How the ‘Things’ Speak: The Usage and Applications of Sensors in IoT

 The Internet of Things (IoT) has been massively revolutionizing human lives for the last few decades. The powerful and steady advancements in the field of science and technology have aided this process immensely. As a result, almost all aspects of our lives have grown smarter. Nowadays, life is almost unthinkable in the absence of IoT-enabled smart devices, such as smart televisions, smart computers, smart-phones, smart fitness trackers, etc. Needless to say, all these devices enjoy ever-growing popularity in this era of smart technology. This development is propelled by the existing digital communication backbone – the Internet. The very Internet, over which human communication started just a few decades back, is now being used by each and everything in our surroundings, be it natural or man-made. The advent and inclusion of IoT in recent times have highlighted how trees, crops, fruits, chairs and tables, electrical appliances, and all other objects around us can interact with each other. They are capable of communicating as freely as humans, and based on such communications, these things’ can even behave smartly, individually, and in unison, by making informed decisions in real-time! Given that these things do not possess the gift of life naturally, their ability to express themselves comes from the use of numerous types of sensing devices, also called sensors. The intelligent manufacturing and easy availability of these miniature, cost-effective sensing devices have given a new shape to almost all aspects of our lives. The data regarding the behavior of things, as captured by sensors, is essentially what the things express, and it carries meaning in the particular setting. This data may then be processed and analyzed at the source, transmitted over the internet and processed in a cloud or remote machine. While in some day-to-day applications, the data is used directly for decision-making (for example, in smart electric appliances), in more critical problems, the data needs ample processing and analysis (healthcare, activity recognition, etc.). In the latter case, different mathematical model-based machine learning algorithms are utilized to learn hidden patterns or features in acquired data and extracted features. With the use of a trained learning algorithm called a classifier, the new data is then used for decision-making purposes. The choice of such algorithms is often dependent on the type of sensor data being used and the corresponding application area. Thus, it is seen that IoT-based systems find application in various domains, starting with research and development up to industry, agriculture, defense, etc. In reality, the progress of researchers in different domains leads to smart products that, in turn, make human lives easier. Research in several popular ular verticals, such as Human Activity Recognition, Remote Healthcare, Remote Monitoring, Smart Automation, Smart Agriculture, etc., have yielded many such products. This chapter focuses on the deep-seated relationship between IoT and sensors from the perspective of state-of-the-art research. It offers discussions on the usage of various types of sensing devices, associated data, and their contribution towards solving specific research problems in the respective IoT-based applications. This includes the Video Camera, Inertial Measurement Unit (IMU) Sensors, Ultrasonic Sensors, Electrocardiogram (ECG) Sensors, Passive Infra-Red (PIR) Sensors, Electromyogram (EMG) Sensors, and some commonly used sensing devices for Environmental and Agricultural Smart system development. A pertinent case study is also included to demonstrate the role of sensors in the development of IoT-based systems. This study also highlights how little effort it takes to implement an IoT-based data acquisition system. The different popular application areas are discussed thereafter in terms of some broad categories. This is followed by the description of some of the standard metrics used for evaluation and benchmarking the performance of smart sensing systems. The future of sensing devices has been discussed, followed by the pertinent challenges faced by IoT-enabled smart systems in implementation. Finally, the concluding remarks are offered. The chapter aims to serve as a wholesome source of knowledge, and relevant information to researchers and practitioners who wish to indulge in the development of smart IoT enables sensing systems.