Which PLC?

Hi ,

I dont know much about ,PLC's but my company has a huge automation project with full of PLC's.

We are in the step of deciding which PLC's to use.Possible candidates are
Siemens,Schneider and Allen Bradley

Is there a documentation that you know which compares these ?

And can some1 tell me about what is ModBus,Profibus ?
I would be happy if you email me from
[email protected]
Thasnks

Boy, have you started a fire storm!

Of the three choices you gave, I personally prefer Allen Bradley. Siemens is hard to learn and hard to work with, and, in the US anyway, Schnieder is losing market share and not a big player.

My first choice is Koyo (sold as AutomationDirect.com in the US) and if you are o0pen to other possibilities you should look at them.

The most critical thing, especially since this is your first project, is local support. Any of the above can probably handle your requirements, so go with the unit that has a very good local technical support group that you can access often and quickly and that have a good local inventory of components. Any differences in first cost between the various supppliers will quickly become irrelevant if you can't get the support you need.

Your choice will most likely be made on the basis of commercial considerations rather than technical specifications. Any of the three options you're considering will probably have models to suit your needs.

If the project is as large as you imply, then you have tremendous leverage with your suppliers. Invite them all to bid on the project, and tell them you expect them to include technical support in the form of training for your people, application engineering support, deep discounts on multiple software licenses, commitments to keep spares for your system in stock, and anything else on your wish list. See who makes the best (and most credible) offer.

Get to know the local sales and support people. You'll be spending a lot of time with them. Make sure you're comfortable working with them. Find out how long they have been in the business and how long they have been working for their current companies. Be wary of dealing with a company that has a history of high employee turnover rates.

Steve,

I personally like to use Modicon PLCs but the correct choice will depend on some questions.

Do you require redundancy in you system?
Is cost a big consideration?
Where are the PLCs going to be located and would remote I/O be better than using multiple PLCs?
Will you be using TCP/IP protocol for communications between your PLCs and HMIs (assuming you are using HMIs).
There are many other considerations to take in to count.

I would be glad to help with your questions.

John

I agree with Tom Jenkins.But my first choice is Omron then AB.Keep away from Siemens.Evrey think you can imagin will take much more time with Siemens.

Arik

Well ,

First of all thanks for answers.I totally agree with Tom Jenkins ,this is a fire storm.I2m an software engineer and my profession PIC's , and other microprocessors.
PLC is a new thing to me.In Turkey I dont think we can find Koyo or get local support.

I have been looked at Siemens datasheets.Siemens is the offset for me.I will compare it with other PLC's.But let me tell you about our project.It's a "tunel automation project ".

There are almost 10 subsytems.We need to communicate with these subsytems and from te SCADA monitor an operator will watch these operations.


I have looked up the catalogs of Siemens S5 and S7 series.Primary criteria for me is the CPU , number of digital,analog I/0,serial interface(does it support CAN or RS-232/485),and if it supports fiber optic ,can it work in 220 V ,50 Hz AC.Can I build an TCP/IP ntw wþth them.Because point to point (CPU-CPU) connections isn't evry health or long distances as I can see.

And redundancy is vey important too.As I learnt , in automatin applications there is always a "master PLC" that SCADA communicates.
And fail safe working is important.In order to achieve fail safe operation there is a stand by "master PLC" which will start to operate when real master fails.Is it true ?

So , there will be redundancy in my design too.But I dont think it affects other "field PLC's".
Things like aritmetic operations it can do , or it's instructions cycle length are the second,may be third ,criteria for me

I hope this message is more detailed for you to give other toughts.


Am I missing any important point in criteria ?

Hi tguclu,

First, stay away from Siemens S5. This is obsolete by now !

Second, a SCADA dont have to connect to a master PLC. A SCADA can connect to several PLCs at the same time.

Third, you say that your project is "tunel automation". Does this mean that it shall handle ventilation, lighting, warning signs, etc. in a tunnel used for public transportation.
If so, you DEFINITELY need a socalled redundant PLC with hot backup.
Siemens has a complete range of socalled increased availability PLC systems (S7-400H). Others will have someting similar.

If you are new to PLC systems, then I recommend that you get experienced help (a consultant) to estimate the need for PLC redundancy when it comes to safety issues.

A good SCADA system that is very powerful and easy to use is Citect. www.citect.com. It has the very best SCADA trend pages as standard and is happy with DDE, OPC, just about every PLC known to man. The drivers for the various PLCs are free with the package, with a few exceptions such as AB because AB require a licence fee on the drivers when sold with the SCADA.

If you require redundancy, how much redundancy do you want? Omron have full redundant PLCs in the CS1 range but they are very expensive, as are AB etc. There is a cheaper version coming out with less redundancy. Talk to your Omron rep.

I am another one that would suggest you stay well away from Siemens. They very much have their own way of doing things. You will find people either luv 'em or hate 'em. YUCK!!!!

Omron have support for Device Net, Profibus, Ethernet etc. They also have radio Device Net. The only system I have seen of this type. Also full fibre optic support - you can also mix fibre optic and wire in the same system. A lot of new product here.

AB also strongly support Device Net but their configurator is no where as easy to use as the latest Omron offering.

Several other things about Omron'c CS1 that are very attractive are 96 bit input and output cards - save space - save racks - save money, serial cards that can be mounted in the processor and/or on the rack that are specifically designed for serial communications via RS232/RS422/RS485 to any serial device. A very good set of software is available called CX-Protocol. This allows you to write very simply a protocol to communicate with any serial device. I use it all the time for Modbus, CAT X15 (X25?) protocol and anything else I need to connect to the PLC. Saves heaps of time and money.
beerchug

tguclu, when the guys are giving you their opinions, they only know what is going on in their geographic area. I think for what you are asking there is only one in your area that can provide what you are asking for. That is Siemens. Yea, some people don't like 'em. Most of them have only worked on small stuff. What you are asking for is on the large scale. Siemens is about the only one that has everything you need. Keep all of the HMI, PLC communications, redundacy, etc with ONE company and should should be good to go. Less headaches and NO finger pointing. Very few PLC manufacturers are sold or supported in Turkey. I do know that Siemens is the largest there and in the rest of the world. Maybe not in the US, but that is not what you are asking. Yes, I agree the S5 platform had it's issues. The S7 platform is where you want to look. Siemens has a transportation group that does trains, bridges, tunnels, etc. Keep looking.

Although I worked for Rockwell Automation for many years, since then I have had the opportunity to use Siemens S7 and Omron CS1 on several significant projects.

The Engineering Company I am Business Development Manager for has used ALL the major PLC systems in over 500 projects spread over 15 years.

For a project of the size and criticality you are outlining there are only two choices, Rockwell's ControLogix and Seimens S7. There are many other competent systems available, and I would indeed rate the Omron CS1 product a decent third.

The S7 family is a strong system, but we really HATE the programming software. It takes us twice as long to program and in the end we have spent a lot of time developing our own VBA driven database system for S7 just to help us develop code and data blocks efficiently.

The two thngs we like about S7 is Profibus which is quite easy to use and popular for that reason. The other aspect is the ability to do partial downloads of function and data blocks, which allows for major surgery to logic while the system is running.

ControLogix in the final analysis is the winner. RSLogix 5000 is a very well organised program we find very efficient to use. The User Defined Table (UDT) is a very strong feature that we make a lot of use of. It allows for highly organised, easy to write code. Virtually everything we do is done with re-usable subroutines and a standard state logic format.

The only disadvantage with UDT's is that their STRUCTURE members cannot be edited online. It is our understanding that this will be fixed in Ver 13 or 14.

The CLX Sequential Function Chart is a recent addition in Ver. 11/12 and is more powerful and far easier to use than the S7 version. We have come to thoroughly ENJOY using it.

ControLogix comms is exceedingly flexible and well thought out. The entire system communication model is well in advance of anything else available. Redundancy is very easy, virtually a plug and play exercise. Multiple processors, multiple communcication paths, and the ability to bridge or "hop" from any subnet to any other is all native to the system.

ControlNet is demands more understandng of how it works than Profibus, but it has much more flexibility and performance. Again ControlNet redundancy is ridiculously easy. Fibre Optic comms and full multipath comms is all available.

Overall we have come to prefer ControLogix because we know that we can deliver excellent automation systems, efficiently, on time, on budget and with happy customers.

PS We do large systems, nothing less than U$50k. In many countries of the world, Autralia, USA, Britain, Germany, Portugal, Malaysia.

Certainly I understand that Seimens will be best represented in Turkey. But this does not mean that Rockwell cannot do good business for you in that country.

After all Seimens does business in the USA , so why is that Rockwell is deemed to be incapable of doing business in Europe?

I just want to pint out for SCADA that InTouch Wonderware has the capability to talk to several PLC's simultaniously and can connect to Any PLC I've used, via serial or ethernet. It also has data collecting and trending support.

I have worked with Seimens, Modicon and Allen Bradley. My prefference is the Modicon Quantum system with the ProWorx editing software. But for ethernet networking multiple CPU's together it gets kind of hairy and loses its user friendlyness. Allen Bradley is much better on the networking side of things. I have never worked with the Siemens S7 platform so I can't give you my opinion on that. Putting a new system together in house is very time consuming and can be quite frustrating at times but the rewards to your company are very substantial. When you contract someone to do it for you, you end up totally relying on them for any modifications, tweeks, changes or additions because most likely they will password protect their program to keep you from doing anything. Being self relient is definately better. Having a good I&C technician to do your programing and maintenance is important.


Eric

hot standby

Hi
as your system is very crirtical as you describe i can recomend schnieder product "Quantum" automation platform .this series offers hot standby module and many levels of redundacy even to the PLC power supply module also safety modules are availble.
Siemens also have hot standby in it's S7 400 as mentioned before in this thread
AB i don't know if they have hot standby modules or not but i am sure that they don't have safety modules.
Also you have to check for what certificates the consultant need because AB is NEMA approved and not IEC.

Ok, now that's it...

I've been using numerous platforms and definitelly the least
desirable one is Modicon - SPECIALLY when combined with ProWorx.
If the Quantum is so great platform, why is it not used anywhere?
I also don't know what are you talking about, when mentioning
Quantum's great power supply!?
This is what I remember first hand about Quantums PSU:
I remember simple system that was rather pain to setup.
Couple of cards in just two racks... Each rack had TWO biggest
PSU units they had and I still had to spend plenty of time
just to figure out working combination. Why...?
Because even TWO power supplies per rack (in numbers 2 per rack!!!) could not supply ENOUGH juice so you can throw the cards in racks
in any order and simply forget about it...

But don't rely on my opinion, go and see for yourself:
Since you are looking at complex equipment, networking is a must.
Select a sample PLC of each PLC family you currently consider then
see how many people you know, have used them. Se if you can
HIRE someone for each of them (at least a contractor so if you get
a problem, there is help...). Search the web and see how hard or
difficult is to find manuals (don't fall for anyone's promisses,
see what YOU can find - chances are your PLC guy or contractor will
have to use same way to look for resources...).
See what is the cost and what is delivery for parts (don't care
about digital inputs and outputs, everyone has those - check what is
delivery for specialty modules).

Having worked in Turkey and several other countries, it was my experience that you will find the best support for Siemens. Siemens makes a good product but I don't believe that it is the best. As many here have said, it is not the easiest to work with. I prefer to use Allen-Bradley myself. As with all, every one prefers to program in different manners. As some one else here has said, Allen Bradley Control Logix can be programmed in both Ladder and in Function Block, so what ever you prefer it is available. Although when I was there a few years ago, AB support was not the greatest. Either way you go both Siemens and AB can do the same things with the proper options, ProfiBus, CAN, Ethernet, Modbus, ControlNet, ect. (not all are available through AB or Siemens, some can be aquired through companies such as SST, and there are others too, just as an addon module). I would Definately stay away from Schneider (Subsiduary Modicon), because of the market share that is out there. I recently recieved a publication (automation news, or something like that) that had a break down of the sales of PLCs and other automation products, that showed Siemens is by far the leader through out Europe, and AB the strongest here in America. There were many others, although Schnieder has been drastically dropping over the last several years. That and it was a major PAIN in the rear to use Schnieder on the several projects that a couple of my customers had specified the use of them.

Good Luck
Having used many of the different types out there I hope this helps.