Gas, Temperature, and Humidity Sensors-Based Onion Quality Monitoring System

Onions are a valuable cash crop for farmers, providing a reliable source of income; thus, monitoring of the quality of onions kept in storage is an important concern. There are various factors, such as temperature, humidity, and storage period, that are responsible for maintaining the quality of onion. The common factor is, onion emits various gases when it starts rotting. Thus, to address this issue, carbon dioxide (CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>), sulphur dioxide (SO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>), hydrogen sulphide (H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>S), ammonia (NH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>), temperature and humidity (SHT40) sensors are used in the proposed onion quality monitoring system. In this letter, we present the approximate ranges of the sensors through repeated experiments on three types of onions: healthy, those beginning to rot and fully rotted onions. In addition, our experiments and the literature both indicate that H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>S gas is the most effective for early rot detection. Moreover, none of the existing literature works have discussed regarding the power consumption of the onion quality monitoring system. Therefore, a novel battery operated, power efficient onion monitoring device is designed, primarily using H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>S and SHT40 sensors. This setup has a battery life of approximately 6.03 days with an 11.1 V / 10 Ah battery. When H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>S levels exceed a threshold indicating the onset of onion rot, all sensors (CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, SO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>S, NH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>, and SHT40) are activated, reducing battery life to 5.41 days.