DH485 Fiber Optic Converters

[Magnaform]

Hi all,

I'm trying to set up a dh-485 fiber optic link between a panelview 600 and a 1761 AIC using a pair of ADAM-4541 fiber optic converters. I've tried several different combinations and I can't get it working.

http://www.advantech.com/products/Model_Detail.asp?model_id=1-23HZ35&BU=&PD=

I had the PLC and panelview running with a 1761-cbl-as03 cable, so I cut the cable and spliced the fiber converters in. I connected the blue/white and white/blue lines to the rs485 data + and - terminals on the converters. There is a pair of orange/white wires in the cable that are connected to the COM terminal of the AIC that I don't have connected to anything.

Does anyone know what the COM terminal and the orange/white wires do? Do I need some sort of termination resistors at both ends?

Any advice would be appreciated as this is my first PLC project.


Thanks,
Jim

 

[Ken Roach]

All RS-485 networks require Data A, Data B, and a COMMON wire. Some systems use the shield or ground connection as a common reference.

DH485 uses a dedicated common wire, so the DH485 network trunk is 3 conductors. Connect that COM wire to the GND screw on the ADAM device.

I'm not certain about the other settings on this device, or if it will work at all with the RS485 timing that DH485 networks use. Let us know how you have the framing and speed settings configured.

 

[ndzied1]

Phoenix Contact makes converters that specifically mention DH-485 on their data sheets:

PSI-MOS-RS485W2/FO 660 E Order No. 27 08 31 3
PSI-MOS-RS485W2/FO 660 T Order No. 27 08 30 0
PSI-MOS-RS485W2/FO 850 E Order No. 27 08 33 9
PSI-MOS-RS485W2/FO 850 T Order No. 27 08 32 6
1. Description
The PSI-MOS-RS485W2/FO... devices can be used
to convert RS-485 2-wire bus systems to fiber optics.
All bus systems with 10/11-bit UART data format and
NRZ data encoding are supported. This includes
popular bus systems such as:
– MODBUS/MODBUS RTU
– SUCONET K
– S-BUS
– DH-485
– Various additional company-specific
bus systems

I do work for a Phoenix Contact Distributor.

 

[Magnaform]

Hi Ken,

Thanks, connecting the COM to the ground terminal got it working.
I do have a second question. I can set the bits per message from 9 to 12 on the converters. How many bits are in a DH485 data frame?


Thanks,
Jim

 

[Mickey]

Hi Ken,

Thanks, connecting the COM to the ground terminal got it working.
I do have a second question. I can set the bits per message from 9 to 12 on the converters. How many bits are in a DH485 data frame?


Thanks,
Jim

See PDF file