Remote Site Communications


Thread Starter

Niall Watson

Dear List

We are looking at a project that comprises a remote pumping station, approx.
1KM from main factory.
The remote station has a Modicon (37??) PLC and a ?? data logger (RS232),
the factory another Modicon (??) PLC with Telway and FIP I/O installed.
We cannot run a cable between the sites, and the customer does not wish to
use licensed radio.
We can install a leased ISDN line at the remote station however, or use low
power (unlicensed) radio.

Does anyone have any simpler solutions than the following:
Install a PC at the remote site, with serial comms to the PLC and
data-logger, and use RAS ISDN communications back to the main factory.
Install PC at factory to integrate data from remote and local systems.

(I would much rather have a "dumb" device at the remote end, that will
"funnel" the PLC and data-logger communications via ISDN / Radio back to the
main factory PLC).

Also does anyone know of good OPC / DDE drivers for Modicon equipment.

Many thanks in advance (and off list commercial replies OK)

Niall Watson
sysero: systems integration solutions

Niall Watson

Phone: 01283 743022

a subsidiary of BI Industries plc

Cristian Gliga

Try PcAnywhere software. You can dial-in using a regular phone line and retrive the logged data from the remote PC's hard drive. You can even automate the process to some degree using VBA.

Hope this helps.

Cristian Gliga
Systems Integrator
Many would lean toward radio and PC at the factory, myself included. The radio link is your biggest concern, you must fully understand the risks of unlicensed ISM (i.e. know the location of nearby paging transmitters, cordless phones, garage door openers, baby monitors, etc.. and what they can do to your link, what IMD levels are in the area) and do a site survey before going that route. If you are in a congested urban area, the noise floor for ISM might be a problem.

This list's archives have a number of radio-related threads that might help. Ian's SCADA gospel list has some dated archives on this topic at
More recent stuff is out there, but I don't know where.

You might want to try to figure out why your customer is against licensed channels. In the US getting 12.5 KHz UHF channels or MAS pairs is really not that big a deal in most areas, and most radio vendors will help out with the licensing. The big advantage of course is legal protection from interference and higher power limits, which may or may not be important on your 1Km link.

Good luck,

Joe Manns
You can use GSM modems (Global System for Mobile) for communication. You can directly connect the GSM modem to the RS232 port of the PC as well as to your system at the remote location. If you need further clarification please don't hesitate to contact me.
Deputy Director
Control & Instrumentation Group,
Electronic Research & Development Centre,
[email protected]
I don't know Modicon very well but have used modems with Basic modules running communication software for PLC Direct (Koyo) and Siemens/TI. PLC Direct has a 3rd party Basic module with modem built in (either radio or leased line). It runs Modbus communication between master and slave stations. We did the same thing with a TI basic module connected to a leased line or radio modem for other applications. No PC is required. AB offers modem communication systems between SLC500 and PLC5 for remote telemetry applications. I don't know what communication protocol they use. Again, no PC is required.

I am sure Modicon must offer some sort of Modbus communication module with modem connection capability. If not, you can create your own with basic modules and a little programming effort.

Robert Willis

Schneider Electric has a OPC Server that will meet your application reuirenments. The part number is:

TLXCDOFS22M OFS FactoryServer Version 2.2

TLXDEMOOFS22M OFS Factory Server Version 2.2 Demo Software

If you can provide me with the excat part numbers of the equipment that you have installed, I can provide additional information. The TSX37 CPU has numerous processors that have different capabilites and I need to verify that the solution I can propose will meet your requirements.

Robert Willis
Schneider Electric
Square D Company
Houston, Texas
E-Mail: [email protected]

B. Dickerson has OPC/DDE drivers for Modicon. You can download and test the driver before you purchase it.