from the Automation List department...
CJB 306 modbus communication
Communications systems and equipment. topic
Posted by Bahadir Adiyaman on 30 September, 2003 - 9:39 pm
I have three different modbus lines. One of them is 600m, the other is 1200m and the last one is 2000 m. long. I will use CJB 306 modbus line components to make three different modbus line together. Is it possible with using this component? Thank you.


Posted by Lynn at Alist on 8 October, 2003 - 11:54 pm

I have no idea what a CJB306 is, but in a situation like yours it is trivial to use 3 RS-485 repeaters at the central station to form a nice 4-subnet system. The central RS-485 is only a few feet long and works at minimum stress. Each of the 3 "home runs" is a simple point-to-point, which is the most robust, most tolerant form of RS-485.


[MAS]-RS485-+-[REP]-RS485-600M-[SLV]
|
+-[REP]-RS485-1200M-------[SLV]
|
+-[REP]-RS485-2000M----------------[SLV]

Find a nice application note covering isolated RS-485 repeaters here:
http://www.robustdc.com/library/PDFs/an011.pdf

- LynnL, www.digi.com


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