PLC-Modem-telephone Line Communication

Hi All,
My problem: There are 4 working stations, i have to collect temperature, pressure, current, voltage value to a control room that very far from 4 stations (> 200 Km). And from control room, i can control these stations (on-off Valves, CBs ...).

The solution I first think is using PLC, Modem,and Telephone line. But I don't know much about PLC-Modem communication via Telephone line, Anyone can help me about the possibility of this solution and where i can find information about this problem (website..)

Thannks,

about PSTN communications

hi,about PSTN communications in the field of oil or gas, you can do:

1,you can use VB/VC/C/C++ or other software to drive the seriel port of the computer,the other side you can use PLC/RTU(of cause there is a seriel port) to send/receive data or control command.
2,you just use AT command(i.e:ATDT008613817340276, dial the phone number of one of your remote station),
3,read/write data from/to the remote station,
4,close your command use AT command(ATH0).

important:
you can poll a timer to active the communications,
It would be just as well to forbid any non-data transmission,
establish your communications protocol including password.

Chinese sailor
[email protected]

Hello!
The easiest way would be to have a "internet" connection (TCP/IP)to the stations. You have one/several PC connected to the station/-s and
connected to the control room by the internet/line-modem/GSM modem.

On the PC/-s you have the control program and remote operate it from the control-room. You can use eg. PcAnywere or Microsoft thin Client (microsoft terminal server in the PC) for remote operation the system (cheap), Or you can buy a SCADA softaware for that purpose.

If you use the telephone line you will have to pay for the calls all the time, if you can´t buy a permanent line! Also you have to have more than one modemline if you want to communicate with more than one PLC/PC...

Hi Sailor,
Thanks for your advise !
According to your ideal, i'll have to write a PC program to dial remote modem and receive data. At other side, a PLC (i am using ABB PLC) connected to another modem will send/receive data.
Could you please tell me more about communication between PLC-Modem and PC-Modem ? or where i can get documents on this problem. I've been seeking books in many bookstores in Ho Chi Minh city but could not find anything.
Thanks

http://www.abb.com/global/abbzh/abbzh251.nsf!OpenDatabase&db=/global/seitp/seitp161.nsf&v=17E82&e=us&m=100A&c=6401AC42B3A77D7485256C6A0070CC0A

http://search.abb.com/library/ABBLi...ageCode=English&DocumentPartId=&Action=Launch

check these out

This modem has the capability of dialing out as well are reciving calls:

http://www.automationdirect.com/adc/Shopping/Catalog/Communication_Products/Modems/MDM-TEL

It will work with almost any PLC that has a configurable RS 232 port.

Hi,Hien,

You can search 'SIXNET'&'MODEM',choose a fit modem for you.and you must learn the ABB PLC informations about the series port operation.
When the communication is connected, the PLC and PC is connected as local connection directly without modem, so there no much informations.In this way, now you must understand the AT commands and use it in your PLC language.
You'd better setup a system:
first,communication is ok
PC-----serial communication cabel------PLC
then, dial the interlocutor:

AT COMMAND:atdt802---> |
master | slave
PC-modem--line--(switch)--line--modem--PLC
-----------------------|---------------------
| <------AT COMMAND:atdt801
slave | master
PC-modem--line--(switch)--line--modem--PLC
801 802
and process of simulating of data send/receive.
just try it!
Sailor
[email protected]