RE: SLO-SYN 12.7 Amp motors

> -----Original Message-----
> From: Jon Elson [SMTP:jmelson@...]
> Sent: Monday, January 10, 2000 7:40 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] SLO-SYN 12.7 Amp motors
>
> > The operative word here is interrupt. Software that relies on
> the
> > PC's interrupt system is doomed to a bumpy ride. The closest thing to
> true
> > timing control (short of a dedicated board with its own clock and
> profiler)
> > would be had by addressing the clock chip directly with an assembler
> > routine.
>
> Yes, that's exactly how the real time scheduler works on RT Linux. It
> takes over the system interrupt clock, and sets the interrupt rate at
> whatever rate you need. RT tasks take priority over the OS tasks.
>
> > I believe this is how Doug Yeager's program works. It works well
> > too. I ran three axis' simultaneous last night at 15,000 steps/sec and
> it
> > didn't even flinch. This is with a 486.
> >
> > At least one large CNC control builder has solved the PC
> profiler
> > vs. PC windows interface conflict by going to twin (not parallel)
> > processors. One (running under DOS) runs the machine while the other
> (under
> > W95) provides the cute and fuzzy windows graphical interface we all
> want.
> > When you consider how cheap motherboards are, and how powerful the PC is
> > when you leave the video out, this seems like a good approach.
>
> Yup, that is really the way to go. But, I don't think the RT Linux
> environment
> would support that. Of course, an off-the-motherboard CPU could do
> this, and no OS is really needed, just the RT scheduler and some I/O
> management routines. I know some proprietary motion control boards
> work this way.
>
> Jon
>

The Galil servo board has an on-board CPU. Being a Motorola 68000,
it is capable of incredible update rates and encoder frequencies. But the
Galil DMC-1000/4 is $2300 and writing the thunk to interface G-codes with
Galil basic is more trouble than writing the profiler from scratch. A
Servo-to-go board and a dedicated PC motherboard would be half the cost of
the Galil board alone. And then you could have true open architecture -
with your choice of operating system for the interface on the second PC.

Doug

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