Help on determining the infrastructure of a new AC800 network with mutiple I/O:s
I ask for your consultation how to construct a new AC800 system for temperature measurements in a processing plant. There are many ways to interconenct between cabinets (ring-topology, star topology etc) and at the moment I really don´t know whats best. (I normally program applications).
As attached, the new system means pretty much that the old obsolete system is removed but the location where the cabinets where placed should be intact (don´t want to move the incoming cable with process signals). Between the existing cabinets 1-8 there´s a sensitive ring-net without any fault tolerance. I would like to install new AC800/S800 equipment in each of these cabinets and get them interconnected somewhere where I can them all to a central place.
In an earlier project which I was the designer in we had the exact same situation but with the dfference that the copper wire between the cabinets where not exchangable due to severe costs (complex industry). In this case we put a PM851 with I/O:s in each cabinet and reused the existing wiring via a HDSL ethernet to ethernet connection to the 'Central'. This works fine and is way cheaper.
In this project I have more "space" for making a better solution.
So.... What are your ideas? Central CPU and distributed I/O:s? Or local I/O:s and CPU? What protocol and physical media to interconnect between the cabinet? I haven´t drawn any lines between the objects on the attached files but the controller and cabinet no 8 are the outmost parts.
Every idea is appreciated and the cost isn´t necessarly that important. The system must be robust (no need for redundancy though) and one fault in one cabinet must not affect any other. Wheter it includes new fibre optic cabels, a dedicated cabinet in the plant which gathers all the other cabinets with it´s own CPU, you have free hands.
So guys.... What do you think?
Off the top of my head I would say you want 2 controller room "bases" that will communicate w/ each other via access variables or communication variables over fiber (https://www.800xahardwareselector.com/product/tb820v2).
In your diagram you have #'d CPU's w/ # of IO...are these staying in place? Are each of those separate AC800M controllers? How is the system functioning now?
Is there any SIS level control attached to any of these IO?
Sorry I can't be more detailed! - Ben [2020-03-18 08:36 EDT]
Source: Personal experience
In our case, we used Profibus for communication (CI854 at controller / CI801 at remote IO drops), with a fiber ring between all panels.
As was pointed out by Ben Merryman, there are questions that could affect the approach:
- Are there any SIS application, or all non-SIS?
- Do you need separate CPU, or can you combine all control into a single CPU?
- Are you able to pull fiber to each location if needed?