RE: Parallel port isolation

Hans;

I have also considered the optoisolation approach but was concerned that
30Khz might be too much for opto devices. (I am using microstepping.) Are
the inexpensive opto chips capable of this speed? Is the parallel port
reliably capable of this speed?

Doug

> -----Original Message-----
> From: hansw [SMTP:hansw@...]
> Sent: Monday, November 22, 1999 4:20 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] Parallel port isolation
>
> From: hansw <hansw@...>
>
> Doug,
> It would be wrong to say it can't happen, however I think if the circuit
> is correctly designed and a good circuit board is used, the problem is
> no greater than when a printer is connected.
>
> Remember printers use stepper motors, and some of the heavy duty page
> and line printers use very large stepper motors and no isolation, and
> some of the older version pen plotters also used large stepper motors...
>
> Stepper drivers are relatively slow devices, and putting an opto
> isolator in each signal line is not problem except expense and board
> size.
>
> regards
> Hans Wedemeyer
> http://home.swbell.net/hans_w
>
>
> "Harrison, Doug" wrote:
>
> > The notion of using the Parallel port to control machinery has
> > fascinated me
> > for 15 years. However, as one who obeys speed limits and never uses
> > stairs
> > without holding on to the rail, I am naturally concerned about hooking
> > my
> > non-isolated parallel port I/O to an 80 volt amplifier controlling
> > inductive
> > devices.
> >
> > Has anyone experienced fried computer syndrome from stray currents in
> > large
> > stepper systems? I know this can be a problem with servo systems,
> > usually
> > from ground loops.
> >
> > Doug Harrison
> >
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> > Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems in the above catagories.
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