The refrigerator is the key component to keep the medicine and biological sample in the hospital. However, the refrigerant that commonly used in the refrigerator will bring a negative effect to the environment. Other than that, the domestic refrigerator also has the problem of larger size and heavier weight since to the compact system like condenser, compressor, evaporator and expansion valve are assemble and use in the refrigerator. This study focused on the development of temperature control of the portable thermoelectric refrigerator for medical purpose. Thermoelectric cooling is using the thermoelectric refrigeration method through a thermoelectric module. This project is to analyze the space scales of the system which can perform a desired temperature control for the thermoelectric refrigeration. A commercial portable thermoelectric cooling is modified, which is able to achieve the temperature within the range of 8°C to 15°C by controlling the input current. Modification of this refrigerator is done by changing the original circuit of the refrigerator into a new circuit. The resistance temperature detector is used to replace the original thermostat that used to measure the inner temperature of the refrigerator. The input current is controlled by MOSFETs by using the pulse width modulation method. The temperature response of normal and small scale of thermoelectric cooling is 13.88°C and 10.91°C when input current 3A injected.
