Re: [CAD_CAM_EDM_DRO] Parallel Port to Power Supply Grounding Differential

Ok, one more clarification....
For the 5v supply needed for the optoisolators in the Gecko input common
line (and other places possibly needed) it would be easier for me to utilize
a spare existing winding in one of my toroids, than pulling 5V from a game
or PS2 port on the PC. What if I simply extend the PC's parallel port
ground to the negative DC side of a DC supply rectified from that small
winding to get an isolated 5v? So long as I stay away fom the case and
other existing grounds, wouldn't I be safe? Thanks again for all your help!


R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: <JanRwl@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, July 08, 2003 12:52 PM
Subject: Re: [CAD_CAM_EDM_DRO] Parallel Port to Power Supply Grounding
Differential


> In a message dated 7/8/2003 12:09:49 AM Central Standard Time,
> elson@... writes:
>
> > If you have the Gecko drives that can only work with a negative common
> > terminal, then that common should be connected to the parallel port's
ground.
> > You will likely need pull-up resistors from the step and direction
signals to a
> >
> > +5 V derived from the computer as above.
> >
> If your parallel port has "old TTL output-chips", not newer 74HCnnn types,
> you may have difficulty "powering" the opto-inputs to the Gecko drives, as
these
> draw 16 mA (nevermind the paperwork! I measured the actual current into
each
> of FOUR such inputs on recent G210's, connected "Neg. Common", and they
EACH
> drew 16 mA!) Using "pull-up resistors" will "partially illuminate" the IR
> LED's in the opto-isolators, and expecting the "TTL high" outputs to pull
those
> inputs sufficient/reliably to sufficient + level to "fire" the LED's
properly
> will be, well, "poorly defined".
>
> What I have found works well is to use a 74HCT541 octal non-inverting
buffer
> on the 8 data-lines of the PP. This will give you "guaranteed" 25 mA per
> line, with a min. output voltage of 4-4.5 volts! I know, I MEASURE
things, once
> working! That buffer IC is NOT an "opto-isolator", but it DOES further
> separate things, and won't cost much at all! Long live 'HC ! ! ! Jan
Rowland
>
>
>
> [Non-text portions of this message have been removed]
>
>
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