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'[EE]: Piezo buzzer question, how to connect it'
2004\06\16@052534 by Lindy Mayfield

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Hi.  I bought a couple of little piezo buzzers to use with my pics.  But I'm not sure exactly how they are supposed to work!

The buzzer (no datasheet) is a round copper colored flat disc about 1.5 cm in diameter.   One side is all metal and the other side has a 1.25 cm diameter flat whitish disc on the back, very thin, in the middle of the main metal disc.  In the middle of the white disc is soldered a 3 cm red lead.

Has anyone any experience with these?

Thanks,
Lindy

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2004\06\16@054230 by hilip Stortz

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if it only has 2 leads, you probably connect one to positive and one to
negative, obviously i'd try red positive first.  if it has 3 leads, you
need a feedback circuit to drive it (these aren't very common).  if it's
just a piezo transducer and not a buzzer, you'll just get a click unless
you send it a more interesting waveform than just turning it on.

Lindy Mayfield wrote:
>
> Hi.  I bought a couple of little piezo buzzers to use with my pics.  But I'm not sure exactly how they are supposed to work!
>
> The buzzer (no datasheet) is a round copper colored flat disc about 1.5 cm in diameter.   One side is all metal and the other side has a 1.25 cm diameter flat whitish disc on the back, very thin, in the middle of the main metal disc.  In the middle of the white disc is soldered a 3 cm red lead.
>
> Has anyone any experience with these?
>
> Thanks,
> Lindy
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2004\06\16@055515 by Lindy Mayfield

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It only has 1 lead!  (-:  
I've tried with a PWM wave.  If I plug the positive red lead to the output pin and touch a negative wire to the smooth, shiny backside, it buzzes nicely, I think.

>
> if it only has 2 leads, you probably connect one to positive and
> one to
> negative, obviously i'd try red positive first.  if it has 3
> leads, you
> need a feedback circuit to drive it (these aren't very common).
> if it's
> just a piezo transducer and not a buzzer, you'll just get a
> click unless
> you send it a more interesting waveform than just turning it on.
>
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2004\06\16@064739 by Russell McMahon

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> It only has 1 lead!  (-:
> I've tried with a PWM wave.
> If I plug the positive red lead to the output pin and touch
> a negative wire to the smooth, shiny backside, it buzzes nicely, I think.

You can get twice the voltage and about 4 times the power out of one of
these by driving them with two pins with signals on them in anti-phase. When
A is up B is down and vice versa.  This can make the difference between low
& OK output levels.

An interesting caution. When using these directly connected to a processor
pin NEVER tap them sharply. They act as voltage generators when mechanically
excited and a tap can generate enough energy to destroy a processor ;-(.
Some designs have failed when a piezo which is mounted inside a box has been
subject to a severe shock. The technology is essentially the same as used in
piezo fire lighters. I've never heard of anyone using a fire-lighter as a
speaker, but ... :-)


       RM

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2004\06\16@064947 by Jinx

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> I've tried with a PWM wave.  If I plug the positive red lead to the
> output pin and touch a negative wire to the smooth, shiny backside,
> it buzzes nicely, I think

You'll probably find it has a resonant frequency, at which it will
be very noticeable. I have some invulturated from greeting cards
and they vary from 1.6kHz to around 4kHz. These types are likely
to have a low voltage rating, maybe 4-5Vrms. Others can have
up to 20+Vrms across them (not the DC-operated ones, they go
to about 30VDC and have oscillator circuitry built in)

You can improve the volume by suspending it in mid-air as best
as possible. A piece of double-sided tape on the brass side for
example

If the one wire you have is soldered to the white ceramic side, do
try to keep that connection. They are buggers to re-attach

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2004\06\16@065608 by Jinx

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> I've tried with a PWM wave

BTW, they can be quite capacitative, a few 100nF. This will
tend to mess up square waves from the PIC pin. If you find
that you get a good enough sound at 5V-ish I'd use the piezo
as the high side load with an external transistor. Just a little
one will do, like a BC548 or ZTX450

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2004\06\16@094606 by At van Wijk

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> An interesting caution. When using these directly connected to a processor
> pin NEVER tap them sharply.
> They act as voltage generators when mechanically excited ..

Yes, they can be used as input sensor (push switch), although you must apply
a "shock" pressure, with some mechanical help ( fingertips are to soft ).
A light hit with a peace of wood or a pencil can generate more than 5 volts
with ease, but of coarse for a very short moment. If mounted under glass or
pvc it works too, make sure that the pressure is applied around or besides
the
solder blob, to prevent cracking of the coated area.
So, an input actuator with audio feedback is what this can be.
If manual actuation is wanted, then add an opamp with 1000x gain (or more).

At van Wijk.

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2004\06\16@095643 by Russell McMahon

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> > An interesting caution. When using these directly connected to a
processor
> > pin NEVER tap them sharply.
> > They act as voltage generators when mechanically excited ..

> Yes, they can be used as input sensor (push switch), although you must
apply
> a "shock" pressure, with some mechanical help ( fingertips are to soft ).
> A light hit with a peace of wood or a pencil can generate more than 5
volts
> with ease, but of coarse for a very short moment. If mounted under glass
or
> pvc it works too, make sure that the pressure is applied around or besides
> the solder blob, to prevent cracking of the coated area.

YMMV.
Voltage achieved will depend on the piezo used, rate of tap and more. Also
very much on impedance delivered into. As noted, direct into a pin can be
fatal without something to damp and limit the waveform.

If you have an oscilloscope available, try this with direct connection to
the scope probe alone (typically 1 Mohm , 10 pF). Compare this to
capacitance of a bare PIC pin.



       RM

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2004\06\16@121209 by Shawn Wilton

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Don't forget these need a lot of voltage.  I have a bunch of the 3 lead
kind and you can run it with one lead, but you get low-moderate noise at
20 volts.

Lindy Mayfield wrote:

{Quote hidden}

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2004\06\16@130501 by Lindy Mayfield

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If I understand correctly from what I've so far read, then the answer is that it only needs one lead, but I just need more juice.  I'll try plugging it into the wall socket, see if I get a 50 Hz buzz.

Thanks to all who answered on this.


> Don't forget these need a lot of voltage.  I have a bunch of the
> 3 lead
> kind and you can run it with one lead, but you get low-moderate
> noise at
> 20 volts.
>
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2004\06\16@131114 by llile

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Yow!  Don't plug it into the wall socket!  You'll get a buzz all right,
and a bang too!

-- Lawrence Lile





Lindy Mayfield <spam_OUTLindy.MayfieldTakeThisOuTspamEUR.SAS.COM>
Sent by: pic microcontroller discussion list <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
06/16/2004 12:03 PM
Please respond to pic microcontroller discussion list


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       Subject:        Re: [EE]:  Piezo buzzer question, how to connect it


If I understand correctly from what I've so far read, then the answer is
that it only needs one lead, but I just need more juice.  I'll try
plugging it into the wall socket, see if I get a 50 Hz buzz.

Thanks to all who answered on this.


> Don't forget these need a lot of voltage.  I have a bunch of the
> 3 lead
> kind and you can run it with one lead, but you get low-moderate
> noise at
> 20 volts.
>

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2004\06\16@134521 by Matt Pobursky

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I'm always surprised how few people (especially newbies) ever go right
to the source for information on these things. A google search would
turn up many manufacturers of piezo buzzers. They virtually all have
applications notes and theory of operations on their web sites. The
internet (and Google or your favorite search engine) is your friend!

I would suggest visiting Murata Erie, AVX  and Kyocera web sites. THese
are all manufacturers I've used in the past and they have quite a lot
of technical data and application information available online.

Also, many distributors like Digikey have data sheet links for the
prodcucts they sell as well as links to the manufacturers web sites.
This makes finding information even easier and faster.

(trying to politely and non-offensively say find and RTFM... ;-)

Matt Pobursky
Maximum Performance Systems

On Wed, 16 Jun 2004 11:54:14 +0200, Lindy Mayfield wrote:
{Quote hidden}

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2004\06\16@135143 by Shawn Wilton

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You know, I did a google search for piezo and I couldn't find anything.
 I did however search on piezo element instead of buzzer.

I personally found information on piezo to be a tad sparse.



Matt Pobursky wrote:

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2004\06\16@140147 by Matt Pobursky

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On Wed, 16 Jun 2004 09:12:57 -0700, Shawn Wilton wrote:
> Don't forget these need a lot of voltage.  I have a bunch of the 3 lead
> kind and you can run it with one lead, but you get low-moderate noise at
> 20 volts.

There is an old trick for getting much higher volumes out of piezo
transducers (especially at low battery voltages like 1.5V~3V) I learned
almost 20 years ago. It's also shown in many applications notes for
these devices.

Basically it works like this:

1. Find the capacitance of the piezo device, almost always listed in
the spec sheet.
2. Calculate the devices capacitive reactance at the frequency you will
be driving the device.
3. Calculate an inductor value for the equivalent inductive reactance.
4. Place an inductor of said value in parallel with the piezo device.
5. Drive the whole parallel piezo/inductor circuit with a
FET/transistor rated ~10x higher voltage than your voltage source.

What you're doing is making a resonant tuned circuit that will generate
a much higher driving voltage for the piezo buzzer at the tank
circuit's resonant frequency. This is the method used for wrist watches
and other devices that may run off, for example, Lithium button cells.

You can also determine the inductor value empirically by trial and
error, although calculating the value will get you much closer much
faster.

I once had to generate a VERY loud piezo warning beep for an electronic
pill bottle (medication reminder) that ran on a CR2032 button cell. The
circuit described above generated ~20Vac drive voltage to the piezo and
was extremely loud. We also used a tuned chamber (acoustic resonance)
to augment the output.

Matt Pobursky
Maximum Performance Systems

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2004\06\16@140807 by Matt Pobursky

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On Wed, 16 Jun 2004 09:12:57 -0700, Shawn Wilton wrote:
> Don't forget these need a lot of voltage.  I have a bunch of the 3 lead
> kind and you can run it with one lead, but you get low-moderate noise at
> 20 volts.

You can greatly augment the acoustic output of piezo devices by edge
mounting them (this keeps mechanical damping to a minimum). Most piezo
manufacturers sell PCB mounting clips that hold them by the edges and
provide electrical contact especially for this purpose.

You can also greatly increase the acoustic output by mounting the piezo
element in a tuned (resonant) enclosure. This is why many piezo buzzers
are sold in plastic cases. The case itself holds the piezo element by
it's edge in an enclosure tuned to it's resonant frequency.

I wouldn't consider myself a piezo buzzer expert, but I've used almost
every type I have seen in dozens of applications over the past 25
years. Most of this information is available from the manufacturers
directly.

Matt Pobursky
Maximum Performance Systems

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2004\06\16@141015 by Shawn Wilton

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But you have to know the manufacturer to begin with.  All the ones I
picked up were from surplus and there's no indication of manu.

Matt Pobursky wrote:

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2004\06\16@142716 by Matt Pobursky

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C'mon Shawn, have a little resourcefulness... ;-)

If you look at datasheets for a variety of physically similar devices,
you'll see that they all have specs in the same basic range for
capacitance and resonant frequency. This is basic physics, they're all
made from the same materials using the same basic process. You can
always find the resonant frequency by driving the piezo element with an
external signal generator and listen for the loudest frequency. You can
also measure it by putting a small resistor in series with the piezo
and look for the largest voltage drop across the piezo element -- this
will be it's resonant frequency.

It really doesn't take very long to characterize a given piezo element,
even if there are no markings on it at all.

Matt Pobursky
Maximum Performance Systems

On Wed, 16 Jun 2004 11:10:51 -0700, Shawn Wilton wrote:
{Quote hidden}

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2004\06\16@142717 by hilip Stortz

picon face
actually, i think it's best to support them in a couple of places around
the outer edge.  also, conductive epoxy fixes the problem of trying to
solder to things that are hard to solder.  i'll be getting some slightly
flexible conductive epoxy soon and repackaging it in roughly 1 gram kits
for about $3 ea. (i'll know for sure after it's done), should you need
some and if you can wait a while.  the epoxy is also good up to 450 deg
F and the flexibility makes it nearly stress free.  good stuff, i just
wish i didn't have to repackage it.

Jinx wrote:
{Quote hidden}

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2004\06\16@143131 by Shawn Wilton

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Ah, see I didn't know any of that.  Not to mention I've never been able
to find a datasheet for this particular type of element.  Trust that
I've done some searching, just never turned anything up and I had to
move on.  But since it's been brought up, might as well beat the horse
till it drops, right?

Matt Pobursky wrote:

{Quote hidden}

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2004\06\16@144551 by Matt Pobursky

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On Wed, 16 Jun 2004 11:31:08 -0700, Shawn Wilton wrote:
> Ah, see I didn't know any of that.  Not to mention I've never been able
> to find a datasheet for this particular type of element.  Trust that
> I've done some searching, just never turned anything up and I had to
> move on.  But since it's been brought up, might as well beat the horse
> till it drops, right?

Indeed! :-)

http://www.mps-design.com/misc-images/deadhorse2.gif

Seriously though, I did try to include most of the useful information
I've learned over the years and pass it on to others who may not have
any practical experience with piezo elements. I can be a bit surly at
times (part of getting older I guess... ;-) but I am really a generous
and helpful guy at heart. I just get irritated when people don't put
much effort into learning things for themselves (I'm not talking about
you in this case, I mean in general). I have very little time or
patience for people that fall into that category.

Matt

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2004\06\16@145832 by Lindy Mayfield

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> I'm always surprised how few people (especially newbies) ever go
> right
> to the source for information on these things. A google search
> would
> turn up many manufacturers of piezo buzzers. They virtually all
> have
> applications notes and theory of operations on their web sites.
> The
> internet (and Google or your favorite search engine) is your
> friend!


I agree with you.  And I apologize if my question lead to the belief that I didn't search before asking the group.  I've had these buzzers for a couple of months now, and I did search for how to use them, but found nothing (or found nothing I could comprehend).
My ignorance may be in recognizing a buzzer with a one-wire only lead from the web search results.  I may have found the answer but it was buried in a schematic that wasn't obvious to me.

Which is why I asked the group.  Thanks to all who answered.  (-:

Cheers, Lindy

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2004\06\16@155157 by Lindy Mayfield

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> Seriously though, I did try to include most of the useful
> information
> I've learned over the years and pass it on to others who may not
> have
> any practical experience with piezo elements. I can be a bit
> surly at
> times (part of getting older I guess... ;-) but I am really a
> generous
> and helpful guy at heart. I just get irritated when people don't
> put
> much effort into learning things for themselves (I'm not talking
> about
> you in this case, I mean in general). I have very little time or
> patience for people that fall into that category.
>
> Matt
>


I'm also very generous at helping people, and I too get frustrated when people don't make the effort that I think they should.  For example, I will do a lot to help a person learn something, but I draw the line when I think they are trying to get me to do their work for them.  (The fish or teach a person to fish deal.)

One of the favorite things I do in my job is teach beginners MVS, an IBM mainframe operating system.  This keeps me humble.  The burden is on me to know and understand the information well enough to be able to convey it to others, especially beginners, no matter their learning style.  Some people need things explained in words, some need to see it, some need to actually do things with their fingers (on the keyboard), or perhaps some combination between all three.  
I'm not having many problems with the programming of PICs.  I took to PIC assembler like a duck to water.  Logical things, on's and off's, algorithms, protocols, these things I can understand.
Ever since I've been a boy I can remember (I'm 40 now) being interested in electronics.  And it's taken from then to now for me to learn enough to do the simple things I'm doing now.  But unfortunately some things I don't understand just yet.  
Also sometimes it is hard to ask a question on a list the right way to get the right answer.  I try to be brief even if it makes me look stupid, since people's time and the answer is more important than how I look.

So I do check the books I have, google, etc. before asking in a public forum.  I do have this respect for other people's time.  
Cheers, Lindy



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2004\06\16@163635 by John N. Power

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> From:         Lindy Mayfield[SMTP:.....Lindy.MayfieldKILLspamspam.....EUR.SAS.COM]
> Sent:         Wednesday, June 16, 2004 1:03 PM
> To:   EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
> Subject:      Re: [EE]:  Piezo buzzer question, how to connect it

> If I understand correctly from what I've so far read, then the answer is
> that it only needs one lead, but I just need more juice.
> I'll try plugging it into the wall socket, see if I get a 50 Hz buzz.

> Thanks to all who answered on this.

The element you have is just the transducer, not a complete buzzer. An
AC voltage must be applied to it in order for it to make noise. In order
to apply this voltage, there must be two wires connected to the element.
The first wire is the red one soldered to the piezo material on one side
of the brass disk. The second connection is to the brass disk itself. As
mentioned in a previous post, the connection to the piezo material
is difficult to make, so a wire is supplied to make life easy for you. The
second wire, to the disk, can be attached rather easily, so it may be
omitted. If so, you must solder the wire yourself without damaging the
piezo material in the process. Also realize that the disk vibrates
when making sound, so you must make connections to it and mount it
such that it is free to move (vibrate) without being excessively
damped.

Never plug one of these into a wall socket. First, it's dangerous.
Second, the voltage is too high. Third, the frequency is most likely
too low; typically you need kilohertz signals.

John Power

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2004\06\16@180925 by Peter van Hoof

picon face
I have seen a couple of examples where the piezo was soldered at three
points to a pcb with a hole in it a little smaller than the copper part of
the piezo. (Lindy the red wire is the first , the brass plate is the second
connection to the piezo) this makes it pretty loud because it uses the pcb
as a resonance board.

Peter


{Original Message removed}

2004\06\16@194034 by Peter van Hoof

picon face
A nice article about these kind of buzzers:
http://www.thedigitalshop.net/techdocs/piezo.pdf

Manufacturer links catalog with some driver examples and data for their
piezo's though these have a second wire soldered on the brass plate:
http://www.murata.com/catalog/p37e18.pdf
http://www.east-mingtao.com/p01_20.htm


Hope this helps

Peter


{Original Message removed}

2004\06\16@204227 by Matt Pobursky

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On Wed, 16 Jun 2004 19:39:32 -0400, Peter van Hoof wrote:
> A nice article about these kind of buzzers:
> http://www.thedigitalshop.net/techdocs/piezo.pdf

Excellent peter! That's exactly the application manual I was looking
for!!! I have a copy of this somewhere in my printed literature -- and
now in my pdf archives :-)

Anyone interested in piezo alarms should read this.

Matt Pobursky
Maximum Performance Systems

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2004\06\17@045538 by Lindy Mayfield

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Thanks Peter.  That did help a lot.  From this document I have concluded that I need to solder a negative wire on the lower edge on the same side as the red wire.  (Instead of on the other side in the middle which is what I tried.  It worked ok I guess.)

One more question on this please if I may.  I found that with the little encased piezo speaker I have that if I feed it a pulse with a 33% duty cycle I get a better sound than if I use 50%.  
However I read somewhere that you should never use anything other than 50% as anything else may damage the piezo.  I find anything about that in this excellent write up below.  Has anyone else heard this about the 50%?



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2004\06\17@063112 by Peter van Hoof

picon face
I think there are two answers to your question

- if the piezo is louder when you drive it with a duty cycle other than 50 %
it probably  means that the pwm base frequency is not ideal (not the
resonance frequency) of the piezo, it would be very coincidential if this
happened to be exactly right since ther are not many choices for the base
freq. driving it with other than 50% just creates harmonics that are closer
to the resonance freq.

-the piezo will be damaged (plating corrodes of the piezo) if the dc
component of your signal is other than 0 volt. When driving the piezo
directly connected from one pin of your pic you will always have a dc
component, at 50% duty cycle for a 5 volt pic the dc component would be
(50*5 + 50*0 )/100 =2.5 volt
the two ways i know to prevent the dc component are
(1) driving the piezzo from two different pins of opposite polarity at 50 %
duty cycle this would give you a 0 volt dc component
(50*10+20*-10)/100=0 volt
(2) connecting a capacitor in series with the piezo ( this is ment with the
blocking capacitor in the article) this will remove any dc component even
without maintaining a 50% duty cycle.

Kind regards
Peter

{Original Message removed}

2004\06\17@063528 by Peter van Hoof

picon face
OOPS made a typo in one calculation
----- Original Message -----
From: "Peter van Hoof" <pvhspamspam_OUTADELPHIA.NET>
To: <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Sent: Thursday, June 17, 2004 6:31 AM
Subject: Re: [EE]: Piezo buzzer question, how to connect it


> I think there are two answers to your question
>
> - if the piezo is louder when you drive it with a duty cycle other than 50
%
> it probably  means that the pwm base frequency is not ideal (not the
> resonance frequency) of the piezo, it would be very coincidential if this
> happened to be exactly right since ther are not many choices for the base
> freq. driving it with other than 50% just creates harmonics that are
closer
{Quote hidden}

HAS TO BE (50*10+50*-10)/100=0 VOLT

> (2) connecting a capacitor in series with the piezo ( this is ment with
the
{Quote hidden}

as
> the red wire.  (Instead of on the other side in the middle which is what I
> tried.  It worked ok I guess.)
>
> One more question on this please if I may.  I found that with the little
> encased piezo speaker I have that if I feed it a pulse with a 33% duty
cycle
{Quote hidden}

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2004\06\17@070057 by Jinx

face picon face
> I found that with the little encased piezo speaker I have that
> if I feed it a pulse with a 33% duty cycle I get a better sound
> than if I use 50%

Just a guess - I mentioned that the piezos are quite capacitive.
Could it be that the 50% square wave (presumably still directly
from the PIC) is being integrated by the piezo ? That is, the
spaces between the pulses is being filled in somewhat and so
the effective M:S ratio is higher than 50%. At 33% the gaps
between are obviously wider. Sounds like a job for your new
scope eh ? - find out the quality of the wave

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2004\06\17@075124 by hilip Stortz

picon face
in which case, a couple of back to back zeners or a tvs would be an
excellent idea!  especially if it's going to be used for a while and can
be moved or dropped while in use which would shock the piezo nicely, and
possibly the micro without protection.  a couple of diodes from each
line to the power and ground lines might be wise as well, and probably
an even better idea than a tvs.  i.e. a diode to direct voltages
generated to power and ground, hence keeping them from exceeding the
supply rails too much.  the pic probably has protection diodes to do
this, but it's best to add external ones as the internal ones aren't
rated for much abuse and may eventually fail.

Russell McMahon wrote:
---------
{Quote hidden}

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2004\06\17@093519 by David VanHorn

flavicon
face
>
>However I read somewhere that you should never use anything other than 50% as anything else may damage the piezo.  I find anything about that in this excellent write up below.  Has anyone else heard this about the 50%?

Nonsense.

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2004\06\17@124322 by Lindy Mayfield

flavicon
face
Thanks.  Now I cannot find where I read that (I've read so many web pages over the last week).  Maybe I dreamed it.  (-:


> >
> >However I read somewhere that you should never use anything
> other than 50% as anything else may damage the piezo.  I find
> anything about that in this excellent write up below.  Has
> anyone else heard this about the 50%?
>
> Nonsense.

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2004\06\17@131540 by Russell McMahon

face
flavicon
face
> Thanks.  Now I cannot find where I read that (I've read so many web pages
over the last week).  Maybe I dreamed it.  (-:

You are learning so much so fast that it's hard to fugure out what goes
where :-) !
You must be having great fun! :-)

You MAY be confusing this with the square wave applied to an LCD which MUST
be 50% duty cycle. If not 50% then there is a DC components and you get an
elctrolytic cell and the LCD dies rather quickly.

The actuial requirement is "no DC" so you can actually have e4g a 40/60
square wave BUT it would need to be assymerical above and below ground so
mean DC = 0. Using a series capacitor to fed the voltage ensures this.

       RM

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2004\06\17@154711 by Jinx

face picon face
> Maybe I dreamed it.  (-:

Back in the good old days, when even Captain Sensible could
have a hit single.......

"You got to have a dream
If you don't have a dream
How you gonna have a dream come true"

Got around to PIC tunes yet ?

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2004\06\17@172139 by Peter van Hoof

picon face
quote:

DC Precautions

In order to prevent depolarization of the ceramic elements it is necessary
that every precaution be taken to prevent them from being subjected to
direct current. murata recommends the use of appropriate blocking capacitors
for this purpose.

{Original Message removed}

2004\06\17@202808 by David VanHorn

flavicon
face
At 06:22 PM 6/17/2004 +0200, Lindy Mayfield wrote:

>Thanks.  Now I cannot find where I read that (I've read so many web pages over the last week).  Maybe I dreamed it.  (-:

LCD displays need a 50% duty cycle, otherwise you'll plate off the tin, and you'll be sad.

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2004\06\17@212620 by David VanHorn

flavicon
face
At 05:21 PM 6/17/2004 -0400, Peter van Hoof wrote:

>quote:
>
>DC Precautions
>
>In order to prevent depolarization of the ceramic elements it is necessary
>that every precaution be taken to prevent them from being subjected to
>direct current. murata recommends the use of appropriate blocking capacitors
>for this purpose.

Got a URL?

I've never seen this, nor even a hint of it, till today.

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2004\06\17@214527 by Peter van Hoof

picon face
The url was in one of my previous posts
www.thedigitalshop.net/techdocs/piezo.pdf
and here is another one with the same kind of story to tell
http://www.scottwestern.com/pdf/page8.pdf
I'm not sure if this is actually true , just some info I have dug up.

Murata is an important player in piezo and ceramics.

Peter.

{Original Message removed}

2004\06\17@220847 by Spehro Pefhany

picon face
At 09:45 PM 6/17/2004 -0400, you wrote:
>The url was in one of my previous posts
>www.thedigitalshop.net/techdocs/piezo.pdf
>and here is another one with the same kind of story to tell
>http://www.scottwestern.com/pdf/page8.pdf
>I'm not sure if this is actually true , just some info I have dug up.
>
>Murata is an important player in piezo and ceramics.
>
>Peter.

I've also read of issues with DC across the ceramic- but note
that none of Murata's suggested circuits include such capacitors.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
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