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A wireless sensor networkA wireless sensor network
Dr. Miguel Sánchez LópezComputer Engineering department
Universidad Politécnica de Valencia, Spain
Leipzig, November 2008
Presentation OutlinePresentation Outline
Introduction Developed system Conclusions
System architectureSystem architecture
Wireless sensor networkWireless sensor network
Sensors data is gathered by coordinator node
Data flow is one way No anytoany
communication
Routing on our WSNRouting on our WSN
Beacon messages are sent periodically by coordinator
Upon receiving a beacon nodes store the source and retransmit it
Thus nodes learn routes to coordinator
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Sensor nodesSensor nodes
Nodes transmit temperature, humidity and light level every five seconds
Nodes are based on open platform Arduino and Xbee RF modules
There is plenty of information and free development tools
RF module has its own processor but we use it as a peripheral only
Arduino platformArduino platform
Coordinador nodeCoordinador node
It's PC running Linux Coordinator software is
written in Java Xbee module is
connected using a USB adaptor that emulates a serial port
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Sleep modesSleep modes
What to do in between two data transmissions?
Being awake is ”expensive”: Almost 100 mA@5V Arduino design has other
advantages but it did not focus on lowpower (serial regulator, USB2serial)
Newer versions go to 400uA@3V or better (if power LED is removed)
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Why yet another WSN?Why yet another WSN?
In our case the answer is simple: Cost One Arduino board costs around 18 Euros Same as one Xbee 802.15.4 module
A second reason is for our students to develop their own system
We want to make our own mistakes :)
Coordinator administrationCoordinator administration
A javabased software running on a PC that allows to configure sensor locations on building maps and to view stored (or realtime data)
Realtime data
Sensor location
Configure sensor
Webbased data accessWebbased data access
Gathered data can be acessed via a web interface
Acess from anywhere
ConclusionsConclusions
Having a working system shows your mistakes quickly
Newer version needed if battery operation is required (sleep modes need to be in the uA range not mA!!)
Project done with a shoestring budget Several improvements in the pipeline
Lowpower, improved routing, data agregation
ThanksThanks
If you have any question ...