A sensor node, which can also be referred to as a sensor pod or a mote, is a component of a larger network of sensors. Each node in the network is responsible for collecting data about the environment around it and sending that data to processors in the network. Though the concepts that gave rise to the sensor node have been around for several decades, experiments at National Aeronautics and Space Administration (NASA) and the University of California system in the late 90s and early 2000s have led to further development of this technology.
There are a number of different environmental conditions in which a sensor node can detect changes. Temperature and pressure changes are some of the most common. Most such nodes are designed to detect changes that occur slowly, though modifications can be made in data compression to allow these sensors to function in high-speed environments.
The sensor component of the sensor node can have a range of different features. Some sensors are designed to collect information from only a particular direction while others, such as the sensors used to detect radar signals, perform an omni-directional sweep. The sensors can be designed to gather information unobtrusively, waiting for the data to come to them, or they can be designed to actively probe for information. Sensors of this second type may affect the environment they are sensing.
Once the sensor has collected the data, it transmits it throughout the network using a transceiver. These devices are made up of both a receiver and a transmitter and can send information wirelessly in a few different ways. The use of lasers and infrared devices can be utilized to transmit data, though both of these modes of communication require a clear line of sight from the transceiver to other components of the network. Radio signals are commonly used when the sensor node is not within sight of the piece of the network it needs to communicate with.
The sensor node also contains computer components that both instruct it and store data it has collected. The node requires a source of power, which is almost always a battery. These nodes that do not use a battery can be designed to run off of energy from the sun or from vibrations in the environment.
