Hardware Reference
In-Depth Information
Chapter 8
Android Sensor Networks
A sensor network is a series of stand-alone distributed sensor nodes that communicate information to a gateway for
retrieval. Sensor networks are used to monitor a wide range of conditions over a greater area than is possible with a
single sensor package. There is no typical setup for a sensor network; networks can range from just a few nodes to
hundreds, collecting any kind of imaginable data. Sensor networks are commonly used for industrial, security, and
scientific applications and can be set up as passive data collectors or active controllers. Sensor networks are not made
upon any single technology; they are made by integrating a variety of other technologies.
Arduino provides a great development platform for sensor packages for data logging and system control.
A sensor node is created when a sensor package is integrated with a communication method such as Bluetooth,
Ethernet, XBees, Cellular/GSM, or light to create a network. Arduino has been used to make sensor networks to
monitor environmental changes. For example, a distributed sensor network was created for the Fukushima nuclear
disaster to keep track of radiation levels. The network for Fukushima used a combination of GSM and Ethernet to
pass information from a Geiger sensor to a web service. Sebastian Alegria, a high-school student from Chile, created
another successful example of a sensor network to detect and warn of earthquakes. Sebastian's system used a simple
seismometer to detect events that could cause destruction, his system passed the information through the Internet via
Ethernet and used a buzzer to provide a local warning.
Sensor networks don't have to be as grand as these two examples, however. For example, they can be made to
monitor temperatures around a house or keep track of inventory being shipped out of a warehouse. When developing
a sensor network, keep in mind of all the development requirements and choose the sensors and communication
methods accordingly. For systems that monitor a smaller area, XBee modules can be used to avoid the need to
run cabling. In harsh environments, a network that uses cabling might be needed. XBee modules and cable-based
systems are great methods for creating stand-alone networks that don't rely on other infrastructure systems but limit
the range in which a sensor network can feasibly be created. To increase a senor network to a range that can monitor
across a country or the world, it might be preferential to use an existing communication infrastructure, such as the
Internet or telephone.
Android is a useful platform to integrate into a sensor network because of the variety of roles it can fill, along with
its popularity and ease of development. Android can be used as a method to receive or send sensor information via a
web service. Bluetooth can be used to wirelessly obtain data from a factory's sensor network. Android in conjunction
with the Open Accessory development kit can provide a portable method to retrieve data from a stand-alone sensor
network.
This chapter focuses on building a small sensor network that integrates XBees, Android, and Arduino. The sensor
network uses hardware that has been used in other chapters. The Mega ADK, SD breakout, XBee modules, XBee
adapters, and an Android device are all required for this chapter. openFrameworks, Eclipse, and Arduino IDEs will
also need to be available to complete the sensor network in this chapter.
This chapter uses concepts from and builds upon Chapters 3, 4, and 5. I recommend reading these chapters
(on openFrameworks, the Android ADK, and XBees, respectively) before continuing with this chapter.
Caution
 
 
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