Choosing the right PLC

[tragically1969]

But is M241 and M251 pogrammable with EcoStruxure? (found the answer, yes.)

EcoStruxure is merely Schneider's fancy name for a family of products, not one specific piece of software, M251 is EcoStruxureMachine Expert, M340/M580 is EcoStruxure Control Expert, neither of which are capable of programming each others PLC range.

 

[mad4x4]

I would think the key here is to choose the PLC based on the functionality you require. It you require to interface and IO counts, special cards such as timer or VoltageMeter may drive the choice. But a General rule of thumb could be (many may disagree) :

Porfibus devices -> Siemens
Modbus devices/Omron -> Modbus
Ethernet IP -> Allen Bradley

CodeSYS plc's like WAGO/BECKHOFF etc can be great for interfacing as they speak profibus/modbus/ethercat/etc/etc and have loads of IO options, but they use high level languages can be hard to get some applications to work 100% of the time and there are many rabbit holes to fall into . Although Beckhoff does support Ladder it is not as rich and powerful as Allen Bradley or Siemens which are ladder first / STL second.

 

[parky]

Yes I do disagree, all have Ethernet either on-board or as an optional card, many of the newer hardware comes with ethernet in-built. Modbus is available on Mitsubishi and AB, not sure about Siemens but I bet there is. Every person will have their favourite and that choice is at least 50% what they are used to, The problem for someone that has not had any exposure is making the right choices, there is no doubt that geographical location may have some influence on it, for example USA almost certainly AB (RW), Germany Siemens, South East Asia Mitsubishi Omron etc. In the UK types of hardware is often depicted by many companies where their head office is in another country. Here in the UK it seems to be any of the Well known PLC's although in general most of the big systems do tend to be AB or Siemens.

 

[kallileo]

CodeSYS plc's like WAGO/BECKHOFF etc can be great for interfacing as they speak profibus/modbus/ethercat/etc/etc and have loads of IO options, but they use high level languages can be hard to get some applications to work 100% of the time and there are many rabbit holes to fall into .

I can't agree with this statement...
You just can do so much more with ST and much faster than with LD as well. The readability is also much better. It's much easier to read 50 lines of text code than scrolling through hundreds of rungs of equivalent ladder code.
The last time I touched ladder was in 2014 and I don't intend to use ladder again unless it's absolutely necessary.

 

[LadderLogic]

It's much easier to read 50 lines of text code than scrolling through hundreds of rungs of equivalent ladder code.

Conversely, it is much easier to spot an open permissive condition that prevents something from starting in a single rung of a ladder with a few dozen of such conditions in series than in an equivalent text code.

Everything has its uses. Nothing is perfect for everything.

 

[tragically1969]

I can't agree with this statement...
You just can do so much more with ST and much faster than with LD as well. The readability is also much better. It's much easier to read 50 lines of text code than scrolling through hundreds of rungs of equivalent ladder code.
The last time I touched ladder was in 2014 and I don't intend to use ladder again unless it's absolutely necessary.

Bit of a sweeping statement!

Programming language in PLC's is entirely application dependent, we mainly use ladder as it suits our product, but we also use ST and FBD depending on what we need

Also good luck trying to talk a less experienced engineer through reams of ST code at 3.00AM when you have a fault on site!

 

[kalabdel]

EcoStruxure is merely Schneider's fancy name for a family of products, not one specific piece of software, M251 is EcoStruxureMachine Expert, M340/M580 is EcoStruxure Control Expert, neither of which are capable of programming each others PLC range.

Any idea what the reason for that is? Is that hardware so different that one software approach wouldn't work for both and in what sense are they different? Just curious.

 

[tragically1969]

Any idea what the reason for that is? Is that hardware so different that one software approach wouldn't work for both and in what sense are they different? Just curious.

M241/251 use Schneider's implementation of CodeSys, M340/M580 is their traditional PLC software/hardware, basically different operating systems in the PLC's, i'm sure you could take a chunk of IEC161131 code and get it between the PLC's but you can't program with the each others package.

They have just commercialised a new smaller PLC that was used internally for Solar projects called the MC80, only 3 models but low I/O and that uses Unity Pro (EcoStruxure Control Expert)

https://www.se.com/ww/en/product-range/62396-modicon-mc80/

 

[drbitboy]

...
You just can do so much more with ST and much faster than with LD as well. ...

Programming language in PLC's is entirely application dependent, we mainly use ladder as it suits our product, but we also use ST and FBD depending on what we need

Also good luck trying to talk a less experienced engineer through reams of ST code at 3.00AM when you have a fault on site!

Yes, even getting the person that wrote it to figure out what it does three months down the road is at best an uncertain proposition. To be honest, ladder can be only about one quantum step better, and either way adequate diagnostics should be on HMI screens to begin with, but at least there is a chance that a technician or maintenance electrician can work it out before they even think to call the engineer.


The main flaw in the "more with ST and much faster than with LD" line of thinking is that is that the programming is not where the money is made: it is made in the operation; and the PLC does not care what language was used because the in-PLC program will the same. One time with the line down trying to suss out what the heck some "magical" line of ST is doing, or waiting for the engineer who wrote it to arrive, and all of the claimed benefit is gone in a puff of smoke; at that point ST is a liability and a disaster.


ST has its place, but it is not a panacea - and I am one who has written many many many lines of code in similar languages.

 

[kallileo]

Schneider has also the M221 line of PLC which programmed by using Ecostruxure machine expert basic which is similar M241 but without Codesys. So for ladder lovers it should be a very decent and cost effective option.

Regarding PLC language preference depends, it on many factors. The first programming language I was taught in college was C so when I saw ladder in the last semester it looked like complete nonsense to me.
Then again in our industry it's very difficult to find people who can do some basic electrical troubleshooting let alone reading any type of code.
So prefer to program using the most efficient and fast way there is by using ST and lately OOP as well which makes a huge difference and invest more time into commenting my code, creating proper documention, performing intensive debugging of the machine and making diagnostics routines for all the I/Os and the main functions of the system.
There are so many useful tools and programming technics in traditional programming that are not used in PLC programs and most PLC programmers don't even know that their exist.

 

[drbitboy]

...

If the blinders are on and one is looking at only the programming side, then of course ST has a decent chance of being the best choice.


But a blanket statement that ST is a win for the life of every project is not even close to a rational statement.


I say this with forty decades in Basic, Fortran, C, C++, C#, gawk, BASH, CSH, Python, Java-/ECMAscript, Perl, IDL, Matlab, etc., and only playing up ladder very recently. The choice of language has not mattered to me for years.


But language debates will continue forever, I expect. Every few years in one company I consult with, someone comes along and decides to port the base code to some new language; all that happens is new bugs are introduced and I get paid. I like C (all the power of assembler with all the convenience of assembler) and have written a fair bit of code in it, but I used to have a tag line "The only problems in C are its proponents."

 

[Rson]

I can't agree with this statement...
You just can do so much more with ST and much faster than with LD as well. The readability is also much better. It's much easier to read 50 lines of text code than scrolling through hundreds of rungs of equivalent ladder code.
The last time I touched ladder was in 2014 and I don't intend to use ladder again unless it's absolutely necessary.

I couldn't disagree more!

I personally write programs to be handed off to a facility and let them deal with it after that point. A well-written ladder program is easy to troubleshoot for maintenance personnel. I know some guys always want to be called to update their software, but I don't want my phone ringing again if I can avoid it!

It is much easier for facilities to find a trained technician who will understand ladder than it is to find someone who understands programming - much less the programmer himself who originally wrote it.

Of course, if the facility has trained personnel and wants to use structured text or other programming languages, that is their choice. My personal experience has been that I can teach a guy how ladder works & how to spot a problem, but a (non-visual) programming language is much more difficult if not impossible for some.

 

[kamenges]

Originally posted by drbitboy:

I say this with forty decades in...

You, my friend, hold your age well.

Keith

 

[drbitboy]

You, my friend, hold your age well.

Keith

apparently not, that's my second factor of 10 blooper in two days!


:-/

 

[Toine]

You, my friend, hold your age well.

Keith

How very eloquently put
I was just thinking Marty McFly.



In the mean time I do agree with drbitboy. I came into this field from a history of 20 years PC programming. That probably helped to learn ST with ease. Yet I still write many parts in ladder because for some logic it just works well, it is easy to troubleshoot visually and last but not least it is the only Codesys language that my co workers know how to troubleshoot at all.