A cool and free software download that is pretty awesome. People may already know about this but I just found it last night. It's called PLX-DAQ from the Parallax website. Instead of buying a data logger shield for the Arduino and having to take the memory card out when you want to look at the data this cool software lets you connect right to you Arduino. I think you can have up to 20 inputs and it sends it right to excel. It's just an excel file with a Macro created to connect to your Arduino and some other micro controllers. It does not show that it is compatible with the Arduino but it worked fine for me. You write your normal program in the Arduino IDE. Upload the code. Click connect on the excel macro. And boom you're off to the races.
I have my Arduino set up as of last night measuring just room temperature right now and recording it in excel every half hour. Once the data is in excel it is putting it in a pretty graph. What I am going to do with it is put one temperature sensor in a pot of soil (or three) and then leave one outside in the room temperature. What I want to do is see how the soil temperature varies based on the surrounding air while it is in a bucket and it somewhat exposed as an "object." I would like to get a couple different types of soil (i.e. top soil, sandy soil, clay soil, and rocky soil) that way I can see if there is a thermal efficiency (Maybe that's the word I'm looking for?) between different types of soil. Once I determine that at a small scale I want to take the whole thing outside and see how the ground soil at my house changes based on the above ground temperature.
The goal I am trying to achieve because I apparently have nothing better to do with my life is make a determine how quickly the soil temperature changes based on outside temperature to see if my garden will survive a night outside in the cold. By knowing this I could look at a weather forecast to see what the night temperature is supposed to be and then know if I have to cover my plants or if they will survive. Maybe eventually even have some wifi shield for the Arduino look the weather up and determine for itself and then notify me via email if I need to go cover them.
This project will put me one step closer to an automated garden. I already have an automated watering system based on Arduino clock controlling a solenoid for a set time to allow the specific amount of water needed to individual rows.