Arduino PWM output

[slijin]

Originally Posted by sand500

Why does the higher end of the pwm, have a smaller range, 200-255, while the lower end of the pwm has a bigger range, 40-170. When I was running the motor, I could see the motor hit a higher speed in the 40-170 range than in the 200-255. So why would a motor rotate faster in one direction than in another direction?

Again, purely hypothetical here:

There are multiple reasons that this could happen, both electrical and mechanical.

On the electrical side, it could be an intentional design point (unlikely). It could also be that it's designed to take a different type of pulse (also unlikely). The most probable reason is an amalgam of 1) manufacturing inconsistencies and 2) a design "flaw" stemming from the circuit design (see the discussions about Victor and Jaguar signal driving; I can't do an explanation of these mechanisms justice, nor will I attempt to).

On the mechanical side, it could be a damaged bearing/bushing or shaft that gunks up in one direction and offers no resistance in the other (almost like a ratchet).