Using 3 ultrasound sensors without libreries and one LED


const byte numSensors = 3; //const means constant variables,bytes means that we are using small space in memory, numSensor is the variable name.
const byte ECHO_PIN[numSensors] = {2, 5, 8};//We create an array to be used in a for loop
const byte TRIG_PIN[numSensors] = {3, 4, 7};

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  for (byte s=0; s < numSensors; s++) { /*Due to for loop, we reduce pinMode instructions from 6 to only 2.
  
  pinMode(3, OUTPUT);
  pinMode(2, INPUT);
  pinMode(4, OUTPUT);
  pinMode(5, INPUT);
  pinMode(7, OUTPUT);
  pinMode(8, INPUT); */
  
  
    pinMode(TRIG_PIN[s], OUTPUT);
    pinMode(ECHO_PIN[s], INPUT);
  }
}

float readDistanceCM(byte s) { /* This is a function with a parameter (s) and return a value that depends on the duration of 
                                a pulseIn function and a mathematical calculus with the velocity of sound divided by 2 because 
                                the ultrasound goes and return back*/


  digitalWrite(TRIG_PIN[s], LOW);/* We need to have the trigger pin controlled to a low value in order to measure the duration of the HIGH value that is proportional to the distance of the sensor*/
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN[s], HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN[s], LOW);
  int duration = pulseIn(ECHO_PIN[s], HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  bool isNearby = false;
  Serial.print("Measured distance: ");
  for (byte s=0; s< numSensors; s++) {
    float distance = readDistanceCM(s);
    isNearby |= distance < 100;
    Serial.print(distance);
    Serial.print(" ");
  }
  Serial.println();
  digitalWrite(LED_BUILTIN, isNearby ? HIGH : LOW);
  delay(100);
}

int ledPin1 = 2;
int ledPin2 = 3;
int ledPin3 = 4;

int trigPin1 = 6; // trig és el emisor del ultrasonido y echo el receptor
int echoPin1 = 7;

int trigPin2 = 8;
int echoPin2 = 9;

int trigPin3 = 10;
int echoPin3 = 11;

void setup() {
  Serial.begin (9600);
  pinMode(trigPin1, OUTPUT);
  pinMode(echoPin1, INPUT);
 
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
 
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin3, INPUT);
 
  pinMode(ledPin1, OUTPUT);
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  digitalWrite(ledPin3, HIGH);
}

void firstsensor(){ // This function is for first sensor.
  int duration1, distance1;//I create 2 local variables to have an space in the microcontroller memory
  digitalWrite (trigPin1, HIGH);// Activates trigPin to send the ultrasonic signal
  delayMicroseconds (10);
  digitalWrite (trigPin1, LOW);
  duration1 = pulseIn (echoPin1, HIGH);// Activates echopin in high to recive the ultrasound backwards.
  distance1 = (duration1/2) / 29.1; // converts value of ultrasound duration like a time of flight into a distance with using a mathematical formula. 

      Serial.print("1st Sensor: ");
      Serial.print(distance1); 
      Serial.print("cm    ");

  if (distance1 < 50) {  // Change the number for long or short distances.
    digitalWrite (ledPin1, HIGH);
  } else {
    digitalWrite (ledPin1, LOW);
  }   
}
void secondsensor(){ // This function is for second sensor.
    int duration2, distance2;
    digitalWrite (trigPin2, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin2, LOW);
    duration2 = pulseIn (echoPin2, HIGH);
    distance2 = (duration2/2) / 29.1;
 
      Serial.print("2nd Sensor: ");
      Serial.print(distance2); 
      Serial.print("cm    ");
  
    if (distance2 < 50) {  // Change the number for long or short distances.
      digitalWrite (ledPin2, HIGH);
    }
 else {
      digitalWrite (ledPin2, LOW);
    }   
}
void thirdsensor(){ // This function is for third sensor.
    int duration3, distance3;
    digitalWrite (trigPin3, HIGH);
    delayMicroseconds (10);
    digitalWrite (trigPin3, LOW);
    duration3 = pulseIn (echoPin3, HIGH);
    distance3 = (duration3/2) / 29.1;

      Serial.print("3rd Sensor: ");  
      Serial.print(distance3); 
      Serial.print("cm    ");
  
    if (distance3 < 50) {  // Change the number for long or short distances.
      digitalWrite (ledPin3, HIGH);
    }
 else {
      digitalWrite (ledPin3, LOW);
    }  
}

void loop() {
Serial.println("\n");
firstsensor();
secondsensor();
thirdsensor();
  delay(100);
}



Solution with Liquid Crystal library. Here

#include #include #include "LiquidCrystal.h" LiquidCrystal lcd(A0, A1, A2, A3, A4, A5); const int trigPin1 = 9; const int echoPin1 = 10; const int trigPin2 = 5; const int echoPin2 = 6; const int trigPin3 = 7; const int echoPin3 = 8; long duration1; long duration2; long duration3; int distanceCm1, distanceInch1; int distanceCm2, distanceInch2; int distanceCm3, distanceInch3; void setup() { Serial.begin(9600); lcd.begin(16,2); pinMode(trigPin1, OUTPUT); pinMode(echoPin1, INPUT); pinMode(trigPin2, OUTPUT); pinMode(echoPin2, INPUT); pinMode(trigPin3, OUTPUT); pinMode(echoPin3, INPUT); pinMode(12,OUTPUT); pinMode(11,OUTPUT); pinMode(3,OUTPUT); } void loop() { digitalWrite(trigPin1, LOW); delayMicroseconds(2); digitalWrite(trigPin1, HIGH); delayMicroseconds(10); digitalWrite(trigPin1, LOW); duration1 = pulseIn(echoPin1, HIGH); digitalWrite(trigPin2, LOW); delayMicroseconds(2); digitalWrite(trigPin2, HIGH); delayMicroseconds(10); digitalWrite(trigPin2, LOW); duration2 = pulseIn(echoPin2, HIGH); digitalWrite(trigPin3, LOW); delayMicroseconds(2); digitalWrite(trigPin3, HIGH); delayMicroseconds(10); digitalWrite(trigPin3, LOW); duration3 = pulseIn(echoPin3, HIGH); distanceCm1= duration1*0.034/2; distanceInch1 = duration1*0.0133/2; distanceCm2= duration2*0.034/2; distanceInch2 = duration2*0.0133/2; distanceCm3= duration3*0.034/2; distanceInch3 = duration3*0.0133/2; Serial.print("Distance1: "); Serial.println(distanceCm1); lcd.clear(); lcd.setCursor(0,0); lcd.print("Ultrasonic1 "); lcd.setCursor(12,0); lcd.print(distanceCm1); //delay(500); Serial.print("Distance2: "); Serial.println(distanceCm2); lcd.setCursor(0,1); lcd.print("U2 "); lcd.setCursor(3,1); lcd.print(distanceCm2); Serial.print("Distance3: "); Serial.println(distanceCm3); lcd.setCursor(9,1); lcd.print("U3 "); lcd.setCursor(12,1); lcd.print(distanceCm3); if(distanceCm1 < 150) { digitalWrite(3,HIGH); // LED ON } if(distanceCm1 >150) { digitalWrite(3,LOW); // LED OFF } if(distanceCm2 < 150) { digitalWrite(12,HIGH); // LED ON } if(distanceCm2 > 150) { digitalWrite(12,LOW); // LED OFF } if(distanceCm3 < 150) { digitalWrite(11,HIGH); // LED ON } if(distanceCm3 > 150) { digitalWrite(11,LOW); // LED OFF } delay(1000); }