Transcript Industrial and Social Applications of Wireless Sensor Nets

Industrial and Social
Applications of Wireless Sensor
Nets with “Energy Scavenging”
With a case study on “batteryless” tiny-temperature nodes for
“smart building applications”
Paul Wright, Jan Rabaey, David Culler, Eli Leland, Elaine
Lai, Sue Mellers, Michael Montero, Jessy Baker, Brian
Otis, Rob Scewczyk, and Shad Roundy (now at The
Australian National University)
Energy Scavenging
GOAL: Design an ‘infinite life’ power source for a sensor
node
APPLICATION: Wireless Sensor Networks in Buildings
VISION: Millions of self-powered sensor/transceivers,
each the size of a speck of dust, will infiltrate a building
and create a smart environment
PROOF OF CONCEPT: To power a Mica2Dot Mote using
vibrations from a wooden stairway in the Naval
Architecture Building
Battery, Solar, and
Vibrational Energy
Common Sources of
Vibrations
Frequency
of Peak
(Hz)
Peak
Acceleration
(m/s2)
Kitchen Blender Casing
121
6.4
Clothes Dryer
121
3.5
Door Frame (just after door closes)
125
3
Small Microwave Oven
121
2.25
HVAC Vents in Office Building
60
0.2-1.5
Wooden Deck with People Walking
385
1.3
Bread Maker
121
1.03
External Windows (size 2ftx3ft) next to a
Busy Street
100
0.7
Notebook Computer while CD is Being
Read
75
0.6
Washing Machine
109
0.5
Second Story of Wood Frame Office
Building
100
0.2
Refrigerator
240
0.1
Vibration Source
The Piezoelectric
Effect
• Constitutive Equations
Usable Modes of PZT
   Y  dE
33 Mode
3
2
1
D  E  d
 = strain
 = stress
Y = Young’s modulus
d = piezoelectric coeff.
D = electrical displacement
 = dielectric constant
E = electric field
+
V
-
31 Mode
3
2
1
+
V
-
F
Tungsten proof mass, glued base, PZT bender
Pirelli Piezoelectric Device
Staircase Piezoelectric device
Piezoelectric Bimorph
Generators
Piezoelectric generator
C
Vs
Rs
m e A
P
2
4 T
2
Wooden Stairs
Peak Frequency at 26.8 Hz
FFT of frequencies
Power generator
must match peak
frequency of
vibration source for
max power output
Vibrations from walking down stairs
Bender Design
Characteristics
• Piezoelectric: PZT
• Tungsten Alloy Mass: 52 g
• Beam Dimensions:
1.25” x 0.5” x 0.02”
Behavior
40V peak–to-peak
output from bender
when someone walks
down the stairs
• Resonant Frequency: 26.8 Hz
• Power Output: 450 μW
Tiny Temp
Storage
Capacitor
Power
Circuit
Mote
Piezoelectric
Power Generator
Thermistor
Power Circuit
Voltage Out
to Mote
Voltage In
from Bender
Rectifier
Voltage
Regulator
~ VIN
Piezo
Bender
CST
6600μF
Enable
Regulator
Rectifier
Comparator
(3.5V – 5V)
Comparator
Storage
Capacitor
Vout = 3.3V DC
Load Requirements
• Mica2Dot Mote
• 3.3 Input Voltage
• 800 ms ‘Startup Time’
• 45 mW to take temperature
reading and transmit information
FDM Packaging
Upper Case
Temperature
Sensor Hole
Capacitor
Holders
PCB Holder
Bridge
Bender Platform
Lower Case
Case Tabs
Proof of Concept #1 (CEC)
Procedure
• 3 people ran on the
stairs for 40 minutes
Capacitor Discharging
5V
3.5 V
Results
816 ms
Power Out
• 3.28 V for 816 ms
• 2 temperature
readings transmitted
Proof of Concept #2 (Fire)
Proof of Concept #2 (Fire)
Next Steps: Short Term
Charge Up Time
Mica2dot
mote
PicoRadio-based
node
Efficiency
Next Steps: Long Term
Design a variable resonant frequency MEMS bender
which adapts to vibration sources with different peak
frequencies.
Inertial
Mass
Cantilever
Beam
Substrate
TMSM
PDMS
SiO2
Si
PZT Platinum
Si3N4
Aluminum
SiO2
Si
Flip and Bond Assembly
Many Thanks!
• Thanks to CITRIS, NSF & the California
Energy Commission for their sponsorship