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A sensor tag that delivers its data to a targeted website through any available access point or wireless router, has shown its ability to run from solar power and deliver readings to Pachube.

The Pachube web application enables users to share real-time sensor data from objects, devices and spaces around the world.

This is just one combination of data-collection hardware and remote-analysis/display software that utilises the Instrumentation Cloud, so-called 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 some applications it is desirable to have the Tag4M tag powered by a solar cell in continuous operation.

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 that must 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 210mA and the unit operates from 2 to 3.7V DC.

His final design powers the Tag4M from a solar cell connected to a capacitor array through a buck-boost converter, all augmented with a rechargeable lithium-ion accumulator and a charger.

This setup provides real-time feeds of temperature, pressure and humidity data, as well as key system parameters on the tag itself, including solar-cell voltage and sleep time through the Pachube website.

In order to send sensor data to Pachube, users 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 TCP/IP write commands to the internet and the Pachube website.

Finally, the Pachube website captures the data and posts it on a feed that is visible to anyone who logs onto that particular web page.

To eliminate the PC in this process, Cores Electronic is developing a Tag4M Pachube Version whose onboard processor will create the EEML script and send this feed through an access point directly to the Pachube website for display.

The current solar-based combination is an example of the Instrumentation Cloud whereby sensors send their readings directly into the internet.

Users anywhere in the world can examine them and, if the setup allows it, send commands to digital I/O on the sensor tag.

In this case, the experiment is running in Cluj-Napoca, Romania, the web page is hosted in London and users with a web browser anywhere in the world can access it.

Because it leverages RFID technology this small, credit-card-sized measurement board contains everything needed for true remote standalone operation.

It starts with a Wi-Fi radio chip that communicates with a nearby wireless access point and provides measurement circuitry including an A/D and digital I/O.

Its CPU controls the operations of those subsystems and executes user measurement and control scripts.

Low power consumption means that, depending on the frequency of wake-up periods, a tag can operate on a small battery or from solar power.

Adept Scientific

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