TEMPERATURE CONTROLLER SYSTEM BASED ON PLCs

Abstract: Temperature control is a critical parameter across a vast spectrum of industrial applications, including chemical reactors, food processing, metallurgical furnaces, and HVAC systems, where maintaining thermal stability directly influences product quality, safety, and operational efficiency. Traditional temperature control methodologies, often reliant on manual oversight or rigid analog instrumentation, frequently suffer from significant thermal lag, steady- state errors, and poor adaptability to dynamic load changes. This paper presents the design, development, and implementation of an automated, closed-loop industrial temperature control system utilizing a Programmable Logic Controller (PLC).

The core architecture of the proposed system leverages a three-tiered automation framework. At the input stage, a high- precision industrial sensor—specifically a PT100 Resistance Temperature Detector (RTD)—continuously monitors the environmental temperature,

Converting thermal variations into standardized Analog signals. These signals are processed by the PLC's Analog input module. The PLC serves as the central processing unit, executing a robust Proportional-Integral-Derivative (PID) control algorithm programmed via Ladder Diagram (LD) logic. Based on the real-time error computation between the process variable and the user-defined setpoint, the PLC modulates its output signals to drive a Solid*-tate Relay (SSR), which precisely regulates the power delivered to the heating elements and auxiliary cooling fans.

To enhance operational visibility and human-centric control, a Human-Machine Interface (HMI) is integrated into the architecture. The HMI provides real-time data visualization, graphical trend logging, alarm management for thermal overshoots, and an intuitive platform for dynamic setpoint adjustments. Experimental results demonstrate that the PLC- based PID configuration significantly minimizes temperature overshoot, dampens thermal oscillations, and reduces settling time compared to conventional ON/OFF control strategies. Ultimately, the developed system offers a highly modular, scalable, and noise-immune solution capable of achieving precise, continuous thermal regulation in demanding manufacturing environments.