Design of Multi-station PLC Control System for Temperature and Liquid Level

Abstract

In the actual industrial PLC control system, if the size of the controlled object is large, more than one station is needed. Based on this background, we study the multi-station control system problem in this paper. The control system takes one PLC as master station, the other as slave station. The Profibus-DP network is used as the communication mode between the master and slave station. The master station controls the boiler temperature and the slave station controls the water tank liquid level. First, the hardware system is designed, including temperature acquisition circuit, solid-state relay on-off control circuit, liquid level acquisition circuit and water pump control circuit. Then the control programs are designed, including the initialization programs, temperature acquisition program, temperature control program, solid-state relay PWM control program, liquid level acquisition programs, liquid level control program, and the dada transmission program between the master and slave station. Finally, the computer monitor interface is designed, including the main control interface, temperature curve and liquid level curve interface based on WinCC. Debugging results show that the temperature and liquid level can be effectively controlled, the temperature steady-state error is less than 4%, the water level error is less than 0.3%.