2rlp Posted November 10, 2010 Report Share Posted November 10, 2010 Hi, As attached, I have an application using a V280 & 9 Slave devices. The drawing attached is the exact representation of the system. Kindly advise me as to where are the End Terminating Resistors to be installed? Thanks Ron ModbusTermination.pdf Quote Link to comment Share on other sites More sharing options...
Damian Posted November 11, 2010 Report Share Posted November 11, 2010 Hi, As attached, I have an application using a V280 & 9 Slave devices. The drawing attached is the exact representation of the system. Kindly advise me as to where are the End Terminating Resistors to be installed? Thanks Ron Are you running your cable from drive to drive in series, or are you branching out to all the slaves from the master in a starlike topology? If you have all the devices linked "in line" then you need just to have the resistors at the extreme ends. If you are doing a star topology (generally not recommended) then it can get complicated. Are these devices all short runs, or are they long distances? Quote Link to comment Share on other sites More sharing options...
Damian Posted November 11, 2010 Report Share Posted November 11, 2010 oops, sorry. Didn't notice the distances before. Across slave 1 and across slave 9. Quote Link to comment Share on other sites More sharing options...
Emil Posted November 11, 2010 Report Share Posted November 11, 2010 RS485 is pure daisy chain! Don't even dream about "star". Don't even think about "stubs! The cable must be passed strictly from unit to unit. I recommend using our connector MJ10-22-CS66, which will let you connect two cable to one RJ11 connector with minimum stub (about 2 cm). Termination must be set on the ends of the cable. It doesn't matter what is the ID of the unit. If the units are aranged in the way you show in te scheme, there needs to be unit 1 and 9. Quote Link to comment Share on other sites More sharing options...
2rlp Posted November 11, 2010 Author Report Share Posted November 11, 2010 Thank you both Damian & Emil. Ron Quote Link to comment Share on other sites More sharing options...
Damian Posted November 11, 2010 Report Share Posted November 11, 2010 RS485 is pure daisy chain! Don't even dream about "star". Don't even think about "stubs! The cable must be passed strictly from unit to unit. I recommend using our connector MJ10-22-CS66, which will let you connect two cable to one RJ11 connector with minimum stub (about 2 cm). Termination must be set on the ends of the cable. It doesn't matter what is the ID of the unit. If the units are aranged in the way you show in te scheme, there needs to be unit 1 and 9. Emil, your too rigid! Star topology can work just fine if all the nodes are very close together and baud rates are not that high. I've done this a few times in the past to avoid trying to daisy chain RJ45 or RJ11 connectors that don't repeat the signals on another set of pins. Generally if your devices are all mounted next to each other on the same panel and each leg is kept to a couple feet max (which is a common situation) you will not experience issues. Quote Link to comment Share on other sites More sharing options...
Emil Posted November 11, 2010 Report Share Posted November 11, 2010 Hi Damian, I'll never do "Star" topology with RS485 and, of course, will not recommend such thing to anyone. If someone wants to experiment on his own responsability, I cannot forbid him. But to recommend... Quote Link to comment Share on other sites More sharing options...
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