Transcript Applications of the Piezoelectric Effect from Vibration

Jonathan T. Gold
ECE499, EE Capstone Design Project
Supervisor Professor James Hedrick
February 28, 2009
Piezoelectricity: Refers to the force applied to a segment of material, leading to the appearance
of an electrical charge on the surface of the segment. The source of this phenomenon
is the specific distribution of electric charges in the unit cell of a crystal structure.
Motivation:
•The idea of power a small device on the controlling gesture itself is amazing.
•A remote for the TV you never have to change battery for.
Applications
• High Voltage Power Sources
•Energy Harvesting
•Sensors
•Detection and Generation of
Sonar Waves
•Actuators
•Piezoelectric Motors
•Loudspeaker
•AFM and STM
•Inkjet Printers
Piezo Systems Inc.
Piezoelectric stacks are monolithic ceramic
structures, constructed of many thin
piezoceramic layers, electrically connected in
parallel.
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The Principal Characteristics
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Part #:TSI8-H5-202
High Energy Conversion Efficiency
Low Voltage Operation
Large Force
Low Motion
Fast Response
No Electromagnetic Interference
Piezoelectric Pushbutton Igniter
Energy Source
Solar (direct and illuminated
light)
Performance
100mW/cm2
Thermoelectric
60μW/cm2 at 5°C
gradient
0.93W at 100mmHg
Blood Pressure
Vibration Micro-Generators
Piezoelectric Push Buttons
4μW/cm3 (Human
Motion-Hz)
800μW/cm3
(Machines-kHz)
50μJ/N
Notes
Common polycrystalline cells are
16%-17% efficient, while monocrystalline cells approach 20%
Efficiency ≤ 1% for ∆Ti40°C
Generates μW when loaded
continuously and mW when loaded
intermittently
Highly dependent on excitation, power
tends to be proportional to ω and yo.
Quoted at 3V DC for the MIT Media
Lab Device.
A look at Battery, Solar, and Vibration energy sources
Operating at 10% mechanical-to-electrical efficiency, delivers 3mJ of energy per push.
Actual Results
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I obtained 2% mechanical-to-electrical efficiency, delivering 0.6mJ of energy per push.
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Room To Improve
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RF Wireless Sensor *IEEE
Piezoelectric Pushbutton
 Reconfigure spring-loaded hammer to
softer strikes
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Transformer Design
 Redesign step down transformer (90:1)
 This “LC” electrical resonance to equal the
element’s mechanical resonance for
optimum energy transfer.
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Capacitor Choice
 Ultra-Capacitor, Tantalum Cap., or Regular
Electric energy harvested was 67.61µJ,
Allowing 2.5 digital words to be transmitted
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Piezoelectric Element
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Piezoelectric Pushbutton Igniter
Mechanical resonance near 50kHz
 Capacitance of 18pF
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Transformation & Impedance Matching
High voltage at low currents to Lower voltage at high currents
 Matching resonance of element, for optimal power transfer
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Voltage Rectification
Convert active current (AC) to direct current (DC)
 Minimize power loss – used Schottky diodes
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Energy Storage
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Voltage collection through selected capacitor
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Piezoelectric Element
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Kinetic Energy Converted into Electrical
Energy
Voltage Rectification AC - DC
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 Lower voltage drop, allows less power loss
 Fast recovery time
Impedance Matching (kV – V)
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Optimal Resonance Matching
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Conserve power loss
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Ferrite Core
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Working range of low frequencies 1 to 50 kHz
Mixture of ferrite and ceramic minimal heat loss
0.3V at a forward current of 100mA
Capacitor
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Schottky Diode
Tantalum Electrolytic (2-3 Time More)
 Low equivalent parallel resistance
 Power does not dissipate as fast
 Equivalent series resistance ( 900mΩ )
Piezoelectric Element
When the hammer strikes the element, a pressure wave is generated. As a result , the pressure wave is reflected
multiple times in both the element and the hammer. This creates a resonance in the piezoelectric element
and is shown in the several AC voltage pulses in the top waveform.
Piezoelectric Element Voltage
15
Actual Pulse Voltage around 5kV (not to scale)
10
Volts (V)
1. Piezoelectric element in a voltage divider circuit.
5
0
-5
0
100
200
300
400
500
600
Time (us)
700
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900
1000
0
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Time (us)
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1000
30
Zoomed in view of second voltage pulse
20
Volts (V)
2.
10
0
-10
Transformed Voltage
Matching mechanical resonance of the Element’s resonance to optimize maximum power transfer. Used to
couple the most energy when the tank circuit matched the elements frequency to allow the element to work
as maximum efficiency.
Transformer Output
1. Waveform Output from Transformer
Volts (V)
40
20
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-20
0
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Time (us)
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Time (us)
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2.
Zoomed in view
Volts (V)
10
0
-10
-20
DC Voltage After Rectifier
Full Wave Rectified Voltage
80
With Schottky Diodes
60
Volts (V)
1. Voltage of the Full Wave Rectifier
40
20
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0
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Time (us)
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Time (us)
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2.
Zoomed in view
Volts (V)
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50
0
-50
Capacitor Voltage
Capacitor Voltage
1. Voltage waveform of capacitor
With LED circuit - drawing 10mA
Volts (V)
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2
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-2
0
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Time (us)
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Time (us)
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2.
Zoomed in view
Volts (V)
4
2
0
-2
New Capacitor Voltage
Tantalum Capacitor - 15μF at 35V
2% Efficiency With One strike – Storage
0.6mJ at 9 V
Capacitor Voltage
10
9
8
7
Volts (V)
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2
1
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-1
0
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Time (us)
700
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
Holland, R. "Representation of dielectric, elastic, and piezoelectric losses by complex
coefficients," IEEE Trans. Sonics Ultrason., SU-14, 18-20, Jan. 1967.

IEEE Standard on Piezoelectricity, IEEE 176-1978; Inst. Electrical, Electronics Engineers, New
York, 1978.
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"Piezoelectricity." Wikipedia, The Free Encyclopedia. 29 May 2008, Wikimedia Foundation, Inc.
5 Jun 2008 <http://en.wikipedia.org/w/index.php?title=Piezoelectricity&oldid=215622383>.

Joseph A. Paradiso and Mark Feldmeier, A compact, wireless, self-powered pushbutton controller,
MIT Media Laboratory, 2002.
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W.G. Cady, Piezoelectricity, New York, McGraw-Hill Book Co. Inc., pp.2-8, 1946.
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K. Y. Hoe, An Investigation of Self Powered RF Wireless Sensors, National University of
Singapore, 2006.