Home Monitoring System – Version 1.0

Having worked on my home monitoring system on an off for the last number of weeks I have finally gotten to version 1 for the host board and the sensor nodes.

Temperature And Humidity Sensor Node

I completed the development and testing of the wireless temperature and humidity sensor nodes.

This board was installed in an enclosure as shown below. The board was designed to fit snuggly into the enclosure which takes two AAA batteries to power the sensor.

The sensor implements a simple channel scanning and handshake protocol which allows it to determine the radio frequency channel the wireless hub is listening for packets. When the channel is found by sending a NodeHello packet to which the wireless hub replies with a NodeHelloAck packet. The NodeHelloAck packet contains configuration data that the node uses to setup it logical RF channel.

Once the handshake has completed the node enters a loop where it sleeps for a period, which is provided as part of the handshake data, wakes up and transmits the latest temperature, humidity and battery voltage readings to the wireless base station.

Wireless Hub

I chose a Netduino Plus 2 as the hardware for the wireless hub. The hardware setup is pretty straight forward. An NRF24L01P radio module is connected to power and the SPI port on the Netduino.

The Netduino implements a simple web server, based on embeddedwebserver, that hosts a set of pages that renders the sensor data from each of the sensors, allows configuration changes to be made and log file viewing. Since the Netduino has limited memory and CPU most of the processing for data rending is offloaded onto the browser. The sensor data page uses a JavaScript graphing component called Rickshaw. The pages are rendered on the client side browser as a single page application using AngularJs as the MVVM framework and Bootstrap to provide a responsive UI that scales to different device screen sizes.

Sensor Data Display

The sensor data is rendered on the main page of the application. The interface allows selection of a number of days of data. Multiple sensor feeds can be rendered, the graphing component supports hoover details when the mouse is over a point on the graph.

Nodes Configuration

The nodes configuration page shows active nodes and the node types. The nodes name can be modified.

System Log

The logging level is set on the configuration page from 0 to 4, 0 = None 4 = Debug

Configuration

The configuration page allows the following to be configured:

• The radio channel
• The radio device address
• The log level
  • None
  • Info
  • Warn
  • Error
  • Debug
• Update interval, the rate that the sensor will push readings

Future Additions

• Minor web UI clean up and changes
• The ability to export sensor data
• The ability to have a node release its allocated id

I would also like to add some additional sensor types, maybe air quality, water,power etc. Later I would like to use the data gathered to directly control the space heating from the netduino, via a relay node that can be used to advance and retard the heating system based on evaluation of the temperature data. For example on a very cold day fire up the heat at an earlier time than the heating control system would normally.