On/Off Terminal Resistor on Profibus DP Cable ???

garu3d

In my system . I see CPU 315-2PN/DP connect to  ET200 by Profibus cable . and i don't understand why they set on/off on ET200 or CPU . I need document for this issue

 Hello,

  The terminating resistor must be in ON position at both ends in order to avoid the signal reflection.

 Please have a look:

 https://support.automation.siemens.com/WW/llisapi.dll/2157453?func=ll&objId=32270600&objAction=csView&ehbid=2157453&query=profibus+resistor&lang=en&siteid=cseus&aktprim=0&extranet=standard&viewreg=WW&load=treecontent

 http://profibus.felser.ch/en/der_busabschluss_fuer_rs485.htm

dchartier

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

 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

garu3d

 

dchartier

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

 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

 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.

Ste39

 

garu3d

 

dchartier

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

 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

 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.

thanks . but in my factory . they turn off att Slave 5 and Turn on at Slave 3 . !!! . but the System working fine .  What happen @@

dchartier

Hello garu;

I would not trust the representation of your network in HWConfig (your Profibus configurator) to determine the first and last station of the network.

Do a sketch of the physical network you are designing, as the stations are physically going to be installed. Look for stations that only have one Profibus cable, either entering or leaving; these will be the first and the last stations on your bus. Every other station will be connected to the preceding and the following station, with 2 cables connected to them. Set the termination resistances to ON on the first and last station ONLY.

I have prepared such a sketch, only as an example. Understand what I mean about 1 and 2 cable distinctions. Notice where I have placed the "T" for termination.

Hope this helps,

Daniel Chartier

 In this Systems . both CPU and Slave turn Off . but  the System working fine . When i turn on at CPU . the System indicate BF SF . ???? 

garu3d

 

Ste39

 

garu3d

 

dchartier

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

 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

 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.

thanks . but in my factory . they turn off att Slave 5 and Turn on at Slave 3 . !!! . but the System working fine .  What happen @@

 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.

garu3d

 

dchartier

Hello garu;

I would not trust the representation of your network in HWConfig (your Profibus configurator) to determine the first and last station of the network.

Do a sketch of the physical network you are designing, as the stations are physically going to be installed. Look for stations that only have one Profibus cable, either entering or leaving; these will be the first and the last stations on your bus. Every other station will be connected to the preceding and the following station, with 2 cables connected to them. Set the termination resistances to ON on the first and last station ONLY.

I have prepared such a sketch, only as an example. Understand what I mean about 1 and 2 cable distinctions. Notice where I have placed the "T" for termination.

Hope this helps,

Daniel Chartier

 In this Systems . both CPU and Slave turn Off . but  the System working fine . When i turn on at CPU . the System indicate BF SF . ???? 

 Hello,

Always the purple cable (PROFIBUS), which comes out of the CPU? A1-B1 or A2-B2? How many meters are far away?