WIRELESS SENSOR NETWORKS

klapdorothypondMobile - Wireless

Nov 24, 2013 (3 years and 8 months ago)

54 views

Rich
Testani

Spring 2013

WIRELESS SENSOR NETWORKS

OVERVIEW


Introduction to Sensor Networks


Demo


Questions


SENSOR NETWORKS


Spatially Distributed Sensors


Frequently mesh network


Used to monitor physical environment


Temp, proximity,
etc


Fully wireless


Powered by batteries or by harvesting power from environment


COMMUNICATION


Generally mesh network


Several standards


802.11


WiFi


802.5.4


low bandwidth short short range wireless communication


Proprietary communications methods also exist




USES


Monitor hostile and remote environments


Deep ocean, volcanoes


Monitor patient health


Military


Maintain view of battleground


Help clear minefields


CHALLENGES


Individual nodes are cheap and unreliable


Redundancy comes from using large number of nodes


Need to operate on severe constraints


Memory, processing, storage, power


Node can be mobile


Need for self healing networks

DEMO


Built a single node from open source
A
rduino

parts and sensors


Monitors simple biometrics


External temp


Body temp


Heart rate


Ambient light


Weight distribution

COMPONENTS


Arduino

Mega


Needed extra analog pins over
Arduino

Uno


Arduino

WiFi

shield


2 x 100lbs force sensors


2 x Flex sensors


2 x TMP36 temperature sensors


Light sensor


Pulse heart rate monitor


Ultrasonic rangefinder



RECORDS


Ambient Light


BPM


Pressure on heel of left and right feet


Flex of left and right hands


External and body temp


Distance to nearest object in front (max ~150cm)


Wifi

signal strength

FRONTEND


PHP page that pulls data out of database and graphs it using
Javascript


Updates every 5s


In theory, could be live updating, but beyond my knowledge of
Javascript


Able to select which data set to graph

BACKEND


Apache webserver and MySQL database


Arduino

calls
data.php

and POSTS its MAC and data that has been collected


PHP script inserts data into database


Each node identified by mac address


DESIGN DIAGRAM


Arduino

uses a language very similar
to C/C++


Actually runs 2 blocks of code


1
st

is the main block that collects data
from all sensor data then calls PHP
script to submit data


2
nd

is an interrupt that gathers and
converts heart rate data.


CODE

LIMITATIONS


Only have one node, can’t demonstrate mesh network


Best for mesh network


Pinocchio


Recently announced, not released yet


Range (
WiFi

shield does not have external antenna, other shields do)


Security


SSL to webpage not setup due to processing power constraints


RADIUS
Auth

not supported by
wifi

shield, must use WPA2


In order to change
config
, unit needs to be connected to computer via
usb

and
reprogrammed


LIMITATIONS, PART 2


Data submission not reliable other than TCP


Does not buffer data, could be implemented using mini SD card


Slow


Possible causes:
POSTing

too much data and fragmenting packets


Made worse by interrupt

THINGS I LEARNED


Soldering iron are hot.


Http headers need to be fairly exact


How to integrate signals from different sensors and process them


Arduino

part documentation sometimes is awful.


Building something yourself is sometimes not the way to go

RECOMMENDATIO
N


Don’t do it this way unless you need a very specific sensor that no one makes


More trouble than it’s worth and still some
what expensive


Go
with a company that you can yell at when things don’t work.

WHERE CAN I GET A COPY?


Code and other files available at:
http://tehorange.com/projects/
seniorproject.html


SOURCES


Parts


Amazon.com


Sparkfun.com


Information and Code


http
://en.wikipedia.org/wiki/
Wireless_sensor_network


http://arduino.cc/en/Reference/
HomePage


http://net.tutsplus.com/tutorials/php/pdo
-
vs
-
mysqli
-
which
-
should
-
you
-
use
/


http://pulsesensor.myshopify.com/pages/pulse
-
sensor
-
amped
-
arduino
-
v1dot1


http://arduino.cc/forum/index.php?topic=
155218.0