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| 10/30/2008 6:32 PM | |
Joined: 9/27/2006 Last visit: 11/11/2024 Posts: 12293 Rating:
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Hello Ross; First, don't be shy, we all started from nowhere, with no clue. Takes patience and a bit of time, but you'll find many goodanswers on this forum (and others). An ET 200M is one of the family of Profibus-DP slaves offered by Siemens. It uses an IM 153-x (IM=interface module) to collect the data from different I/O modules, and send them to the PLC that is configured as a master. There is no need of an IM 153-1 or othe IM module in the PLC. You use either the integrated DP port of the CPU or a Profibus-DP communication processor (CP 342-5, for example) to establish the link. Profibus-DP (" Process Field Bus - decentralized periphery") is a form of Remote I/O link. You configure the different I/O modules of the ET 200M (by the way, these are S7-300 modules) in the same HWConfig editor as the central rack, except that you set them on the Profibus-DP network that is connected to the CPU. The system will attribute a series of addresses for each I/O module; even if you are using Profibus-DP to read/write the data, the addresses match the ones for the modules in the PLC central rack, and you can use them directly in the program. Here is a FAQ from Siemens describing the setup of an ET 200M as a slave to a CPU 315-2DP: http://support.automation.siemens.com/WW/view/en/31279069 You could also look at thr manual "Configuring Hardware and Communication Connections with STEP 7 ": http://support.automation.siemens.com/WW/view/en/18652631 There is a chapter on setting up Profibus-DP networks in Step 7's HWConfig editor that could give you more information. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 10/30/2008 6:34 PM |
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| 10/31/2008 1:37 PM | |
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Joined: 9/27/2006 Last visit: 11/11/2024 Posts: 12293 Rating:
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Hello Ross; Now we move into a slightly different dimension, we need to talk about Profibus-DP a bit. First, as always, you will need some documentation to fall back on. Here is an excellent pdf from Siemens, showing available hardware (cables, connectors, repeaters, terminators) from Siemens to setup Profibus Networks, over copper or fiber. It also discusses bus speed, segmets and sements length, number of slaves and othe considerations: http://support.automation.siemens.com/WW/view/en/1971286 Another excellent source is Profibus.com, the Profibus International website. If you look around the site (in the Profibus section) you will find presentations, ppts, documents, available products from many manufacturers and in the Technology tab an excellent technical presentation about the fundamentals of Profibus: www.profibus.com Remember that Profibus is an open-vendor protocol, that many, many manufacturers offer certified hardware and software that can be used (I was about to say "freely", but that might not be an exactly appropriate word; better to say "easily") on the bus. Now that we have got that out of the way,
Profibus-DP will support up to 125 nodes on the bus, masters, operator panels andd slaves (I/O racks, drives, protection relays, valves ...). So yes, your 8 nodes will fit without a problem, with room left over for the Sigma unit. Now, there are details to any installation, and the devil is in the details. Profibus-DP is based on the RS-485 physical layer, and is subject to its limitations. -the bus is organized in units called segments; one segment can hold 31 slaves; with repeaters you can go up to the maximum number of nodes; -there is a comprimise that must be understood between the maximum length of a segment and the bus speed. The higher the bus speed, the shorter the maximum length of an individual segment. There are detailed tables in the documents I suggested, but quickly: -> at 12 MB, max.length of a segment is 100m; with max. 9 repeaters, max. length of bus is 1 km -> at 500kB,max.length of a segment is 400m; with max. 9 repeaters, max. length of bus is4 km -> at187,5 kB and less,max.length of a segment is 1000m; with max. 9 repeaters, max. length of bus is 10 km This is for copper cable, using recommended class A Profibus cable, from Siemens or Belden, for example, and approved Profibus connectors with integrated terminators. Fiber optics connections can extend the distances tremendously if required. The Siemens manual I suggested at the beginning is very informative on these subjects. The bus is a daisy-chain topology, where the cable leaving one node goes directly to the next node (not a star network, like Ethernet, or atoken-ring topology). Termination is essential at both ends of the network, whether the master is in the middle does not matter. It is the end points of the network that must be properly terminated at all times, either through the integrated termination switches in the connectors, or through a seperately-power external terminator. Proper grounding and power for all nodes is also required.
Various versions of the IM 153-x exist to offer different levels of functionnalities. IM 153-2 and IM 153-3 offer, on top of the required Profibus-DP connectivity, support for redundant masters, or interfaces to other networks (Profibus-PA for example). In your case, since all you require is straight I/O collection, the IM 153-1 will be more than sufficient, and less expensive too. By selecting a different Profibus-DP on each IM 153-1 (through rotary switches of Dip-switches on the module) and coordinating these addresses in the Profibus configuration they will ber differentiated in the bus. Note that since the I/O modules of the ET 200M are actually S7-300 modules, you will require a S7-300 rail, power supply and I/O modules on top of the IM 153-1 to create the ET 200M slave node. Eachslave on the Profibus_DP bus can exchange with the master up to 244 bytes IN/244 bytes OUT, so the amount onf data in your application seems to be well within this requirement. Now, for the Sigma unit, of which I have no personnal knowledge by the way. But if it is a certified Profibus-DP slave, there is a standard way to integrate it in the configuration. Every manufacturer of Profibus-DP certified slaves must provide a GSD file to the user, generally on their website or on an installation diskette/CD. A GSD file (an acronym from the German meaning General Data File) can have an extension such as*.gsd, *.gse, *gss,... the last letter indicates the language it is written in, e for English, s for Spanish, g for German; a *.gsd is written in the default language, English.... Now, when you open the Siemens Step 7 HWConfig editor, the gsd files for its own Siemens productsare already integrated in the configurator. Which is why they are directly available there. The mechanism to integrate a slave from a different manufacturer is foundin the Tools menu, "Insert GSD file". Once the gsd file from the Sigma unit is on your computer, simply open it with this menu, and it will be added to the configurator's catalog, ready to be inserted as a node on your network. Have a look here for mode details: http://support.automation.siemens.com/WW/view/en/22834942 You can open any gsd file in any text editor, it is a simple text file. You would learn a lot by looking at the contents of a few of them, see how the unit is described, what bus speeds are supported, what data exchange sizes are allowed... The gsd file informs the master on how itcan exchange data with the slave; you configuration in the HWConfig editor will detail exactly the amount of data that will be made available on the bus. So you will need to obtain that gsd file for the Sigma unit, and also examine the Profibus configuration manual that should be available from the manufacturer, telling you how many bytes will be written from the master to the slave (bytes OUT), how many bytes will be sent to the master (bytes IN), and what these bytes actually mean to the slave's logic. You will need some time to digest all his, and more you will need to practice configuring and communicating with a single ET 200M at a time. When you start feeling more at ease and need more info, come back and ask detailed questions. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 10/31/2008 5:24 PMLast edited by: dchartier at: 10/31/2008 1:45 PMLast edited by: dchartier at: 10/31/2008 1:43 PM |
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