Non-ladder Automation Controllers

R

Thread Starter

Ranjan Acharya

<clip>
Can anyone name a successfully marketed PLC that does not run ladder logic?
</clip>

<clip>
modern PLC's do support some other style of programming, but the common
ground they all meet on is ladder logic.
</clip>

PLC's and automation controllers not on ladder. Also, are we talking about PLCs here or Automation Controllers ?

I have seen several (as already pointed out over the years) -- tools such
as:

- APT (Siemens SIMATIC from TI)
- STEP 7 (Siemens from Germany)
- QuickStep (Our good hosts at Control.com)
- ....

OK APT compiles down to (sort of) ladder logic -- fun to follow in TISOFT anyway. The QuickStep controller does not use ladder at all and Siemens are certainly no fans of ladder either. As far as I am aware, the base language of the S5/S7 is not ladder logic. I do not feel that ladder logic is a good common ground for processors. I feel that the common ground for automation
controllers should be an assembler language (instruction list) that can be represented in ladder logic or structured text with little or no difficulty by a higher layer of the application.

How does a modern automation controller with scheduled tasks and so on really run under easy-to-follow ladder? A modern system is not a "single scan" application. A SLC5 with only a limited number of interrupt based routines is hardly useful when you want the OS of the controller to handle tasks that run at 1ms, 5ms, 10ms (and so on) intervals -- that is without
writing a ton of ladder yourself.

I may not like writing simple Boolean tasks in APT, but you cannot beat the Pascal-like syntax for higher level stuff that customers expect in their machines.

It is unfortunate that APT has been somewhat marginalised by the passing of time ... I am about to delve for the first time into Siemens PCS-7 with STEP-7 -- no mention of ladder logic in the Siemens manuals I have read so far.

RJ

Ranjan Acharya
905-634-0844 x 238 (V)
Team Leader - Systems Group
905-634-9548 (F)
Grantek Control Systems http://www.grantek.com/
[email protected]
[email protected]


_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
R

Ranjan Acharya

With regards to the Siemens stuff from Germany, I just did a quick look-up and the S5 appears to be based on a mnemonic system with a top-level of
Structured Text (STL) or Ladder (LAD).

The S7 tools emphasise IEC 1131.3 languages. I saw one mention of STL and LAD as a programming option on the S7 itself, but the STEP-7 tools only care about CFCs, SFCs and all that.

Perhaps a Siemens expert can enlighten us but I do not think that the S5 and S7 use ladder as their base language.

RJ



Ranjan Acharya
905-634-0844 x 238 (V)
Team Leader - Systems Group
905-634-9548 (F)
Grantek Control Systems http://www.grantek.com/
[email protected]
[email protected]


_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
M
Ranjan Acharya wrote:

> Perhaps a Siemens expert can enlighten us but I do not think that the S5 and
> S7 use ladder as their base language.
>

Won't claim to be an expert, but I don't think any PLC speaks ladder as its 'base language'. All PLCs that I'm familiar with (Omron, AB,
Koyo/TI, Arromat/NAIS, and Siemens, etc.) actually execute a boolean machine language. The data I have on early Modicon history from Dick
Morley describes his 'ladder lister' as a high-level rule based language.

Every PLC I know of allows the user to program in ladder logic. If this project is to be call the LinuxPLC it will have to have ladder logic as
a programming method. If not, most potential users will stay away.

Mark

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
R

Ranjan Acharya

Sorry about any confusion implying that the base language on Siemens is not ladder and so on. By base language on a controller I mean the one that the manufacturer pushes the hardest. What language it is compiled down to or interpreted to is irrelevant to the end user. I just think that making ladder the "main language" is a poor choice for this project. Ladder should be just part of the suite.

RJ

Ranjan Acharya
905-634-0844 x 238 (V)
Team Leader - Systems Group
905-634-9548 (F)
Grantek Control Systems http://www.grantek.com/
[email protected]tek.com
[email protected]


_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
S
On Tue Jan 11 15:06:32 2000 Ranjan Acharya wrote...
>
><clip>
>Can anyone name a successfully marketed PLC that does not run ladder logic?
></clip>
>
><clip>
>modern PLC's do support some other style of programming, but the common
>ground they all meet on is ladder logic.
></clip>
>
>PLC's and automation controllers not on ladder. Also, are we talking about
>PLCs here or Automation Controllers ?
>

OK, I propose that if we don't intend to provide a fully functional ladder programing language very early in the life of the project, that we rename the project to the Linux Automation Controller.

--
Stan Brown [email protected] 843-745-3154
Westvaco
Charleston SC.
--

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
On Tue, 11 Jan 2000, you wrote:
> <clip>
> Can anyone name a successfully marketed PLC that does not run ladder logic?
> </clip>
>

Has anyone heard of Flowcharting based machine controls, like FloPro, Open(closed) Control, SteepleChase/NetSolver, or LabView?

Granted, these are PC based machine controls, but they do NOT use Ladder as a base language and they are extensively used for machine control. Whether they are 'successfully marketed' is a matter of interpretation.

Ron Gage - Saginaw, MI
([email protected])

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
S
On Tue Jan 11 16:26:24 2000 Ron Gage wrote...
>
>On Tue, 11 Jan 2000, you wrote:
>> <clip>
>> Can anyone name a successfully marketed PLC that does not run ladder logic?
>> </clip>
>>
>
>Has anyone heard of Flowcharting based machine controls, like FloPro,
>Open(closed) Control, SteepleChase/NetSolver, or LabView?
>
>Granted, these are PC based machine controls, but they do NOT use Ladder as a
>base language and they are extensively used for machine control. Whether they
>are 'successfully marketed' is a matter of interpretation.

The question was "successfully marketed as a PLC".

--
Stan Brown [email protected] 843-745-3154
Westvaco
Charleston SC.

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
K
On Tue, Jan 11, 2000 at 09:03:40PM -0500, Stan Brown wrote:
> On Tue Jan 11 16:26:24 2000 Ron Gage wrote...
> >
> >On Tue, 11 Jan 2000, you wrote:
> >> <clip>
> >> Can anyone name a successfully marketed PLC that does not run ladder logic? >> </clip>
> >>
> >Has anyone heard of Flowcharting based machine controls, like FloPro,
> >Open(closed) Control, SteepleChase/NetSolver, or LabView?
> >
> >Granted, these are PC based machine controls, but they do NOT use Ladder as a
> >base language and they are extensively used for machine control. Whether they
> >are 'successfully marketed' is a matter of interpretation.
>
> The question was "successfully marketed as a PLC".<

Please define a PLC.

It might be good for this and other terms to be defined, for the purposes of the Linux PLC project, and perhaps posted on the project's web site.

To me the term PLC can be taken in a very specific way, but it can also be used in a more general way, which might well encompass other
Automation Controllers. It seems likely that the project may have a better chance at success if the initial target isn't too broad, but OTOH, perhaps it is possible to define a model that fits the PLC "classic" but also can accomodate other types of Automation Controllers.

--
Ken Irving
Trident Software
[email protected]


_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
On Tue, Jan 11, 2000 at 04:27:39PM -0500, Stan Brown wrote:
> On Tue Jan 11 15:06:32 2000 Ranjan Acharya wrote...
...
> >PLC's and automation controllers not on ladder. Also, are we talking
> >about PLCs here or Automation Controllers ?
>
> OK, I propse that if we don't intend to provied a fully functional
> ladder programing language very early in the life of the project,
> that we rename the project to the Linux Automation Controler.

This feels like storm in a teacup: stepladder is sufficiently simple and widely-known that you can be pretty sure it'll be provided very early in
the life of the project (within days of the C interface materializing).

Stepladder won't the base language, but it *is* a base requirement. The base language will be C.

Which is not to say that I don't agree with you in re the name of the project - "linuxPLC" is certainly not very imaginative (then again LAC
would end up being pronounced "lack" which isn't too good either).


Jiri
--
Jiri Baum <[email protected]>
On the Internet, nobody knows if you are a @{[@{[open(0),<0>]}-1]}-line
perl script...

_______________________________________________
LinuxPLC mailing list
[email protected]
http://linuxplc.org/mailman/listinfo/linuxplc
 
M
<p>You are mistaking Siemens S5 STL (STatement List) for IEC STL (Structured Text Language). In S5 STL==IL.

<p>S7 allows full programming in ladder and instruction list.

<p>Instruction list is convertable into ladder in most PLCs with which I am familiar (Mitsubishi, Omron).

<p>CSF is Siemens original equivalent of FB programming.

<p>In the S5 the conversion between ladder, statement and function block was incomplete using most programming packages including Siemens Step 5, Quadriga from Pantek was about the most complete.

<p>Though IEC 1131-3 states that full conversion is not necessary it is not imposible to achieve.

<p>Even AB has a text based version of ladder (though it is nothing like IL).

<p>The following code is equivalent in three forms (Structured Text is omitted).
<pre>
Ladder:
| VAR1 VAR2 VAR3
|-----] [----+----] [-----+---------( )--
| | |
| | VAR4 |
| +----]/[-----+




IEC IL:
LD VAR1
AND( VAR2
ORN VAR4
)
STORE VAR3

Siemens STL:
A VAR1
A(
O VAR2
ON VAR4
)
= VAR3

Siemens CSF:

+-------+
| |
VAR1 ------------+ & |
| |
+-------+ | |
| | | |
VAR2 ----+ | | |
| 1 | | | VAR4
VAR4 ---0| +---+ +-------------( )--
| | | |
+-------+ +-------+

</pre>
<p>Take it from me, a PLC that did not support ladder logic would remain a very minor player in the UK.
 
Top