What's wrong with this codes:

Jarvan

The second Ping sensor on the right as the picture shown above. In order to make the Activitybot moves parallel with the wall.

  while(1)
  {
      int n1,n2;
      n1 = Right_distance();
      pause(500);
      n2 = Right_distance();
      if(n1 > n2)  // moving close to the wall 
         drive_speed(30,40);
      if(n1 < n2)  // moving away to the wall
         drive_speed(40,30);
      else drive_speed(30,30);
  }

When the ActivityBot moves away, it can turn back, but if it moves close to the wall, it can not turn to the other side.
It's seems to simple but I can find what is wrong.

Andy Lindsay (Parallax)

Try this:

      if(n1 > n2)  // moving close to the wall 
         drive_speed(30,40);
      else if(n1 < n2)  // moving away to the wall
         drive_speed(40,30);
      else drive_speed(30,30);

You can also incorporate deadband by saying things like: if(n1 > n2 + 4)....else if(n1 < n2 - 4)... else...

Andy Lindsay (Parallax)

Jarvan,

Please let us know if this solution had the desired effect.

Thanks, Andy

Andy Lindsay (Parallax)

On closer inspection of the robot picture, I noticed that wires are connecting the Ping))) sensors to the I/O pins. The 3.3 V propeller input needs protection from the 5 V Ping))) output. Here is an example of a Ping))) circuit with the correct resistor protection applied:

http://learn.parallax.com/propeller-c-simple-devices/sense-distance-ping

Jarvan

Andy,

Thank you very much , the problem have been solved.
I have made two stupid mistakes, if..else..programming mistake and incorrect circuit connection .

Andy Lindsay (Parallax)

Hi Jarvan,

Thank you for the update. I will mark this thread solved.

Andy