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Arguino distance sensor


PING range finder

The PING range finder is an ultrasound sensor from Parallax able of detecting objects up to a 3 mts distance. The sensor counts with 3 pins, two are dedicated to power and ground, while the third one is used both as input and output.

 

The pin dedicated to make the readings has to be shifting configuration from input to output according to the PING specification sheet. First we have to send a pulse that will make the sensor send an ultrasound tone and wait for an echo. Once the tone is received back, the sensor will send a pulse over the same pin as earlier. The width of that pulse will determine the distance to the object.

 

The example shown here was mounted by Marcus Hannerstig, while the software was created by David Cuartielles. The board is connected as explained using only wires coming from an old computer.

 

 

Ultrasound sensor connected to an Arduino USB v1.0

 

 
/* Ultrasound Sensor
 *------------------
 *
 * Reads values (00014-01199) from an ultrasound sensor (3m sensor)
 * and writes the values to the serialport.
 *
 * http://www.xlab.se | http://www.0j0.org
 * copyleft 2005 Mackie for XLAB | DojoDave for DojoCorp
 *
 */

int ultraSoundSignal = 7; // Ultrasound signal pin
int val = 0;
int ultrasoundValue = 0;
int timecount = 0; // Echo counter
int ledPin = 13; // LED connected to digital pin 13

void setup() {
  beginSerial(9600);                  // Sets the baud rate to 9600
  pinMode(ledPin, OUTPUT);            // Sets the digital pin as output
}

void loop() {
 timecount = 0;
 val = 0;
 pinMode(ultraSoundSignal, OUTPUT); // Switch signalpin to output

/* Send low-high-low pulse to activate the trigger pulse of the sensor
 * -------------------------------------------------------------------
 */

digitalWrite(ultraSoundSignal, LOW); // Send low pulse
delayMicroseconds(2); // Wait for 2 microseconds
digitalWrite(ultraSoundSignal, HIGH); // Send high pulse
delayMicroseconds(5); // Wait for 5 microseconds
digitalWrite(ultraSoundSignal, LOW); // Holdoff

/* Listening for echo pulse
 * -------------------------------------------------------------------
 */

pinMode(ultraSoundSignal, INPUT); // Switch signalpin to input
val = digitalRead(ultraSoundSignal); // Append signal value to val
while(val == LOW) { // Loop until pin reads a high value
  val = digitalRead(ultraSoundSignal);
}

while(val == HIGH) { // Loop until pin reads a high value
  val = digitalRead(ultraSoundSignal);
  timecount = timecount +1;            // Count echo pulse time
}

/* Writing out values to the serial port
 * -------------------------------------------------------------------
 */

ultrasoundValue = timecount; // Append echo pulse time to ultrasoundValue

serialWrite('A'); // Example identifier for the sensor
printInteger(ultrasoundValue);
serialWrite(10);
serialWrite(13);

/* Lite up LED if any value is passed by the echo pulse
 * -------------------------------------------------------------------
 */

if(timecount > 0){
  digitalWrite(ledPin, HIGH);
}

/* Delay of program
 * -------------------------------------------------------------------
 */

delay(100);
} 
 
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