Re: Parallel port isolation

Doug,
Depends on the type of opto coupler device. The H11L1 is cheap and will
have no problem doing 30KHz, I think it's rated in the low
megabits/second range.
The parallel port can handle 30K bytes second, it's more a question what
can the program do and the OS it's running under.

I think the big mess with optoisolation is the number of couplers needed
for a parallel port, which would be 17 as I see it. and then there's the
question of if you want bi-directional abaility it's even more
complicated...

Hans Wedemeyer



"Harrison, Doug" wrote:

> 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.
> To Unsubscribe, read archives, change to or from digest.
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> Log on, and you will go to Member Center, and you can make changes
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