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Re: open-plc

Bill Gatliff:
> Karl Hammar wrote:
> >  Do anyone of you where the proper place to discuss open hardware is?
> > I am going to start a project to replace plc's.
> I've gone down this route many times.  Never found the end, however.  :)
> I would consider gEDA over kicad, it's more mature.  But a somewhat
> steeper learning curve, perhaps.

I'll check that out, thanks.

> The main challenge isn't going to be the hardware, it's going to be the
> programming environment.  Lots of hardware can produce signals that look
> like signals produced by PLCs, but those systems won't be as easy to
> program as existing commercial PLCs without a pretty considerable
> integration effort.

For the moment I'm most interested of the hardware part. It should look
like a plc, be rugged, and have exchangeable io-cards.
I think I'll rule out single board systems and stacked systems like 
pc104. It should be easy to exchange io-cards, if possible hot-pluggable.

Software is another project, but for now I'll do it in c. And I don't 
think I'll invest time to make it that plc-like. My main points is to 
make better hw that my current programs could run on. And in that sense 
it might be better to call it something else than open-plc.

> If you do your job right, you'd be able to realize your "plc" hardware
> as a PC with a USB-connected GPIO device, at least for some definitions
> of "plc".  And that would be a pretty interesting achievement in itself!

Yes, I've thought about that, but I don't want to have a mess of 
usb-cables. I could use printed circuit usb lines, but spi looked more 
suited for the job.

> The MatPLC software is one place you might look for the software
> pieces.  There are other examples, like EMC2, and so on.   Google is
> your friend here, for sure!
> This article is a little old, but might still be relevant:
> http://www.linuxjournal.com/article/1339
> A communications stack, among countless others:
> http://www.ctiplcio.com/
> The "beagleboard" would be a super-fast CPU, but with 1.8V i/o it would
> need a daughtercard in order to make it useful.  Cogent's CSB740 uses
> the same CPU, but has a little friendlier 3.3V i/o.  But neither comes
> with any software stack to make it as programmable as a PLC.  Both
> support Linux already, however.

I have looked at beagleboard, but it does not have ethernet.

> Have fun!

Yes I will!

> http://www.linuxjournal.com/article/4603
> http://en.wikipedia.org/wiki/IEC_61131

Thanks for all the links.

I'll put up some pages att http://aspodata.se/openhw/ when I have 
something to show.


Karl Hammar                    Aspö Data               karl@aspodata.se
Lilla Aspö 148                                                 Networks
S-742 94 Östhammar          +46  173 140 57                   Computers
Sweden                     +46  70 511 97 84                 Consulting

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