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- /* HC-SR04 Sensor
- This sketch reads an HC-SR04 ultrasonic rangefinder and returns the distance to the closest object in range. To do this, it sends a pulse to the sensor to initiate a reading, then listens for a pulse to return. The length of the returning pulse is proportional to the distance of the object from the sensor.
- The circuit:
- * VCC connection of the sensor attached to +5V
- * GND connection of the sensor attached to the ground.
- * TRIG connection of the sensor attached to digital pin 2
- * ECHO connection of the sensor attached to digital pin 4
- */
- const int trigPin = 2;
- const int echoPin = 4;
- void setup() {
- // initialize serial communication:
- Serial.begin(9600);
- }
- void loop()
- {
- // establish variables for the 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);
- delayMicroseconds(2);
- digitalWrite(trigPin, HIGH);
- delayMicroseconds(10);
- 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(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;
- }
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