PCOM and GPRS Modem

[serban.b]

Hello,

 

Is there a way to read/write (send) data between 2 plc's via gprs modem, using pcom? I'm using V130 and Siemens TC65 at both ends

 

Thanks in advance!

[AlexUT]

Hi,

What are models of OPLCs you use?

How many and what data you wish to send/receive?

How many PLCs will be in network?

Keep in mind that communication speed is limited to 9600 bps.

BR.

[serban.b]

2 PLC's. I want to be able to read/write MB's, MI's between PLC's. There will be 2 pcs V130.

Thanks

[AlexUT]

Hi,

You can use MODBUS.

After establishing connection via GPRS, or dial, do MODBUS Configuration and enable ScanEX for Slave, or MODBUS Configuration and Read/Write for Master.

I hope this helps.

BR.

[serban.b]

I know I can use MODBUS, but I asked if there is a way to accomplish a communication between 2 plcs via gprs modem using pcom protocol.

 

thanks in advance!

[Emil]

Theoretically yes. But you need ot implement PCOM Master in one of them. You have a very good description of PCOM in our site and I guess you can accomplish the task in 2-3 weeks. Compared with Modbus, where the programming can take 2-3 hours...

[serban.b]

OK, Thanks. I cannot use MODBUS, I think. The problem is I have a SCADA application build by me, and it's using only pcom to communicate with 3 plc's. (V130). So, beside that, 2 of these plc's must have a communication bewtween them.

Lets say, plc1, plc2 and plc3 and scada. PLC1,2,3 communicate with scada, and plc1 communicate also with plc2, directly, not thru scada. All PLC's are using siemens tc65 for communication, and scada use a internet connection.

 

It's possible for a V130 to establish two connections? - one MODBUS and one PCOM with a single gprs modem? MODBUS for communication with other plc and PCOM for communication with scada.

 

scada reads data from all 3 plc's at 10 sec interval.

 

Thanks!

[Emil]

No. On GPRS you have only one communication channel. Theoretically, you can switch between Modbus and PCOM once established GPRS connection. But this means that you will have only part time connection between SCADA and PLC and it will be difficult to synchronize between controllers themselfs.

Idea - use cellular router instead GPRS modem. It will let you to open 4 communication channels. While one port will be opened for the SCADA, with other ports you can communicate Modbus Master Slave or even better TCP or UDP Raw.

If you are interested in such solution, I can give you some more info.

[serban.b]

OK, that is a solution, is the same thing as connecting the plc's to the internet thru cable . I think I just need 2 gprs modems with ethernet. 

Or, other solution is to connect 2 gprs modems to the PLC, on COM1 and COM2.

 

It could be good to implement FB's for using PCOM with gprs modems connected to plc on serial port.

 

thanks!

[Emil]

Yes, connecting controller via Ethernet to Cellular router is like connecting it to cable Ethernet. In some cases (depends on routher and network) it's even faster and more stable.

Two modems - out of elegancy of this solution, which I'm a little in doubts, I'm not sure if the contfroller can handle such configuration. Again - because of elegancy, we never tried it.

[serban.b]

I understand. Thank you, we will try to use gprs modems with ethernet.

 

Have a nice day!

[serban.b]

I understand. Thank you, we will try to use gprs modems with ethernet and come back with results!