Development of control and monitoring system for tea leaf withering

Abstract

Tea withering is a critical stage in black tea production, directly affecting the quality, flavour, and aroma of the final product. In many Sri Lankan tea factories, this process is still monitored manually using conventional methods, leading to variability, inefficiency, and labour dependency. This study presents the design and development of an automated, real-time monitoring and control system to optimise the tea leaf withering process using Internet of Things (IoT) technology. The system utilises an ESP32 microcontroller integrated with waterproof DS18B20 digital temperature sensors and a capacitive moisture sensor to measure dry and wet bulb temperatures and leaf moisture levels. Based on calculated temperature depression, the system automatically adjusts airflow through servo-controlled louvres. When the depression exceeds 5 ◦C, fresh air louvres fully open and hot air louvres partially close; if leaf moisture falls below 60%, hot air louvres close completely to avoid over-drying. Conversely, if the depression is below 5 ◦C, both louvres open fully to increase airflow. Real-time feedback is displayed on an LCD, while alarms and cloud-based logging via ThingSpeak enable continuous monitoring and analysis. A custom mobile application further supports remote access. Prototype testing at Sisiramba Tea Factory demonstrated improved uniformity, reduced manual intervention, and enhanced energy efficiency. This system offers a scalable, cost-effective solution for modernising tea withering in Sri Lanka.