4 HC-04 Ultrasonic sensor

Projects General Guidance
1

Hello everyone,
I just received my 4 hc-04 that I had ordered on eBay.
I had written some code to try to get it working.

int trig1 = 22; // attach pin 3 to Trig
int trig2 = 23; // attach pin 23 to Trig
int trig3 = 24; // attach pin 24 to Trig
int trig4 = 25; // attach pin 25 to Trig
int echo1 = 30; //attach pin 30 to Echo
int echo2 = 31; //attach pin 31 to Echo
int echo3 = 32; //attach pin 32 to Echo
int echo4 = 33; //attach pin 33 to Echo


void setup() {


// initialize serial communication:
Serial.begin(9600);
}

void loop()
{
pinMode(echo1,INPUT);
pinMode(echo2,INPUT);
pinMode(echo3,INPUT);
pinMode(echo4,INPUT);
pinMode(trig1, OUTPUT);
pinMode(trig2, OUTPUT);
pinMode(trig3, OUTPUT);
pinMode(trig4, OUTPUT);

long duration1, cm1;
long duration2, cm2;
long duration3, cm3;
long duration4, cm4;

/*
//TEST ONLY DO NOT ENABLE
pinMode(trig1, OUTPUT);
pinMode(trig2, OUTPUT);
pinMode(trig3, OUTPUT);
pinMode(trig4, OUTPUT);
digitalWrite(trig1, LOW);
digitalWrite(trig2, LOW);
digitalWrite(trig3, LOW);
digitalWrite(trig4, LOW);
delayMicroseconds(2);
digitalWrite(trig1, HIGH);
digitalWrite(trig2, HIGH);
digitalWrite(trig3, HIGH);
digitalWrite(trig4, HIGH);
delayMicroseconds(5);
digitalWrite(trig1, LOW);
digitalWrite(trig2, LOW);
digitalWrite(trig3, LOW);
digitalWrite(trig4, LOW);
*/
digitalWrite(trig1, LOW);
delayMicroseconds(2);
digitalWrite(trig1, HIGH);
delayMicroseconds(5);
digitalWrite(trig1, LOW);
duration1 = pulseIn(echo1, HIGH);
delayMicroseconds(9000);
digitalWrite(trig2, LOW);
delayMicroseconds(2);
digitalWrite(trig2, HIGH);
delayMicroseconds(5);
digitalWrite(trig2, LOW);
duration2 = pulseIn(echo2, HIGH);
delayMicroseconds(9000);
digitalWrite(trig3, LOW);
delayMicroseconds(2);
digitalWrite(trig3, HIGH);
delayMicroseconds(5);
digitalWrite(trig3, LOW);
duration3 = pulseIn(echo3, HIGH);
delayMicroseconds(9000);
digitalWrite(trig4, LOW);
delayMicroseconds(2);
digitalWrite(trig4, HIGH);
delayMicroseconds(5);
digitalWrite(trig4, LOW);
duration4 = pulseIn(echo4, HIGH);
delayMicroseconds(9000);

// convert the time into a distance
cm1 = microsecondsToCentimeters(duration1);
cm2 = microsecondsToCentimeters(duration2);
cm3 = microsecondsToCentimeters(duration3);
cm4 = microsecondsToCentimeters(duration4);
Serial.print(cm1);
Serial.print(" cm for NO1");
Serial.println();
Serial.print(cm2);
Serial.print(" cm for NO2");
Serial.println();
Serial.print(cm3);
Serial.print(" cm for NO3");
Serial.println();
Serial.print(cm4);
Serial.print(" cm for NO4");
Serial.println();

delay(100);
}


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;
}

but I can only seem to get 1 and 3 to work and the others return an 0 cm
Any help will be appreciated.
BTW I am using an Arduino Mega clone and this module has 4 pins

Yours Faithfully,
12458

2

Hi,
Put your pinMode statements in setup(), not loop().
The long declarations can go before the setup().

How have you got your sensors arranged?

Tom.... :slight_smile:

3

Maybe you do not wait long enough between the single measurements
(to avoid picking up signals from a previous ping), you use 9000 µs = 155cm.

I reorganized your code a bit without changing the HC-04 logic

byte trigger[4] = { 22, 23, 24, 25 };
byte echo[4] = { 30, 31, 32, 33 };

unsigned long duration[4];
unsigned long distance[4];
byte index;

void setup() {
  for (index = 0; index < 4; index++) {
    pinMode(echo[index], INPUT);
    pinMode(trigger[index], OUTPUT);
  }
  Serial.begin(9600); // why not 115200 ?
}

void loop()
{
  for (index = 0; index < 4; index++) {
    measure(index);
    delayMicroseconds(9000); // wait for US to fade out (= 155cm??????)
  }
  for (index = 0; index < 4; index++) {
    Serial.print(distance[index]);
    Serial.print(F(" cm for NO"));
    Serial.println(index+1);
  }
  //  delay(100); // what should this be good for?
}

void measure(byte idx) {
// the pins start out LOW and will be reset to low after usage
//  digitalWrite(trigger[idx], LOW);
//  delayMicroseconds(2);
  digitalWrite(trigger[idx], HIGH);
  delayMicroseconds(5);
  digitalWrite(trigger[idx], LOW);
  duration[idx] = pulseIn(echo[idx], HIGH);  // add a timeout here... see documentation of pulseIn
  distance[idx] = microsecondsToCentimeters(duration[idx]);
}

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;
}

You should have a look at the NewPing library,
which does a very good job without using pulseIn.