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Topic: Driving a piezo loudly! (Read 751 times) previous topic - next topic

Danielvt

So the whole problem revolves around the fact, that i need to drive the piezo to the highest possible DB-level from a 3v battery. I've designed and 3D-printed a resonance chamber which seems to work okay. My biggest succes has come from driving around 4.6kHz from the output arduino pin to a transistor and from there to a parallel setup with a 4.7kH inductor and the piezo. The piezo is measured as 18.5nF which by my calculations should result in a ressonance frequency around 17068Hz. However this is far from where i get my highest voltage when measuring vAC. Around 4.6kHz is where i get the highest voltage (around 6.2vAC). Any suggestions on how to increase the voltage across the piezo? My current setup just doesn't seem to cut it. It needs to be louder :( (it's for an alarm)

Thanks again for inputs!

Paul_KD7HB

So the whole problem revolves around the fact, that i need to drive the piezo to the highest possible DB-level from a 3v battery. I've designed and 3D-printed a resonance chamber which seems to work okay. My biggest succes has come from driving around 4.6kHz from the output arduino pin to a transistor and from there to a parallel setup with a 4.7kH inductor and the piezo. The piezo is measured as 18.5nF which by my calculations should result in a ressonance frequency around 17068Hz. However this is far from where i get my highest voltage when measuring vAC. Around 4.6kHz is where i get the highest voltage (around 6.2vAC). Any suggestions on how to increase the voltage across the piezo? My current setup just doesn't seem to cut it. It needs to be louder :( (it's for an alarm)

Thanks again for inputs!
Look for a PULSE TRANSFORMER with winding ratios that will give the voltage you want. Use to be almost free from surplus establishments. Now probably hard to find used.

Paul

allanhurst

Presumably you don't mean 4.7kH ( 4700H)

What value is it?

Allan

allanhurst

#18
Jun 11, 2018, 03:55 pm Last Edit: Jun 11, 2018, 03:57 pm by allanhurst
Putting about 80mH in series with the piezo would give a reasonable current through it at 4kHz - see enclosed.

The voltage depends on the internal resistance of the piezo.

Allan

Danielvt

Presumably you don't mean 4.7kH ( 4700H)

What value is it?

Allan
Sorry, i mean 4.7mH ofcourse!

Putting about 80mH in series with the piezo would give a reasonable current through it at 4kHz - see enclosed.

The voltage depends on the internal resistance of the piezo.

Allan
I don't have a 80mH inductor unfortuanently. Only have 56mH  :-(  But why would you put it in series? According to what i've found



they should be in parallel? :-)

For some weird reason my calculations of ressonance frequency don't seem to match the reality of what i'm measuring :-(




allanhurst

#20
Jun 11, 2018, 05:03 pm Last Edit: Jun 12, 2018, 01:07 am by allanhurst
You've drawn a parallel resonant circuit which presents a low impedance except at resonance - and only allows twice the supply volts across the piezo.

A series resonant circuit becomes low impedance at resonance, and forces a lot of current to flow through the piezo. It  has no such limitation .

If you used my circuit with a 56mH and added a 2.2nF across the piezo you'd also acheive resonance, and it ought to work at about 4.6 kHz

Note you can't use a single transistor driver here - try an arduino  output to start with and tweak the extra C for best output.

Allan

Danielvt

You've drawn a parallel resonant circuit which presents a low impedance except at resonance - and only allows twice the supply volts across the piezo.

A series resonant circuit becomes low mpedance at resonance, and forces a lot of current to flow through the piezo. It  has no such limitation .

If you used my circuit with a 56mH and added a 2.2nF across the piezo you'd also acheive resonance, and it ought to work at about 4.6 kHz

Note you can't use a single transistor driver here - try an arduino  output to start with and tweak the extra C for best output.

Allan

Awesome, i'll give it a try, when i get back to the measuring equipment at Uni tomorrow! However i'm not quite sure what you meant about driving the transistor through the Arduino? Currently i'm using a wave-generator with square-wave output at around 4.6kHz with 1.5v amplitude, 50% duty ratio. I've attached the setup here.
I get (with the 15nF dummy acting as the piezo) around 6.2vAC from a 3.3vDC source. and a 4.7mH inductor which is the highest i've managed to get so far.

Thanks again so much for your help! I really appreciate it!


allanhurst

#22
Jun 11, 2018, 11:42 pm Last Edit: Jun 12, 2018, 01:13 am by allanhurst
Try it my way with a signal generator. And do some sums .

And download and learn to use simulation programmes such as 'PSPICE' or 'LTSPICE'.

You'll find them very useful.



Allan

edit :  you may find the enclosed driver useful - put the inductor/piezo where I show the loudspeaker.

Danielvt

#23
Jun 12, 2018, 10:02 am Last Edit: Jun 12, 2018, 10:03 am by Danielvt
Try it my way with a signal generator. And do some sums .

And download and learn to use simulation programmes such as 'PSPICE' or 'LTSPICE'.

You'll find them very useful.



Allan

edit :  you may find the enclosed driver useful - put the inductor/piezo where I show the loudspeaker.
Hi again Allan,

I've tried your setup and got the following (check attachment)

I didn't quite understand your resistor however. I tried both 1k ohm and 1 ohm. The 1ohm gave me the 1.5Vpp as the waveform generator is outputting.

It doesn't seem to work for me :/ Do you have any idea, what i'm doing wrong?

Again, thanks a lot for your time! :-)

/ Daniel

ted

For resonance google - 3 wire piezo buzzer

Danielvt

Try it my way with a signal generator. And do some sums .

And download and learn to use simulation programmes such as 'PSPICE' or 'LTSPICE'.

You'll find them very useful.



Allan

edit :  you may find the enclosed driver useful - put the inductor/piezo where I show the loudspeaker.
Ok good news! I got it working with the signal processor, and i finally understand the entire setup, and how the capacitor, inductor and waveform signal processor work together. Managed to get around 16-17vAC from the 3v power source - Amazing!! :D Works like a charm, however when i try to move from the waveform generator towards a transistordriven circuit i get into trouble. I've made the setup as shown on the attachments, however it seems like i only get power from the transistor-gate and nothing form the actual DC power source. How can this be?

By the way, thanks for the tip with simulation-software, it has saved me lots of hours! 

Danielvt

Hi all!

I'm trying to drive a LC/tank -circuit with an Arduino in order to increase the voltage across a piezo. This far i've managed to get the LC-circuit working perfectly with an increase from 3.3vAC to 16-17vAC when the 3.3vAC is supplied through a waveform generator. However since i need to run it from the Arduino i'm trying to get this to work with a transistor. I just can't seem to get it right. Whatever i try, it seems like the only source of power is the base-input of 1.5vAC from the simulated Arduino pin. And the 3.3v from the DC source doesn't affect the output at all - even tried changing it to 5v, 12v, and 60v in the simulations - no change in output.

What on earth am i doing wrong?

I've attached both setups in the 'Schematics.jph' file.

Thanks in advance for any inputs!

Best regards
 / Daniel

Danielvt

Woops, ofcourse schematics is the other way around:

pwillard

I really don't like simulators... but shouldn't it look a wee bit more like this?





DVDdoug

Quote
And the 3.3v from the DC source doesn't affect the output at all
Where's the (simulated) meter connected?    Of course the important thing is the voltage across the piezo.

Is the capacitor supposed to be the Piezo or is it supposed to be the resistor?

Of course, if you can supply a higher DC voltage in the real world you wouldn't have to be playing-around with resonant circuits.  ;)


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