Noob piezo resonator question:

[The First Blarg on the ne]

Sorry to be such a novice, but can someone tell me if a piezo electric
crystal resonator will make an audible sound
if I hook it up to a small battery?
I'm looking for any miniature lightweight electronic sound generating object
for a miniature toy I'm developing.

I have small transducers that work well, but I'd like to go smaller and
someone said piezo crystals are what they use
to make watches beep, etc.

Thanks in advance.

P.S.

I've seen some the specs for which mention 1.8 mhz to 50 mhz as the
frequency range, but I'm guessing
all of the above will be inaudible(?)

 

[Nemo]

Sorry to be such a novice, but can someone tell me if a piezo electric
crystal resonator will make an audible sound
if I hook it up to a small battery?
I'm looking for any miniature lightweight electronic sound generating object
for a miniature toy I'm developing.

I have small transducers that work well, but I'd like to go smaller and
someone said piezo crystals are what they use
to make watches beep, etc.

Thanks in advance.

P.S.

I've seen some the specs for which mention 1.8 mhz to 50 mhz as the
frequency range, but I'm guessing
all of the above will be inaudible(?)

You are on the right track but you have a number of half truths which
are misleading you. Here's the rest of the story.

Piezo devices come in all kinds of frequencies from audio (sub 20kHz)
through ultrasonic (60kHz is the kind of freq they used to be for things
like position sensors) to MHz these days (not sure what they use those
for, probably all kinds of things). Anyhow, you want the audio frequency
ones. You can find these in various catalogues like Digikey under
headings like "piezo sounders".

There ARE a few with a circuit built in which just need a battery
attached but most need an oscillator attached. For the loudest output,
one which resonates at the resonant freq of the piezo element as it
flexes. Piezo devices usually have a fairly sharp resonance so are good
for high pitched beeps but not for speech reproduction (speech is
generally below, um, 4kHz I think and piezos only really start making
appreciable volume at 2 - 4kHz). Although for very small air volumes
like inside your ears, piezos can produce a better range of sounds -
don't ask me why - which is why iPod earpieces use them.

The two main sounder technologies (for small items anyhow) are piezo and
electromagnetic (coil). Coil sounds better for audio but is only about
2-5% efficient so for battery operated things piezo is often used - a
massive 10% efficiency, = longer battery life. Piezo usually needs 2-4
times as many volts to give te same volume as coil, but because it needs
less current it's less power overall. For a battery operated toy, piezo
is probably cheaper and will definitely give you more battery life.

What you need is an example circuit here, but I've run out of time.
Um... try googling "piezo circuit", this gives you various example
pages.

Oh one other thing. Piezo elements are sometimes sound as bare disks.
Don't buy them unless you know what you're doing as you then need to
build a cavity round them and somehow attach wires. For your first piezo
circuit, at least, go for one with a plastic moulded case and 2 actual
pins or leads. Some have 3 pins, which use a different circuit to drive
them.

 

[The First Blarg on the ne]

Thanx for the response! You are the only one who answered me. All I need
is the smallest, lightest
thing that I can hear. A beep or even continuous tone. The beep tone from a
wristwatch would suffice.
I know virtually nothing about circuits, but I will take your advice and
google piezo circuits.

Anyway, many thanks!

K.



"Nemo" <Paul@nospam.nospam.nospam.nospam.co.uk> wrote in message
news:Uzu7sfBzcABHFwuT@furfur.demon.co.uk...

Sorry to be such a novice, but can someone tell me if a piezo electric
crystal resonator will make an audible sound
if I hook it up to a small battery?
I'm looking for any miniature lightweight electronic sound generating
object
for a miniature toy I'm developing.

I have small transducers that work well, but I'd like to go smaller and
someone said piezo crystals are what they use
to make watches beep, etc.

Thanks in advance.

P.S.

I've seen some the specs for which mention 1.8 mhz to 50 mhz as the
frequency range, but I'm guessing
all of the above will be inaudible(?)

You are on the right track but you have a number of half truths which are
misleading you. Here's the rest of the story.

Piezo devices come in all kinds of frequencies from audio (sub 20kHz)
through ultrasonic (60kHz is the kind of freq they used to be for things
like position sensors) to MHz these days (not sure what they use those
for, probably all kinds of things). Anyhow, you want the audio frequency
ones. You can find these in various catalogues like Digikey under headings
like "piezo sounders".

There ARE a few with a circuit built in which just need a battery attached
but most need an oscillator attached. For the loudest output, one which
resonates at the resonant freq of the piezo element as it flexes. Piezo
devices usually have a fairly sharp resonance so are good for high pitched
beeps but not for speech reproduction (speech is generally below, um, 4kHz
I think and piezos only really start making appreciable volume at 2 -
4kHz). Although for very small air volumes like inside your ears, piezos
can produce a better range of sounds - don't ask me why - which is why
iPod earpieces use them.

The two main sounder technologies (for small items anyhow) are piezo and
electromagnetic (coil). Coil sounds better for audio but is only about
2-5% efficient so for battery operated things piezo is often used - a
massive 10% efficiency, = longer battery life. Piezo usually needs 2-4
times as many volts to give te same volume as coil, but because it needs
less current it's less power overall. For a battery operated toy, piezo is
probably cheaper and will definitely give you more battery life.

What you need is an example circuit here, but I've run out of time. Um...
try googling "piezo circuit", this gives you various example pages.

Oh one other thing. Piezo elements are sometimes sound as bare disks.
Don't buy them unless you know what you're doing as you then need to build
a cavity round them and somehow attach wires. For your first piezo
circuit, at least, go for one with a plastic moulded case and 2 actual
pins or leads. Some have 3 pins, which use a different circuit to drive
them.

 

[Gary Tait]

"The First Blarg on the net" <blarg@threadender.net> wrote in
news:3s_Mi.290$lE2.164@newssvr22.news.prodigy.net:

Thanx for the response! You are the only one who answered me. All I
need is the smallest, lightest
thing that I can hear. A beep or even continuous tone. The beep tone
from a wristwatch would suffice.
I know virtually nothing about circuits, but I will take your advice
and google piezo circuits.

Anyway, many thanks!

K.

Another option might might be the sort if ring sounder they use in cell
phones.