Curs d’Arduino – Exercicis: Sonar (HC-SR04)

Sonar hc-sr04

El sonar HC-SR04 és un element que permet controlar la proximitat d’objectes. El seu ús més directe és per a controlar moviments de robots, tot i que també pot tenir altres aplicacions en enginys voladors, com ara quadcopters o avions, controlats per Arduino.

 

Pràctiques:

Exemple 1.

Aquí hi ha un error, a veure…

#define trigPin 3
#define echoPin 2

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

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

  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  delay(100);
}

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;
}

Exemple 2

  • Instal·lar llibreria NewPing.
  • Mostrar dades del sonar pel monitor serial.
  • Mostrar les dades pel serial del Bluetooth en una App del mòbil.
  • Encendre un LED vermell quant la distancia sigui inferior a 5 cm i un de verd mentre sigui més gran de 5cm.
  • Si anem allunyant un objecte fer més llum a un LED.
  • Si anem apropant un objecte fer més llum a un LED.
  • Amb 3 leds representar el % de la distancia assignada.
// —————————————————————————
// Example NewPing library sketch that does a ping about 20 times per second.
// —————————————————————————
#include <Servo.h>
#include <NewPing.h>#define TRIGGER_PIN  3  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     2  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 20 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

#define SERVO_PIN  8
Servo ser1;

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

void setup() {
ser1.attach(SERVO_PIN);
pinMode(5, OUTPUT);
Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
delay(100);                // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.

//int cm = sonar.ping_cm(MAX_DISTANCE); // Send ping, get distance in cm and print result (0 = outside set distance range)
int cm = sonar.convert_cm(sonar.ping_median(7));
if (cm != 0)
{
int p = map(cm, 0, MAX_DISTANCE, 0, 180);
ser1.write(p);
Serial.print(cm);
Serial.print(”  “);
Serial.println(p);

p = map(cm, 0, MAX_DISTANCE, 0, 100);
if (p >= 66 && p <= 100)
Serial.println(“100-66%”);
if (p >= 33 && p <= 66)
Serial.println(“66-33%”);
if (p >= 1 && p <= 33)
Serial.println(“1-33%”);

//  int cm = sonar.convert_cm(sonar.ping_median(5));
//  //int cm = sonar.ping_cm(10); // Send ping, get distance in cm and print result (0 = outside set distance range)
int v = map(cm, 0, 25, 0, 255);
if (v > 255)
v = 255;

//  Serial.print(cm);
//  Serial.print(” “);
//  Serial.println(v);
analogWrite(5, v);
}
}

 

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