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Lighting Piezoelectric Crystals
Name: Steve
Status: educator
Grade: 9-12
Location: CA
Country: N/A
Date: 1/25/2006
Question:
Is it possible to create a Piezo crystal / led
substance that lights upon applied pressure? Could the Piezo
crystals and leds be formed together in a very small fashion so as
to be incorporated into plastics or paint for example?>
Replies:
Piezoelectric crystals produce a change in voltage in response to a
change in strain (usually produced by putting some load on them).
However, the crystals produce an electrical output only when they
experience a *change* in load. So as soon as you stop changing the
load (by pressing harder or more lightly), the electrical output would
stop. So some other electronics would be required to collect the
charge and sustain it for a useful amount of time (like a capacitor,
for instance). The voltage produced by the piezo crystal also varies
depending on how hard it is pressed, so something is necessary to
regulate the power produced.
In addition, the current through an LED needs to be controlled to avoid
damage and to control the brightness. Most LED's achieve their rated
cycle lives with about 20 mA of current. More current reduces their
lives (but increases brightness). So again, some additional circuitry
would probably be required to control the current so the LED would act
the way you want and last as long as you want.
So producing a single substance that would do what you describe in a
consistent manner is unlikely. However, with the current state of
miniaturization that is available, it is most likely possible to
produce an electronic module with integrated piezo transducer, LED and
current-conditioning circuitry all contained in one unit.
Hope this helps!
David Brandt, P.E.
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Update: June 2012
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