RE: Parallel port isolation

Hans;

Optoisolation of the output (or is it the input - can't remember) requires
an external power supply. Jameco sells a DC-DC converter for about $6 that
will do this. I used one on a servo system for the limit switches. The
opto chips and converter could all be put on a breakout board with all
necessary screw terminals for connection to the machine, limits, etc.

Plans at this time are to stick with DOS. I am mulling over Doug Yeager's
CNCPro right now. The price is right, but I can't determine from the demo
if the software performs to my level of expectation. The lack of a feed
rate override knob troubles me too. Bridgeport used keyboard FRO on the
newer CNC's and I don't like it at all. Microkinetics uses keyboard feed
hold and I know from experience this is not safe. One tap stops the feed.
Tap it two times (in a panic) and it keeps going.

Doug

> -----Original Message-----
> From: hansw [SMTP:hansw@...]
> Sent: Monday, November 22, 1999 6:19 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] Parallel port isolation
>
> From: hansw <hansw@...>
>
> 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
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