Re: [CAD_CAM_EDM_DRO] Re: Shared Direction pins vs dedicated

There are those flat little jahotcho's about 2.5"X3" that take ether cable on
one end, and parallel on the other. I think they go for about $40-$50 or so.

Bill

On Wed Feb 12 07:00:10 2003 Tony Jeffree wrote:

>I'm amazed that there aren't solutions readily available that use Ethernet
>connections rather than the parallel port.
>
>Regards,
>Tony
>
>At 14:52 12/02/2003 +0000, you wrote:
>>Bernard,
>>
>>Ditto.
>>
>>And even though the p-port is disappearing,(but will not "really" be
>>gone for awhile) the current crop of pc-based cnc controllers is
>>including support for additional i/o with the use of another p-port,
>>or support of generic i/o cards, or usb, game port or otherwise...
>>
>>In other words, it's a solution in search of a problem, IMO.
>>
>>Ballendo
>>
>>P.S. But a neat idea!
>>
>>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bernard R
>><bwjarandall@c...>" <bwjarandall@c...> wrote:
>> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Doug Fortune <pentam@c...>
>> > wrote:
>> >
>> > Doug,
>> >
>> > While there is no technical difficulty doing time division
>>multiplex
>> > with muliple controllers, I don't really see the need. The current
>> > limitaion is using a single parallel port as the computer
>>interface.
>> > From what little I've seen the G2002 project is well in hand so the
>> > limited output pins should soon be history.
>> >
>> > From the practical side I could see a lot of people having problems
>> > with the concept and trouble shooting such a system would be a
>> > nightmare for the average hobbyist with limited technical knowledge
>> > and virtually no test equipment.
>> >
>> > Bernard
>> >
>> > > 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

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