Experimental Physics and
Industrial Control System

Hi, TechTalk,

Here I have a system architecture block showed as below.

Background: Last week I set up an environment consists of epics, python, s7nodave, which I can talk to PLC(siemens 1200). I use wxpython to generate a GUI to turn on a light of PLC, also I use django framework to generate a web page, in which I can control a light of PLC by clicking a button. The environment is in Ubantu.

1, My first question is, according to this function block, there are two parallel methods to communicate with hardware. But, why need OPC approach, since I can talk to PLC without OPC? What is the difference between the method I use and OPC?

2, My second question is: the hardware in the bottom layer, is a serial of PLCs. Manufacturer of these PLCs offers a DLL file, which is a API of these PLCs. Does that mean I can only build the whole system in windows OS but not Linux? Since DLL is a concept of windows. Also, OPC is also a concept of windows but not Linux.

3, Last, can you comment on the system block below? Anything helps me to get more clear about it is welcome.

Thanks a lot ^_^ ^_^ ^_^