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Profibus Piggybacking

Created by: r_coakley at: 2/15/2012 4:57 PM (9 Replies)

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2/15/2012 4:57 PM	Rate (0)
r_coakley Posts: 16 Rating: (0)	New to this and fairly new to PLC's so a couple of questions please. Have a s7 300 (315 2dp) cpu. Have a number of individual test process rigs. I can connect to these rigs through profibus dp from my main cpu to an et 200m with anolog and digital cards and can monitor and control etc. I want to control two or more of these individual process rigs via profibus from the one main (master) cpu. The other test process rigs also have an et200m modular devices. I presume i can piggyback to have two profibus cables leaving the main plc and going to a rig each. Could i alternatively piggyback from et200 to et200 and return via the one cable. Is there a limit to the amount of piggybacking one can do Any help and links to siemens piggyback type data would be greatly greatly accepted. Regards
r_coakley Posts: 16 Rating: (0)
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2/15/2012 6:04 PM	Rate (0)
umencho Diamond Expert Joined: 3/21/2006 Last visit: 3/14/2025 Posts: 10239 Rating: (1183)	Hello, Because for me is not clear the issue there - can you make a sketch drawing and attach it here for our reference. best regards, Hristo Mihalev

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2/15/2012 6:54 PM	Rate (0)
r_coakley Posts: 16 Rating: (0)	Will try and make up a sketch. Basically one plc station will control a small little rig we have set up. There is three or four seperate instrument rigs that communicate diretly (via profibus rs cable) to only one different plc station. I want one plc station to be able to connect to all of the rigs.Each instrument rig has its own rack with analog and digital i/o cards and an et200m card Ive only just found profibus repeaters whicj i think could be my answer
r_coakley Posts: 16 Rating: (0)
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2/15/2012 7:16 PM	Rate (0)
umencho Diamond Expert Joined: 3/21/2006 Last visit: 3/14/2025 Posts: 10239 Rating: (1183)	Yes, using Repeater you can 'split' the profibis network in two...Just be carefull of numbers of master profibus devices... Best regards, Hristo Mihalev

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2/15/2012 7:33 PM	Rate (0)
r_coakley Posts: 16 Rating: (0)	Basically the attached is what i have and what i want. Can a reapeter allow me to break it into three ways or only two ? Regards Attachment have_and_want.zip (125 Downloads)
r_coakley Posts: 16 Rating: (0)	Last edited by: O_Moderator at: 2/16/2012 8:23 AM pictures transferred to attachment
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2/15/2012 7:50 PM	Rate (0)
umencho Diamond Expert Joined: 3/21/2006 Last visit: 3/14/2025 Posts: 10239 Rating: (1183)	As I can see, there you have more then one master. If you want to keep existing 'networks' - use a DP/DP Coupler. Or leave only one PLC Master and 'extend' the network with all slaves connected. best regards, Hristo Mihalev

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2/16/2012 5:39 PM	Rate (0)
r_coakley Posts: 16 Rating: (0)	i want to have one master to connect to the different slaves. Is this daisy chain linking ? ? I dont understand what you mean by extend the network. Are repeaters needed only to keep the baud rate clean or can i join profibus cable to the three different slave racks from the three seperate et200m modules wothout the repeaters. greatly appreciated Regards
r_coakley Posts: 16 Rating: (0)
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2/16/2012 7:58 PM	Rate (0)
Marciano Bronze Member Joined: 4/30/2007 Last visit: 3/9/2023 Posts: 231 Rating: (23)	r_coakley i want to have one master to connect to the different slaves. Is this daisy chain linking ? ? I dont understand what you mean by extend the network. Are repeaters needed only to keep the baud rate clean or can i join profibus cable to the three different slave racks from the three seperate et200m modules wothout the repeaters. greatly appreciated Regards Hello r_coakley I guess you are asking about bus Topology, and on Profibus you can haveLine or Start topologyand even combined. And the repeaters are a good way for segmenting you network. However (and answering your question)if your racks are nor far apart then you don't really need usinga repeater. Rgds Marciano Attachment Repeater.jpg (135 Downloads)

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2/20/2012 7:27 PM	Rate (0)
Rated X Posts: 1547 Rating: (129)	The repeater.jpg is corresponding very nicely to the want.jpg. But the repeater is only necessary if the total cable length between all 4 stations (master and 3 slaves) is too long for the requested baud rate. (e.g. 200m is maximum length at 1.5MBaud, 400m at 500kBaud). Otherwise you simply connect all stations in one line. At the 2 ends the plug only will have one cable entrance on its incoming connector and the termination resistor will be switched on. The plugs of the stations in the middle will have incoming and outgoing connection, and termination resistors must be switched off.
Rated X Posts: 1547 Rating: (129)
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2/21/2012 8:19 PM	Rate (0)
r_coakley Posts: 16 Rating: (0)	^^^^^ thanks for the reply lads really put me on the right track. Kind of got lost in the specs of the machines and lost the real point. thanks again
r_coakley Posts: 16 Rating: (0)
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