RE: Wonderboard PC interface original message!

Yes, we did get a little carried away with this one. I did manage to get
plenty of feedback, so much that I printed it into a big stack of paper
(more trees died) and took it home to read over the weekend. Thanks to all
who contributed.

I still have some more research to do before I commit to the final
specification. Perhaps I should clarify my goals, which have not changed.
The plan was to design a board with enough dummyproofing to use in
industrial applications yet simple enough to be inexpensive and quick to
build. I see the potential to use this board as an interface with several
parallel port step motor programs. However, CNCPro is the one program I
feel comfortable enough with to support for retrofits. That is the program
I am designing the board for. This is not meant to be a negative comment on
other software and I would be happy to work with developers of such programs
if they wish to communicate their wants and needs. The info I have on most
of them is inadequate to work with.


The preliminary specification looks like this:

1. Separate board - not in PC. ( I may change this again if I succeed in
solving the DC-DC converter issue. Shucks! I might even go both ways.)
2. All input and output lines optoisolated.
3. All optos socketed.
4. Selection of optos to allow interchangability between cheap and high
speed optos for step/direction lines.
5. Sockets for optional SS relays on control lines.
6. On board 5V power.
7. DB25 and screw term capable input - your choice
8. DB9 and screw term options for step/dir lines.
9. Screw terms for limits, e-stop and control outs.

Several of you noted that it should not be necessary to use optos to drive
the step/dir amp inputs because most drivers are already optoisolated. Some
of them aren't. But the main reason I stuck to my guns here is that there
is a tendency (and I've seen it) to use the same 5V supply for the driver
optos as is used for the limit switches. The drivers are protected but the
parallel port is tied to the limit lines. Not good. The data out optos
will be supplied by the PC 5V supply. Yes, I know this means more than just
a single cable from the PC - another argument for making the board fit into
a PCI/ISA slot.

Doug

> -----Original Message-----
> From: Dean Sala [SMTP:adsala@...]
> Sent: Friday, February 25, 2000 8:25 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: [CAD_CAM_EDM_DRO] Wonderboard PC interface original message!
>
> From: "Dean Sala" <adsala@...>
>
> It seems as though this thread has went off on a tangent. I originally
> replied to Doug about a parrallel interface card that I had designed to
> work with CNCpro. But it seemed to never appear on the message board
> except in Doug's reply to it. The reply is in the "Interface Update"
> thread. Anyway, It seems as though some of you are getting confused
> between what Doug is proposing and what I have done. So I want to clarify.
> I designed an proto typed external interface card to work with CNCpro. I
> am building a homebrew CNC system so my design is catered towards that. I
> believe Doug has different requirements and is building a more robust
> board catered towards industrial use. Am I right? I'm not completely
> clear about his requirements yet. But this is what I wrote to him.
>
>
> Here is my original message to the "Interface update" thread.
>
> --------------------------------------------------------------------------
> ----------------------------------------------------
> Doug,
> It's real great that you are trying to resolve this problem. I completely
> agree that we need some sort of breakout box that could get us up to speed
> faster. With an on board 5vPS, relays, screw in terminals and such. It
> just so happens that I have already designed a proto type of this board to
> work with CNCpro. Except that it does not use optoisolation on the
> board.
> I already have optoisolation on board my step drivers.
>
> The proto type plugs into the parrallel port via cable. It has it's own
> DB25 connector on one side and has a series of screw terminals on the
> other.
> It consists of a SN74S244 hex schmit trigger driver to drive the step and
> direction data (3 or 4 axis or whatever)into the Step motor drivers. The
> auxillary outputs, 3 in all so far (CNCPro at least) go through ULN2003a's
> (that can be parralleled for more current) to drive 1amp 5v relays.
> Also,
> the homing inputs are hooked up to IR switches with their own terminal
> block. The other inputs are just tied high through 4.7ks. I am still
> working on the design and am thinking about making it more universal for
> other parrallel port NC programs that aren't as configurable as CNCpro.
> But
> first I'm keeping it simple. I'm sorry for not getting ideas from you
> guys
> but now I have a feeling what you want. Are you sure you need
> optoisolation
> on the board too? I can add them right to the output of the SN74S244 but
> then the opto isolators would be driving opto isolators. Maybe I can put
> a
> switch selector to bypass opto isolation if the step drivers have them.
>
> Possible enhancements: On board 5V power supply(otherwise supply external
> 5v
> PS). Connectors to connect 120v to stepper power supply with fuses etc.
> Diagnostic LEDs connected to various outputs. Connectors for main power
> switch and power light. Oh, limit switch connectors tied to turn off
> stepper PS. There you have it! All-in-one wonder board!
>
> About using the parrallel port for drive LED's....you should sink them of
> course but it's always better to put a buffer inline like an S series TTL
> driver which can source 28ma and sink 64ma perfect for this situation,
> more
> noise resistant and just what their made for. This way you don't have to
> worry about how much power the parallel port can provide.
>
> Good luck
> Dean
>
> --------------------------------------------------------------------------
> -------------------------------------------------------------
>
> Please read Dougs reply in the "Interface Update" thread if you are
> interested in his comments. It is a message stored under his name
>
> If you have any questions about my design please reply. I left a few
> things out of the above description.
>
> Thanks
> Dean Sala
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
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