Piezoelectric Power From Crystals
By: David Hanson and Miles Brouard
Piezoelectricity:
Electricity produced by a crystal when pressure is applied to it
Hypothesis:
We can power a light bulb with this electric power
How Crystals Work
Molecules in a crystal are arranged in repeating patterns
called lattices
A pressure force on the crystal gets evenly distributed to
all the molecules in a lattice
They interact with one another in such a way that electric
charges on molecules become unevenly distributed
Early on, we contacted the
Toyocom Company in
Longview, WA
The main product of their
facility are pure artificial
quartz crystals
They agreed to let us keep
some spare quartz blocks
Testing Procedures
All tests were done on the large crystal blocks from
Toyocom and the igniter from an electric butane lighter
Instruments used for testing included:
 Simpson analog multimeter
 digital multimeter
 digital voltage probe and graphing software in CAL
 Oscilloscope
 analog ammeter (0-25uA)
On the digital multimeter, the igniter showed intense
spikes in voltage
On the analog meter we saw no deflection from voltage
and very little current (about 1uA).
The crystal blocks showed no voltage or current
The voltage probe in the cal showed the following
results for the igniter…
We hypothesize that the igniter created voltage events too short to
accurately record
Connecting the igniter to an oscilloscope, a similar reaction
occurred.
The voltage events appeared nearly exactly the same for any
measured length of time
Reverse Progress
At this point we made an important discovery…
The LED flashed when connected
to the igniter circuit –
whether current flowed one way
or the other!
We succeeded in lighting an LED
light, but simply because a spark
was jumping through it!
The spark jumps a little less than 1 cm –
at about .9 cm the spark would not jump.
A reference table from the Handbook of Chemistry and Physics
(p. E-58) reports that a spark jumping .85 cm through dry air
embodies:
1.0 * 10^4 Volts
We sought to prove this known value:
V = 10,000 Volts if a spark jumps .85 cm
By experimentally using Ohm’s Law:
V = IR
AND…
measuring current (not voltage) through a circuit activated
by the igniter
We used 3 different analog meters, with ranges of 25 uA, 100
mA, and 10A, respectively.
Assuming values for current (I) in the ranges of their meters:
 I-1 = 20mA = 2.0*10^-2 A (for the 25mA meter)
 I-2 = 50mA = 5.0*10^-2 A (for the 100 mA meter)
 I-3 = 5A (for the 10A meter)
We can then solve for the resistance (R in Ohms) required to
observe the assumed values of I in each circuit.
V = IR
V/I = R
[1.0*10^4 volts] / [I-1 = 2.0*10^-2 Amps ] = R-1 = 5.0*10^5 Ohms
 R-1 = 500,000 Ohms
[1.0*10^4 volts] / [I-2 = 5.0*10^-2 Amps ] = R-1 = 2.0*10^5
Ohms
 R-2 = 200,000 Ohms
[1.0*10^4 volts] / [I-3 = 5.0 Amps ] = R-1 = 2.0*10^3 Ohms
 R-3 = 2000 Ohms
These values for R are true:
ONLY IF
Voltage produced by the igniter = 10,000 V
(and of course, we see our assumed values for current)
UNFORTUNATELY…
FOILED AGAIN!
We observed almost no deflection on behalf of us clicking the
igniter.
This is mysterious because…
It implies that:
 The meter could be broken
 The igniter could be broken
 A spark over a 1cm gap is not necessarily caused by 10,000V
 Because I = V/R, R is larger than we thought
 Analog meters do not accurately read piezoelectric currents
We tested the meters with batteries, they worked.
We still observed the igniter to cause a spark to jump about a 1cm gap
We reasoned that there could be some hidden resistance.
The meters showed
showed the circuit to
have the expected R
Therefore, the
resistance had to be in
the material itself
Another Possibility
The meters were working but inaccurate
 No analog voltmeters showed any response to a
pressure across the large quartz block or the igniter
 The digital voltmeter showed a response from the igniter but
not the large crystal block
 The voltage probe in the CAL did not take data points for
the value of voltage fast enough
In conclusion:
Piezoelectric materials potentially create enormous
amounts of voltage…
BUT
high resistance of the piezoelectric material itself limits the
current (I), and therefore power (P)
P = IV and I = V/R
OR
The length of time this voltage is sustained is extremely short
Further Possibilities:
If the latter is the case, a force would need to act on a piezoelectric
material with a frequency
 in shoes, walking or running
 in transportation - bicycles, cars, boats, etc.
 by a compressional wave or sound wave
Its interesting to note that…
If a crystal is tuned to oscillate at a certain frequency, say 440
cycles per second (or hertz Hz),
Then sound waves vibrating the crystal at that frequency
induce alternating piezoelectric current.
amplification would also occur.
This rise in amplitude would continue until the crystal
shattered itself.
Works Cited
The Toyocom Coorperation
West, Robert C. The Handbook of Chemistry and Physics 49th ed.
p. E-58
http://blogs.sun.com/roller/resources/richb/Oscilloscope.jpg
(oscilloscope pic)
http://www.kirkwood.k12.mo.us/parent_student/khs/BartinJ/led.jpg
(LED pic)
http://search.globalspec.com/goto/PDFViewer?pdfURL=http%3A
%2F%2Fetd%2Elibrary%2Epitt%2Eedu%2FETD%2Favailable%
2Fetd%2D12092002%2D153537%2Funrestricted%2FSHKIMA%
2Epdf (Article on harnessing piezoelectric power)