ABSTRACT

Yohanes Letsoin, A Virtual Plant of the Programmable Logic Controller-(PLC)-based Process Control Systems (supervised by Rhiza S. Sadjad and Zahir Zainuddin)

A virtual process control plant - in this case a model of the water level control system - is developed as an application software and run in a personal computer. The plant is controlled by a physically real programmable logic controller (PLC) system via a real microcontroller-based communication interface.

The virtual plant program is developed using Visual Basic (???) programming tools to imitate a water level control unit consisting of a ..... liter water tank, a pump and a manual valve. Two level sensors to detect the minimum and maximum level are also simulated. The Universal Serial Bus (USB) port of the computer is used for communication with the S7-200 programmable logic controller through an AVR ATMega8535 microcontroller operating as the communication interface between the virtual plant and the physically real controller. 

The accuracy of the simulation time is measured experimentally. The results show that there is an 8.74 to 8.82 % of time error caused by the delay due to the computational processes of the personal computer. The computational processes contributing to the delay are assumed to include the port-scanning process of the microcontroller, the data conversion at the USB port, the open and close process of the contacting-relay, and error due to the observation method and equipment.