Incremental encoder direction signal decoding

[AlexResch]

Too keep it short : what is the easiest way to get a direction signal from an incremental encoder ? I need to control the direction ( and position ) of a small stepper motor and the drive wants pulse and direction. Pulse I can do, direction not.

[Wimberleytech]

For a rotary encoder...

[cncjerry]

if you hook two steppers back to back (without power) you can turn one with the other based on the EMF generated by the one you turn.  Not much torque at all but it is interesting.

Look up quadrature encoding.  This is how you decode encoders with a microprocessor.  The two pulses are offset so that dependng on how the encoder turns, one or the other pulse will lead or lag the other and based on that, you get the direction and step.

So turning one way you'll get a pulse train of ABABABAB as to which leads the other; The other way, BABABABABA.  Remember, that the transition from A to B and from B to A is which leads.  So you really have A, and while A, then B;  The other way, B and while B, then A.  I think they call it quadrature because you can have four states: not A & not b; A; B; A & B.  Most microprocessor libraries have quadrature encoder libraries or code.

Jerry

[intabits]

Looking at some old assembler code I did for a servo controller, it's simple in software if you have a microcontroller involved.
On the falling edge of one encoder channel (I used that as in interrupt), look at the other channel. If that's high, it's rotating one way, if low, it's rotating the other way...
(which is what the circuit above does in hardware)

[SiliconWizard]

I have used the principles given here successfully in a few projects: https://tutorial.cytron.io/2012/01/17/quadrature-encoder/

[PA0PBZ]

If pulse for the drive would trigger high- or low going you could hook the encoder directly to it, it's not going to be simpler than that. 

[Wimberleytech]

For a rotary encoder...

If all you want is DIR, you can eliminate the inverters since CLK is buffered internal to the 4013.