Rancang Bangun Prototipe Robusta Coffee Bean Dryer Berbasis ESP32 Dengan Kontrol Suhu Otomatis dan Monitoring Melalui BLYNK

Abstract

The coffee bean drying process is one of the post-harvest stages that affects bean quality, but conventional drying still depends on weather conditions and takes a relatively long time. This study aims to design and build a prototype ESP32-based Robusta coffee bean dryer with automatic temperature control and a monitoring system via Blynk. The system was designed using a modified 750 W electric oven as the drying chamber, an SHT30 sensor to measure temperature and relative humidity, an OLED display and a joystick as the local interface, and a Solid State Relay (SSR) to control the heating element. Temperature control is performed using the Proportional-Integral-Derivative (PID) method with parameters Kp = 1.5, Ki = 0, and Kd = 0.7 at a setpoint of 65°C. Temperature and humidity data are transmitted in real-time to Blynk via a Wi-Fi network and recorded in Google Sheets to support the monitoring and analysis process. Testing was conducted under two scenarios: drying using an oven with PID control at a setpoint of 65°C and conventional drying by sun-drying. The test results showed a rise time of 8 minutes with an overshoot of 4.62% (peak temperature of 68°C) and a steady-state average temperature of 64.58°C. The relative humidity in the drying chamber decreased from 93% to 19.8% in approximately 8 hours and 37 minutes. The results of the moisture content test using the gravimetric method showed a final moisture content of 12%, which meets the maximum limit of 12.5% based on SNI 01-2907-2008. In conventional testing, the sample mass decreased from 400 grams to 130.4 grams over seven days. These results indicate that the designed prototype is capable of performing the drying process with integrated temperature control and monitoring of the drying chamber conditions.