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The Use of Piezoelectrics as a Battery-less Power Source

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Title: Applications of the Piezoelectric Effect from Vibration and/or Pressure Author: Jonathan Gold Last modified by: Jonathan Gold Created Date – PowerPoint PPT presentation

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Title: The Use of Piezoelectrics as a Battery-less Power Source


1
The Use of Piezoelectrics as a Battery-less Power
Source
  • Jonathan T. Gold
  • ECE499, EE Capstone Design Project
  • Supervisor Professor James Hedrick
  • February 28, 2009

2
Piezoelectricity
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

3
Low Voltage Piezoelectric Stack
Piezo Systems Inc.
  • Piezoelectric stacks are monolithic ceramic
    structures, constructed of many thin piezoceramic
    layers, electrically connected in parallel.
  • The Principal Characteristics
  • High Energy Conversion Efficiency
  • Low Voltage Operation
  • Large Force
  • Low Motion
  • Fast Response
  • No Electromagnetic Interference

Part TSI8-H5-202
Piezoelectric Pushbutton Igniter
4
Common Energy Sources Power Output
Energy Source Performance Notes
Solar (direct and illuminated light) 100mW/cm2 Common polycrystalline cells are 16-17 efficient, while mono-crystalline cells approach 20
Thermoelectric 60µW/cm2 at 5C gradient Efficiency 1 for ?Ti40C
Blood Pressure 0.93W at 100mmHg Generates µW when loaded continuously and mW when loaded intermittently
Vibration Micro-Generators 4µW/cm3 (Human Motion-Hz) Highly dependent on excitation, power tends to be proportional to ? and yo.
Vibration Micro-Generators 800µW/cm3 (Machines-kHz) Highly dependent on excitation, power tends to be proportional to ? and yo.
Piezoelectric Push Buttons 50µJ/N Quoted at 3V DC for the MIT Media Lab Device.
  • A look at Battery, Solar, and Vibration energy
    sources

5
Desired Outcome
  • Operating at 10 mechanical-to-electrical
    efficiency, delivers 3mJ of energy per push.
  • Actual Results
  • I obtained 2 mechanical-to-electrical
    efficiency, delivering 0.6mJ of energy per push.

RF Wireless Sensor IEEE
  • Room To Improve
  • Piezoelectric Pushbutton
  • Reconfigure spring-loaded hammer to softer
    strikes
  • Transformer Design
  • Redesign step down transformer (901)
  • This LC electrical resonance to equal the
    elements mechanical resonance for optimum energy
    transfer.
  • Capacitor Choice
  • Ultra-Capacitor, Tantalum Cap., or Regular

Electric energy harvested was 67.61µJ, Allowing
2.5 digital words to be transmitted
6
Design Implementation
  • Piezoelectric Element
  • Piezoelectric Pushbutton Igniter
  • Mechanical resonance near 50kHz
  • Capacitance of 18pF
  • Transformation Impedance Matching
  • High voltage at low currents to Lower voltage at
    high currents
  • Matching resonance of element, for optimal power
    transfer
  • Voltage Rectification
  • Convert active current (AC) to direct current
    (DC)
  • Minimize power loss used Schottky diodes
  • Energy Storage
  • Voltage collection through selected capacitor

7
System Block Diagram
  • Piezoelectric Element
  • Kinetic Energy Converted into Electrical Energy
  • Impedance Matching (kV V)
  • Optimal Resonance Matching
  • Conserve power loss
  • Ferrite Core
  • Working range of low frequencies 1 to 50 kHz
  • Mixture of ferrite and ceramic minimal heat loss
  • Voltage Rectification AC - DC
  • Schottky Diode
  • Lower voltage drop, allows less power loss
  • Fast recovery time
  • 0.3V at a forward current of 100mA
  • Capacitor
  • Tantalum Electrolytic (2-3 Time More)
  • Low equivalent parallel resistance
  • Power does not dissipate as fast
  • Equivalent series resistance ( 900m? )

8
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.
  • 1. Piezoelectric element in a voltage divider
    circuit.
  • Actual Pulse Voltage around 5kV (not to scale)
  • 2. Zoomed in view of second voltage pulse

9
Transformed Voltage
  • Matching mechanical resonance of the Elements
    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.
  • 1. Waveform Output from Transformer
  • 2. Zoomed in view

10
DC Voltage After Rectifier
  • 1. Voltage of the Full Wave Rectifier
  • With Schottky Diodes
  • 2. Zoomed in view

11
Capacitor Voltage
  • 1. Voltage waveform of capacitor
  • With LED circuit - drawing 10mA
  • 2. Zoomed in view

12
New Capacitor Voltage
  • Tantalum Capacitor - 15µF at 35V
  • 2 Efficiency -
  • With One strike Storage 0.6mJ at 9 V

13
References
  • 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.
  • "Piezoelectricity." Wikipedia, The Free
    Encyclopedia. 29 May 2008, Wikimedia Foundation,
    Inc. 5 Jun 2008 lthttp//en.wikipedia.org/w/index.p
    hp?titlePiezoelectricityoldid215622383gt.
  • Joseph A. Paradiso and Mark Feldmeier, A compact,
    wireless, self-powered pushbutton controller, MIT
    Media Laboratory, 2002.
  • W.G. Cady, Piezoelectricity, New York,
    McGraw-Hill Book Co. Inc., pp.2-8, 1946.
  • K. Y. Hoe, An Investigation of Self Powered RF
    Wireless Sensors, National University of
    Singapore, 2006.

14
Questions?
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