Ignition Design Pathways

Hi All,
We have a client that has been using Ignition for nearly 2 years that was used mainly for trending and real time plant status. Ignition has been connected to a single Allen Bradley CompactLogix PLC. As the plant is expanding and there are more “Stand Alone” devices with PLC control (mainly Allen Bradley CompactLogix or MicroLogix), I am looking for opinions on the best network design.
i.e. Have a single dedicated PLC (CompactLogix / ControlLogix) connected to Ignition SCADA and use this PLC to “message” all the other Control Devices to obtain the real time data. Or alternatively set up Ignition to interrogate each PLC individually.
I don’t think there is a right or wrong answer, I am interested in other opinions and why. Also is there a limit to how many PLCs can be connected via a single driver. This site could easily reach upto 15 PLC’s in the next year or two.
Any thoughts or comments will be most welcomed.

I would go for a Device for each PLC. Why make more work for yourself putting all the data from the PLCs into a concentration PLC?

With a device for each PLC, you will get diagnostics for each PLC individually.

AFAIK, there is no limit to PLC device drivers, it more so depends on the server hardware spec - that it can cope with them. That said, if your 15 PLCs each have 1 million tags… then yeah you might want to divide and conquer a bit. 15 will be no bother, even if they have 10K tags each. But again, make sure your server hardware is up to the task.

Maintenance for messaging that exists for no other reason than to provide data to Ignition is sufficient reason for me to call that a “wrong answer”. If Allen-Bradley hardware is configured to allow such messaging, Ignition can even use connection paths to cross networks to make direct connections. Let the PLCs do the control, while Ignition does the SCADA. What each does best.


Thanks to Phil and Matrix Engineering for your replies. I was leaning towards individual pathways to each device but wasn’t sure if messaging was easier. Another client has a done it with messaging to a central PLC, so I was happy to ask the question.
After the good advice offered, I will be taking the suggest path of individual connections.
Thanks again
PS: I don’t think there will be an excess of 150 - 200 tags per Device.

data concentrators are always a headache. that sort of mess used to be necessary back when people were using serial connections and had data limitations, but should be a relic of the past.