Modbus Communication

adam_lhadi

Member
Join Date
Feb 2022
Location
algeria
Posts
59
Hi everyone
i have a delta VFD-M series with RS-485 protocol RJ-11 (Modbus communication) and cm1241 rs-485 siemens module (6ES7 241-1CH32-0XB0)
so i needed to transfer the DB9 connector to RJ-11 to establish the communication between the vfd and the plc
the picture shows how i managed do adapt the two connectors
please correct me if am wrong

kind regards

RS485 db9 to RJ-11.png
 
If DB9 pin 1 is truly signal ground, then yes, you have the correct connections.


I have seen other devices use pin 8 for A(-), pin 3 for B(+) and pin 5 for signal ground.


Be aware that some manufacturers define the A and B driver lines backwards so that A to A and B to B does not work.


If the driver lines are connected backwards, there's no damage, but communications will not work. The fix is to swap the lines on one end.
 

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