2 PLCs 10 kms apart to be controlled from one station

  • Thread starter DHANYA KULKARNI
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Thread Starter


Hello members, 2 PLCs with 100 i/o s situated at 2 stations 10 kms apart have to be controlled and monitored from one of the stations,the other being unmanned. which is the most cost effective method for communication? whether standard PLC s like AB,GE-FANUC etc can be used for this? Any help is appreciated Thanks in advance, DHANYA KULKARNI <[email protected]>
This is not a difficult task. With Schneider PLC's you can use fibre to extend Remote I/O or Modbus Plus to this distance. Another possibility is to use a serial protocol (like Modbus) with dedicated phone lines and line drivers. It is also possible to use Ethernet between the two PLCs. And, spread spectrum radios may work but you would likely need a repeater to carry the signal that far. These have all been done and all work quite well.
I would recommend a Modicon Quantum, Momentum, or Premium PLC and wireless ethernet. Check with Data-Linc (www.data-linc.com) and Modicon (www.modicon.com). Of course the Data-linc solution will work with any ethernet PLC, but they have rack-mountable modules for Quantum and Compact. According to their catalog, the wireless ethernet modems can transmit up to 15 miles with line of sight. They also have regular wireless modems, which can go 20 miles. One issue as always will be speed. The amount of data you have to copy over the wireless link will take a certain amount of time, but good PLC programming can usually keep communications to a minimum.

I think the cost effective method communicating shall be inter-connecting with Modem /RTU/ RS 232(or) 485 ports on both ends and running Telephone cable between Manned and Unmanned PLC's, speed of data transfer shall be a constraint but the application required to be studied. Also the another way shall be through single mode Fiber optic cable with repeater station in-between because single mode have constraint of not more than 8 Kilometer. I hope above two option will help. P.Suresh Bechtel India