PLC recommendations

[cjd1965]

Hi I am looking at mid range plcs to try and get something cheaper than S7-300 type.

It must support profibus (maybe as an add on would be fine)
It must be ethernet capable
It must support SFC/Structure text/Ladder
It must be able to support a minimum of 10 PID loops, ideally self tuning

Apart from that it must be cheap.......

I am looking at Omron site and seem OK so far.

S7-1200 seems to be inadequate for all of the above especially programming languages

Interested to hear opinions

 

[JesperMP]

Have you ever heard about IM151-8 ?

It is a CPU for ET200S i/o.
It has PN on board (3-port switch).
Can expand with a Profibus master module (but NOT as Profibus slave, at least not directly).
Programming is exactly like any other S7-300.
It costs approx. 600 Euro.
The performance is like an S7-314 of the latest generation. Which is quite performant actually.
Has webserver on board for several neat functions.

We use the IM151-8 as the standard CPU for our smaller projects.

edit: here is a link to a post with pictures of a small panel with IM151-8 and ET200S i/o:
http://www.plctalk.net/qanda/showpost.php?p=329234&postcount=149

 

[adkot]

Got VIPA?

If you're looking for something similar to S7-300, look at VIPA's 300S system. It is also programmed with Step7. It should handle all you need plus come in under the price of a comparable Siemens.

http://www.vipa.co.uk/

I've been learning a lot about these lately (since we have lots of machines shipped from Europe with these in them) and like 'em.

http://www.vipa.de/
Is the main site since they are based in Germany.

 

[cjd1965]

Jesper
I have looked at it before and it in consideration but i am interested in 'what else is out there'. We have had major trouble lately with PID control (more us than Siemens i expect lol) but the struggle has got us thinking about other brands

 

[PLC]

Jesper
I have looked at it before and it in consideration but i am interested in 'what else is out there'. We have had major trouble lately with PID control (more us than Siemens i expect lol) but the struggle has got us thinking about other brands[/QUOTE



Wouldn't it make sense to just learn how to program pid's
In Siemens than to switch brands?
Get someone in from Siemens to explan and teach you how to
Tune and use.

 

[TurpoUrpo]

Hi I am looking at mid range plcs to try and get something cheaper than S7-300 type.

It must support profibus (maybe as an add on would be fine)
It must be ethernet capable
It must support SFC/Structure text/Ladder
It must be able to support a minimum of 10 PID loops, ideally self tuning

Apart from that it must be cheap.......

I am looking at Omron site and seem OK so far.

S7-1200 seems to be inadequate for all of the above especially programming languages

Interested to hear opinions

If you are used to Siemens, you dont really want to switch to omron imho.

What kind of problems there were with PID loops?

 

[cjd1965]

Hi there is also cost issues. We are losing tenders due to higher costs... competitors using cheap lowest end stuff but we try to be 'main stream' and provide equipment worldwide so try to use equipment available worldwide.

With regard to the pids
We know FB41 PID and used it lots, with sucess, but the last job was a nightmare with 5 cooling loops with varying flows, temperatures etc and we couldnt find a sweet set of parameters. A hard wired controller on permanent autotunewould crack this much easier. it was left with clamps instead of true PID, and the tolerance for the temperatur was opened up. That was after 8 man days of testing by trial and error and following various schemes like ziegler nicholls etc

Cheers

 

[TurpoUrpo]

So what you really think you need is autotune? Where do you expect to get cost savings in hardware side? What kind of hw do you have now?

What are you going to do when that wont work? Would it not be better to learn the tuning?

TIA V11 seems to have autotune blocks for PID's on S7-300 (that means also im151-8 CPU). Do you have it yet?

ps. I remember your short thread in here about temperature PID tuning.

 

[cjd1965]

I fully agree with learning the PID tuning

However when on sites in front of customers it is difficult to learn things like this. I tuned the 2 other loops (flow and heating) with no problem what so ever, FB41

The cooling loops (negative gain) were so hard to tune and when i did get a reasonable response the next day it did not work because of variations in cooling water temperature to the HX and the variable product flowrate. I assume that this was the reason because FB1 was working fine for the first 2 loops.

I did post here at the time and the nice guy Peter Natchway pointed me to a good site but some of the maths was over my head.

I did try the Siemens auto tune block towards the end, which we bought out of desperation. The example project worked ok on my laptop in plcsim but when i loaded it to the PLC and substituted a real world process and control values it didnt work and i ran out of useful time to read the manual more than twice and i failed to understand why it did not work. We find it very hard to get Siemens to come to site and help without paying them.

I have used PID on GE Fanuc, Mitsi A/Q and CompactLogix and I find all of them easier than the Siemens.

Remember I am also looking at COST.

Cheers

 

[TurpoUrpo]

Here is screen from TIA, have not used it, but maybe it would be way to look for you?

 

[cjd1965]

It looks pretty good but not for S7-300 i believe.

I have tons of SCL code i use and S7-1200 is not acceptable for SCL.

Also S7-1200 still a bit experimental in my opinion for critical uses like beverage and pharma type projects.

The IM-151 suggested by Jesper would meet the cost saving (partly) and would allow me to reuse my code which is all good but i am interested in ideas etc... I see IDEC has dedicated PID modules that seem to mimic a proper temperature controller for example

Cheers

 

[cjd1965]

For info I usually use a 3152DP with S7-300 modules in the main rack and MP277 10 inch touch HMI and sometimes ET200s remote io if required

Cheers

 

[GeoffC]

If you want a powerful alternative you could look at the M340 from Schneider
Ticks all your boxes
plus it is 'mainstream' and backed by a global company
I have used it extensively - latest project was a process control application with at least 40 PID loops, Profibus interface to all the motor starters (TeSysU) and ethernet to all the io and vsds (Altivar). All programmed in function block (all 5 IEC languages are supported)

 

[JesperMP]

Another significant saver would be to go from the MP277-10 to the TP700 panel in the new Comfort Panel line. The screen size will drop from 10" to 7", but the price will be less than half. Apart from that there is mothing cheap about the comfort panels. Read my review of the KP700.

 

[paraffin power]

Omron's UK support is outstanding. Worth considering imho.