Cacao fermentation is a critical post-harvest process that strongly influences cocoa bean quality and farmer income, yet it is commonly managed using fixed time-based rules that fail to reflect real-time microbial activity. This results in inconsistent fermentation outcomes, particularly for smallholder producers. This paper presents the system design and pilot implementation of a low-cost Internet of Things (IoT)-based cacao fermentation monitoring device that uses continuous temperature sensing to guide fermentation management. The system employs a PT100 platinum resistance temperature detector (RTD) interfaced with a MAX31865 RTD-to-digital converter, managed by an ESP32 Wi-Fi microcontroller, and transmitting data to a Blynk cloud dashboard for remote monitoring and automated alerts. A rule-based algorithm incorporating an exponential moving average (EMA) signal to smooth temperature data identifies characteristic temperature rise and peak patterns associated with microbial phase transitions, enabling timely notifications for aeration (bean turning) and the progression of the fermentation cycle. The complete firmware architecture, hardware integration, signal-processing approach, and cloud-communication framework are documented. Pilot deployment under real fermentation conditions confirmed that the device reliably captured temperature profiles consistent with established phase transitions in fermentation. The total hardware cost of approximately 3,680 Thai Baht (approximately USD 105) demonstrates the feasibility of sensor-driven fermentation guidance as a scalable, affordable approach to improving post-harvest cacao management for smallholder producers.

Keywords

Cacao fermentation, IoT, Temperature monitoring