Transcript Test Poster Font Arial – pt 44

Senior Project – Electrical Engineering – 2009
The Use of Piezoelectrics as a Battery-less
Power Source
Jonathan T. Gold
Senior Advisor: Professor James Hedrick
Abstract
Our landfills are full of toxic dead batteries from small handheld devices such as TV remote controls. In my presentation, I describe a
method for harnessing the energy created from human activities to power handheld devices. For example, the force of pushing the
button on a TV remote control could be used to power the remote, itself. In this project, I investigated a battery-less system, which
generates its energy using a piezoelectric element combined with a spring-loaded hammer to strike the piezoelectric material one time.
Piezoelectricity is the ability of some materials, notably crystals and certain ceramics, to generate an electric potential in response to an
applied mechanical stress. An electric voltage results from a separation of electric charges across the elements crystal lattice. This is what
allows piezoelectric materials to convert mechanical energy—you pushing on the TV remote button—and transform it into electrical
energy. Implementation of a piezoelectric system in daily human activities, with applications of low voltage devices from an initialized
applied force was investigated. The piezoelectric ‘pushbutton’ was adapted to matching circuitry, composed of voltage transformation
with a step-down transformer and energy storage with a capacitor. In my presentation, I will be describing the design and
implementation of this piezoelectric system, as well as the results I have achieved.
Block Diagram
Common Energy Sources Power Output
Design Specifications
Waveform Analysis
Piezoelectric Element
Piezoelectric Element
•Piezoelectric Pushbutton Igniter
•Transformation & Impedance Matching
15
10
Volts (V)
•Mechanical resonance near 50kHz
•Capacitance equal to 18pF
Piezoelectric Element Voltage
5
•High voltage at low currents to Low voltage at high currents
•Piezoelectric Output to Capacitor Input
0
-5
•Voltage Rectification
200
300
400
500
600
Time (us)
700
800
900
1000
0
100
200
300
400
500
600
Time (us)
700
800
900
1000
20
Volts (V)
•Voltage is collected through a capacitor
100
30
•Converts AC to DC currents
•Energy Storage
0
10
0
-10
The measurement of the piezoelectric voltage was achieved through
the use of a voltage divider circuit.
Bottom waveform is zoomed in view of the second voltage pulse (not to scale)
NOTE: Actual Pulse Voltage around 5kV
Capacitor Output
Capacitor Voltage
10
9
8
7
Results
Experimental results: From one pushbutton depression, averages
a maximum force of 15N. Measured results from my test circuit
indicated a stored energy of 0.6mJ in the capacitor at 9V.
Volts (V)
6
5
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3
2
1
0
-1
0
100
200
300
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600
Time (us)
700
800
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1000
The stored capacitor energy was recorded, the Tantalum Capacitor was a 15μF at 35V
This shows that on one pushbutton compression the capacitor stores 9V
NOTE: Capacitor is discharging 10mA to an LED