Programmable Logic Controllers, PLCs are widely used in the modern process control systems. The controllers are larger and more powerful, thus able to perform increasingly complex tasks. Even a single PLC can manage a larger, and more complex area, instead of a local, fragmented control system.
In these cases the process instrumentation, effective interconnection of the inputs and outputs are more and more important. The modules, that are connected to the industrial bus, far form the PLC, can achieve insensitive signal handling, and reduce failures caused by wiring effectively.
My task was to develop a module, which is capable of handling remot inputs and outputs. The power supply of the circuit should be 24 V. The device is featured to cope with communication in MODBUS TCP system, which is widely applied in industrial environments.
I give a description of the circuit design process in my thesis. I present how the schematic was developed, how the components were selected and finally how the printed circuit board was designed. Then I demonstrate the structure of the software.