This is what finished system looks like.
The Sensor Node
The Base Station
How does it work?
The (many) sensor nodes consists of a Moteino (an Arduino clone with an RF transceiver), a soil moisture sensor, a humidity sensor, temperature sensor and a battery meter. Once the sensor node collects the sensor readings, it transmits the data via the transceiver over the 915mhz ISM band to the base station.
The base station houses another Moteino, which acts as a gateway to recieve the RF signals, and a Raspberry Pi where the data is logged into a MySQL database and serves the data to the Plant Friends mobile app. The Plant Friends app is an Android app, written in Processing, that displays the senor node data in a pretty way. :)
I love plants! Lets do this!
AWESOME! This tutorial is aimed at users slightly above the beginner level. I'll assume you have some basic experience with Arduino hardware and Arduino IDE (like making LEDs blink, installing libraries, etc.), basic knowledge of the Raspberry Pi (install Raspbian OS, etc.), and you know how to handle a soldering iron!
Before I send you off on a shopping spree, lets outline some goals for the system as it will dictate how the system operates. For my Plant Friends system, I wanted the following things:
1. Remind me to water my plants. Alert me via email and/or SMS.
2. Be able to monitor multiple plants. I have plants in different rooms in my home so I'd like to be able to monitor all of them at once.
3. I like to shuffle my plants around so the system needs to move freely. This means minimal wires and reasonable size. To do that, the system needs to run on batteries which leads to my next point.
4. The system needs to be low power. I want the system to run on a set of batteries as long as possible so I don't have change them out often. Because, lazy. I feel 4 – 6 months between each battery swap is reasonable.
5. Android app. Because even bathroom scales have one nowadays. I'm kind of a stats junkie so being able to look at the data from my phone is a plus.
7. Low maintenance! Again, lazy.
8. Some sort of enclosure to organize and protect the electronics.