Created Date: February 23,2011

Created by: johnomg

Thanks for the responses.

Regarding the poll time, the MRX box is polling the indicator on each scan provided the port busy (SP116) relay allows it.

I 've tried switching the TXD/TXD wires but no change. What was strange to me, was that the RXD/TXD lights on the PLC still flickered in the same way after switching the wires. I don't know if that is normal?

I 've ordered a RS232/485 converter so that I can poll the indicator from a PC. That should arrive tomorrow and should help me isolate whether it's the indicator or something else

Created Date: February 28,2011

Created by: johnomg

I'm making slow progress.....

I 've have confirmed that the PLC & the indicator are talking. If I query the address for the indicator's model number, I get the correct response. Same for the serial number, so at least I know the comms are working. Thanks bcarlton for the tip about adding one to the address in the device's listing.:)

I still can't get anything other than a zero in the V-memory location for the scale reading :confused:

Created Date: March 08,2011

Created by: johnomg

I resolved this eventually after discovering an obscure text file on a disc shipped with the indicator that explained the particular implementation of Modbus. If this had been included in the manual it would have saved a lot of frustration! Incidently the model is a Datatrack Tracker 240.

The indicator uses a 16 bit integer (scaled) for the display value and uses a "mirror " address to convert it to a real number. I keyed in the mirror address into the MRX box and bingo! I'm not clear on why it does it this way, but the upside is I can read a real number directly from the indicator without having to do a conversions in the ladder logic :D

Thanks for the help along the way.

Created Date: February 23,2011

Created by: johnomg

I'm struggling to get a loadcell indicator to talk to my DL06. The indicator supports MODBUS and I have it connected to port 2 on the PLC. I get both the TXD & RXD lights active on the PLC so I think :confused: the wiring is correct (2 wire RS485).

When I use the MRX box to poll the indicator I get nothing in the V register I'm trying to write to. At this stage I have a PC connected to port 1 and I'm using the "value=? " function in DS5 to query the V memory locations

I 've checked the 2nd comm port setup and it matches the indicator as follows:

Protocol: Modbus

Baud rate: 9600

Parity: none

Stop bits: 1

Station: 1 (PLC is master)

RS485 2 wire

The slave addresses match

I 've tried reading a number of locations in the indicator and get nothing everytime.

I'm probably missing something quite obvious or fairly basic, but any help would be greatly appreciated as this is driving me nuts..........