HC-SR04 error

Hello all, i bought a hc-sr04 sensor a few days ago and i´m trying to make a sketch. i have tried sereval that i found in the internet with the same result, my sensor always returns a value equal to 2 or 3, never mind the proximity. This is my code:

const int trigPin = 2;
const int echoPin = 4;

void setup() {
// initialize serial communication:

void loop()
// establish variables for duration of the ping,
// and the distance result in inches and centimeters:
long duration, inches, cm;

// The sensor is triggered by a HIGH pulse of 10 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
pinMode(trigPin, OUTPUT);
digitalWrite(trigPin, LOW);
digitalWrite(trigPin, HIGH);
digitalWrite(trigPin, LOW);

// Read the signal from the sensor: a HIGH pulse whose
// duration is the time (in microseconds) from the sending
// of the ping to the reception of its echo off of an object.
pinMode(echoPin, INPUT);
duration = pulseIn(echoPin, HIGH);

// convert the time into a distance
inches = microsecondsToInches(duration);
cm = microsecondsToCentimeters(duration);
Serial.print(" ");
Serial.print("in, ");

long microsecondsToInches(long microseconds)
// According to Parallax's datasheet for the PING))), there are
// 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
// second). This gives the distance travelled by the ping, outbound
// and return, so we divide by 2 to get the distance of the obstacle.
// See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
return microseconds / 74 / 2;

long microsecondsToCentimeters(long microseconds)
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.
return microseconds / 29 / 2;

The connections are ok, phisically it seems to be ok, i need you help, thanks.

In your code, move the pinMode() functions to setup(). That is the only thing in your code that looks incorrect. I use pretty much the same code for my HC-SR04’s. Is the supply to the rangefinder 5V? .Is the ground connected to Arduino ground?

moved and no results, i have tried with usb and with batteries supply and nothing, and yes, the ground is connected

I connected an HC-SR04 to my Uno with trigger to pin 2 and echo to pin 4 like your setup. I moved the pinModes to setup and ran the sketch. It worked fine, returning the range, so I don't know what else to tell you. I did set the delay to 1000 (versus 100 in your original code) to slow down serial output.


Try make some delay (maybe 100 microseconds = 1 millisecond) between trigger finish and reading the duration.
I think you must give the signal enough time to travel and return back, then measure the duration and calculate distances.

try something like this.


good luck