One goal for my AutoMove robotic arm is automatic object detection. Here are the inital tests to see if the sonar sensor can see a few objects. A 'COMP444 feature', an eraser, and a bottle of Wite-Out are put under the sensor and measurements are sent to serial. The sonar echo time measurements are filtered by the Arduino. I used Excel to plot the results so you could see how it worked for yourself.

Here are the results:

It worked really well! The 'feature' wasn't detected, but that's okay. (It was a long shot, anyway.)

I made a short video of the measurements being performed: [Sonar Object Detection Experiment #1 - YouTube.com]

Here's a link to the relevant code: [GitHub permalink to line 327 of AutoMove.cpp, git commit #5befc96]

 while (1)
 {
   Serial.print(F("Sonar sum: "));
   delay(500);
   int count = 0;
   uint32_t sum = 0;
   do {
     sum += sonar.getMeasurement();
     delay(25);
   } while (count++ < 100);
   Serial.println(sum);
 }