7i96s and WJ200 VFD

Hi all,

I am wanting to hook up my 7i96s motion control board to my Hitachi WJ200 VFD using modbus.  I have read the modbus page and have sees the WJ200 modbus driver - so all that seem good, it is just the protocol and the  hardware connections. I have a couple of questions I could not find answers for by searching.

(1) The modbus page says "For RS422 Modbus RTU communications these should be connected at the Mesa card Tx+ to Rx+ and Tx- to Rx-".  The WJ200 is RS485.  I have read that RS485 bus components can be used with RS422 network, I just want to make sure this will work.

(2) The modbus pages says "Typically Rx+ and TX+ will connect to the B- pin on the modbus device and Rx- and Tx- will connect to the A+ pin"  The WJ200 has SN and SP connections for RS485 (I presume this means serial neagative and serial positive).  So does this mean:  I connect the Rx+ and Tx+ together on the Mesa board and then connect that to the SN connection a=on the WJ200?  (same for the Rx- and Tx- to SP)

 If you have connected your Mesa motion control baord to the WJ200 using modbus, please let me know any other tips that may be useful.

thanks!

 

Yes I think you have polarity correct.
In addition on the 7I96S you need bias
resistors (100 to 300 Ohm)
from +5V to SP and GND to SN