A LoRa-based IoT Sensor Node for Waste Management Based on a Customized Ultrasonic Transceiver

This paper discusses the use of an integrated ultrasonic transducer for the realization of a LoRa-based Smart Bin architecture, to be employed for waste management in the Smart Cities context. In particular, the paper analyses the usability of waterproof ultrasonic sensors for the measurement of waste level inside a trash bin: in this context, a solution is described to increase the directionality of the sensor. Indeed, ultrasonic sensors used in common off-the-shelf waterproof ranging systems are characterized by a wide radiation lobe, corresponding to an aperture angle up to 70°: this means that, when employed in trash bins, these sensors detect the presence of the lateral surface of the bin and are not able to detect the garbage layer top or its position in the bin. In this paper we propose a tailored cap, designed to be mounted on a commercial ultrasonic sensor, able to reduce the detection angle down to around 28° degrees. The modified sensor can thus be exploited in this application. The proposed sensing structure is integrated into a sensor node provided with a LoRa transmission module, that allows to employ it for the development of city-scale monitoring infrastructures.