# Soft PLCs



## emtnut (Mar 1, 2015)

NC Plc said:


> Exactly where do these get used? My book describes what they are but not where they are best suited to be used.


I'm probably old school ... but they'd be used nowhere !

Maybe in a class room, or some low budget job.
But why would you use a PC to simulate an actual PLC ?


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## NC Plc (Mar 24, 2014)

I'm not sure. I don't like PC based tools like PC based oscilloscopes, for example. There are just so many things that can knock out a PC I can't imagine why you would want one over a PLC. The hardware differences alone worry me.


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## splatz (May 23, 2015)

I am watching these very, very closely and mark my words there will eventually be tremendous growth in PCs in automation. 

The hardware has a TON of horsepower. It's not needed for a lot of things, but those that do, it's impressive. 

A PC operating system allows tight integration with the rest of the enterprise's IT. You can achieve this with the PLC separate from the PC, but sometimes the better setup is to have the two in one machine. 

Getting a PC involved opens the door to far, far richer HMI, by orders of magnitude. Honestly the HMIs that PLC makers brag about are impressive for 1989. (Look at your phone.) 

The PLC tolerates harsh environments better, but PCs hold up fine in most shops. In the really harsh shops, it may be that the PC doesn't have to be in the shop - just the I/O. We already seem to be seeing the separation of the brain and the I/O in PLCs. It might be that ultimately all the brains will be in the data center, just I/O in the shop. 

Everyone bags on Windows reliability and rightly so. Having the machine's operating system entirely dedicated to automation is an obvious advantage. However I have PC based DAQ system running in a shop for a few years now and really it's a non-issue. They basically stay up from power outage to power outage. It's more than adequate for this application, and I think for many applications. Of course you have to know what you're doing with PCs to achieve and maintain decent reliability.


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## AK_sparky (Aug 13, 2013)

On mobile equipment we often use software based PLC. The Computer is a ruggedized Windows or Linux system integrated to a touchscreen. It does all the display and the 'thinking', while a few IO modules spread around the machine do all the IO handling. On mobile equipment space and access is incredibly limited (think about space for 'extra' stuff in your car), so having a device like that is highly beneficial there.


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## emtnut (Mar 1, 2015)

I'm stickin with old school 

But, I mainly do Gov't jobs, and to get a PC you usually have to go through the IT dept.

Even in plants that have 2 separate networks .... The 'email machine' and the process network, a lot of the processes wouldn't be too happy waiting 5 mins for the friggin windows to boot up :blink: .... or for the multitude of 'windows' processes that like to run on their own every now and then, and slow the PC down for a few minutes.

I could see a Unix/Linux/Qnx based machine being better, but I have no experience with them (PLC simulator wise)

Looking forward to hearing other users experiences though


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## oliquir (Jan 13, 2011)

i see that a lot now in new plants, they use just one pc that controls all io (remote io module wired or wireless) and have integrated touch screen scada. only one program for everything. But programming is made by computers software developpers not by plc programmers ( a lot of text coding!)


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## NC Plc (Mar 24, 2014)

oliquir said:


> i see that a lot now in new plants, they use just one pc that controls all io (remote io module wired or wireless) and have integrated touch screen scada. only one program for everything. But programming is made by computers software developpers not by plc programmers ( a lot of text coding!)


How do they handle voltage sensing? Fiber optics?


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## gnuuser (Jan 13, 2013)

NC Plc said:


> How do they handle voltage sensing? Fiber optics?


along with the properly configured sensors they function quite well and with a fiber-optic interface there is no electrical path for unwanted feedback such as emi.
the benefit of a soft plc is real-time modification of a function such as timers and counters and other sensors, including how the data is handled.
quite often can be done on the fly without shutting down the equipment and uploading a new program.

of course one of the downfalls is the need for more rigid protection for the pc equipment inside (ie: errant voltage spikes, brownouts, etc.)
that and cost.

i think the hardest hurdle to deal with is the operating system requirements of the programs and getting adequate training with the software the systems use.
true there are companies that offer to train you but there is the questions 
how good is the training?:001_huh:
do they guarantee their training?:blink:
and the foremost question from accounting, how much is the @$$ rape for this training gonna cost?:laughing:

myself i prefer linux and scada over windows tripe primarily because of all the time ive had to spend fixing F****d up computers running windows,(endless defrag, endless virus infections, and worst of all monumentally F*****d up registries from careless installers and under qualified personnel)


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## NC Plc (Mar 24, 2014)

Well I hope if and when the industry switches to soft PLCs there is still room for me to repair and adjust the electronic components of sensors and plugs. :laughing:


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## emtnut (Mar 1, 2015)

NC Plc said:


> Well I hope if and when the industry switches to soft PLCs there is still room for me to repair and adjust the electronic components of sensors and plugs. :laughing:


Just my opinion ... but if software guys start doing the programming, there will be MORE than enough work for all of us :whistling2:


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## NC Plc (Mar 24, 2014)

emtnut said:


> Just my opinion ... but if software guys start doing the programming, there will be MORE than enough work for all of us :whistling2:


How so? I imagine you're hinting that they're going to demolish control systems due to a lack of understand when it comes to signals and sensors? :whistling2:


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## KennyW (Aug 31, 2013)

This thread is about 5 years late. Theres no real dividing line between plcs and "soft" plcs any more. Many many plcs are built on top of a real time Linux OS. You can't see it, but it's there. I could show you two Wago plcs, one that is a soft plc and one that is conventional, and you would not be able to distinguish between them.


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## NC Plc (Mar 24, 2014)

KennyW said:


> This thread is about 5 years late. Theres no real dividing line between plcs and "soft" plcs any more. Many many plcs are built on top of a real time Linux OS. You can't see it, but it's there. I could show you two Wago plcs, one that is a soft plc and one that is conventional, and you would not be able to distinguish between them.


Maybe for some industries but all I have worked with are normal brick or modular PLCs, there are no soft PLCs being used. I assume it's because the environments are full of grit, dust, oil, grease, massive amounts of electrical noise, massive amounts of vibration, etc.


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## KennyW (Aug 31, 2013)

The difference between a traditional PLC and a Soft PLC really has nothing to do with vibration or temperature resistance. Both PLC hardware and PC hardware can be purchased with whatever environmental ratings you'd like. 

As an extreme example, this Perfectron Mil Spec computer is more durable than any PLC you've ever worked on, can has an intel Core i7 in it. 











A soft PLC is a software concept, the hardware is irrelevant. It's all circuit boards and transistors in the end. There is a sea of industrial PC's out there.

The reason to use them is processing power. We have some projects where we interface with lasers that send sequential data packets 1ms apart and the packets aren't small. Using a PLC to parse that data and do the associated control without missing any packets was literally impossible. We moved the PLC program to an IPC running a realtime linux OS that was only 30% faster in terms of clock speed, and it does it easily. Other than the part number being different and being able to SSL into linux in the background, form a shop person's perspective the change would be undetectable (programming is exactly the same).


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## NC Plc (Mar 24, 2014)

KennyW said:


> The difference between a traditional PLC and a Soft PLC really has nothing to do with vibration or temperature resistance. Both PLC hardware and PC hardware can be purchased with whatever environmental ratings you'd like.
> 
> As an extreme example, this Perfectron Mil Spec computer is more durable than any PLC you've ever worked on, can has an intel Core i7 in it.


They can, but cost is a factor. I imagine PLCs are for the low end operations now, then, and PC based systems are more high end. I don't know if low end is the right word.













KennyW said:


> A soft PLC is a software concept, the hardware is irrelevant. It's all circuit boards and transistors in the end. There is a sea of industrial PC's out there.


Well I know that PLCs, even affordable ones, are industrially hardened to resist harsh environments. I don't disagree that PCs are capable, but I wonder what the cost curve is. I know I saw a graphic somewhere describing, cost wise, when PLCs are better and when PCs are better.



KennyW said:


> The reason to use them is processing power. We have some projects where we interface with lasers that send sequential data packets 1ms apart and the packets aren't small. Using a PLC to parse that data and do the associated control without missing any packets was literally impossible. We moved the PLC program to an IPC running a realtime linux OS that was only 30% faster in terms of clock speed, and it does it easily. Other than the part number being different and being able to SSL into linux in the background, form a shop person's perspective the change would be undetectable (programming is exactly the same).


Now that's an explanation I like. This is why I ask questions on here, neither my teacher nor my book covered any of that.


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## macmikeman (Jan 23, 2007)

What would the one buried under the floor mat right over top of the transmission in my 14 Chevy Express van be, a soft PlC or a real PLC? I haven't dug it up yet. With the shape of the pavement on Oahu roads, it must be one tough bugger. My understanding (rumored) is the entire fuel to engine process is now done entirely with software and no cable to the carburator from the accelerator pedal is involved, and similar for the gear shift management. I haven't even bothered to look at the engine compartment to verify any of this yet, just put the key in and go.


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## emtnut (Mar 1, 2015)

macmikeman said:


> What would the one buried under the floor mat right over top of the transmission in my 14 Chevy Express van be, a soft PlC or a real PLC? I haven't dug it up yet. With the shape of the pavement on Oahu roads, it must be one tough bugger. My understanding (rumored) is the entire fuel to engine process is now done entirely with software and no cable to the carburator from the accelerator pedal is involved, and similar for the gear shift management. I haven't even bothered to look at the engine compartment to verify any of this yet, just put the key in and go.


My son-in-law is a mechanic (Automotive Technician he keeps sayin!)

Your gas pedal is an electrical signal sent to the on-board computer. There is an output to the injectors ... all electronic.

So much for fixing broken cables with spit bolts :laughing:


**Edit** Carbs ?? :no:


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## KennyW (Aug 31, 2013)

NC Plc said:


> They can, but cost is a factor. I imagine PLCs are for the low end operations now, then, and PC based systems are more high end. I don't know if low end is the right word.
> 
> Well I know that PLCs, even affordable ones, are industrially hardened to resist harsh environments. I don't disagree that PCs are capable, but I wonder what the cost curve is. I know I saw a graphic somewhere describing, cost wise, when PLCs are better and when PCs are better.


It's not about cost, really, it's about using the right tool for the job. There are cheap PLC's and expensive PLC's. Cheap PC hardware and expensive PC hardware. Industrially hardened, and not. An application can reach a point where there are memory, processing power, or other interoperability requirements that make a PLC impractical. 

And again something like a Wago IPC really blurs the lines. It looks exactly like a PLC (a "brick" as you call it, with IO modules that slot in to form a chassis), but its running Linux in the background.


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## emtnut (Mar 1, 2015)

KennyW said:


> It's not about cost, really, it's about using the right tool for the job. There are cheap PLC's and expensive PLC's. Cheap PC hardware and expensive PC hardware. Industrially hardened, and not. An application can reach a point where there are memory, processing power, or other interoperability requirements that make a PLC impractical.
> 
> And again something like a Wago IPC really blurs the lines. It looks exactly like a PLC (a "brick" as you call it, with IO modules that slot in to form a chassis), but its running Linux in the background.


I can see it being used in a high end application. 
But ultimately, hardware is faster than software ... Period.
If your relying on communication, then a _dedicated _Linux machine would obviously fare better than any PLC.

When Linux/Qnx/Unix/Windows machines come into play, then you generally need someone who is proficient with software.

Generally speaking, guys on the floor and software guys speak 2 different languages. 
From my experience, what you have is a lot of finger pointing when a process is down.


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## NC Plc (Mar 24, 2014)

emtnut said:


> I can see it being used in a high end application.
> But ultimately, hardware is faster than software ... Period.
> If your relying on communication, then a _dedicated _Linux machine would obviously fare better than any PLC.
> 
> ...


To be fair, I can see a LOT of potential for using a soft PLC. There are just one or two things I don't care for.

First, cost. The cost of the PLCs we use are a fraction of what a soft PLC would cost.

Second, reliability for 24/7 operation. I am just not convinced that they are reliable enough to justify using one for a remote 24/7 installation.


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## KennyW (Aug 31, 2013)

emtnut said:


> When Linux/Qnx/Unix/Windows machines come into play, then you generally need someone who is proficient with software.
> 
> Generally speaking, guys on the floor and software guys speak 2 different languages.
> From my experience, what you have is a lot of finger pointing when a process is down.


That was true 5 years ago. Like I said, something like a Wago IPC appears no different to a "floor guy" than any other IEC Standard (61131) PLC. You program it and troubleshoot it in Ladder, or FBD, or SFC, IL, or ST using the standard codesys PLC programming suite like a normal PLC. The fact that Linux is accessible is only noticeable to someone who cares. 

This concept you guys are discussing where a Soft PLC equals a Beige PC Box running a bunch of weird software that only computer nerds understand is out of date.


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## splatz (May 23, 2015)

I think we're talking about very different things that could both be called a SoftPLC. 

If it just uses PC hardware architecture and a Linux operating system under the covers, that's one thing. The manufacturer has leveraged existing technology to put a PLC together and if it's reliable and stable, they are likely to come out way ahead. But to the end user it's not really important how they achieved their price / performance: works like any other PLC. It's similar to the Linksys router you buy at best buy, it's Linux under the covers, but the end user doesn't deal with that. The commercial Cisco they don't sell at Best Buy runs a proprietary operating system and hardware architecture. 

I when I think of a soft PLC, I think of a computer running the PLC software as a subsystem alongside the usual things in a PC, and the ability to install other software alongside the PLC. This is where people get scared because they know that the computer they use is not really a hardened, super reliable system, in fact far from it, and it's a valid concern. But this is also where the opportunity for integration with things outside of the automation system (databases, ERP software, etc.) is really interesting. 

I saw one device that is a blend of these two, it's basically a PLC daughterboard / SBC. Even if you restart Windows, the programs on the PLC will continue to run, it has its own operating system, memory, processor on the board. So is it just a stupid trick putting it inside the computer case? I think it would boil down to how robust the integration with the operating system is, for communications between the PLC and Windows, and possibly if it uses Windows to create a more robust console and / or HMI for the PLC.


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## KennyW (Aug 31, 2013)

I guess what I'm saying is that the version of a Soft PLC you are describing is a toy/educational device/marketing gimmick for the most part, but a "real" verison of such a device does exist, and it does have uses.

The version I am describing has the additional power and processing speed without the gimmicks. As far as integration goes, these devices do all of the things you mention - they will read and write into databases directly with no intermediate drivers or devices, have their own integrated HMI server and Webserver, and you can install additional programs on them and pass data in and out of these other programs that run in parallel with the Soft PLC program.


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## gnuuser (Jan 13, 2013)

KennyW said:


> That was true 5 years ago. Like I said, something like a Wago IPC appears no different to a "floor guy" than any other IEC Standard (61131) PLC. You program it and troubleshoot it in Ladder, or FBD, or SFC, IL, or ST using the standard codesys PLC programming suite like a normal PLC. The fact that Linux is accessible is only noticeable to someone who cares.
> 
> This concept you guys are discussing where a Soft PLC equals a Beige PC Box running a bunch of weird software that only computer nerds understand is out of date.


correct that is not a soft plc but a pplc

a pplc is rarely used in most industrial installations anymore due to the advancement of plc/slc 
couple this with the fact that a pplc would require more security and the stability of redundant power supplies with established shutdown procedures

the benefit is it is always connected


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## gnuuser (Jan 13, 2013)

KennyW said:


> The difference between a traditional PLC and a Soft PLC really has nothing to do with vibration or temperature resistance. Both PLC hardware and PC hardware can be purchased with whatever environmental ratings you'd like.
> 
> As an extreme example, this Perfectron Mil Spec computer is more durable than any PLC you've ever worked on, can has an intel Core i7 in it.
> 
> ...


true there are devices like this out there but remember the accounting trolls of most companies do not understand what special requirements mean 
only the cost:laughing:

hell most of those twits would rather we use stone axes and flint spears to control a nuclear reactor 

you know us we'll try to make it work just to see the chagrin on their faces when the $h!t hits the fan from their stupidity and they have to explain the waste of money and time:laughing:


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## KennyW (Aug 31, 2013)

gnuuser said:


> true there are devices like this out there but remember the accounting trolls of most companies do not understand what special requirements mean
> only the cost:laughing:
> 
> hell most of those twits would rather we use stone axes and flint spears to control a nuclear reactor
> ...


In my company's case the hardware cost of the controller for the sort of projects that would use such a thing is actually a tiny percentage of the total project cost. It's barely even a line item on the quote. 20k for the controller when the network gear is 5x that means nothing in the grand scheme of things, but I'm lucky in that sense I guess.


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