Embedded Fuzzy Logic Control System for Refrigerated Display Cabinets

Having done in this study, embedded fuzzy logic control system (EFLCS) was designed and implemented for closed refrigerated display cabinets (CRDC) to meet the required storage conditions for the pastry productions stored in CRDCs. The system keeps the temperature and relative humidity (RH) of CRDC at approximately +4 degrees C and 80% RH, respectively. It has two fuzzy logic controllers. One of them controls the speed levels of the fans, and the other controls the steam level of ultrasonic atomizer. Temperature and RH values are read by sensor SHT11 and transferred to PIC18F4620 microcontroller that is programmed with fuzzy Logic approach. On the other hand, the compressor was controlled with on-off control in the range of 3-5 degrees C. On the condition of starting from +7 degrees C temperature, the time to approach to the set values (4 degrees C and 80% RH) for traditional system and EFLCS is 191.8 and 109.6 s, respectively. Additionally, the ranges of temperature and RH obtained by EFLCS are between 4.44 and 3.69 degrees C and between 81.33% RH and 78.57% RH, respectively. The temperature and RH values obtained by traditional system are between 5.56 and 3.2 degrees C and between 61.81% RH and 57.45% RH, respectively. Traditional system never reached to desired humidity value (80% RH). It has been seen that developed EFLCS becomes stable in shorter time than traditional system and kept the desired values as almost constants.