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I have a project I am working on for which I would like some advice. The following is a rather lengthy letter, but I wanted to make sure that you have enough information to make an informed opinion. We are planning to implement a system which automatically monitors production equipment for values such as cycle time, down time, numbers and types of faults, etc. The type of production we do is assembly work, often involving parts transported on palletised conveyor systems. We have not made any definite decision on the software which will log the data and create and present the reports, but we are reviewing several very promising possibilities. I don't believe a typical MMI solution (e.g. Wonderware, etc.) is a good fit for us. Briefly though, at the highest level the system will be software which runs on a PC server and the results can be viewed through a web browser on any PC in the plant. This software will communicate with the manufacturing equipment via OPC server software. The server PC would preferably be located in our computer room with all the other network servers. At the lowest level, we will need to make certain programming changes in each PLC to create some times, counts, and alarms for this software to monitor. The majority of PLCs are Siemens S5, with some Siemens S7-200, and a small amount of AB, Omron, GE, etc. as well as a number of computers. We may decide to not monitor the really difficult cases. Our initial project is to create a prototype system with about 10 machines, but the system chosen must be scalable. Most of the Siemens S5 PLCs have a Profibus FMS port, as we have been considering doing this project for several years now and have been specifying our equipment accordingly. The problem I would like to discuss is how to make the connection between the two levels. I am strongly leaning towards interposing a "data concentrator" device between the two levels, with one data concentrator for each line or zone (about two dozen altogether). This device will be responsible for polling the individual PLCs and presenting the data in a consistent way for the top level. The equipment in the plant is constantly changing and moving, so I would like to isolate the top level to some extent from the differences in hardware. The data concentrator may also be called upon to perform some of the calculations (e.g. timing and some boolean logic). This may be especially useful with lines which require interfacing a variety of simpler devices which don't have good networking abilities. In this case we could use digital I/O (possibly using ASI) to get a limited amount of information. I would like this data concentrator to be readily available equipment that will be rugged, reliable, and consumes a minimal amount of space (cheap would be nice too of course). It should also be easy to program. I don't have any fixed ideas on what this device should be. One possibility which has been suggested is to use a Siemens S7-300 PLC with a Profibus card (to connect to those PLCs which have a Profibus port), and an Ethernet TCP card (to connect to the top level). The Ethernet TCP card may be able to connect to our existing office network backbone, which I believe has gigabit capacity. I would like to point out that no control functions are being contemplated, only monitoring. I am told that we have plenty of excess capacity on this backbone. All of the precision timing is being done at the PLC level (or in the data concentrator) so a high polling rate or deterministic response is not required. The purpose of connecting to this backbone is strictly one of convenience. The top level will poll the middle level at regular (settable) intervals. I expect to have the information required to calculate the amount of data traffic within a few weeks. One advantage this system may have is that it is a technology which is readily understandable to the type of people who will deal most directly with it (PLC programmers to implement the system in existing equipment, machine builders for new equipment). I intend to perform all the work for the initial system myself, but further implementation will be done by people we will hire for the job to work to our detailed spec (with the first system as an example). New lines will have this installed when they are built. I have spoken with our Siemens rep about this application. The local rep was very helpful and understands what I want to do, but he doesn't feel he has the necessary background to give me the best advice on this subject. He passed me on to someone at Siemens in Toronto. This second fellow unfortunately seems more interested in trying to sell me WinCC than in listening to what my real question is (which is how to make the connection in the middle using their hardware and software, regardless of what is at the upper end). Any advice or opinions on any of the above would be appreciated. I am not fixated on any particular solution, but I do want something that is simple, flexible, and reliable. Michael Griffin London, Ont. Canada [email protected]