Quote:
Originally Posted by Thomas DeSilva
... I could tell about how many different speeds it was going by listening to the gearbox and watching the output shaft. Not exactly scientific, but it was precise enough for my needs.  |
... I was hoping that you had actually measured the number of speeds. This is an extremely flawed test plan.
8 bits of resolution across the entire servo pulse range gives you less than 4 bits of resolution across the active range. To properly run this test, you need at least 9 bits of resolution across 0.5ms-2.5ms, preferably more. apalrd did a great job of explaining what the signal looks like, and you need your test signal to be more precise that the measurement equipment (the vic/jag).
Calculate what your test signal resolution is, and use that to predict how many steps a "perfect" (infinite resolution) device would give. If you later measure a number of steps within a factor of 2 or 4 of this, your test signal doesn't have enough resolution.
Second, you need a better way of actually measuring the number of steps. Your ears just ain't going to cut it. An honestly, I wouldn't even really trust a method that involves measuring the rotational speed: That would put the motor's imperfections into your measurement of the speed controllers' quality.
Stick an oscilloscope across the outputs and measure duty cycle. Plot output duty cycle vs input duty cycle. You should get a piecewise step function. Again, you should have at least 4 input duty cycle points per step, or the test is flawed.