OK, I did as you said, and it did the same thing. I plugged the IR into a different slot, and it started to work, but it didn't work entirely. It detected things and scanned as it should, but it only scanned a small area of the servo's radius. I think that this is because I am not using an HS-311 as instructed, but an HS-55. The 55 may be slower and so the code is not meant for it. To test this theory, I decided to swap to an HS-325HB, but then I got no response at all. I then swapped the batteries out for new ones, but still no response so I swapped the scanning servo back to the HS-55. Still no response. I switched back to the old batteries. I got a response once, then no more. Am I missing something? This project is driving me crazy! My questions are:
1) Would using a servo different from that used in the tutorial be the problem, if so would an HS-311 solve all my problems?
2) Why did the old batteries work and the new ones didn't when both are alkaline 1.5V AA's?
3) Could there be a problem with my microcontroller?
I found the solution! It's a bit embarrassing, but you were supposed to plug it in to the 3rd sensor slot, not the first. I must have mistaken weird jittering for response. Sorry I wasted your time, everyone, but it was a valuable learning experience for me. It works now, but instead of chasing objects and running into them, it tries to go around. I had it spin around my leg for a while. Not what I expected, but it's OK.