I have an existing machine with a SLC5/04 processor. It communicates to a Mettler Toledo IND780 scale controller via remote I/O and a 1747-SN scanner module in slot 1.
The machine has worked for years and suddenly lost comms from the scale to PLC. The DH+ cable is daisy chained from the 1747-SN to the scale controller, then to another rack with a scanner module elsewhere with terminating resistors at the ends. The other rack is communicating so I assume the cable is good. The cable also reads good with a meter. The original scale controller was obsolete so I had it replaced with a new one with the RIO board. It still doesn't communicate.
I think maybe there was a power outage and the original controller lost its parameters. I don't have these parameters documented anywhere so I'm not sure what the settings should be. The scale does work and we are able operate manually but very slowly. The scale is used to make chemical blends. The comms light on the PLC blinks green slow.
Here are the scale RIOparameters:
Node address (this was called rack number in the old controller)
Start Quarter (choice of 1-4)
Last Rack (yes or no)
Data rate: 19K 56k, 230k (DIP switches on 1747-SN are set to 230k)
Block Transfer (enabled or disabled)
Data format: Integer, float, etc.
Byte Order: Word swap, byte swap, or historical
In the PLC, the Inputs start at I:1.16 so I assume the node is 1, but I have tried 1-4. I have also tried start quarter 1-4, still no comms.
I attached a file showing some setup tips when going to a newer version of the scale and another file from the rung comments in the PLC. I also attached a screenshot of the 1747-SN settings.
Any info would be appreciated.
Semper Fi!
The machine has worked for years and suddenly lost comms from the scale to PLC. The DH+ cable is daisy chained from the 1747-SN to the scale controller, then to another rack with a scanner module elsewhere with terminating resistors at the ends. The other rack is communicating so I assume the cable is good. The cable also reads good with a meter. The original scale controller was obsolete so I had it replaced with a new one with the RIO board. It still doesn't communicate.
I think maybe there was a power outage and the original controller lost its parameters. I don't have these parameters documented anywhere so I'm not sure what the settings should be. The scale does work and we are able operate manually but very slowly. The scale is used to make chemical blends. The comms light on the PLC blinks green slow.
Here are the scale RIOparameters:
Node address (this was called rack number in the old controller)
Start Quarter (choice of 1-4)
Last Rack (yes or no)
Data rate: 19K 56k, 230k (DIP switches on 1747-SN are set to 230k)
Block Transfer (enabled or disabled)
Data format: Integer, float, etc.
Byte Order: Word swap, byte swap, or historical
In the PLC, the Inputs start at I:1.16 so I assume the node is 1, but I have tried 1-4. I have also tried start quarter 1-4, still no comms.
I attached a file showing some setup tips when going to a newer version of the scale and another file from the rung comments in the PLC. I also attached a screenshot of the 1747-SN settings.
Any info would be appreciated.
Semper Fi!
Last edited:
