Ultrasound Sensor

Projects Programming
1

So I have an ultrasound sensor. The kit in itself works fine. However, when I run it with the following code, sometimes distance returns the correct distance. Sometimes it returns a number above 32,000 (but which fluctuates). Can anyone see an obvious problem? I appreciate your help...

/* This function controls the panning servo for the ultrasound sensor
   so that the arduino can decide which way it points.
*/
void pan(int degreEs) // determines the number of degrees the servo pans.
{
  servoPan.writeMicroseconds(ccwLim - rtAngle + (degreEs * 10));
}
/* This function returns an accurate distance from the ultrasound sensor
   using timings and geometry.
*/
int distanceFind(){                     // finds the distance of an object
  //int distance;                         // this is now a global variable.
  distance = 0;
  unsigned long echoTime;               // this measures the length of the echo
  echoTime = 0;
  
  digitalWrite(trigPin, LOW);           // sets the trigger pin to low to preven erraneous measurement
  delay(20);
  
  digitalWrite(trigPin, HIGH);          // send a pulse to the trigger pin
  delay(10);                            // must be a 10us pulse
  digitalWrite(trigPin, LOW);           // end of pulse
  
  echoTime = pulseIn(echoPin, HIGH);    // measures length of incoming pulse
  echoTime = echoTime / 2;              // which must be divided by two (as distance is there and back)
  distance = int(echoTime / 2.9);       // see maths in lab book
    
  //converts the distance integer to a string for printing
     String strOne =  String(distance, DEC); 
     char dist[6]; 
     strOne.toCharArray(dist, 6); //converts string to char array
     codeBotLCD(dist); //prints the distance from the US sensor
  return distance;
}
2

I can't imagine why the distanceFind() function needs to return a global variable. I can't imagine why distance needs to be global.

3

well it didn't work with a local variable either so not sure what the relevancy is

4

so not sure what the relevancy is

I'm not sure how your posting snippets of code is relevant, either, so I guess we are even.

5

Your delays are in milliseconds, should be delayMicroseconds. Don't know if it will make a difference.

delay(10); // must be a 10us pulse

6

groundfungus:
Your delays are in milliseconds, should be delayMicroseconds. Don't know if it will make a difference.

Thanks.... it hasn't solved the problem but has been duly changed!

7 
String strOne =  String(distance, DEC); 
     char dist[6]; 
     strOne.toCharArray(dist, 6); //converts string to char array

What a horrible way of doing it...

Abandon the String class and do something like this:

 char dist[6];
sprintf(dist,"%d",distance);