Hi all!
I am a graduate student-lurker in this list. I am working on a college lab automation project, where I need to control some processes
using a PLC, and web-enable them.

Could someone recommend/rate current industry standard PLCs in terms of their linux friendliness? Which PLC lines have the best open
source s/w available for linux. I will be in a position to hack/add on to such software, but would rather go for whichever PLC already supports linux best.

Procurement will be easier for me if I stick to known brands (here in India) like Allen Bradley,Modicon/Schneider , GE-Fanuc etc

--Ideally, I'd like to program, monitor and if possible even write to the PLCs registers. Is it possible? Can I directly intervene to set PLC
outputs through a PC? Can I re-program a PLC on the fly using a PC?

--A decision that I have to make is whether to look for simple RS232 for communication..in which case I do not need to much supporting s/w as
RS232 libraries are easily found/developed, or to go for Ethernet which will make web-enabling easier.What about MODBUS or any other open
standard..any libraries out there?


Any advice/comments are welcome. I hope this question is not too off topic for this list.

thanks for your time
Gaurav

P.S. If anyone is interested, I have a small oscilloscope like program running comedi and GTK+ on a linux box, which we use for general purpose DAQ and display, I'll be happy to make the source available to anyone who needs it. No GUIs and stuff..code only

_______________________________________________________________________________
Gaurav Jain H-3/228
Department of Aerospace Engineering,
Indian Institute of Technology, Powai , Mumbai
India 400076
_____________________________________________________________________________
"The argument goes something like this: `I refuse to prove that I exist,'says God, `for proof denies faith, and without faith I am nothing.'
"`But,' says Man, `The Babel fish is a dead giveaway, isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. QED.' (s.42)
--The Hitchikers Guide to the Galaxy

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Hello Gaurav,

How much time and money do you have for this project and what are the I/O counts?
You can get a lot of PLC's with Modbus connectivity, which should help (I mean the modbus connectivity).
Plese ensure you get the right Modbus connection for the driver that you obtain or write (there are several modbus variants).

Several vendors charge for their programming software but generally DOS versions are free. Bargain and negotiate this properly while getting a PLC.

Yes you will be able to write to registers and do all jugglery that you want to do once you have the driver working properly.

If you are not bound by time (have a few months in store) and have programmers (C and Gtk+), then we can all meet and do the entire job right out of the Linux box with some I/O cards added. I know a couple available in Mumbai itself which have said Linux drivers available on the manuals. This could use a lot of the modules of the LinuxPLC and probably we may be able to add a few modules. And economics would be right where you want it to be. the reason for suggesting this is that you may be on a tight budget and may be able to afford a more or less obsolete PLC, which will add to your woes later on.

You can be in touch from 1-8-01 at 95219250873, preferrably after 21:30 Hrs to 22:00 Hrs, E mailis possible till then,since I am going to Kalyan for a few days on some family related matter, in case you have any specific issue to discuss. I am currently free, as of now.

Anand.


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Yep, it works. Some students of mine did it as a small (well tiny actually) project. We have some schneider PLCs with ethernet cards around here. We have Siemens and OMRON too.

Cheers,

Mario.

----------------------------------------------------------------------------
Mario J. R. de Sousa
[email protected]
----------------------------------------------------------------------------

The box said it requires Windows 95 or better, so I installed Linux

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Hello Guarav,

Ron Gage has written a library for communicating with ethernet enabled
Allen Bradley plc5 processors. It is called the Allen Bradley Ethernet
Library (ABEL) and is available at sourceforge.



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AB has a Open Automation thing, where they provide the PLC hardware and you supply the software.

=====
Phillip Mastroianni
[email protected]
[email protected]



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> Could someone recommend/rate current industry standard PLCs in
> terms of their linux friendliness? Which PLC lines have the best open
> source s/w available for linux.

<snipping part while suppressing laughter>

> --Ideally, I'd like to program,monitor and if possible even write to the
> PLCs registers. Is it possible? Can I directly intervene to set PLC
> outputs through a PC? Can I re-program a PLC on the fly using a PC?

For most vendors, most of those answers are yes. On the fly (as in "don't stop to reload") is not universal, but common.

If it's just for experimentation, does it have to be Linux? I'm all for Linux, but if it's a one-off project, you'll find a lot more people Windows
compatible.

But if you're already using Linux, I bet the first Linux "friendly" PLC vendor will probably be Automation Direct. Can you buy their stuff from India?

> --A decision that I have to make is whether to look for simple RS232 for
> communication..in which case I do not need to much supporting s/w as
> RS232 libraries are easily found/developed, or to go for Ethernet which
> will make web-enabling easier.What about MODBUS or any other open
> standard..any libraries out there?

I'm sure you can get Modbus drivers in C, Basic, Pascal.

> Any advice/comments are welcome. I hope this question is not too off topic
> for this list.

I think it is right in line with the list.

> thanks for your time
> Gaurav

No problem. Let us know how you make out.

Rufus

P.S. Dont forget to look in on the Linux PLC at mat.sourceforge.net (or now: mat.sf.net)

Not ready for prime time, but every day in every way....

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Thanks for the reply; believe it or not, its the other way around here..windows developers are scarce in my college, linux rules It has to be linux because nearly all machines in the campus run linux, all apps are on linux, a windows machine would unnecessarily mean dual
booting and network problems.

I am thinking of settling for some Modicon stuff. I like their Modbus over TCP idea. Someone with experience with Modicon/Schneider PLCs
please confirm that I will be able to get/write software to communicate with the PLC, even if I cant program it via a PC. I saw some code samples
on their site, which seems to make it possible.

BTW our idea is to computerise-then network- enable controls and instrumentation experiments in the chemical engineering department's
controls and instrumentation lab. Features planned include allowing instructors to remotely monitor what the students are up to, and doing all
the drudgery of graph drawing and date acquisition for the students. Has anyone here done anything like this? Any comments/suggestions?

thanks and regards
gaurav

_______________________________________________________________________________
Gaurav Jain H-3/228
Department of Aerospace Engineering,
Indian Institute of Technology, Powai , Mumbai
India 400076
_____________________________________________________________________________
"The argument goes something like this: `I refuse to prove that I exist,' says God, `for proof denies faith, and without faith I am nothing.'
"`But,' says Man, `The Babel fish is a dead giveaway, isn't it? It could not have evolved by chance. It proves you exist, and so therefore, by your own arguments, you don't. QED.' (s.42)
--The Hitchikers Guide to the Galaxy

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Gaurav Jain wrote:
>
> > In a message dated 7/25/01 9:20:42 PM Eastern Daylight Time, [email protected]
> > writes:
> >
> > > If it's just for experimentation, does it have to be Linux? I'm all for
> > > Linux,
> > > but if it's a one-off project, you'll find a lot more people Windows
> > > compatible.
>
> Thanks for the reply; believe it or not, its the other way around
> here..windows developers are scarce in my college, linux rules
> It has to be linux because nearly all machines in the campus run linux,
> all apps are on linux, a windows machine would unnecessarily mean dual
> booting and network problems.

Sounds like my kind of place :^)

> I am thinking of settling for some Modicon stuff. I like their
> Modbus over TCP idea. Someone with experience with Modicon/Schneider PLCs
> please confirm that I will be able to get/write software to communicate
> with the PLC, even if I cant program it via a PC.I saw some code samples
> on their site, which seems to make it possible.

While I shouldn't express an opinion, I do think they are the most open and our best bet for cooperation.

> BTW our idea is to computerise-then network- enable controls and
> instrumentation experiments in the chemical engineering department's
> controls and instrumentation lab. Features planned include allowing
> instructors to remotely monitor what the students are upto, and doing all
> the drudgery of graph drawing and date acquisition for the students.Has
> anyone here done anything like this? Any comments/suggestions?

I would keep these networks seperate and local.

Regards

cww

--
Free Tools!: Machine Automation Tools (LinuxPLC) Free, Truly Open,and Publicly Owned Industrial Automation Software For Linux. mat.sourceforge.net.
Day Job: Heartland Engineering, Automation and ATE for Automotive Rebuilders.
Consultancy: Wide Open Technologies: Moving Business and Automation to Linux.

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Hello,
Protocol converters are available for industrial networking, so one need not stick to products communicating in the same protocol, so you can go for the best systems aviliable in the market, i.e if your going for allen bradley plc which communicate in DF1 protocol you can use a DF1 to modbus converter to interface it with a modbus network.