Batteryless Smart Sensor Tags for Remote Food Freshness Monitoring

Abstract

In this thesis, the author presents a design of high frequency RFID system for remote food freshness monitoring. The proposed system has two main components: interrogator and transponder. First one, the interrogator is made up of a microcontroller, a RF reader module, a booster circuit to enhance power signal before transmitted to a loop antenna. The proposed interrogator operates at a frequency 13.56 MHz and used to collect data from the smart sensor tag at a distance approximately 30 cm. Second one, the smart sensor transponder comprises of a RF tag chip, a microcontroller, a loop antenna and sensors. The transponder uses a loop antenna to communicate with the interrogator through an electromagnetic field, in which generated by the interrogator. On the smart sensor transponder, an energy harvesting circuit is also designed to deliver power from an electromagnetic field. The delivered of power is used to supply to its own electronic circuits. In addition, all the food commodities have their own spoilage in the development difference that related to several gases such as hydrogen sulfide (H2S), ammonia gas (NH3), as well as the effect of the temperature in environment storage. Therefore, two of the electrochemical gas sensors, H2S sensor and NH3 sensor, are used for measuring the hydrogen sulfide and the ammonia gas in this thesis, respectively. Moreover, a specific design of low power consumption interface circuit for electrochemical sensors and a microcontroller is also presented. Based on the measurement results from the smart sensor transponders, the food freshness could be predicted. Then the printed circuit board (PCB) is fabricated to implement and validate above design. The proposed system could be used to monitor packaged food freshness and helped the customers choose the best quality of the foods.