System use cases and refrigerator experience

In Uncategorized on May 7, 2010 by salvadormrf

System overview

SAWA can be considered as a platform, with a set of services and web application. It uses XMPP Protocol to transport all sensor data in real-time, and allowing secure connections. Using XEP-060, Publisher-Subscribers paradigm it is possible to share data with multiple users with flexibility and scalability.This project uses soxlib with modifications from Sensor Andrew project.

Project blog, Project source

Web application
In web application is possible to manage networks and sensors, manage XMPP nodes, define policies, and share data.


Google Maps, Flexigrid, Open Flash Charts 2, jQuery, Ajax, JavaScript, Openfire Css, CodeIgniter, PHP, C, MySQL



This service is responsible to store sensor data in database, when published in nodes


This service is responsible to match all sensor data with existing policies, and launch these actions when policy matches.
Each notification type is included as plugin, making this service more easy to extend.


This service is responsible to order the previous services to subscribe or unsubscribe from PubSub nodes.


glib-2, gmodule, libloudmouth, soxlib, mysql, C, XML, XMPP

Openfire XMPP Server
MySQL database server
Apache HTTP Server
Postfix email server


install soxlib and sox_tools



-sox_tools config

create .sox_tools.cfg in your home

– in this example we are publishing the value 25 with unit “C” from variable 14 in user123_network network

sox_tools publish user123_network 14 25 C

Bash script (HTTP method)

# user credentials
# publish Url
# data value

How to use this system?

Create account


After creating an account, login with your credentials.

Create Network

When creating a new network it is possible to specify the access level, and network location.

Create Sensor

To create a sensor, we have to select the network which will belong to, the type (sensor or actuator), location and the variables of the sensor (this variables can be for example door status, open time and closed time count from a door switch sensor). After this steps, we are now able to upload data and see them on charts.

Publish data

There is two methods of sending data, one is HTTP POST, useful for simples devices, without capabilities of parsing XML and establishing SSL connections. The other method is using sox_tools, a specific XMPP client for this system. Last one has the ability to publish, listen events and manage pubsub nodes.

using XMPP Client ( sox_tools recommended )

sox_tools publish myHome 11 14698


curl -d -m 10 “[]=11&NODE=myHome&DATA=14698” $URL

View data charts

All sensor data is set to be recorded by default, in “Data” menu, select the chart type and sensor variables to be represented, and to finish click on interval to generate graph.

Create policies

In policies we have, four types of notifications, email, sms, url and publish events to actuators, in this example I created a policy to alert me when thee door is more than 300 seconds open. I repeated the same test with all notifications types, the results are bellow.

Email notification

Email notification working

URL notification

Datarecorder service output, policy Url being called

SMS notification

SMS notification arrived

Node event

Event published on node

Practical use cases

Monitoring a refrigerator

I used this experience to test the system, so the objective was to record sensor data.
The variables I selected to record was: door status(open or closed), time open (number of seconds the door was open), and temperature.
Since arduino is very resource limited, i used HTTP POST method to publish data.


  • sensors
    • 1 temperature sensor
    • 1 photo-resistor
  • devices
    • 2 arduinos
    • 1 ethernet shield
    • 1 RF kit

Network diagram

Sensor Network diagram

– The arduino on refrigerator sends messages to gateway (arduino in router) with format msg_id:sensor_variable:value (example: 455:door:1:temperature:10)
– Then gateway sends via HTTP POST the sensor value with user credentials and sensor identification
– Then on server, this data is published to XMPP node


Refrigerator with Arduino

Arduino with RF transmitter module (with yellow wire as antenna)
Blue wire is energy source, red, black and white are connected to sensors

Instead of having a door switch, I used a photo-resistor as door switch, which measures the amount of light. So when we open the door, the light from refrigerator will go up and go down when door is closed.

Here is two basic sensors the “door switch” and temperature sensor

My sensor gateway, responsible for receiving data through RF and send to server

Arduino+Ethernet Shield+RF Reciver

Data charts

Possible experiences

Inteligent Mail box

adding soon

Wine monitoring

adding soon

Energy savings

turn power off from all standby devices, if inactivity in a room is greater than a number of seconds
arduino or pc+PIR+Relay


create policy with geographical limitations (square), when device enters this area an action will be triggered

One Response to “System use cases and refrigerator experience”

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