Sensor Networks with Java (Part I) by Enzo

End of last year I’ve started to build a little Sensor Network that I’ve placed in my house. I never thought that many people are interested in that but I was wrong, nearly every time I did a presentation about that topic many people asked me for a blog post about the project…and here it is 🙂
First of all this is not really about a Smart Home or something similar, this is simply a project to monitor data (temperature in my case). The original idea was monitoring multiple cold stores which seems to be something that is really useful 🙂
But because I didn’t had the cold stores I’ve decided to measure the temperature in nearly every room of our house.
The things I was interested in have been the behavior of the room temperature compared to the temperature outside. Does the temperature in the rooms follow the temperature outside of the house and how fast does it follow. To be able to compare those values I had to measure the conditions outside and in inside of the house.
Well measuring is one thing but you also have to analyze the data right? This means I needed to store the data somewhere and also needed to visualize the data somehow. Because I’m working from home I don’t have a big server room where I can put a computer that acts as a server so one other requirement was to use as many embedded devices as possible in the whole setup (means for communication, storage, etc.).
Wife factor
One very important (if not most important) factor in the whole project was what I call the "Wife factor". When I’ve started with the project I’ve used hardware like Raspberry Pi, BeagleBoneBlack and Arduino Yun to measure the temperature in different rooms in our house. It worked very nice BUT most of these devices have some kind of status led or I/O led which is blinking all the time. In addition all of those devices needed a power supply which means you have to place them close to a power plug. When my wife saw all these lights blinking and wires lying around she was not very amused.
I figured out that as long as she does not see the so called Sensor Nodes everything is fine.
Size matters
That said one thing was pretty clear, the Sensor Nodes have to be small and they should run on batteries…for months!!! I’ve tried different hardware like Raspberry Pi, Arduino Yun, Arduino + XBee but all of these approaches did not really work out well.
The biggest problem was the need for a power supply which limited the location I could place the Sensor Nodes. In the end I’ve took a closer look to the XBee itself which looks like follows… Read the complete article here.

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