 8 cm
10:46:43.020 -> Distance: 0 cm
10:46:43.020 -> Distance: 8 cm
10:46:43.687 -> Distance: 0 cm
10:46:43.731 -> Distance: 8 cm
10:46:44.412 -> Distance: 0 cm
10:46:44.412 -> Distance: 8 cm
10:46:45.100 -> Distance: 0 cm
10:46:45.100 -> Distance: 8 cm
10:46:45.804 -> Distance: 0 cm
10:46:45.804 -> Distance: 8 cm
10:46:46.501 -> Distance: 0 cm
...
2

By looking at the documentation, you seem to be hitting the sensor way to often. Try waiting for a second or longer before triggering again.

3

Hi, thanks for the reply.

But one second is too long for me as I'm trying to detect objects in front while it was moving. :sweat_smile:

4

It might be wise to try a delay of x time. I'd start with delay(10) and work up from there till a good delay time has been reached.

A delay using millis() would not stop the rest of loop() from running.

unsigned long sr04Interval = 10;
unsigned long pastsro4Time;
//
void loop() {
 
if( (millis() - pastsro4Time) >= sro4Interval )
{
// Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  // Calculating the distance
  distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
  // Displays the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  pastsro4Time = millis();
} //if( (millis() - pastsro4Time) >= sro4Interval )

distance=0; // something to do when not pinging

}

something like that, not tested.

the op might want to consider setting a timeout value for pulse in of less than a second pulseIn(pin, value, timeout)

The OP might consider the mixed data types used to determine distance and the possibility of error introduction.

Here the OP declares int distance; // variable for the distance measurement an int.

Here the OP declared long duration; a long int.

Here the OP does mixed data type math distance = duration * 0.034 / 2; The OP might benefit from making distance into a float and doing distance = (float)duration * 0.034 / 2.0;

5

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