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Making piezo louder

P

Pooh Bear

Jan 1, 1970
0
it seems to be impossible what I want :/

You need to tackle the problem more systematically. I'd suggest starting by
connecting an oscillator to the piezo to find out first of all exactly how many
volts ( and milliamps ) drive are required.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
imagine you are drivie a motorbike 200km/h and the device is very near
to your ear, then you need to here beeping ...

That is probably quite loud !

How big is the piezo ? Do you a model number - link to a datasheet etc.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
no I do not have any datasheet it has 24mm

And have you tried an oscillator driving it ( and measured the current ).

Graham
 
J

James Thompson

Jan 1, 1970
0
Hi all!

Could someon help me in making my piezo louder? I am using AVR
microcontroler, like for now my piezo is connected throu NPN
transistor, and across the piezo i`ve connected an indcutor which i
took from old whatch , but my piezo is still not loud enough.
It is also important for me to safe place on my PCB ...

best regards
David
For what you seem to need the piezo for, why not consider an led at the edge
of the helmet to alert you, instead of sound. As like you said about
background noise on a motorcycle going down the road. ??
 
i did not connect an scope couse i have none :( I`ve build and
altimeter for parachuters and it needs to signal specified altitiudes
with sound, it can not be led becouse it is placed near ear...the
falling speed is b
 
bout 50m/s and belive me it is very noise in there ...

Why don't you try to find a datasheet for a similar part? That will at
least give you a starting point.
funny but i couldn`t find any datasheet ..
 
S

Spehro Pefhany

Jan 1, 1970
0
no I do not have any datasheet it has 24mm

Why don't you try to find a datasheet for a similar part? That will at
least give you a starting point.


Best regards,
Spehro Pefhany
 
B

Brian

Jan 1, 1970
0
bout 50m/s and belive me it is very noise in there ...


funny but i couldn`t find any datasheet ..

Here is a start for you... post a picture of the device you are using.
 
R

Rich Grise

Jan 1, 1970
0
imagine you are drivie a motorbike 200km/h and the device is very near
to your ear, then you need to here beeping ...

In that case, you don't want to amplify the beeper - you need to install
foam sound insulation around your ears; then you'll be able to hear it
just fine just the way it is.

Good Luck!
Rich
 
That inductor will be designed to resonate with the *original piezo that was in
the watch*. Also you don't know what frequency it resonates at and you're
probably using a different drive frequency on your PIC.

This *has* to be done right to work or you might as well not bother. In the
meantime remove the inductor, it's probably messing things up.

Graham

.... but don't lose sight of the fact that, with the NPN buffer, it
won't work at all without the inductor (no DC path). Maybe instead
connect from AVR through inductor to piezo to ground (assuming the
AVR's protection diodes are OK)? With this arrangement, the piezo
voltage can exceed the supply by many times if driven at resonance,
but it will still work well at any lower frequency.

But the other important thing is the acoustic loading on the piezo.
Most loud piezo alarms also have a cavity in front of the piezo, and
the self-oscillating circuit uses the resultant acoustic resonance
(reflected as an electrical impedance) in order to oscillate, thus
keeping both acoustic and electrical systemes near resonance, and thus
working efficiently. It would be very hard to achieve anything like
this when generating the signal in an AVR.

Tony
 
S

Spehro Pefhany

Jan 1, 1970
0
... but don't lose sight of the fact that, with the NPN buffer, it
won't work at all without the inductor (no DC path). Maybe instead
connect from AVR through inductor to piezo to ground (assuming the
AVR's protection diodes are OK)? With this arrangement, the piezo
voltage can exceed the supply by many times if driven at resonance,
but it will still work well at any lower frequency.

But the other important thing is the acoustic loading on the piezo.
Most loud piezo alarms also have a cavity in front of the piezo, and
the self-oscillating circuit uses the resultant acoustic resonance
(reflected as an electrical impedance) in order to oscillate, thus
keeping both acoustic and electrical systemes near resonance, and thus
working efficiently. It would be very hard to achieve anything like
this when generating the signal in an AVR.

Tony

The size of the hole in the cavity is important. A simple open-ended
tube probably has too low a Q.


Best regards,
Spehro Pefhany
 
The size of the hole in the cavity is important. A simple open-ended
tube probably has too low a Q.

Best regards,
Spehro Pefhany

It's certainly more convenient (and more compact) to use a
conventional closed resonant cavity with a hole in it, but I would
expect a plain open-ended quarter-wave tube to work at least as well,
maybe better (larger volume should make the exit impedance match the
air better).

Regards,
Tony
 
P

Pooh Bear

Jan 1, 1970
0
... but don't lose sight of the fact that, with the NPN buffer, it
won't work at all without the inductor (no DC path).

But he says it does work which suggests to me that maybe there's something here that
he hasn't mentioned.

Graham
 
M

Mark L. Fergerson

Jan 1, 1970
0
Hi all!

Could someon help me in making my piezo louder? I am using AVR
microcontroler, like for now my piezo is connected throu NPN
transistor, and across the piezo i`ve connected an indcutor which i
took from old whatch , but my piezo is still not loud enough.
It is also important for me to safe place on my PCB ...

From reading the whole thread I finally got enough information to
hazard an opinion.

Go find the watch you took the piezo and inductor out of and put the
piezo back in (I'll assume it came from the back of the case, which is
usually where they are). Back it up with something with audio properties
similar to the watch guts (you're basically using the "speaker
enclosure" designed around the piezo by the watch manufacturer, and
since they did all that work, you might as well take advantage of it)
and install the inductor appropriately.

Then figure out what the original driving signal looked like and
duplicate that as closely as you can with the microcontroller. Mount the
piezo+"enclosure" in whatever piece of headgear you are gonna use for
skydiving. Test it on the ground first, because it'll likely be _too_
loud. Remember that watch alarms are meant to be unmistakably heard from
arm's length but you'll be putting it right next to your ear.

If the rest of the watch isn't available/doesn't work, go buy a
WalMart or similar cheapo (I wouldn't spend the time designing what you
want for that for the six bucks or so the watch will cost) for parts and
do as above.


Mark L. Fergerson
 
P

Phil Hobbs

Jan 1, 1970
0
Mark said:
From reading the whole thread I finally got enough information to
hazard an opinion.

Go find the watch you took the piezo and inductor out of and put the
piezo back in (I'll assume it came from the back of the case, which is
usually where they are). Back it up with something with audio properties
similar to the watch guts (you're basically using the "speaker
enclosure" designed around the piezo by the watch manufacturer, and
since they did all that work, you might as well take advantage of it)
and install the inductor appropriately.


Sorry to be late to the party.

To make the piezo louder, you want more voltage across it--so the
inductor goes in series, not in parallel.

Cheers,

Phil Hobbs
 
M

Mark L. Fergerson

Jan 1, 1970
0
Sorry to be late to the party.

Yeah, well, I believe the OP has wandered off...
To make the piezo louder, you want more voltage across it--so the
inductor goes in series, not in parallel.

I completely missed that he said "across" above. I shoulda said "as
originally used" of course.

I just couldn't see why he wanted to reinvent the wheel and then
wanted help figuring out where the axle goes. ;>)


Mark L. Fergerson
 
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