WiFi instrument tag sends data to real-time data-brokerage platform
A recent application of the Cores Electronic Tag4M sensor tag illustrates two aspects for using this credit-card sized device that delivers its data directly to a targeted web site through any commercially available access point or wireless router. The application proves the ability to run the low-power WiFi sensor information collector and transmitter from solar power, and it is delivering its readings to Pachube, which enables users to tag and share real time sensor data from objects, devices, and spaces around the world.
Cores Electronic, makers of the Tag4M device, says this is just one combination of data-collection hardware and remote analysis/display software that falls into the Instrumentation Cloud, which gets its name because users can read and control a sensor tag from anywhere in the world using any web-enabled device from a PC to an iPhone. In this demonstration, it is possible to read live data from the device, presently in Romania, at the Website www.pachube.com/feeds/7277.
Solar cell powered WiFi tag
Given the relatively high power requirement of a WiFi device, Cores says it has configured the Tag4M device such that it can be powered by a solar cell in continuous operation. The company advises that in creating a setup, you must ask questions regarding the solar cell’s ability to store energy during the day such that you can use it at night, its capability to supply enough current for Wi-Fi communication sessions. In addition, the solar-power scheme’s overall size, complexity and cost must be sufficiently low to make it cost competitive with batteries.
For this demonstration, Dr. S. Folea at the Automation Department at the Technical University of Cluj-Napoca, Romania, researched the best way to meet the requirements of a sensor tag located in non-optimum lighting conditions, but that must still provide data 24 hours a day. His design takes into consideration the power needed during the tag’s boot sequence, transmission period, measurement period, and receiving period. The peak current required at any time is 210 mA, and the unit operates from 2.0 to 3.7 Vdc. His final design powers the device from a solar cell connected to a capacitor array through a buck-boost converter, all augmented with a lithium-ion accumulator and a charger.
Currently, the setup provides real-time feeds of environmental data, including temperature, atmospheric pressure, and humidity, as well as key system parameters on the tag itself like solar cell voltage and sleep time through the Pachube web site. Cores also provides the ability to create proprietary web pages that accept and display sensor tag information. http://demo.tag4m.com
To send sensor data to Pachube, you must bundle it into a script written in EEML (extended environments markup language), a protocol for sharing sensor data between remote responsive environments, both physical and virtual. In this case, an application running on a local PC reads sensor data from Tag4M over a wireless link, bundles the data into an EEML script in a format Pachube understands and sends it using a TCP/IP Write command to the Internet and www.pachube.com. Finally, the Pachube web site captures the data and posts it on a feed that is visible to anyone who logs onto that particular web page.
Using RFID technology, Cores says the Tag4M device is a WiFi tag and contains everything needed for remote standalone operation. It starts with a WiFi radio that communicates with a nearby wireless access point, provides measurement circuitry including A/D and digital I/O, and its CPU controls the operations of those subsystems as well as executes user measurement and control scripts. In addition, extremely low power consumption means that, depending on the frequency of wake-up periods, a tag can operate on a small battery, another external supply, or solar power.
Cores spoke to Control Engineering at Sensors Expo and Embedded Systems Conference, co-located in Rosemont, June 8-10, 2010.
See other sensor and wireless products on the Sensors new product channel and on the industrial new product channel. Also see www.controleng.com/wireless.
– Edited by Peter Welander, Control Engineering, www.controleng.com