PC-based PLC

R

Thread Starter

Rizwani

I'm working on my final year project and I really need help on how to write a program that can make our PC to PLC including create an editor for building a Ladder Diagram and simulating it using C++ or any language that easy
 
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FAKHER AHMAD

Hello dear it's nice if you have this much experience at University Level. Depending upon your input and output you can use serial or LPT parallel port of your computer Study the parallel port LPT by this you can have 8 inputs and 8 outputs and it is very easy to make a small simmulating circuit for. It will help you in the programming of the . For programming use USE inp() and outp() functions or you may find the list of functions in Visual c++ help for . for simmulation you can use Debug i for in put and o for input. Best wshes Fakher
 
Also I now write a simulation program for continuous systems b visual basic and I have a problem. the program is based on the state space representation of the system I have find matrices [A],,[C],[D] and then calculate the correspondent [G],[H] ie(G=exp(AT)) and H= integral of (G.dt*B) but I have a problem when I supply T (Sampling time ) generates an overflow . so if you have another simple method please help me best regards Abdulrazak Elbargathi Garyounis univ. Benghazi liby
 
Visual Basic is the correct tool, especially if you're the only one working on this project.

Writing an editor in it is easy; and since VB is an intepreted language, generating and running new code is easy.

It will also be a lot easier for implementing your editor. The serial port as suggested is a good and cheap I/O, else you can buy a cheap I/O board from computer Boards.

You may also want to implement the PLC itself in Visual C++ as an active X control or com object for otimum speed and then do your inteface and programming front end in VB. This will allow you to squiz max performance, determinism but with more work.

Since you intend on using the ladder paradigm, all you need to do is then replace each diagram smybol with a function. Then you can create a main loop that will read the rountines from a file and execute them over and over...

Good luck

Walt Njuh
 
C

Curt Wuollet

You could also poke around at www.linuxplc.org, Hugh Jack has one in Java I believe. If you write a compatible ladder editor and contribute it to
LPLC, you would be held in high esteem.
Regards

cww

 
D
Rizwani ,
This may be a long shot, but there is an interesting little (8 people last I checked) company actually named "SoftPLC" down in Texas (who ever believed everything in Texas is big?) that has a PC based PLC. It's a great product, and they even have a "C toolkit" to enable you to add to or modify the included instructions. I tried there product at Honda for an app were I needed determinism within 1ms. I ended up using a custom programmed microprocessor module to do what I needed. (communicate with a Bosch ABS modulator ECU during evacuation and fill of brake systems)

The point is, Richard Hollenbeck who wrote the software (in C) and founded the company is easily accessible by phone, and I've found him to be a very friendly fellow. I wouldn't be the least bit surprised if he were willing to give you (since you're a student trying to do something he is very interested in) some pointers and maybe even email you some snippets of code. Of course his code is what feeds his family, and he has a business to run, but I'd give it a shot if I were you. Maybe you could even work for him in the Summer to get deep in the trenches.

He even wrote an essay or his website, "Make your own open architecture PLC-reliably." check it out at http://www.softplc.com/

SoftPLC is it's own kernel, runs on diskless pentium SBC boxes or a more rugged PLC like platform. I was most impressed by one press release from them about the Army Corps of engineers evaluation of their product and
several other PLC and PC based control systems. Apparently Soft PLC was the only PC based system that didn't crash during their test which lasted
over a year. SoftPLC was selected to control a number of hydro-Electric Dams.

Of course most of the PC control systems run on NT boxes, so few should be surprised. I don't buy the separate kernel arguement.

Maybe one of you Puffin guys could get SoftPLC to take an interest in your project. I'm sure there is some way he could profit from it. I would
think that his hardware would be very well suited to the Linux PLC as he has already solved many of the issues related to using PC's with PLC
reliability.

BTW, how does one deal with instantaneous boot, and unclean shutdowns with Linux?

Dale Malony
Honda EqStaff
 
C

Curt Wuollet

Hi Dale

> Dale Malony wrote:
> Rizwani ,
> This may be a long shot, but there is an interesting little (8 people last
> I checked) company actually named "SoftPLC" down in Texas (who ever
> believed everything in Texas is big?) that has a PC based PLC. It's a
> great product, and they even have a "C toolkit" to enable you to add to or
> modify the included instructions. I tried there product at Honda for an
> app were I needed determinism within 1ms. I ended up using a custom
> programmed microprocessor module to do what I needed. (communicate with a
> Bosch ABS modulator ECU during evacuation and fill of brake systems)
>
> The point is, Richard Hollenbeck who wrote the software (in C) and founded
> the company is easily accessible by phone, and I've found him to be a very
> friendly fellow. I wouldn't be the least bit surprised if he were willing
> to give you (since you're a student trying to do something he is very
> interested in) some pointers and maybe even email you some snippets of
> code. Of course his code is what feeds his family, and he has a business
> to run, but I'd give it a shot if I were you. Maybe you could even work
> for him in the Summer to get deep in the trenches.
>
> He even wrote an essay or his website, "Make your own open architecture
> PLC-reliably." check it out at http://www.softplc.com/
>
> SoftPLC is it's own kernel, runs on diskless pentium SBC boxes or a more
> rugged PLC like platform. I was most impressed by one press release from
> them about the Army Corps of engineers evaluation of their product and
> several other PLC and PC based control systems. Apparently Soft PLC was
> the only PC based system that didn't crash during their test which lasted
> over a year. SoftPLC was selected to control a number of hydro-Electric Dams.
>
> Of course most of the PC control systems run on NT boxes, so few should be
> surprised. I don't buy the separate kernel arguement.

I don't buy it for a 3 million code line monolith, but it makes sense if you can customize to only what is needed. It becomes the easiest way to provide the variety of features people are demanding. An RTOS becomes problematic as the add ons mount. The biggest feature is ease of
development with almost everything under the sun available as source and customizable to the desired footprint. You write a lot less code to do a given task.

I have a box with an embedded PLC with 48 lines of IO expandable to God knows what, comm server with 10 serial ports, 4 machine vision tasks, 4
robot consoles, HMI, and image storage and management with remote programming and management and the box isn't even breathing hard. The
tasks that need to be are integrated through a shared memory map. I doubt that I've written more than 1500 lines of code. I'm very happy. And it will talk to any host over Ethernet and support a dozen X terminals for remote monitoring with no per seat license cost. That's in addition to all the normal Linux stuff like a built in webserver,
scheduled execution ,StarOffice, remote access, etc.,etc. I didn't have to buy any software. It was done quickly and with very few snags. The only
disadvantage I see is that it doesn't do ladder logic. Since I don't do ladder logic either, that's not much of a drawback. This box hasn't been up very long, I just built it in the last month, but the Linux vision systems already in production run as long as there is power, that has been the limiting factor. The customer, (my day job) is happy also. For the type of work we are doing, nothing will even come close to competing. That's why I'm excited about Linux in automation, it's even greater than Linux ATE.

> Maybe one of you Puffin guys could get SoftPLC to take an interest in your
> project. I'm sure there is some way he could profit from it. I would
> think that his hardware would be very well suited to the Linux PLC as he
> has already solved many of the issues related to using PC's with PLC
> reliability.

I have looked at their hardware for exactly those reasons. In fact I have been considering SoftPLC going forward for automation projects at my day job to ease conversion to the LPLC when the time is right. Alas, I was compelled to use Linux immediately by time constraints and it has run on
commodity hardware longer than any NT box I've ever seen which takes away my justification for buying their rather spendy hardware even if it
looks more conventional. But when we get the cell I'm working on installed, I plan to look again at SoftPLC as I would rather buy equipment with an
upgrade path than proprietary hardware. GE and Horner are not faring well compared to my Linux systems, even on uptime which was shocking to me. Actually, I like SoftPLC as a product from what I've seen so far. I would like a little openness and more language choices, but it would be a good transitional product if IO were chosen carefully for compatibilty with Linux.

> BTW, how does one deal with instantaneous boot, and unclean shutdowns with
> Linux?

Flash disk and journaled filesystems and a good UPS. We have had some discussion and there were several things proposed. The one I like is a memory map mmap() ed from ramdisk on NVRAM. I'm not sure which idea will win out, we're a democracy. I don't think instantanious boot is
critical to too many applications, but I'd be interested to hear what is really needed. The journalled filesystems are showing up now and the
enormous amount of embedded Linux activity may point the way before we even need to worry about it. I am amazed at how many of this type of issue are being solved before they become a problem for us. Soft realtime is in the works for the mainstream kernel without need for special coding and hard realtime is available from many vendors.
A lot of the barriers are dissappearing thanks to the sharing and ability to build upon what others have done. The progress in the last year is almost unbelieveable. It's difficult to keep up. But, that's a problem I like to have.

Regards

cww
 
Hi.

I'm working for a company and I was written a SoftPLC based on an IBM-PC AT, which simulates (or is better to say executes) the STL code of
a SIEMENS SIMATIC-S5 Series of PLCs (ROM based or normal).

I dont know how can I help you, but if you want to simulate these series of PLCs I would be glad to help you.

The SoftPLC configuration was:

Hardware: 386+ IBM PC AT
640KB RAM (up to 3 MB)
there is no need to HDD/FDD using
BOOT ROM.

First serial port configured as link to Programming unit (PG).

Second serial port as standard COM525 connection with 3964/R, RK512 protocols.

Siemens CP948-B Instruction Compatible.

excuse me for poor english.

with Best Regards.

reza.
[email protected]
 
Hi,
I have interest in developing a softPLC.But i don't have any idea to step forward.My idea is to develop control engine and that should understand the ladder program developed on third party editors like step7 etc...

I want to buy an editor .But my softPLC should execute the program developed on the editor.

any one can help me...

regards

bsbrao
 
M
There is a system called APACS that was developed bu (the now defunct) Moore Products Company. Now Siemens owns the line. APACS is one of the most comprehensive implementations of the IEC-1131 standard that is commercially available, and they have a control simulator that ships with the package. You can actually fire up multiple instances of the simulator and simulate a whole plant if you wish. The simulator is free with the base package (ask for the Process Suite Control CD). Since you are using it for academic purposes, you can probably get a consignment license from your local sales office (which you should be able to find by pokling around www.mpco.com).

Good luck
 
R

Robert Dusza

Hi,

You might want to try Intellution. They have a PC-based PLC which we use here at the Wastewater Plant. This replaced a DCS system. The product is Paradym-31 or P-31 for short. The software can be set up for hard realtime or soft realtime execution. You can check out the basic information at "www.intellution.com/products/fixparadym31":www.intellution.com/products/fixparadym31 .

they use IEC-61131-3 software for SFC, LL and FB . We have been able to use this software to replace a DCS system and have Global distribution of the I/O points throughout the system as well as no unscheduled shutdowns from software failure. If you need any other information let me know.

Bob


Robert J. Dusza, Jr.
Project & Technical Support Manager
(V) 1-860-647-3219
(F) 1-860-647-3150
E-mail - [email protected]
Manchester Water & Sewer Dept.
125 Spring St. P.O. Box 191
Manchester, CT 06045-0191
 
I've done a softwate for supporting of testing plc programs and I can say that only ladder diagram editor won't bi enough for your project. there must be a compiler for using in the soft-plc language such as assembler. I think that the worst thing to do is analyse the ladder diagram. I've got some libraries for creating and bompiling ladder diagrams like used in SUcosofts40. if you intrested in it contact me.
 
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