Implementing a PLC-based temperature controller with PID algorithm

PID controllers are used in most automatic process control applications in industry nowadays. PID controllers can be used to regulate flow, temperature, pressure, level, and many other industrial process variables. In this text I have specified guide lines to design and implement a temperature controller system using a mid range SIMATIC S7-300 PLC with PID algorithm. In text based on a defined project specification, we shall see how a SIMATIC S7-300 PLC hardware and its related developed control programs could be designed to implement a temperature control system that uses a close loop process control to maintain the temperature of a dyeing machine tank based on 4 typical predefined time temperature tables embedded in the main program ready to be used by the operator by which he can edit the data related to each function programs F1, F2, F3 or F4 depending on his particular application.
To ensure the ease of operation of the controller by the system operator, two other application programs are developed to establish communication between two types of HMI devices: a typical HMI panel and a PC-based one.
In application of both a PC based and a regular HMI device, the operator can view SV (set-point variables) and PV (process variables) values in real time when the system is executing the PID control program and in case of a PC’s monitor, operator can even view both values with respect to the time of a process.
All control program related to this project is written based on Siemens SIMATIC Step 7 platform but the algorithm of the developed control program and software can be applied to any brand of PLCs manufactured by different companies.