Re: Shared Direction pins vs dedicated Direction pins

Ballendo,

No. I try to stay calm.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo <ballendo@y...>"
<ballendo@y...> wrote:

> Mariss,
>
> No hysteresis?
>
> Ballendo
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
> <mariss92705@y...>" <mariss92705@y...> wrote:
> > Doug,
> >
> > I have a circuit worked out that is very simple that shares step
> and
> > direction on a single line. If the duty cycle of the step pulse

is

> > less than 50% it's CW, if more than 50% it's CCW.
> >
> > CW = 100010001000...
> > CCW = 11101110111...
> >
> > Mariss
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Doug Fortune

<pentam@c...>

> > wrote:
> > > re: dedicated Direction & Step pins need 2*N output lines
> > > vs shared Direction & dedicated Step pins need N+1 output

lines

> > > (N is number of axes), thus saving output pins which are

limited

> > > in number on a parallel port, and hence often a constraint.
> > >
> > > Chris L wrote:
> > >
> > > > >>It would appear to be for some type of "single axis at a

time

> > positioning"
> > >
> > > Doug wrote:
> > > > >Absolutely not!
> > > > >This is a general scheme for lathes, mills, routers and
> hexapods
> > >
> > > > Maybe by a "hand cranker".... but, On a CNC mill or

Router ??

> > Now I am
> > > > lost..... Even on my simple 3 axis router, I assure you I can
> and
> > do
> > > > have more than one motor turning, and in opposite directions

at

> > any
> > > > given time, even for simple 2d profiles.
> > >
> > >
> > > Hi Chris:
> > >
> > > Yup, lots of motors turning simultaneously at different speeds,
> > > accelerations and directions, thats how S&D motor drivers work
> > > (as you well know!).
> > >
> > > Yes, I think you are missing something obvious.... the Step
> > > signals to the motor drivers are of the order of 1 uS (1
> millionth
> > > of a second). Apparent smooth motor motion results from

emitting

> > > one of these pulses (say 20,000 times/sec or once every 50
> > millionths).
> > >
> > > In other words, you could have many (50 channels in this

example)

> > > sharing a common direction pin, and neither the motors nor the
> > human
> > > would be able to detect any measurable difference. However the
> > Geckos
> > > (much as I like them) have a hold-time constraint on the
> Direction
> > line
> > > which precludes their use in a "shared-direction" scheme.
> > >
> > > <more written offline to Chris>....
> > >
> > > Doug Fortune
> > > http://www.cncKITS.com