We would like to know how we can access our remotely located PLCs using MODBUS TCP/IP to view, trouble shoot and modify the PLC logic (similar to how we would locally connect a Laptop PC to the MODBUS Ports) and what software and hardware would be necessary to achieve this. We understand also that this software is downloadable and wuold appreciate further information.

Thank you,
Steve Carvalho
PETROTRIN

 

Try Modicon's own ModBus RS-232/484 to ModBus TCP/IP Ethernet gateway (174-CEV-300-10). This gateway can interface these two media/protocols to the point that devices on either side will almost not know the difference. In your one-to-one ModBus RS-232 application you can configure the gateway to ignore its "Dest_Index" parameter which basically gives your legacy 984-685e a "virtual" ModBus TCP-IP address. The later you configure through simple ARP commands. BTW, this unit can also behave as the trusty BM-85 ModBus to ModBus Plus Bridge by storing serial to IP (or vice versa) look-up routing tables.

 

Steve:

In your message you do not indicate the programming package that you are using with your current Modicon PLC's. It would also be helpful to know the particular model number of the PLC's that you have installed.

Currently Schneider Electric has the following software packages available that can communicate using the Modbus TCP/IP Protocol.

ProWORX NxT (984 Ladder Logic Editor)
ProWORX 32 (984 Ladder Logic Editor)
Concept (IEC61131 Compliant)

Depending on the specific Modicon PLC's that you have indstalled you may have to add a 140NOE771xx module to get a ethernet connection to the TSX Quantum. Schneider Electric also has a Modbus TCP/IP to Modbus Bridge for those PLC's that will not support a native Ethernet module.

Regards
Robert Willis

 

There shouldn't be any software required other than your PLC programming software.

Your best bet is a wireless ethernet radio modem, and there are several vendors. We've used Data-Linc and Locus, and Grayhill also has an offering. They can be set up for a master to multiple slave configuration. So you can have a master connected to your existing ethernet network and add slaves at the PLCs. Then the PLCs can be given IP addresses and you can access them over ethernet.

CK

 

If you are not set on ethernet, as the PLC listed do not support ethernet except throught a bridge, you may wish to consider a wireless modbus serial network. Data-Linc offers a good solution to do this as well as wireless ethernet. The modbus solution would be just as fast, and allow for the programming as you desire, since the limiting factor of you whole system is the plc serial connection. Ethernet is a better solution long term if you plan to upgrade the plcs eventually.

 

Robert,
The programming software used is MODSOFT Ver 2.61 and the MODICON Controller types are 984-685E and 984-785E.

Regards,
Steve Carvalho
email scarvalho @petrotrin.com