Getting the project page set up today and thought I'd share some initial information about my progress. I began with an ESP-12E which I soldered into a socket so I could use it on a breadboard. I am using a 3.3v FTDI USB-to-serial converter for uploading code. All of the components I am using have been ordered from ebay to keep costs low. I have probably spent more on my breadboard and power supply setup than I spent on all the components for this project.

So far this week I have spent a lot of time working with a small OLED display. Although this likely will not be included in the final project, it is helpful in displaying immediate sensor data so I can see if I am reading the components correctly.

The DHT22 and soil sensors have been connected and I am getting solid data from both. However since there is only a single ADC port on the ESP-12E, I need to multiple it in order to add the photoresistor. Some examples I have seen make this an easy prospect, I just need to pick out 'enable' pins and write up the code to read each device individually. Once that is working, I will move on to collecting data on a web page.

Last night I received some new AAA battery holders. These hold three rechargeable cells, providing 3.6V to the circuit. I was rather disappointed to see that, although the wifi radio hasn't been enabled yet, the batteries did not last through the night. I'm not sure if the ESP is drawing that much power, or if the OLED display is doing the damage. The ultimate goal is to use deep-sleep mode, waking up once every 5 minutes to record data, then sleeping again, however I may also need to find a way to power off the DHT22 if I find it is drawing a lot of power. Solar power is the goal, but power consumption has to be low enough to run on batteries for several days without a strong recharge.

Finally, the completed module has to be enclosed in such a way that water from the sprinkler system doesn't get inside, but the case is still open enough to give accurate temperature and humidity readings. For this, I am thinking of creating a stake from PVC pipe with a chamber for the components. Because of the large number of available pipe pieces, I think I can put together something quickly without any machining other than using a drill. I want to keep the components about three feet off the ground so that air humidity isn't effected by ground moisture, and I can read the conditions at the same level as my garden plants.