@Robin2: is not relevant or me. Practically these counter is like an simple and convenient alternative for using time interval. Also should be better than the use of time because it is independent of the load on each motor.
@TomGeorge: i want to control independently how much each gate it's open.
@MarkT: thanks for suggestion but is hard to implement these sensors because each motor is well assembled. Also i don't know if I open open one of these motor how could such a sensor be mount. Anyway, few counts error should not produce an important effect. I need 340 counts for each second of move, so 5-10 count difference would not be noticeable.