DPU2000R MODBUS Communication

H

Thread Starter

hatemhabib

I have DPU2000R protection relay with part no. 587R0410-61000. i installed AUX24 communication card and a new security key so the part no. became 587R0412-61004. i changed the communication setting as following:

Parameter 1: 3
mode parameter 1: Disabled
mode parameter 2: Disabled

i tried to connect with KEPserver OPC using modbus RTU driver using RS-232 port and i got all readings from the relay.

But when using the RS-485 i got no response although i did the connections as per the relay manual and using many different RS-232/RS-485 converters.

please can anyone help me?
 
Some comments on RS-485 or converters

1) I never use a port powered converter on a laptop because the serial port is not likely to supply sufficient electrical power for reliable use. Even on a desktop PC I will power the converter.

2) The labeling of RS-485 lines is all over the map. The EIA standard does not mandate any terminology and the results are the different divisions within the same company will label one line as (+) while another division will name its opposite (+).

Connecting the (+) and (-) lines backwards does not damage the drivers but the connection doesn't work.

Try swapping lines to see if you're in a Alice in Label Land situation.

3) If you were using a USB/RS-485 adapter, those install on a virtual com port which you need to identify in Windows' Device Manager under Ports

4) The flashing LED's can be a big help in determining whether the Modbus polls are getting through the converter.
 
H
Thank you for useful comments

I tried two different types of external powered converters. i got same results, flashing TX but no RX (Flashing LED).
 
R

R.K.Roy.Choudhury

Hello!

Please note that all the time RS-232-RS 485 can't work properly due to several reasons. Better go for RS 485 - USB converter. But before proceeding further please let me know the following :

1)Whether your devices are 2 wire/3 wire device.

2) Are you using LAPTOP/Desk top.

Have a good day !!
 
H
Thank you for your reply

1)The device is 3 Wire

2)I am using Laptop

the RS-232-RS-485 is working as i tried it with RS-232 port and converted to RS485 by RS-232-RS-485 converter then converted with another converter to RS232 and connected to Laptop by RS-232 to USB converter and it worked.

However i used RS 485 - USB (Hexin HXSP-2108G USB 2.0 To RS-485/RS422 Converter) but i got same results

i need to check the device rs-485 port if its working or not because it does not give any indication but i don't know how?
 
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