Sunday, September 11, 2011

Can you guess what it is yet - the update

Well the more astute visitors to the site correctly identified the mystery object as Emilys weather sensor array project.

The device designed and built mainly by Emily is an ethernet connected sensor array, measuring Light, Temperature and Relative Humidity.

There is of course, an Arduino lurking in there as the main device, along with the ethernet shield. Sensors are TMP36 for temperature, A simple LDR for light and an HF3223 Humidity sensor. All of these live in the top enclosure.

The lower enclosure and antenna system were added when it was discovered that the TMP36 sensors were somewhat prone to false readings when subjected to local high RF fields (the array is not too far away from my R7000 HF and UHF collinear antennas). Inside the enclosure is a modified RF pre-amp followed by a simple diode rectifier circuit feeding one of the analog inputs on the arduino - giving a relative filed strength measurement. This allows data which may be subject to false levels to be dropped when processing the data.

Data is collected via one of our servers every 60 seconds by making an http request (scripted in phpcli) to the ethernet shield on the arduino - results are returned from the sensors as a simple comma separated string. The phpcli script then saves the data - including the RF levels to a MySQL database.

The resulting livedata, and historical data is then processed using php and the GD image libs along with JPgraph to produce dynamic images in her blog site:

see :

There will be a full writeup with photos, hardware diagrams, networking info, description of making a "power over ethernet cable",  arduino code, php and mysql etc on Emilys blog site shortly. I will post a crosslink when its finished

Congratulations to Emily on this fine piece of work - almost all the hardware, software, networking and database work was done by Emily herself. Brilliant effort and a great project over the summer holiday.

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