Re: Parallel port isolation

Doug,
Yes I have a few ot them, if you are referring to the 5Vin to 9Vout...
they work just fine, but there is really no need to use them as a simple
transformer isolated PSU achieves the same thing. Remember isolation is
limited to the signal side, because there will be a common ground
through the 115V AC outlet.

I did a design for NMEA ( the boat lot not nema) that requires complete
isolation on certain lines, and then I used the DC-DC converters to that
end...

It is also a requirement in medical electronics, but for a mill, what
you are trying to archieve will be done by a good quality transformer
based PSU..

CNCPRO.EXE I have it and like it, because the interface is simple and
easy to use. You name sake Doug does a good job of supporting it.

I am unclear what you mean by feed rate override..

You can increase and decrease the feed rate while a cut is being done.
The amount you increase the F/R by is set in the setup. I have mine so
that I can increment/.decrement F/R by 0.1ipm This is done by pressing
the "F" for increase and "f" for decrease.
Stop is done by pressing the space bar, and all feed's stop. You then
have the option to continue or over ride by doing manual jog...

Is that what you meant ?

regards
Hans Wedemeyer




"Harrison, Doug" wrote:

> 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
> discussion of shop built systems in the above catagories.
> To Unsubscribe, read archives, change to or from digest.
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