Planning the PLCs and network

IA have an excellent resource available in IU for learning the basics is Ignition SCADA /DB/Tags/Visualization/alarms etc. However they don’t have guidelines for planning the PLCs the IO modules the LAN where these PLCs are connected to SCADA etc. IU just tells how to connect to various PLCs supported by Ignition. However for a green field plant or a retrofit plant how does one go about deciding how many PLCs are required and how many IO points are required etc.

Is there a guideline document available for selection of PLCs, planning the IO points / UDTs depending upon the motors/pumps/valves/conveyors etc in the process being controlled whether its manufacturing or continuous process or batch process.

This may be out of scope for IA but this is an important step in execution of a project. Any guidelines will help the new comers / students/ starters in SI business.

Rockwell, for example, has tools like ProposalWorks to help with things like that. I imagine other manufacturers have similar tools.


Wow! That’s fantastic! This is exactly what I was looking for! I request the forum members to share similar information that they may have about all the other vendors at least those supported by Ignition! I believe Siemens and Rockwell cover about 90% of the market! Hope similar info is available for Siemens as well though my experience with Siemens documentation and products are horrible to work with! (Someone can please prove me wrong!)

We use Schneider Electric modicon plc’s, and they do have a product selector though i admit that i have never used it. My network and PLC design usually involves a sort of labor vs hardware cost benefit calculation. Where i can get away with using remote backplains i do, though sometimes it is more cost effective to just add another PLC. As for the IO modules i always leave myself room to add extra modules even though i have budgeted enough IO for my purposes.

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Thanks for your reply. So PLC/network/IO selection is more of a combination of art and science. However one has to also think its impact on the configuration on SCADA. By the way which industry you service ?

Usually, you don’t have much of a choice, unless you are designing cradle to grave. If, for instance, you have an assembly line with multiple machine builders working on it, you will have multiple PLCs. And, even if you give them a programming standard to follow, it does not guarantee that it will be followed.

[rant]There is a special place in hell for OEM programmers that write code more complex than the task the machine is supposed to do.[/rant]

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I know , its not an ideal world with ideal conditions all the time!

It must be a challenge to focus on and coordinate and integrate your piece of system with other vendors in the overall system! How does one set the boundary conditions and integrate and test before going live? (I know its always get it working asap requirement from the customer.)

For me yes it is, though i may be an outlier. I work mainly in detention facilities, so i am almost 100% discrete IO which does change things. I control buildings for the most part, not machines.

That’s nice. However I wonder you choose Ignition SCADA for Schneider PLCs where as they have their own EcoStruxure or AREVA SCADA! Is it a cost advantage or feature advantage or ease of use etc. Not sure if you integrate with their Energy meters as well thru Ignition as they have some advanced analytics features built into their (Schneider’s) EMS Scada. (This is just out of curiosity, as I had come across a situation where EMS was required using Ignition with integration with their EM devices).

I inherited this setup. Everything was done with symax PLC’s over thinnet, and later upgraded to Modicon PLC’s. We evaluated ignition in its infancy, and found the drawing tools to be lacking, so we stuck with wonderware and rsview32, but now ignition is fantastic i have pushed to replace those.

I may be full of it, but by my experience there is no better value than ignition. I come from a background of rockwell and wonderware where you are limited per tag, per window etc. not to mention the insane support contracts. The amazing support ignition offers is value enough for me, even this forum is reason enough.

We do have an outdated Schneider ION system for power meters, which i was quoted an exorbitant amount to replace with their new product. I was able to use Ignition to retrieve the information i need from the meters directly.


Nice to hear and learn from experiences of different people! This give us assurance that we are on right track! As well as IA is! Thanks a lot.

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