8/15/2016 5:18 PM | |
Joined: 1/21/2013 Last visit: 6/6/2024 Posts: 4620 Rating:
|
Hello, The terminating resistor must be in ON position at both ends in order to avoid the signal reflection. Please have a look: http://profibus.felser.ch/en/der_busabschluss_fuer_rs485.htm
|
Last edited by: Ste39 at: 8/15/2016 5:21:27 PM |
|
This contribution was helpful to
2 thankful Users |
8/15/2016 5:48 PM | |
Joined: 9/27/2006 Last visit: 8/16/2024 Posts: 12277 Rating:
|
Hello garu; To add another important technical ressource to Stefano's excellent answer, I suggect you look at the documentation available from Profibus.com. This is a techncal group dedicated to Profibus and Profinet, and their download section offers many very interesting guides for installers and designers of these networks. They are provided outside of ny manufacturer's offerings, so they are independant and very reliable guides. This link (and extract) will take you to the Profibus installation guidelines manual: www.profibus.com/download/installation-guide/ 3.1.3 Planning bus terminations Bus terminations are required for ensuring proper functioning of the PROFIBUS DP/DP-IS and should be considered accordingly in the planning phase. In order to ensure an offset voltage in the bus quiescent state (i.e. no telegrams) and to minimize line reflections you have to provide a bus termination at each end of the segment and nowhere else. With PROFIBUS DP and PROFIBUS DP/IS the bus terminations have a combination of resistors that are often integrated in the connectors. Bus terminations are sometimes provided on repeaters when used as the start of a segment With PROFIBUS DP/DP-IS the bus terminations are integrated in the connectors and can be activated and deactivated by a switch. The bus terminations are active and must be electrically powered.This supply voltage for the active bus termination can be taken from the connected bus node. This applies to the first and last node of a segment. However if one of these bus nodes is switched off during operation, e.g. for troubleshooting, the bus termination is no longer powered. As a result, no proper bus termination will be available and the network may become unstable. To solve this problem, active bus termination elements are available, which are independent of the PROFIBUS nodes and can be powered separately. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 8/15/2016 5:54:02 PM |
|
This contribution was helpful to
3 thankful Users |
8/15/2016 7:26 PM | |
Posts: 51 Rating:
|
but i can not How to determine First Point and End point of segment For example : which first point and end point in this picture |
8/15/2016 8:07 PM | |
Joined: 1/21/2013 Last visit: 6/6/2024 Posts: 4620 Rating:
|
Hello, From the attachment First point is CPU and Last point s Slave 5, so start out of CPU by A1-B1 end finish by A1-B1, but pay attention how you do the segment , for example if you have the CPU in the center and 1 slave to the left and 1 to the right ( exit the CPU with 2 cables A1-B1and A2-B2 ) the terminating resistor must be Set to ON both slave but NOT the CPU. |
Last edited by: Ste39 at: 8/15/2016 8:09:07 PMdaniel too fast :-) |
|
8/16/2016 6:22 AM | |
Posts: 51 Rating:
|
thanks . but in my factory . they turn off att Slave 5 and Turn on at Slave 3 . !!! . but the System working fine . What happen @@ |
8/16/2016 7:11 AM | |
Joined: 1/21/2013 Last visit: 6/6/2024 Posts: 4620 Rating:
|
Hello, not about the number, you have to physically see how it is done, take a pen and paper and follow the purple cable (PROFIBUS), start from the CPU to the last slave and marks the node numbers. |
Last edited by: Ste39 at: 8/16/2016 7:14:55 AM |
|
Follow us on