Re: [CAD_CAM_EDM_DRO] Re: Parallel Port Interface

In a message dated 03-Nov-01 11:04:56 Central Standard Time, currinh@...
writes:

> So, you might consider in designing the opto-isolation, if you use it,
> to not invert the signals. This particularly if using EMC.

Hugh: Probably not really necessary, if you use a CMOS buffer IC (at least)
such as the 74HCT541 in series with the parallel-port. While not a "Galvanic
isolator" as is a true opto-isolator, it will "fry" before sending sufficient
current "backwards" into the poor computer's printer-port, unless the "fault"
is "line-voltage" (120 VAC or worse), etc! But I do not encourage one who is
not an "IC whiz" to "get brave"! Not by any means!

Seeing opto-isolators on the input to my Superior Electric drive/power-supply
"box" was somewhat reassurring, but I have found, in use, it precludes
"sudden where-did-THAT-come-from?" steps, my older home-brew circuitry finds,
when the coffee-maker at the shop down the street comes on/off! (etc.)

Jan Rowland, Ignernt Old Troll


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