TKJ Electronics

Today I recieved a Ultrasonic Range Sensor bought on eBay.

It’s much like the Parallax Ping))), except that it has got a Trig and a Echo pin, instead of the Ping)))’s multipin (Trig and Echo on the same pin)

I quickly made some code in the Arduino IDE and got it running quick…

Just a sidenode from the physics class; as the sound is travelling thru air with a speed of 340 m/s, this can be recalculated to 0.034 cm/microsecond, which is the same as 29.411 microsecond/cm

Arduino with Ultrasonic Sensor

For those who may be interested the code is here:

/* Ultrasonic Sensor

This sketch reads a 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:
* +V connection of the Ultrasonic Sensor attached to +5V
* GND connection of the Ultrasonic Sensor attached to ground
* Trig connection of the Ultrasonic Sensor attached to digital pin 2
* Echo connection of the Ultrasonic Sensor attached to digital pin 3

created 25. Januar 2010
by Thomas Jespersen

*/


// this constant won't change.�  It's the pin number
// of the sensor's output:
const int TrigPin = 2;
const int EchoPin = 3;

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, mm;

// The Ultrasonic Sensor is triggered by a HIGH pulse of 2 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
digitalWrite(TrigPin, LOW);
delayMicroseconds(2);
digitalWrite(TrigPin, HIGH);
delayMicroseconds(5);
digitalWrite(TrigPin, LOW);

// Read the signal from the Ultrasonic Sensor a HIGH
// pulse whose duration is the time (in microseconds) from the sending
// of the Trig to the reception of its echo off of an object.
duration = pulseIn(EchoPin, HIGH);

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

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

delay(100);
}

long microsecondsToInches(long microseconds)
{
// According to Parallax's datasheet for the PING)))
// (another ultrasonic range sensor),
// 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.

// 340 m/s
// 34000 cm/s
// 34 cm/ms
// 0.034 cm/micros

// 1/0.034 cm/micros = 29.411 micros/cm

return microseconds / 29.411 / 2;
}

long microsecondsToMillimeters(long microseconds)
{
// The speed of sound is 340 m/s or 29 microseconds per centimeter,
// and then we multiply with 10 to get in in millimeters.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.

// 340 m/s
// 34000 cm/s
// 340000 mm/s
// 340 mm/ms
// 0.34 mm/micros

// 1/0.34 mm/micros = 2.9411 micros/mm
return microseconds / 2.9411 / 2;
}