I’m eyeing the 172:1 gearmotor with 48 CPR encoder (#2288, pololu.com/product/2288). One thing I’m interested in in comparing this and motors from other sources (mainly robotshop) is the way the encoder resolution is cited. They give pulses-per-rotation at the motor shaft, and the gearbox output shaft, which differ by the gear ratio. That’s fine and makes sense. I’m wondering, however, if what’s cited is the number of windows in the encoder disk (or, equivalently, poles in the magnet for hall-effect encoders), or the maximum achievable resolution, which is four times this (counting both rising and falling edges of both encoder channels).
Separately, what’s a good duration for an encoder interrupt service routine? 100us? 400us? At the speeds these motors turn, and the stated resolutions, it makes a difference whether theyr’e citing the x4 maximum resolution, or x1 minimum one. I don’t want to get stuck with two $40 motors whose encoder output is faster than my mega can handle, nor do I want such low resolution that I don’t have the option of implementing smooth PID speed control.