Optical encoder A and B channels are interchangeable?

Hello, I have motor with optical encoder, I was able to find pinout, but I’m not sure about the correct order of A and B channels. Are they interchangeable, can I connect them in any order?

I will use Pololu Jrk 12v12 to drive it.


The signals from the A and B channels of quadrature encoders like these are very similar, but the order in which the changes on the two channels occur determines the direction of rotation. If you swapped the two signals to a board that was reading them, the board’s sense of whether the motor was spinning forwards or backwards would be reversed. There is a good description of how these work under the “Incremental rotary encoder” section of this wikipedia page:

You could use either the A or the B channel as a tachometer signal for frequency control on the Pololu jrk, but you should note that the jrk cannot do position control with encoders.


Thank you for reply, I don’ t need positional control for my project, just speed control with feedback. So that the motor speed is as constant as possible. It seems the speed control can be adjusted with simple POT? No arduino needed?

So the jrk12v12 would not work for 3D printer then without positional control?

It should be possible to set up the jrk to control the speed from a simple pot without an Arduino.

The jrk probably would not work well for a 3D printer, though those also commonly use stepper motors for position control, not a brushed dc motor/encoder combination.