homemade moisture sensor
Hi,
Perhaps the easiest to use temperature/humidity sensor is the sht11, but it is also expensive. I haven't used these yet, but they seem like a nice easy way to measure humidity, and as a bonus, they do temperature.
I have used the Humirel HS1101, but these take a fair bit of work. You need to set it up as a capacitive load in an oscillator, which will output a frequency dependant on humidity. The output is non linear, so you will have to do some calculation. Additionally, these are cheaper than the SHT11, but not by very much.
I would not try implementing my own humidity sensor; seems like it would be quite difficult, and time consuming.
For the light sensor, I'm thinking a photo resistor in the feedback circuit of an op amp should do the trick nicely. I have this on my to do list, but haven't started working on it yet.
I like your project, as it seems along the lines of some of what I'm doing now.
Best of Luck,
Robert