Thursday, January 20, 2005

Expanded Mode Mojo Testing

Bob and I met and tested his code for controlling more than 5 motors at once. It worked fine, he's overcome a few steep hurdles to get to this point. One of which was traced back to the compiler environment not handling a 16bit word as expected and causing the script to abort early.

We tested bob's program with normal range (1-2ms) pulses, then tested the mojo board on it's "extened range" (.5-2.5ms) pulses. That corresponds to -8000 to +8000 on the hex code.

In normal mode, there is about 90deg of rotation from the small servos. In extended mode, we had hoped for a full 180deg. But all we witnessed was about 135deg of rotation. Wheather using 6000 or 8000 didn't seem to matter much.

Tonight I revisited the issue and set expanded mode to 8000 then 6000. I noticed that there was hardly any difference at all. Plus the motors were getting hot. We didn't notice this with the larger motors.

I loosened the screws on one of the motors and it's range increased. So I'm suspecting poor alignment and possibly out of alignment internal stops. (I've skipped teeth on some of these motors, while turning them by hand. This is bad.) If the internal stop is out of position, it will be stalling the motor in middle ground positions. I may try cutting the internal stops out entirely on one to see how far the 8000 will go.

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