Arduino Circuits – Ultrasonic sensor

/**

• HC-SR04 Demo
• Demonstration of the HC-SR04 Ultrasonic Sensor
• Date: August 3, 2016
  • Description:
• Connect the ultrasonic sensor to the Arduino as per the
• hardware connections below. Run the sketch and open a serial
• monitor. The distance read from the sensor will be displayed
• in centimeters and inches.
  • Hardware Connections:
• Arduino | HC-SR04
• ——————-
• 5V | VCC
• 7 | Trig
• 8 | Echo
• GND | GND
  • License:
• Public Domain
  */

// Pins
const int TRIG_PIN = 7;
const int ECHO_PIN = 8;

// Anything over 400 cm (23200 us pulse) is “out of range”
const unsigned int MAX_DIST = 23200;

void setup() {

// The Trigger pin will tell the sensor to range find
pinMode(TRIG_PIN, OUTPUT);
digitalWrite(TRIG_PIN, LOW);

// We’ll use the serial monitor to view the sensor output
Serial.begin(9600);
}

void loop() {

unsigned long t1;
unsigned long t2;
unsigned long pulse_width;
float cm;
float inches;

// Hold the trigger pin high for at least 10 us
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);

// Wait for pulse on echo pin
while ( digitalRead(ECHO_PIN) == 0 );

// Measure how long the echo pin was held high (pulse width)
// Note: the micros() counter will overflow after ~70 min
t1 = micros();
while ( digitalRead(ECHO_PIN) == 1);
t2 = micros();
pulse_width = t2 – t1;

// Calculate distance in centimeters and inches. The constants
// are found in the datasheet, and calculated from the assumed speed
//of sound in air at sea level (~340 m/s).
cm = pulse_width / 58.0;
inches = pulse_width / 148.0;

// Print out results
if ( pulse_width > MAX_DIST ) {
Serial.println(“Out of range”);
} else {
Serial.print(cm);
Serial.print(” cm \t”);
Serial.print(inches);
Serial.println(” in”);
}

// Wait at least 60ms before next measurement
delay(60);
}