Your primary criteria appear to be the following:
- Reasonably high throughput (for sending camera capture data)
- 802.15.4/Zigbee specification
- Flexibility in various aspects, including interfacing with sensors and/or Arduino
Based on those criteria, the Xbee Series 1 (802.15.4) and Xbee Series 2 (ZigBee) would be strong candidates for your project.
These modules are available in pin-to-pin-compatible high- and low-transmission-power variants (i.e., longer range and shorter range, but also higher power consumption and lower power consumption). They have an on-board MCU and thus allow direct interfacing with sensors via I/O pins, or alternatively UART interfacing with an external microcontroller.
Depending on what your project cost goals are, you may want to keep in mind that Xbee modules cost $20-$35 depending on which model. They are fairly large in size, with a 20-pin 2.0mm-header form; this form does have the advantage of allowing you to adapt your PCB/design without further modification in case you decide to do a future replacement with similar form-factor modules (e.g., RN-XV for 802.11 Wi-fi, or Bluetooth Bee for BT communicaition).
If you choose to use these modules, they are extensively documented across project pages and forums in the Arduino and other similar communities, however, a good starting point would be Rob Faludi's book. If you are using Arduino's variant of C, or Java, as your development medium, there are the popular (xbee-arduino)[http://code.google.com/p/xbee-api/] and (xbee-api)[http://code.google.com/p/xbee-arduino/] libraries created by Andrew Rapp.
You mentioned air quality data and camera image data as examples of payloads you will be transmitting.
Here are corresponding examples for air quality data transmission and camera image data transmission using Xbee modules: (1) Air quality data and (2) Camera image data
Note that the Xbee units do have some disadvantages; here are some alternative suggestions for your project based on each disadvantage:
Large size/Cost: If Xbee unit dimensions or per-unit price are too large, you may want to consider a smaller-scale SMD alternative, e.g., the Atmel Zigbit or TI's CC2530
Large power consumption: If the Xbee units' current draw (ranging by scenario from 50 mA to 250 mA) is too high, then although you stated that 802.15.4/Zigbee is your chosen protocol, you may want to consider newer, more power-efficient alternatives such as Bluetooth LE, for example the BLE112
To begin with, there are several technologies for water sensing, with varied degrees of robustness. See these questions: Are there existing electronic sensors that can sense if underwater or not? and How does this soil moisture sensor work?, as well as some others on this site.
Some of these options, including a variant on the Grove sensor in the question, can be made robust enough to last years - simply by environment-proof epoxy / conformal coating of the entire sensor circuit other than the sensor strips themselves. This is one of the methods used by remote weather monitoring stations.
The soil moisture sensor is particularly attractive, as those are designed to be deployed for years of operation anyway.
Given that it is rain that needs to be sensed, an alternative approach would be this:
- Place a microphone close to a window or touching the attic ceiling (if an accessible attic exists) of the house to be monitored.
- Capture the sound, and code a set of filters and thresholds such that a trigger is generated on the patter of raindrops
- Use this trigger to actuate pumps or other equipment, or even to send captured images back to you for post-facto verification.
Best Answer
Temperature is a measure of the average thermal energy. A temp sensor will not tell you if we are talking a dry or wet bulb temp. The temperature is the same for both.
Wet or dry comes into play when you start thinking about how much thermal energy would be required to change the temperature of the air or how much condensation you will have if you lower the temperature of the air, etc.
To measure wet bulb, you need temperature and relative humidity. With those two sensors, you should have what you need.