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making a piezo louder

M

Mike_in_SD

Jan 1, 1970
0
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

Here is a pic of the board to show you why I had a problem
finding it.

www.mikeamick.com/all.jpg

the round thing that LOOKS like the piezo is made of ferrite and is
a compass module ( I belive ) .. the white chip below it .. is
the piezo.


ANYWAYS ....................................

I soldered a couple leads to where the piezo used to be .. and have
been buying every small piezo I can find and hooking it up to the leads
to find one that is louder ..

Of course I only use one's that are close to the voltage and current
parameters of the first one.

Its amazing the varience .. some a little louder and some you can
bareley hear.

question .. can I hook up two of them in parellel(sp?) will it hurt
anything ?

or is there something else I can hook up .. that is triggered by the
old piezo signal ... ??



thanks
mike
 
E

Eeyore

Jan 1, 1970
0
Mike_in_SD said:
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

Here is a pic of the board to show you why I had a problem
finding it.

www.mikeamick.com/all.jpg

the round thing that LOOKS like the piezo is made of ferrite and is
a compass module ( I belive ) .. the white chip below it .. is
the piezo.

ANYWAYS ....................................

I soldered a couple leads to where the piezo used to be .. and have
been buying every small piezo I can find and hooking it up to the leads
to find one that is louder ..

Of course I only use one's that are close to the voltage and current
parameters of the first one.

Its amazing the varience .. some a little louder and some you can
bareley hear.

question .. can I hook up two of them in parellel(sp?) will it hurt
anything ?

They'll draw more current of course. The unit may not like that.

I'd simply go for the most effcient sounder you can get.

Graham
 
C

Chris

Jan 1, 1970
0
Mike_in_SD said:
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

Here is a pic of the board to show you why I had a problem
finding it.

www.mikeamick.com/all.jpg

the round thing that LOOKS like the piezo is made of ferrite and is
a compass module ( I belive ) .. the white chip below it .. is
the piezo.


ANYWAYS ....................................

I soldered a couple leads to where the piezo used to be .. and have
been buying every small piezo I can find and hooking it up to the leads
to find one that is louder ..

Of course I only use one's that are close to the voltage and current
parameters of the first one.

Its amazing the varience .. some a little louder and some you can
bareley hear.

question .. can I hook up two of them in parellel(sp?) will it hurt
anything ?

or is there something else I can hook up .. that is triggered by the
old piezo signal ... ??



thanks
mike

Hi, Mike. If you HAVE to get a bigger sound from that dinky piezo
beeper, it's probably going to be a little more complicated than just
buying another beeper. But the good news is you can probably cobble up
what you need from the Radio Shack in the Pierre mall.

First, a little background. Bare piezo beepers are driven by AC -- the
alternating voltage causes the piezo element to flex like a speaker.
If you flex the piezo element at its mechanically resonant frequency, a
lot of the electrical energy will be converted into sound.

Since 4KHz sine waves are kind of hard to generate, you can do
something like this with two microcontroller output pins (view in
fixerd font or M$ Notepad):

|
| Piezo
| Beeper
| |.-.|
| || ||
| |\ || || /|
| A o--| >O--|| ||--O< |--.
| |/ || || \| |
| || || |
| |'-'| |
| |
| A'o---------------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

If A' is the inverse of A, you will have one side at 5V (if that's the
operating voltage of the uC -- could be 3V or 3.3V) and the other side
of the piezo element at 0V. When A and A' switch, the second side has
5V and the 1st side has 0V. That's the same as applying a 10Vp.p.
square wave from a function generator to the piezo element, and
actually produces louder sound than a square wave, because the fast
transitions cause the piezo element to move faster.

Now you could just replace the piezo element with a bigger one, but
you're probably not going to get better results. That's because the
piezo element is seen by the two digital outputs as a capacitive load
(probably several thousand pF). The primary limitation will be how
hard the uC outputs can drive that capacitive load. Not only that, but
different piezo elements have different mechanical resonances. If it's
the wrong frequency, you'll waste a lot of the energy from the two
logic gates, which means it won't even be as loud as the original.

Now there is another way to do this. If you can pick off the logic
signal, you can use it with an external power supply and a transistor
to switch, to drive a separate self-driven piezo beeper. Here's the
circuit:
|
| A o-------o---------o---o-----------o------------.
| | |10K| | |
| 1000pF | .-. | | |
| --- | | | | |
| --- | | | | |
| | '-' |e .-----o-----. |
| | ___ | |< | + | |
| B o--|<---o--|___|--o-|2N3906 | Beeper | |
| 10K b|\ | with | +| 9V
| 1N4001 |c | Control | ---
| o-----oC Pin | -
| | | RadioShack| |
| .-. | 273-68 | |
| 10K| | | - | |
| | | '-----o-----' |
| '-' | |
| | | |
| '-----------o------------'
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Every time the piezo turns on, A' will be several volts lower than A
3000 times a second or so. That will result in current being pulled
out of the base of the PNP transistor, which will turn it on. A
positive voltage will appear at the control pin of the 80dB piezo pulse
buzzer, which will result in an annoyingly loud intermittent beep.
Trust me, this will work fine with a 9V battery, only uses 10mA when
it's on and essentially nothing when it's off, and will be pretty loud.

So go to the Shack, get a 9V battery with snap on connector with flying
leads, a small perfboard, some 10K resistors, a 2N3906 or other PNP
small signal transistor, and the specified beeper, and you're good to
go.

Cheers
Chris
 
M

Mike_in_SD

Jan 1, 1970
0
Now there is another way to do this. If you can pick off the logic
signal, you can use it with an external power supply and a transistor
to switch, to drive a separate self-driven piezo beeper. Here's the
circuit:
|
| A o-------o---------o---o-----------o------------.
| | |10K| | |
| 1000pF | .-. | | |
| --- | | | | |
| --- | | | | |
| | '-' |e .-----o-----. |
| | ___ | |< | + | |
| B o--|<---o--|___|--o-|2N3906 | Beeper | |
| 10K b|\ | with | +| 9V
| 1N4001 |c | Control | ---
| o-----oC Pin | -
| | | RadioShack| |
| .-. | 273-68 | |
| 10K| | | - | |
| | | '-----o-----' |
| '-' | |
| | | |
| '-----------o------------'
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

Cheers
Chris


wow Chris .. thats a lot of info .. and really appreciated.

I really doubt that I will be able to find the logic pulse ...
without a schematic .

I would think that I could use the 4khz signal as an input for a
standard transistor amplifier ... pushing more power to another buzzer

another gentleman suggested a small transformer .. this actually
sounds feasible ..

thanks
mike
 
E

Eeyore

Jan 1, 1970
0
Mike_in_SD said:
wow Chris .. thats a lot of info .. and really appreciated.

I really doubt that I will be able to find the logic pulse ...
without a schematic .

I would think that I could use the 4khz signal as an input for a
standard transistor amplifier ... pushing more power to another buzzer

another gentleman suggested a small transformer .. this actually
sounds feasible ..

Beware of trying to drag too much power out of the existing connection.
You could damage it.

Graham
 
C

Chris

Jan 1, 1970
0
Mike_in_SD said:
wow Chris .. thats a lot of info .. and really appreciated.

I really doubt that I will be able to find the logic pulse ...
without a schematic .

I would think that I could use the 4khz signal as an input for a
standard transistor amplifier ... pushing more power to another buzzer

another gentleman suggested a small transformer .. this actually
sounds feasible ..

thanks
mike

Hi, Mike. In small piezo buzzers of this type, you're actually driving
the piezo buzzer with two inverting logic signals, as shown above. If
you get a 9V battery (floating), you can make one of the signals your
common for the driver above, and use the other one to drive the
transistor. Not too hard, especially if you get a beeper with a
separate logic control signal. Although, you could probably turn on
and off a lower current self-driving buzzer (10 to 30mA) with the
transistor.

The primary limitation in your board (and the reason the beeper is
probably so small and weak) is the limitations of the output pins
driving capacitive loads. When the logic switches, the two outputs are
basically discharging and charging in the reverse direction a
capacitor. Even if the output pins of the uC are rated similarly to
standard 74HC-type outputs, loading them down too heavily will stress
them, and result in damaging the outputs. Don't want to go there.
I've been there myself, using two 74HC14 inverter outputs to drive a
piezo in an home-brew add-on annunciator for a several dozen pieces of
factory test equipment. The HC outputs would work for a while (weeks
to months), and then give up their precious smoke. Had to replace 'em
all. Didn't look too good there. Durrr.

Also, having a transformer to pump the output up to a higher voltage
doesn't change the point, as Graham said. There Ain't No Such Thing As
A Free Linch (TANSTAAFL). A louder piezo beeper will require more
power, no matter the voltage. Try drawing more power by using a
transformer, and you just might lose the uC.

Using a separate battery, and treating the uC signal with kid gloves is
usually a good idea, especially if repairs on your piece of equipment
will be inconvenient or expensive.

Good luck
Chris
 
M

Mike_in_SD

Jan 1, 1970
0
[email protected] (Chris) wrote in <1161273690.123681.160140
@b28g2000cwb.googlegroups.com>:
Using a separate battery, and treating the uC signal with kid gloves is
usually a good idea, especially if repairs on your piece of equipment
will be inconvenient or expensive.

Good luck
Chris

ok Chris .. you and Graham have given me lots of good advice ..
let me roll up my sleves and see what happens ..


thanks again
mike
 
J

jimbo

Jan 1, 1970
0
Mike_in_SD said:
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

[snip]

thanks
mike

1) Non-electronic in four delicious flavors:

a) Build a reinforcing acoustic cavity and put the piezo
into it

b) Sandwich piezo between two of (a) and gather sound
from _both_ sides of the piezo and pipe them to the same
physical output/hole/whatever

c) A chamber with a resonant frequency the same as the
output freq of the piezo

d) Combine (b) & (c): Pair of resonant chambers that feed
the same output while _not_ canceling each other out.
Hmmmmmm, the constraint means that one or both won't be able
to be a perfect resonator ... might be able to use/hear the
resulting beat frequency, tho.

2) Not-very-sexy, but electronic: Swap out the piezo with an old-
style "high impedance dynamic earphone" and place said earphone into
ear. I suspect the electronics that drive the piezo should be able
to handle this kind of resistance just fine.

In case I'm wrong about any of these assertions, I'm sure some kind,
gentle soul on the list will eventually call me a Nazi. :)

--jim
 
J

jasen

Jan 1, 1970
0
Mike_in_SD said:
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

Here is a pic of the board to show you why I had a problem
finding it.

www.mikeamick.com/all.jpg

the round thing that LOOKS like the piezo is made of ferrite and is
a compass module ( I belive ) .. the white chip below it .. is
the piezo.
question .. can I hook up two of them in parellel(sp?) will it hurt
anything ?

probably not, most probably not right away. but if it doesn't sound two times
as loud you're overloading the chip that driving it so go back to using one.

or is there something else I can hook up .. that is triggered by the
old piezo signal ... ??

yes, eg this: (use fixed font)
+12V
|
+->|-+
| |
| relay
| coil
| |
+----+
|
/
.001 |/
A ---||-+-->|--+---[1K]-+--| 2n2222A
| | | |\|
`-|<-. | 10K ~\
| | | |
| | | |
.->|-|-' | |
| | | |
B ---||-+-|<-+-------+--+-----+
.001 |
---+---
0V/ground

The relay could operate a horn for example, but that could be considered
overkill :)

Bye.
Jasen
 
J

jasen

Jan 1, 1970
0
Mike_in_SD said:
I have a GPS that uses a piezo for proximity alarms.

I HAVE to have it louder. With help of the boys over at
electronics.design I have found the piezo and unsoldered it.

Here is a pic of the board to show you why I had a problem
finding it.

www.mikeamick.com/all.jpg

the round thing that LOOKS like the piezo is made of ferrite and is
a compass module ( I belive ) .. the white chip below it .. is
the piezo.
question .. can I hook up two of them in parellel(sp?) will it hurt
anything ?


probably not, most probably not right away. but if it doesn't sound two times
as loud you're overloading the chip that driving it so go back to using one.

or is there something else I can hook up .. that is triggered by the
old piezo signal ... ??

yes, eg this: (use fixed font)
+12V
|
+->|-+
| |
| relay
| coil
| |
+----+
|
/
.001 |/
A ---||-+-->|--+---[1K]-+--| 2n2222A
| | | |\|
`-|<-. | 10K ~\
| | | |
| | | |
.->|-|-' | |
| | | |
B ---||-+-|<-+-------+--+-----+
.001 |
---+---
0V/ground

The relay could operate a horn for example, but that could be considered
overkill :)

Bye.
Jasen
 
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