This paper studies on control the humidity in the refrigerator for a vaccine. For the vaccine to be effective, it must be stored at a specific temperature for a vaccine to maintain its potency. The required range of temperature for vaccines is between +2 to +8ºC, while the relative humidity is 20 to 60%. The main problem is that vaccines are quickly diminished and cannot stay if they exposed to the extreme temperature and humidity from the range required. Nowadays, refrigerators are used to store vaccines in the hospital, and manufacturers are not able to control the humidity inside the refrigerator. Therefore, this paper aims to develop and design a humidity controller for a hybrid refrigerator system. This paper will consist of three main parts: integrate vapour refrigerator with thermoelectric, analysis of hybrid refrigerator characteristics, and design humidity controller. Based on the hybrid refrigerator response, the 10 to 50% duty cycyle of pulse width modulation (PWM) current is injected to maintain the desired temperature range. Among the controller tested, the value of PWM with a minimum of 20% to a maximum of 30% - this is deemed to be the most desirable range that would be able to maintain the desired humidity range. The thermoelectric used in this paper will be able to maintain temperature 5 ºC and also to control humidity as desired, which ranged from 20 to 60% to ensure that the vaccine performance would last longer.
