Re: [CAD_CAM_EDM_DRO] Re: Small Problem-how 'bout stepperworld.com

In a message dated 03-Aug-01 08:48:23 Central Daylight Time,
datac@... writes:

> That being said, I have found issues where the drives are touchy to get to
> work correctly with the control. The most common is the polarity of the
> signal for "dir", and that of "step/dir" signal duration.
>
> Best information would be right from the developer of the board.
>

Sorry, but I disagree! Most times, these "ol' boys" who design circuits
haven't a CLUE how to communicate with the outside-world, the ultimate user!
One would assume a "grandfather firm" like Superior Electric would have PR
gurus who would edit manuals, to make such weird topics as "logic sense"
("positive" or "negative" logic), input-polarities, etc., sensible! But on
their actually-quite-fine bipolar-chopper driver-circuit I recently used,
there are (fine-functioning!) opto-isolators, and to affect a "positive-logic
IN", you must SINK about 5 mA from an output. They SHOULD point out that,
though this is a "negative-going input, as it is SINKing current, this is,
actually, a 'logic-HI' signal". But, NO! And when I telephoned, the tech
answering the phone had NO clue, and had to go ASK, and when he came back,
"Ya know, you are the FIRST customer who has asked this question, and we do
NOT know, and don't have a driver on the bench, right now, to check. Suggest
you ASSUME a current-sink IN is "active-HI" positive logic. We will have to
THINK on this! Sorry!" I swear to you! ("Affirm", not nasty-words!)

So, I suggest you TRY it first, on YOUR bench, before designing some
expensive interface thing, only to find you needed an INVERTER IC in there,
somewhere!

That is, knowing "for sure" what it means when they specify, "DIR must be LO
when STEP changes logic-level, and must be set-up for n microseconds, and
held for x microseconds after STEP settles", is sometimes quite impossible
the way "user-manuals" are written!



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