PLC brands comparison 3

[xyzz]

I hereby invite all you to suggest the best by your opinion PLC brand and family.

The suggestion should be argumented, not just a personal preference.
Another words, mention at least one property that makes this PLC a better choice than another ones.

Let's limit the subject to single unit PLCs, the rack type being out of scope at this time.

I think, such poll would be interesting for many of us, experts as well as beginners.

 

[OldPfart]

My 2 cents worth. I work with Mitsubishi, AB, GE-Fanuc, Hitachi and Omron.

GE-Fanuc is not too bad although the instruction list is bit limiting. Ethernet with Global I/O is quite good as the Global I/O runs as a separate layer on TCP/IP. Setting up Modbus RTU communications is not the most friendly thing to have to do with the Horner card, although it works well when written and commissioned properly.

Mitsubishi GX is a pain with having to get another password, as previously mentioned. I also got caught with the lockout. What a pain. GX will also not convert some of the software developed with older versions of programming software. I got caught with SC and had to download from the PLC and recomment the whole lot. Try remembering what you did 3 years ago.

Hitachi is bearable but once again a poor instruction list.

AB is OK but the programming software is very expensive and not as flexible as I would like. The SLC500 has a reasonable instruction list but could be more extensive. My biggest grumble is that the last SLC I used was one of the higher end processors but only allowed 2 expansion racks and then one has to go to slow old remote I/O. Support for busses is quite good. Device Net is a big plus, as it is with Omron. Both PLCs have a good workable configurator. I use Device Net quite a lot.

Omron have one set of software to programme all PLCs in the range, with the exception of the ZEN programmable relay. CX-Programmer is very configurable, powerfull and not very expensive. The instruction set in the CS1 and CJ1 is the most extensive I have worked with in the medium sized PLC range and helps reduce development and commissioning time. Huge numbers of I/O available, dependant on processor, and up to 7 expansion racks for the CS1. the CJ1 mounts on a DIN rail. No rack required.
The other thing that is becoming important is the available space in control panels. Unfortunately, the space taken up by infrastruture in buildings is being reduced to very small spaces as it is not leasable. The important thing these days appears to be to squash plant rooms up and expand leasable space to make money. The CS1 is about the same size as the SLC500 but has 96 bit I/O cards. Saves racks. The CJ1 is about the size of a cigarette packet and has 64 bit I/O cards. Space is becoming very important and these 2 PLCs can save lots of it.
The other things I find very good with Omron are networks, (Controller Link is very powerfull and easy to use) and serial communications. They have a set of software called CX-Protocol which allows one to simply set up serial communications with virtually any device through a serial port. There is also a trace function so that one can trace and trouble shoot any serial comms. There are 2 serial ports on the serial card and one can run a different protocol on each port.

 

[jabaldauf]

I design for an OEM to the paper industry worldwide. Back in 1990 I conducted a thorough weighted analysis of the major brands with respect to the types of equipment we supply. Some brands were strong in features we would not use, but weaker in offering the mix of I/O that we would use (e.g. we use far more OUT than IN, which is not typical). You cannot answer this question without some boundary of applications.

We selected Siemens as the clear choice. About a year later we found that our customers in the US did NOT like Siemens. What a hard lesson. Now we use what our customers use. In the US it mostly AB, Siemens in Europe, and OMRON in China.

 

[Samske]

Hi all,

I had read all posted in this thread; I had found it very informative! Thanks to all of those who contributed.
Any way, I would like to ask your opinion on the following PLCs:
I have to choose between the ABB AC800F or Siemens S7 400 PLCs for my current project. Initially, I was going to use Schneider Electric's PLC. But commercially, both ABB & Siemens could offer much better pricing on their PLCs.
I had never used neither ABB nor Siemens's PLCs before. However, I had lots of experience with the Allen Bradley PLC 5 & SLC 5xx PLCs. I am looking for any pitfalls and disadvantages only not the "so-call" great features from each manufacture. ( I had enough of that from the sales men)Any comment/suggestion/warning would be greatly appreciated.

 

[plcuser]

I would not suggest any brand of PLC so as not to be partial. However, I suggest that you may be able to get an idea of what brand is the best by searching the web for the installed base of the different brands. You can search for websites of system integrators or automation contractors/consultants and find out what brands of plcs they have used for their different projects.

 

[Mike6158]

I've written programs for Siemens TI505 (using Ti-Soft and PLC Workshop), Siemens LOGO!, S5, S7-200, and S7-300/400), various Modicon boxes, IDEC, Direct Logic, Allen-Bradley SLC and ControlLogix, and Square D (I think that's all of them). What I would choose if the decision is mine varies depandant on what the local I&E tech is capable of working with, the amount of IO, and the complexity of the task. For my money the Siemens TI555 is the easiest to implement. It has built in analog alarm blocks and PID loops. The Special Function program capability is handy for specialty programs like gas and liquid flow calcs or creating an interface to a 3rd party serial port with non-standard data packets. The Ethernet card made by CTI for the TI series is easy to program. I have 14 TI545's and one TI555 (with 6 RBC's) networked together in one of our gas plants using this card in each processor rack. There are over 125 PID loops and nearly 200 analog alarm blocks used plus over 1,000 lines of ladder logic and 18 Special Function programs on the TI555 alone. 10 of the PLC's transfer data to the TI555 using peer-peer over the ethernet backbone. I also have two S7 remote IO racks connected to the 555 via the Profibus port on the 555 processor. We used a fiber optic profibus network for that. There are also 5 independant, 6000 plus tag Wondware nodes on this network. Once connected to our WAN (RAS, VPN, or Direct) I can remotely connect to any PLC on the network and troubleshoot a problem or even program (don't like to do that.). I also have the latest Wonderware app on my laptop so I can see what the operator is seeing from anywhere on the WAN. CTI also make a serial comm card (various flavors but we use the 2573-MOD modbus card mostly). The serial card configures very similarly to the Ethernet card. There are 4 ports per card. 2 can be used for MODBUS RTU (RS232 RS485 multidrop) and two for MODBUS ASCII. Typically, in a data concentrator application, we use Port 1 as a MODBUS RTU slave and Port 3 for the MODBUS RTU master. If we need more Master ports for devices that do not use the same baud rate we just add another card. This system has proven to be very reliable (Zero downtime in 5 years). So, for large systems where I want to emulate DCS functionality and provide an easy to learn programming environment for the local tech I would chose the TI model from Siemens and Workshop software from Fast-trak Softworks.

For smaller or single processor jobs I like the Siemens S7. If it's ethernet card was able to handle the density of ethernet traffic that the CTI ethernet card can it would be my first choice. The S7 offers many options on programming language including Statement List, Structured Text, Ladder, Function Block, and ??? one I obviously don't use It allows you to create and compile your own blocks which greatly speeds application developement. For instance, I have a block that I created for lighting a pilot on a burner management system. If I have a 10 burner heater, I call the block 10 times and populate the inputs with the correct addresses for each pilot. Outputs and intermediate operations are stored in data blocks. I also have a pseudo AGA7 calc block (110 internal variables) that I can use in lieu of a MODBUS connection to a flow computer. The S7 is a good data concentrator and MODBUS RTU Slave or Master is easily implemented. Using ProTool integrated with Step 7 it is very easy to develop an application for a local operator interface (touch panel, text display, etc). If I had one complaint it would be that their PID loop is incomplete at best. I've taken their block apart and if I can ever find the time I am going to modify it.

The S7-200 is my first choice for small applications. Especially if I need a MODBUS slave. It's easy to program and has a myriad of features sometimes not found on larger PLC's

I like the Direct Logic line of PLC's. Their PID loop is very robust.

My least favorite? Allen-Bradley. I do not like their programming software. I hate the way they name IO. The aforementioned systems all have a clean import / export feature that I make use of. I am a documentation fiend and I hate having to type information twice therefore I create my IO map in Excel, including symbols and descriptions, and then import that info into the program. Allen-Bradley's import / export feature yields a file cluttered with useless nonsense. When they implemented the ControlLogix line they almost got it right. There are a lot of things that I like about this line however their import / export feature is horrible and they blew it big time with their implementation of Structured Text. What good is Structured Text when there is no way to easily (note that I said easily) associate variables with the instance of the block. The blocks are not compiled and there are no instance variables. Each variable has to have a tag. The tags are not auto-generated. Why is that a big deal? Using my pseudo AGA7 block as an example- There are 110 variables associated with this block. If I implement it in the ControlLogix platform I have to manually create 110 variable tags for EACH INSTANCE of the block. Plus, I have to edit the instance of the block to point to the correct variables (can't use the same variable every time). I could use indirect addressing to mitigate this somewhat but all 110 variables per instance would still have to be generated. I was frankly very disappointed in the way that A-B implemented Structured Text.

 

[Samske]

Mike6158,

Good feedbacks on the Siemens PLCs....I take it that you haven't came across any ABB AC800F/AC800M before?
Anyone else's has any things to add to either ABB or Siemens PLCs?
Thanks in advance,
Samske

 

[wylde]

As a plant engineer and maintenance manager it is necessary to use what fits best with the rank and file. Ge-Fanuc is the easiest for my electricians to use. It is already here and all of the electrician use it. All simple jobs have Ge-Fanuc 90-30. Software is not overly expensive. We have 4 Siemens S5's and it is universally disliked. S7 fares a little better. Software is costly. The six AB SLC and Micro and 5000 all are not liked by the electricians but liked by outside contractors who use AB. I hate their addressing methods. Software is too expensive. As for others I have experience with, IDEC is great. It is easy to program, software is free if you buy a small PLC. Phone support is incredable and so far free. Some old Square D can be programmed with IDEC software. I have used it in Mexico and it took about 10 minutes to get the plant computer guy along with his electrician to use it. I have no Omron in this plant but like it. Omron is very powerful and it uses a simple address system. Very logical. Can not mess it up. Omron plc's seem to like math. It likes networking. Commucating from here to Ireland is as easy as the next office. Price is usually lower than AB or Siemens. Omron is the largest logic control manufacturer in the world. I can see why. If I could start everything over in this plant 50 plc's would be IDEC or Omron.

 

[Mike6158]

Hey Wylde,

I understand your electricians frustrations with the S5. Especially if they are using the Siemens software. But, the S5 a rock solid box. I have one that I will eventually change to an S7-200 but only because the S5 will eventually be mature (might be now come to think of it)and support may become an issue. You might want to look into Fast-Trak softworks S5 programming software for the S5. One of it's strengths is that it will convert some of the statement list commands into ladder which is usually more familiar to electricians. It all depends on how the STL was written and what commands are used. STL (statement list) is a very powerful language but I know a lot of people that hate it. I love it. I don't know as much about it as I would like but every chance that I get I write something in statement list I do. Sometimes I use it just because it's available (S7).

Fastrak is at

http://www.fast-soft.com

and you can dl a demo of their software there.

I'm with you on AB addressing. It's like they think that we like to type or something ) I wish that everyone would take the tac that Fastrak did with their software. No clicking and dragging. Just start typing the address in the rung and you get a NO contact. Hit the / key and it changes to a NC contact. Hit the O key and you get an output. Type SET and you get a SET. RST and you get a Reset. If there was a programming drag race event the 505 with Fast-trak's software would win hands down )

The IDEC is a sweetie but the last time I programmed one it was like the Direct Logic box in that there are no online edits. You have to shut whatever it controls down to be able to download the program changes to it. The box I used was an FA3S so it's possible that IDEC has improved in that respect. I have no idea.

I recently did a project where I replaced an old Square D with a new S7-315 and a WW interface. There was no documentation. No IO list. Nothing but wire numbers with no meaning. It was quite a challenge to determine what went where but that's my favorite thing to do so I had fun. By the time I was done (first Square D for me) I had cleaned up the original Square D program and fully documented it and there was really no need to change it as the problems that they were having were related to trash left in the program when the plant was reworked a few years earlier. The Square D line must have been pretty high end in it's day. I really liked it. Too bad it's mature.

Samske- No ABB for me. Not yet anyway. Counting panel software and Wonderware I think I have 18 different PLC/HMI software packages loaded on my laptop ) The IT people took over our software purchase / maintenance operation a few years ago. They still can't get my stuff right ) so it would be fun to add a few more PLC/HMI's to the list )