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Surpizing results from Piezoelectric coin speaker.

  • Thread starter The Flavored Coffee Guy
  • Start date
T

The Flavored Coffee Guy

Jan 1, 1970
0
Have you ever made a wine glass or crystal sing by wetting your finger?
Would you believe that when you hit the resonant frequency of a tuning
fork, wine glass, or even a plain old drinking glass that is made of
glass, a very small signal, not even audiable, at the resonant
frequency of the glass can be very loud. But, there is a trick too it.
Either the very center of the piezoelectric coin speaker has to be in
contact with the rim of the glass, or the very outer most edge. When
you pull the speaker away, it is quite. But, when that thing has
contact, it is ear piercing.

It almost makes me think that if piezoelectric elements were used, and
formed into bells, that you could use the mechanical resonant frequency
of the object, using mathcad, or some other form of simulation software
find the standing wave in the shaped piezoelectric ceramic, and use
it's resonant frequency to generate more power than you were using.
 
E

Eeyore

Jan 1, 1970
0
The said:
to generate more power than you were using.

Bwahahahahahahaha.

Where's your perpetual motion machine ?

Graham
 
G

Genome

Jan 1, 1970
0
Eeyore said:
Bwahahahahahahaha.

Where's your perpetual motion machine ?

Graham

Errrrr...... you have just responded to The Flavored Coffee Guy.

DNA
 
B

Bob Eld

Jan 1, 1970
0
The Flavored Coffee Guy said:
Have you ever made a wine glass or crystal sing by wetting your finger?
Would you believe that when you hit the resonant frequency of a tuning
fork, wine glass, or even a plain old drinking glass that is made of
glass, a very small signal, not even audiable, at the resonant
frequency of the glass can be very loud. But, there is a trick too it.
Either the very center of the piezoelectric coin speaker has to be in
contact with the rim of the glass, or the very outer most edge. When
you pull the speaker away, it is quite. But, when that thing has
contact, it is ear piercing.

It almost makes me think that if piezoelectric elements were used, and
formed into bells, that you could use the mechanical resonant frequency
of the object, using mathcad, or some other form of simulation software
find the standing wave in the shaped piezoelectric ceramic, and use
it's resonant frequency to generate more power than you were using.

Of course it does NOT generate more power than you are using. What it does
is concentrate the available energy into a single frequency and emit the
energy with much greater effiiciency because of the large area of the glass
vs. the piezo element alone.
 
M

martin griffith

Jan 1, 1970
0
Errrrr...... you have just responded to The Flavored Coffee Guy.

DNA
hope TFCG doesn't mate with that Flying Skybuck dude, could end up
with an extra Startrek episode


martin
 
J

J.A. Legris

Jan 1, 1970
0
The said:
Have you ever made a wine glass or crystal sing by wetting your finger?
Would you believe that when you hit the resonant frequency of a tuning
fork, wine glass, or even a plain old drinking glass that is made of
glass, a very small signal, not even audiable, at the resonant
frequency of the glass can be very loud. But, there is a trick too it.
Either the very center of the piezoelectric coin speaker has to be in
contact with the rim of the glass, or the very outer most edge. When
you pull the speaker away, it is quite. But, when that thing has
contact, it is ear piercing.

It almost makes me think that if piezoelectric elements were used, and
formed into bells, that you could use the mechanical resonant frequency
of the object, using mathcad, or some other form of simulation software
find the standing wave in the shaped piezoelectric ceramic, and use
it's resonant frequency to generate more power than you were using.

Of course you'll never get more energy than you put in (unless you set
the thing on fire), but the same principle is used in those piezo
beepers that are so loud - the cavity in the plastic housing resonates
with the active element.
 
T

The Flavored Coffee Guy

Jan 1, 1970
0
When you are dealing with a mechanical resonant vibration, it's like
applying 5lbs of force to a swing with some-one on it. Each time they
return, the altitude is a little higher, and the energy of interia is
summed up. The action of the pendulum, only looses energy as a product
of wind resistance. A bell, however, is quite different. It's the
combination of the elasticity of the metal, and the elasticity of air.
That's why when you fill a glass with a uncompressable fluid like
water, the crystal will ring at a higher frequency. If you filled with
lanoline, the resonant frequency would drop because the speed of sound
is so much slower in lanoline. It is concievable to move that all down
an octive.

Now, if your material were piezoelectric, which of most is not really
solid, nor hard, but if you had something that wasn't full of holes
like a sponge, you could make a bell, and your first AC connection
would be 90 degrees from the the piezoelectric transducer. The second
would be + 45 degrees. A standing wave in a circular bell, produces a
oval that is oscillating at 90 degrees from zero. But, with a
piezoelectric material, you need a compression zone, and a
decompression zone to produce power.

I have just done this experiment today, and it was too easy. I took
the coin speaker from an old alarm clock, and used my signal generator,
which has a peak to peak output of 2 volts, and the impedance of the
output is 50 ohms. I couldn't turn up the power high enough to but
barely hear that thing at it's own resonant frequency. But, finding
the resonant frequency of a glass that was half full, made a very loud
ear piercing resonant sound. You can talk, but you can't **** with the
real world results.

I don't have the materials to research a machined bell made of
peizoelectric ceramic, nor do I have access to that material. I have
little tiny bits of the substance that is lodged in my cigarette
lighter about the size of a flint. That tiny little object is probably
resonant to frequency in the megahertz, if not nearly gigahertz. It is
too small to evaluate such a set of conditions. The bell would have to
be made of that piezoelectric material. Some materials make crappy
tuning forks, and crappy bells. That could be true, but there are a
range materials that fall into same catagory, that are not used in
making these lighters. Without access, I can't say, and didn't say it
was producing more power than it was using, I only held it in question,
because the sound energy out is very obviously more than the sound
energy in.
 
T

The Flavored Coffee Guy

Jan 1, 1970
0
If you looked at the base of a brass tuning fork. If there were a seat
for a piece of piezoelectric material from a lighter right at the base,
and you could electrically isolate it ridgedly with glass on one end,
to place a piece of wire, and have set screw making the whole tuning
fork ground, then a measurement could be made in respect to the energy
in vs energy out. But, you would have to have some pressure applied to
the crystal constantly, and that pressure would have to vary with the
mechanical oscillation of the tuning fork. The majority of the mass
would be working for you, and right at the fulcrum of the event, your
piece of piezoelectric material would be working. Your set screw and
mounts would be right at the base of the fork where the metal started
off into two directions.
 
T

The Flavored Coffee Guy

Jan 1, 1970
0
Then you could use a step down transformer, determin phase, and finally
see if the audio transformer didn't make the tuning fork continue to
ring.
 
E

Eeyore

Jan 1, 1970
0
The said:
Then you could use a step down transformer, determin phase, and finally
see if the audio transformer didn't make the tuning fork continue to
ring.

You're an idiot.
 
J

John Fields

Jan 1, 1970
0
I only held it in question,
because the sound energy out is very obviously more than the sound
energy in.

---
Yes, but the _power_ of the acoustic output will be less than the
electrical power input to the system.

An experiment you can do which will be equivalent to what you're
experiencing would be to connect an inductor and a capacitor in
series and drive them at their resonant frequency from a voltage
source. If you do, you'll find that the voltage at the junction of
the L and the C is many times higher than the voltage driving the
circuit.

However, if you measure the power going into the circuit from the
generator and the power going into a load from the LC junction,
you'll find that the power going into the load will be less than the
power going into the circuit from the generator.
 
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