Application Focus: Wi-Fi Sensors
Applications designed simply to detect environmental change are numerous, and they can be found in a wide spectrum of commercial and consumer markets.
Some basic examples include monitoring temperature, humidity, air quality, moisture content, and lighting levels. There is an accelerating trend to deploy wireless sensors to monitor changing environments and make intelligent and automated decisions based upon real-world measurements. Wireless sensors have a distinct advantage over wired sensors since they often have lower installation costs and offer rapid scalability.
Applications for wireless sensors are nearly endless. Consider monitoring food temperature across a line of distributors and grocery stores. Freezers and coolers can be conveniently and reliably monitored, alerting staff to fluctuations before costly spoilage occurs. Another common application in residential homes is monitoring water levels in basements or carbon monoxide levels in air. Monitoring systems can be configured to email or send text warnings. One of the major cost advantages of wireless sensor networks is eliminating the expense of retrofitting wiring to existing buildings. Today numerous wireless sensor networks are already monitoring campuses, office buildings, manufacturing plants and residential homes.
Wi-Fi Modules and Sensor Networks
Low-power, low cost Wi-Fi modules have changed the landscape of wireless sensor networks. Autonomous Wi-Fi sensors connect to common and widely available wireless network infrastructure. Sensors send data using standard internet protocols such as TCP/IP which enables the information collected to be accessed anywhere in the world from any computer, smartphone or tablet.
Until recently, many wireless sensors networks were built using proprietary protocols running on sub-GHz radios. These networks may cover a large distance, but they are closed systems and the data is locked away. Likewise sensors networks based on Zigbee radios are also based on a closed system. Both of these wireless sensor networks require additional hardware gateways to get sensor data onto the internet or a users local are network. Gateways introduce a single point of failure and additional cost.
Built on standard 802.11 Wi-Fi infrastructure, remote sensor networks contain three main components: battery-powered sensors, standard Wi-Fi access points, and server software that receives, stores and presents sensor data to end users. Sensor information can be viewed from a device on the network or if desired, any Internet-accessible location. If a sensor is not in range of a Wi-Fi access point an additional access point can be added as a repeater. A sensor only needs to know the Wi-Fi network name and password to join a network; and with a pre-programmed IP address or URL, the sensor can immediately begin sending data direct to a server on the internet.
A sensor can intelligently send data to a server based on a time period, sensor event or even if the data meets pre-configured criteria. Sensor configuration can be setup from a server during the provisioning process when the sensor first connects to a network. If the network goes down or a sensor goes out of range, data can be cached on the sensor itself. When the network connection is re-established, the sensor can bulk upload cached data to the server avoiding potential data loss.