A Web PLC Using Distributed Web Servers for Data Acquisition and Control: Wed Based PLC

Advancement in technology is very well reflected and supported by changes in measurement and control instrumentation. To move to high-speed serial from Parallel bus architectures has become prevalent and among these Ethernet is the most preferred switched Serial bus, which is forward-looking and backward-compatible. Great stride have been made in promoting Ethernet use for industrial networks and factory automation. The Web based distributed measurement and control is slowly replacing parallel architectures due to its non-crate architecture which reduces complexities of cooling, maintenance etc. for slow speed field processing. A new kind of expandable, distributed large I/O data acquisition system based on low cost microcontroller based web server[1] boards has been investigated and developed in this paper, whose hardware boards use 8-bit RISC processor with Ethernet controller, and software platform use AVR-GCC for firmware and Python for OS independent man machine interface. This system can measure all kinds of electrical and thermal parameters such as voltage, current, thermocouple, RTD, and so on. The measured data can be displayed on web pages at different geographical locations, and at the same time can be transmitted through RJ-45 Ethernet network to remote web based data acquisition and control (DAC) monitoring system by using HTTP protocol. A central embedded single board can act as a central CPU to communicate between web servers automatically. The novelty of this proposed system is a substitute of web PLC for industry application.