Soft PLC Evaluation - Would love some Feedback.

Hi everyone, we are currently designing a new product and I would love to get everyone's opinion.

We are building a compressor control panel around a Soft PLC platform. Currently we have a good selling product using AB SLC line and RSView ME but we need to reduce cost and increase custom capability. For this purpose we are looking for a Soft PLC platform with the following minimum specifications.

- Open Architecture Hard Real time OS. Preferrably Windows CE but will consider all other embedded real time systems, with real time extensions built in.
- On board memory, battery backed up ram areas as well as on board support for Compact Flash.
- Onboard Ethernet 10/100 port. dual would be preferred.
- Onboard Graphics Port, provided with either DVI or VGA port.
- 1-2 USB Connectors, 1.1 or 2.0.
- Integrated hardware IO modules preferred, remote if not.
- FTP and HTTP Server built in preferrably.

And the most important item,
- Fully certified for Class 1 Division 2 for Hazardous Locations. The product will be used in Oil and Gas industry and thus requires this certification.

We are currently looking at the following platforms, which very well meet all requirements except the full Class 1 Div 2. Any input on these products would be great! Let me know what you think.

- ICP/DAS Wincon 8000.
- Beckhoff CX-1000.
- Prosoft Prolinx AppSrvCE.

We are not worried about any on board 61131-3 support as we will probably add our own IsaGraph or TwinCAT PLC Engine.

any comments on the three plcs above or if you know of any more, it would be greatly appreciated.

Thanks.

PC Control???


RUN!

Have you looked at www.softplc.com?

Uh-oh, I feel a poll coming!

Mark's Poll

( ) 1 - A Poll for this issue is not nessecary.

( ) 2 - See reponse number 1.

That REALLY scares me.

I hope everything "Fail Safes" to the OFF position.

Check also LabVIEW it look nice and powerfull.

www.ni.com

CaseyK said:

That REALLY scares me.

I hope everything "Fail Safes" to the OFF position.

Click to expand...

Technically a plc is a computer, its just not what is known as a PC. PC is a misnomer, it means personal computer but any computer with any OS can be a PC, MAC is a PC.

The default thought of a PC is something running Windows and the issues that were common with Win 3x and Win 9x, most of those issues are gone now. In reality though there are several options for the OS on a "PC".

With low prices of computer components and advancements in adapting I/O the concept of SoftPLCs or Computers running industrial applications is a foregone conclusion....its gonna happen. It makes sense, why be limited to 32k or 64k of memory when you can have 64MB or more?

I mentioned SoftPLC above because they fill the requirements specified, use embedded Linux (open architecture) as the OS, PLUS they offer direct AB conversions:

If you have an Allen-Bradley SLC-500, PLC-5, PLC-2 or PLC-3 system, you can convert your existing logic and documentation to run in a SoftPLC, saving you untold re-engineering costs! If you are working on a system upgrade, you can most likely keep using the same I/O, communication network, and HMI/SCADA/DCS system as well.

Click to expand...

Technology changes rapidly and economics require that companies obtain the most they can for the least amount so it makes sense that computers will become a PLC/HMI/SCADA system.

The other aspect is that people (everywhere) are learning programming skills at an earlier age so will be more comfortable in the future using high level programming languages. This will not happen over night but in another generation or so you will see things like ladder become less commonly used.

Everything changes over time so expect PCs to become PLCs in the future.

Ron

The only differnt I see between PC and PLC is hardware reliability.
Computers tend to fail more then PLCs.
If I asked what I prefer, I would say the PC.
It cheaper then PLC (PC cost less then touch screen)and more powerfull.
If you ask me if I can put my neck for that, I an not sure.
If it not critical process I would use PC.
For criticl process I prefer to be conservative.
According my experience with PCs in the industry, the HD tend to fail and it shut your line for couple of hours.
When flash memory will be available on the right size and price ,PCs will conquer the industry.
The ladder invented for the electricians of that time.I guess the ladder will stay for old programmers like us.
All of us will have to update our selfs or we will find owr selfs far away.
Peaple from the PC programing area come to the industry and integrat very easy.
I expect the PC will be the popular tool for medium and large projects in the neer future.
I run a project that have abot 500 I/O few PCs few touch screen lot of communications
I am the consultant of this project.
One of the pepole on that plant is PC engineer,he catch all very quickly he wrote the HMI with minor help from me.He understood the PLC ladder and function amazing.
He of course have the right back ground.
That what bring me to think where we will be when those pepole will show around.?

The difference between a PC (low cost - consumer) and PLC is much more than reliability.

PLC's were originally designed to replace relays in an environment full of solenoids, motors, and contactors - the factory floor. The entire design is done with electrical noise in mind.

The main driver for the PC is price. If it's broken and obsolete in 2 years, they don't care. Try to find an exact replacement part for anything over 2 years old. There won't be any tech support for something that "old" either. Forget repair too - all parts are throw-away.

With a PC, lockups requiring reboot is normal. It's very rare to find a software package that is rock-solid. The problem is more severe if you're writing your own code.
No matter how screwed up my PLC program is, I have never "locked up" the processor. Maybe someone has, but it's a rare event.

If you want a PC, you need to consider Industrial PC's. You also need a platform that doesn't lock up. At minimum, that's NT (Windows XP is NT6, but not rock-solid). Unix or Linux is better.

The comparison should be Industrial PC verses PLC. There's not that much price difference.
The major difference is the software approach. The PLC CPU has a hard-coded program. Your Ladder program is a "Recipe" for the hard-coded program. That's why it's so hard to lock it up. You're never changing the main program - only the parameters fed to it.

The PC is a universal computer. It's hard coded software (BIOS) is limited to communications with the hard drive, ports, and plug-in cards.
The rest of the software is loaded into memory from the hard drive during boot up. This makes is very flexable, but boot time can be significant.

Next, what happens during power fail? A PLC has retentive memory. You can program exactly what happens when power returns, including full unasisted recovery. Because the entire software package is stored in chips, the PLC is running in a few seconds.

There are things you can add to a PC to help. UPS, solid state disk, etc. In the end, you beef up a PC to bring it up to the industrial hardness of a PLC.

I can replace almost any part on a PLC in less than 2 minutes. With all the diagnostics and LED's, it doesn't take very long to diagnose the fault either.
With a PC, most of the time you replace parts until it works again.
How long does it take to replace a hard drive, power supply or motherboard?

With a PLC, you try to find a way to make an industrial piece of equipment cheaper.
With a PC, you're taking a cheap piece of disposable consumer electronics, and trying to convert it into something industrial.

The PC does have place when it comes to networking, but if it's not an Industrial PC, then it must live in the air-conditioned office. The Industrial PC also has it's place.

An HMI is better than a PC running an HMI program with a keyboard, mouse, and all the other junk.
An HMI is built for a washdown environment. What happens when you spray your PC or LCD with a water hose?
The LCD backlight is CCFL (Cold Cathode Fluorescent Lamp). That will be dead in 5 years. On most HMI's, this is field or factory replaceable.
Ditto for the touchsceen keypad overlay.
When your consumer LCD goes dark, you'll be told to discard it - it's obsolete.

The PC has a purpose in medium to large applications, but there will still be PLC's as slaves on the machines. The PC will not eliminate the PLC.

Keith

I would not use a soft-PLC, but davephilpot may have his reasons.
He didnt ask if it is a good idea to use a soft-plc, but if there are platforms that can run a soft-plc and can be placed in a hazardous environment.

I think that most Siemens panels are certified for some kind of hazaerdous areas, but I dont know if that includes "full Class 1 Div 2".
You may want to examine Siemens MP270 or MP370 panels. You can load Siemens soft-plc WinAC on these.

Note: S7 (which includes WinAC) is not IEC61131-3 compliant.

WinAC MP

I've inherited a project using a MP-370 with a soft PLC. I haven't had any reliability issues with them but I have moved away from them using a 314 with a standard MP-370 instead. The reasons for switching are:

The screen function suffers unacceptably if the Minimum scan time is set below 30ms, it takes 50 to not notice any effect. A 314 runs the same program at 15ms.

Delivery times were a huge issue, delays in getting the WinAC MP installed in a MP-370 took over a month sometimes. A 314 & standard MP-370 is usually here within a week.

There is no retentive memory, to save recipies, settings, and totals I have to write these values to the EPROM as an offline data block whenever the values are changed.

Clarification

Ok, did not think I would spawn alot of stuff on this issue, most of which unrelated to the question.

firstly, the 3 packages that I stated at the beginning are essentially PLC type packages. They have onboard IO modules which plug into a rack or use PC104 style plug in bus on the side. The "PLC" module, though has an open architecture, has no moving parts and utilizes Flash for all its memory uses. It has full retentative tag capability and boots up in under 10 seconds as it is diskless and an embedded OS. Only difference between this and a standard PLC is that it runs on a platform that has an open OS so that custom tasks can be added. The Virtual Engine, running a full 61131-3 programming suite, runs at the highest priority and will continue to run EVEN IF THE OPERATING SYSTEM CRASHES! As we all know, a PLC also has a multitasking operating system, similar in its way to the Linux, CE, Neutrino, etc. of this world, only difference is that the manufacturer has not made the OS accessible to the user.

I do thank you for the comments on Soft-PLC. I had looked at this as an option but it lacks any on-board video capability or the necessary certification for hazardous locations.

EDAS - CE and about 10 other units I have checked into, running into the same issues as with the Soft-PLC unit above. Having the onboard graphics is essential as a smart touch panel will cost me at least double as a dumb one.

Once again, any feedback on the products I stated or if anybody knows of other solutions, PLC style but with open OS and graphics capability, please let me know.

Thanks.

Pardon my ignorance, but how is the I/O physically handeled?

SoftPLC to real world? I/O cards in the PC or parallel cable to an outside box?
All our stuff goes to a motion control card and it cables to the real world.

Thanks,
Rod

Why in the world would you want to depend on Windows (tons of bugs)and Intel (problems with thermal fluctuation) not to mention hard-drives when PLC's (with their own processors RISC or other) are a lot more reliable? The price, you'll recoup in the long run with a lot less support calls.
A soft PLC will cable with the outside I/O through some form of com. There are some that you can have I/O cards in the PC slots. There are some that you can program in C++. Other than the "virus" (Siemens WinLC) I didn't touch a soft plc in over 10 years. The last one decent was from a company in California and I had I/O cards in the PC with external multiwire cables to terminal blocks. You could have servo cards and analog but I didn't need them for my project.
By the way! SOFT PLC IS DIFFERENT THAN A BOARD PLC. A board PLC will have its own processor, memory etc and will share the power supply and a slot with the PC. A BOARD PLC is a different "animal" that can work very well. A SOFT PLC IS JUST A PROGRAM in the PC that runs from the PC processor (they share the PC processor, memory, hard drive etc.