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Increasing Profibus baudrate

Created by: Survive at: 5/23/2007 1:22 PM (6 Replies)

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5/23/2007 1:22 PM	Rate (0)
Survive Posts: 26 Rating: (0)	Dear Sirs, I have an application with PLC S7-300 315-2DP working with profibus DP with 1.5Mbaud, around 30 devices are connected. Connecting a repeater in the profibus net, can I increase the baudrateto 12Mbaud, for example ? The Profibus cable distance is around 100 meters. Now, with 1,5MbaudIcan monitor the drives (MasterDrive MC) via Drivemonitor and the connection is OK, but when I set itto 12Mbaud I can't monitor them for a long time, the connection shows problems. Is a repeater a good solution to keep stable the connection ? Or what can I do ? Regards !
Survive Posts: 26 Rating: (0)
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5/23/2007 11:34 PM	Rate (1)
neo Posts: 264 Rating: (59)	Survive Dear Sirs, I have an application with PLC S7-300 315-2DP working with profibus DP with 1.5Mbaud, around 30 devices are connected. Connecting a repeater in the profibus net, can I increase the baudrate to 12Mbaud, for example ? The Profibus cable distance is around 100 meters. Now, with 1,5Mbaud I can monitor the drives (MasterDrive MC) via Drivemonitor and the connection is OK, but when I set it to 12Mbaud I can't monitor them for a long time, the connection shows problems. Is a repeater a good solution to keep stable the connection ? Or what can I do ? Hello Survive, I think you have small problems on your profibus. 12Mbaud compared with 1,5Mbaud is much more sensitive to troubles. Even if everything seems to work fine at 1,5Mbaud, you can get problems at 12Mbaud. Possible Problems could be: segment length more than 100m too much devices in one segment (max 31, then you have to use a Repeater) problems with potential on ground mechanical or electrical faults in RS485 Connectors defect RS485 Connectors defect Profibus Devices ... I usually use an RS485 Repeater, when i might posibble expect problems with potentials. For trouble-searching i usually use a Diagnostic Repeater. Both provide you a distance-increase, potential seperation, and work with all Baudrates up to 12Mbaud. A Diagnostic Repeater additionally gives you some more interesting informations, e.g. several distance informations up to 100m. But notice: A Diagnostic Repeater needs a profibus adress, and have to configure it in the S7Hardwareconfig, when you also want to get the extended information. An interesting tool for simple cable and device diagnostic is a BT200. But when you want to check your cables and connectors, you may have to disconnect the devices. But all these thougts bring me to a question: Why do you want to increase your Baudrate? RS485 REPEATER 6ES7972-0AA01-0XA0 DIAGNOSIS-REPEATER 6ES7972-0AB01-0XA0 BT200 BUS 6ES7181-0AA01-0AA0 RS485 Infos: http://support.automation.siemens.com/WW/view/en/37627 Manuals: http://support.automation.siemens.com/WW/view/en/23876799 I hope Iwas able to helpyou... best regards...
neo Posts: 264 Rating: (59)	Last edited by: neo at: 24.05.2007 00:06 Why do you want to increase your Baudrate? Last edited by: neo at: 24.05.2007 00:01
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5/24/2007 12:01 AM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 12/23/2024 Posts: 2705 Rating: (320)	Hi, A repeater is for the next solutions: 1. With higher baudrates getting more length, you might use 9 repeaters in serie, so you can get 1km with 12 Mbit/s; 2. To use more then 32 RS485 users (a repeater is also a RS485 user, so you could use 30 slaves between two repeaters); 3. Potential dividing; 4. Errors "behind" a repeter are not given true the segment before the repeater; And of course the 4 points together or every combination of it
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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5/24/2007 10:22 AM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Hello Survive, I am sorry, but just putting up the Baudrate will not enable you to run 12 MBit. You will have to check If all nodes on the PROFIBUS are able to run 12 MBit (Master and Slaves) If the cableing is suiteable, means if all Cabinet entances and leaves are sufficiently grunded. If the Cable itself is suiteable, not only physics but Tap lines... a.s.o. If you have a Segementlength of less than 100 m it should work, but you will have to check that the Signal on the cable is interfeared by any emiters... so check the EMC. If this all is OK, I see no big problem. Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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5/25/2007 2:27 PM	Rate (0)
Survive Posts: 26 Rating: (0)	Hello, Ok, I understood your suggestions andprecautions. But, now another question appeared in my mind. How can I know the timeto transmitting/receiving with 1.5 Mbaud and 12Mbaud for a distance of 100 m ? Is there anequationto doit ? I wantto increase the baudrate because a I'm working with 30 salves (15 Masterdrive MC)andthree of them is working like an interpolation.Am I right ? Thank you for the answers. Regards, Survive
Survive Posts: 26 Rating: (0)
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5/26/2007 10:59 AM	Rate (0)
Jesper Pedersen Posts: 279 Rating: (30)	Hi Survive. About the last question. I could not really understand what you are asking about. But if you want to know how fast the network is with different baudrates, then investigate the Bus Profile for the Profibus network. There are two values of interest for you "Ttr" is the target token rotation time. If the network is running without problems, then this cycle time will never be exceeded. "Ttr typ" is the typical token rotation time. In other words it is an approximate mean value of the cycle time during normal operation. This is significantly lower than the maximum. About the recommendations that the others have posted, I would add that you have to have a good ground at all stations, and the ground should be the same at all stations. So you may have to pull equipotential grounds around the plant.
Jesper Pedersen Posts: 279 Rating: (30)
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5/27/2007 10:22 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 12/23/2024 Posts: 2705 Rating: (320)	Hi Survive, The TTR_TYP is normally higher then the real time on the Profibus, I measured that a lot of time
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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