Sunday, May 01, 2011

Nanode Serves Solar Monitoring Data

Day 5 of #snowdonbuild - a 6 day collaborative Open Hardware and Open Software hack session.

To further develop Nanode and Open Energy Monitoring Applications - held at a remote farmhouse cottage in rural Snowdonia.

After a morning of intensive hacking here in Snowdonia, the Nanode solar monitoring system serves its first web page with solar data.

As a reminder of the set-up we have here, there is a small 1W solar panel mounted on a wooden frame with a single axis solar tracking system driven by a standard size radio controlled servo.

One Nanode controls the solar tracking algorithm, and is powered from a solar charged 3.6V NiMH battery and super capacitor. The solar generated power, and the serial communications is connected back to the lab area using a 15mm length of telephone extension cable - this was mainly for convenience, as neither my LCD digital scope, used for measurements, nor my laptop screens are particularly visible outside in the sunshine.

The serial output from the measuring Nanode, is connected to the serial input of a Jeenodes wireless module. Glyn has written a small interpreter programme to run on the Jeenode, which takes the 5 fields of comma separated integer data relating to solar voltage, current, wattage, tracking angle and temperature, and converts them into a byte packet format which the JeeNode uses for over air transmission.

The data is received by a RFM12 module connected to a master Nanode, which is in turn connected to the internet. A byte packet decode scheme, takes the off-air data and reconstructs it into the 5 measured arguments.

The Nanode then serves these data fields up to the web, so that they can be viewed by any browser.

The solar data is also served up to the EmonCMS graphing server for long term storage, we have added the graphing capability which is generated by the EmonCMS energy monitoring system server and it is from this server that the graphical data is served.

The bandwidth and update frequency of the Nanode means that it is best used for serving small packets of numerical data, and not data intensive images.

Because we just handle integers at the moment the voltage is actually 5.32V and the temperature is 21.9C.

We've had the solar tracker running since early this morning logging the solar data to file. Although this is a very small scale system it can be easily extended to monitor full size solar installations.

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