future of exisiting PLCs against the Soft PLCS

Can softplcs replace the old PLCs'

  • yes

    Votes: 2 3.8%
  • no

    Votes: 34 64.2%
  • better than old PLC's

    Votes: 1 1.9%
  • worth studying softplcs

    Votes: 16 30.2%

  • Total voters
    53

Sarit

Member
Join Date
May 2003
Posts
11
please go thru the below link
http://mat.sourceforge.net/

I would like to know the future of soft plcs like the one above MATPLCs'. Is it a good area to explore and spend time. How successful this PLCs can be? Please let me know the views of the members.

Thanks in advance
Sarit
 
sarit,

the MAT project has been around for years now. I think these people deserve all the praise of the world for their effort, but the project isnt finished to a degree where others could risk their business on it.

There are other "soft PLCs" out there.
(listed with decreasing degrees of stability, as I judge it):
Some runs their own operating system (f.ex. SoftPLC).
Some runs on commercial (but stable) real time operating systems.
>> MATPLC on Linux
Some runs on Windows CE.
Some runs on Windows with real time extensions.
Some runs on plain Windows.

I havent seen a truly compelling reason for using Soft PLCs.
Its not cheaper. Its far less reliable. Its risky in terms of long term durability.
Soft PLCs that runs on PCs has arguably more computing horsepower than traditional PLCs. But I think it is not an issue for 99.9% of all applications. I for example use S7-400 PLCs, and it refuses to increase its scan time to above 10 ms no matter what code I throw at it - and sub 10 ms is good enough for me.

The achilles heel of the MAT project (if it gets finished) will be that it doesnt have the backing of a large company. Its more or less do-it-yourself. You cant get spares on short notice. You cannot get expert support in the dead of night.

Why is Linux a success ? Because it has gained critical mass.
If the MATPLC shall succeed, it must attract so many supporters that its development moves a lot faster than it has done. It is certainly a good place to spend your time. It has the potential to become succesful, but also the risk of fizzling out.
 
Hmmm...

It's debatable certainly. We have 19 Soft PLCs, Siemens S7s. The justification is that a standard PLC cannot do the calculations neccesary for the application fast enough. The application involves very complex motion control and interfaces with vision software. Each of the first 18 PLCs also communicate with the 19th which is the line controller. Instead of a PLC, motion controller, vision controller, interfaces, etc (which would be a nightmare to implement)-everything runs in parallel on the one machine which is a dual processor PC. It is definitely true that there are concerns over the reliability - most of them stemming from the fractious nature of Windows (ours is NT, apparently for it's networking capabilites??!old **** in my op).If we did not have this we would probably have bespoke systems running something like UNIX, or an Adept controller. All of which would make it less accessible to poor unfortunates of lesser brainpower like myself. I'm going to tick the YES as they can do the job but also WORTH STUDYING as the jury will be out for a while in my opinion.



One only needs two tools in life: WD-40 to make things go, and duck tape to make them stop
DOH! didn't realise you could only vote once - some questions have more than one answer.
 
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Kenny,
thats why I am not happy about most polls, you can only vote on the given choices. By the way, its not me that voted "no".
And I am not sure if the poll is about any kind of soft PLC or only MATPLC.
If it is about any soft PLC I would have voted "I am not using it, but I will not exclude the use of soft PLCs in the future".
If it is about the MATPLC I would have voted "I will not use it, but I will not exclude that others can use it - if it gets finished".
 
1 - Soft PLC's can be much faster than Hardware PLC's (sometimes)
2 - Soft PLC's can save a tiny bit of money, especially if incorporated into an HMI station.
3 - Soft PLC's are extremely reliable in and of themselves (the software side)
4 - A Soft PLC's overall reliability and stability depends 99.9 % of the stability and reliability of the underlying computer/Operating system.
5 - Computer hardware and Operating Systems evolve and become obsolete at a frightening rate.

Because of 4 and 5, I strongly advise all my clients AGAINST soft-plc's. Even the Simatic type 'Sort of Soft' Card PLC's.

I can still purchase S5 CPU's, PLC-5's, SLC-500's, etc, that were designed into a system a decade or more ago. I cannot duplicate any computer that was purchased more than 6 months ago, if that.

A Hardware CPU is a controlled, stable, single-purpose enviornment. Anything running on a generic computer is not. Users WILL install additional software, they WILL apply upgrades and patches, they WILL eventually (even if ill-advised) connect the computer to a network.

Replacing a hardware CPU with a new one, and downloading the program can be accomplished in a matter of minutes. Configuring a new computer, loading software, configuring drivers, installing comms cards, service packs, and the like can easily take a day or more.

I feel very strongly, that there will always be a market for dedicated processing power. I'll stick with cards in racks :)
 
Sarit,

I would like to know the future of soft plcs like the one above MATPLCs'.

They've been working on that project a long time. It seems like it will never be done. :sick: Besides it looks like sixnet may have beat them to it.

I do not think SoftPLCs can replace traditional PLCs.

But, they have a good use. I spend alot of time with pump testing. 90% of my code is in VB for calculations & databasing, 10% in the PLC for basic electrical functions. A soft PLC does just fine in this case since a computer running Windows is already in use.

So, I don't think its a case of 'will one replace the other'. It's which one will fit the application better! (y)
 
Nothing new here but the penguin!

The original DCS (Distributed Control System) was generally running on Unix and was a comm link to single loop controllers.

PC based control has been hanging on the periphery since the mid 80's.

The biggest problem is that you still need I/O hardware to connect to the real world of starters, sensors, etc. That means you have a comm link between the real world and your logic. I don't know about the rest of you, but comm links are and always have been my biggest single problem in getting a system functional.

Another big problem is that every bit weenie in the IT department will now think they can do automation - its just another PC app, isn't it?

The biggest advantage to the soft PLC is ............ I guess I don't see one. Cost isn't it. Programming ease isn't it, at least with most PLC programming interfaces nowadays. HMIs have also come a long ways since the mid-80's in terms of cost, ease of programming, and PLC interfacing.

This is the answer to a question nobody is asking anymore.

My solution, at least for reliable process control, is a number of individual micro PLCs with the independent logic for each unit process and process protection mounted locally, a larger PLC for system coordination and command and data exchange on a comm lnk to the micros, and a PC for data logging and enterprise data exchange and trending and supervisory operator interface.
 
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I have one question for you..

You've been in a horrable auto accident and are suffering from internal bleading etc etc.. they take you into the emergency room and pump you full of plazma to stabalize your criticals. Now they have to run you up on the elevator three floors to the O.R. to open you up and stop the bleading. They have 5 minutes before you die.

Question: Do you want the elevator to be running on a PLC or Windows NT?

I thought so....
 
Can I get an elevator with redundant PLC's? And redundant power for that matter...

Mike, I know you use alot of ADC stuff, and I always get a kick out of the disclaimers in the box that say not suitable for use in life threatening devices, so do hospital elevators run ADC PLCs? :p
 
Who really cares?

Other than the soft PLC and hardware PLC manufacturers who really cares? Well may be some senior project people do.

In my opinion, if you want a PC buy it. If you want a PLC buy it. If you want one to do the job of other just do it. Why does/should the rest of the industry care. If you are building a 400 gazillion ton injection molding press do you really care what type of control is being used in an ice machine?

Anyway, the US marketplace will probably only shift to soft PLCs when Rockwell tells them to.
 
Mark,

Actually I cant recall any hospital elevators with AD PLCs. However a few with GE Series One, (same as AD 305). Mostly GE 90-30. However we have installed AD 205 in quite a few nursing facilities.

Regarding the CYA notice that AD and many other manufactures place on the packaging: Due to liabiliy issues we take note of that, and design the equipment so that the encoder/sensors are not used in a manner so if failire occurs it will not threaten life or limb. Additionally the elevator code ASME A17.1 requires that some circuits be provided with redundency.

We're in the specification phase of a project that may require redundent PLCs. This will be a first for me. I have to check into thoes "safety PLCs" to see if they can do the job. If not it may be two AD DL-06s, or all hardwired relays. I have to submit a reccomendation in a few days. So I'll be glad to take any and all suggestions....
 
If the elevator fails and doesn't directly cause me any harm, but I die because I'm stuck between the ER and the OR can I sue the PLC manf? I sure hope the answer is no, otherwise alot of my stuff is probably vulnerable :D

I don't know anything about redundant or saftey PLC's... Its never come up in the cotton industry and hopefully it'll stay that way.
 
Mark,

No the PLC manufacture usually is'nt on the chopping block. Your attorney will first sue the building owner then me, and then anybody else. But in your case, since your dead, your family will have to sue me. But they wont get as much, as you would if you didnt die and just became brain dead. In regards to civil liabality issues live people are worth much more then dead people.

Now it seems that everybody likes to sue MicroSoft. Hmmmm. Maybe we should go with PCs in elevators????
 
I am darn sure I will not trust any of my critical applications to Bill Gates and his band of merry men, or the cheap and unreliable Taiwanese and Chinese switchmode power supplies that are normally supplied in computers.

I hear the bleatings of the Soft PLC crowd saying that the software runs as a separate application and if Windows crashes the Soft PLC continues to run. What happens when you have to reboot the computer? Or have to turn the computer off to get Windows to start up properly? Too many ifs.

I have had 3 power supplies fail in the last 6 months in different computers. Have not had a PLC power supply fail for many years.

Yes, you can get hot standby PLCs that will changeover in milliseconds. You can also get warm standby PLCs that are not as quick or reliable as hot standby with 2 power supplies, 2 processors etc. The good ones are not cheap, AB, Omron etc. The warm standby units such as Schneider Premium etc are a lot cheaper. Depends on the job requirements.

Be careful Mike as there is a big difference between warm and hot standby. There is also a dig difference between these two and safety PLCs.

Two PLCs tied together are not the same as the above.

The upper end of hot standby PLCs includes duplicate I/O racks as well as processors and power supplies with a changeover unit. They are VERY expensive.

Good hot standby PLCs will also allow you to change I/O cards with the PLC still running.
 

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