Driver question about CW/CCW mode available (optional)

[Glidergider]

John,
I have a question about your drivers. The specs for the drivers indicate:
"CW/CCW mode available (optional)".
What does that mean, imply?
Dave

[Kelinginc]

The pulse can be set as clockwise or counter - clockwise.

[Glidergider]

Kelinginc,
check your PMs. I've got more questions. What do you mean????? Of course your product will turn CW -AND- CCW! That's a feature??? Please expand on your answer.
Dave

[Glidergider]

I'm two shakes from making and order and I want to order your product. I'm evaluating HobbyCNC and Xylotex. Please help me decide why I should choose a Keling system.

[mar999]

: Im pretty sure it has to do with if you running encoders which way it supposed to be turning so if it looses a step it will know

[Mariss Freimanis]

There are two standards, Step/Direction and CW/CCW.

The more modern one is Step/Direction. You send a Step pulse to the drive, it samples the state of the Direction signal at instant of the active Step edge and decides from that which direction to take the step.

The other standard is CW/CCW. If you want to turn a motor CW, you send step pulses on the CW input. You want to go CCW, send step pulses to the CCW input.

CW/CCW is not as popular as Step/Direction for two reasons:

1) Both channels have to be wide-bandwidth while Step/Direction needs only one wide-bandwidth channel. The Direction channel changes state infrequently.

2) CW/CCW is ambiguious. What happens if you send steps to CW and CCW simultaneously? It's undefined. Step/Direction is unambigious.

Mariss

[Xerxes]

I have a bit different opinion about CW/CCW vs step/dir.

1) Both channels of step/dir needs to be high bandwidth if short direction set-up time is required. CW/CCW don't have set-up time or post-hold time troubles at all.

2) "What happens if you send steps to CW and CCW simultaneously?". They cancel each one out, no motion should happen.

However, the best is quadrature mode input. It requires low bandwidth and every edge produces motion.

[Mariss Freimanis]

The CW/CCW interface was developed for the 74193 counter. Both inputs 'low' is illegal for that counter.

You can operate any Step/Direction drive with quadrature inputs if you want to.

Mariss

[Oldmanandhistoy]

Originally Posted by mar999 : Im pretty sure it has to do with if you running encoders which way it supposed to be turning so if it looses a step it will know

Hi,

I have just bought a drive with the CW/CCW option (not Kelin) and am wondering what benefit it would give if any? Is it as already stated to be used with encoders?

Thanks,
John

[Mariss Freimanis]

CW/CCW does not work with quadrature inputs. Step/Direction does. CW/CCW is primarily for legacy (read obsolete) applications.

Mariss

[Oldmanandhistoy]

Originally Posted by Mariss Freimanis CW/CCW does not work with quadrature inputs. Step/Direction does. CW/CCW is primarily for legacy (read obsolete) applications. Mariss

Thank you Mariss as always you are a wealth of information.

Regards,
John

[Xerxes]

Originally Posted by Mariss Freimanis CW/CCW does not work with quadrature inputs. Step/Direction does. CW/CCW is primarily for legacy (read obsolete) applications.

No, quadrature to step/dir will not work properly because every edge is not counted. Counter value starts drifting if position jitters at single "step" edge.

CW/CCW can be done properly using two separate up-countig counters and then do substraction on the two sums. Historical or not, it is good :-)