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Old May 13th, 2022, 11:37 AM   #1

adam_lhadi is offline
Join Date: Feb 2022
Location: algeria
Posts: 6
Modbus Communication

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
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File Type: png RS485 db9 to RJ-11.png (85.7 KB, 35 views)
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Old May 13th, 2022, 03:41 PM   #2
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danw is offline
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Join Date: Oct 2004
Location: midwest, USA
Posts: 3,268
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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