The Determination of the Fuzzy Membership Sets for a Hybrid Coffee Bean Dryer Temperature Controller

Traditionally in Indonesia, post-harvest processing of coffee beans is usually done by drying them in the sun. This method will produce coffee beans with uncertain quality. The use of sophisticated industrial-scale dryers is not easy to implement in rural areas due to the limited supply of electricity or gas as a source of heating energy. In this paper we present the design of a coffee bean dryer temperature controller using the fuzzy logic method. This device can regulate the temperature inside the drying chamber by adjusting the opening size of the hot air valve without changing the amount of heat supply from the heating components. In this way, various heat sources can be used according to their availability in the field. This research tested several fuzzy membership function scenarios in the form of several variations of valve opening sizes and measured the speed and stability of each variation in reaching the desired temperature. Based on the dryer model developed in this study, the most stable control scenario at the ideal coffee bean drying temperature is the fuzzy control scenario with 5 membership functions. The fastest time from 28°C to reach a temperature set point of 40°C is 10 minutes 26 seconds and the fastest temperature drop from 42°C to the same set point takes 3 minutes 19 seconds.