Driving a piezo loudly!

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 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!

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.

amp.pdf (19.6 KB)

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.

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 :confused: Do you have any idea, what i’m doing wrong?

Again, thanks a lot for your time! :slight_smile:

/ Daniel

For resonance google - 3 wire piezo buzzer

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.

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!! :smiley: 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!

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

Woops, ofcourse schematics is the other way around:

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

|500x255

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. ;)

You will destroy the transistor (and may already have) if you fail to use a base resistor (1K - 10K).

To what peak-to-peak voltage have you set the signal generator?

however it seems like i only get power from the transistor-gate and nothing form the actual DC power source.

Please explain why you think this.

Note: I'm indicating you have to drive the BASE of the transistor with a PWM signal. No switching... no voltage... Just feeding DC won't do anything.

Try my driver posted in #22 and read my comments..

You probably don't need the output capacitor - replace it with a short.

You won't get anything from your circuit as there's no way for the transistor to get power...

A capacitor ( such as a piezo) blocks dc current flow.

Allan

If you want to simulate a piezo element, you need to take into account its equivalent inductance, which can be surprisingly large, as well as the internal resistance. At the moment, you are just (incorrectly) simulating an LCR circuit.

Unfortunately decent SPICE/LTSPICE models for a piezo element are hard to find, but here is one attempt.

Please do not double post.

jremington:
Please do not double post.

I just thought the other thread went a bit off-topic in regards to the original post, which is why i made a new post :slight_smile:

DVDdoug: 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. ;)

The voltage is measured at the capacitor - which is yes supposed to act as the piezo. I don't have the possibility of having a higher DC-voltage across the piezo since we're running on a 3v battery - which is why i'm using a LC-circuit :)

Threads merged.

jremington:
You will destroy the transistor (and may already have) if you fail to use a base resistor (1K - 10K).

To what peak-to-peak voltage have you set the signal generator?
Please explain why you think this.

I run the signal generator at 1.5V but if i change it, the output changes (and doesn’t change if i change the DC input!) which is why i think the signal is providing the output.

jremington i have it working perfectly without the transistor, so my ressonant LC circuit is working fine :slight_smile:

pwillard:
Note: I’m indicating you have to drive the BASE of the transistor with a PWM signal. No switching… no voltage… Just feeding DC won’t do anything.

I’m not really sure what you mean - how should i simulate it? Could you elaborate?

Thanks for all your responses! Appreciate it!

/ Daniel

allanhurst:
Try my driver posted in #22 and read my comments…

You probably don’t need the output capacitor - replace it with a short.

You won’t get anything from your circuit as there’s no way for the transistor to get power…

A capacitor ( such as a piezo) blocks dc current flow.

Allan

Hi Allan,

I tried the circuit with no luck (see attached schematics)

I tried the circuit with no luck

You tried a different circuit, which won't work for several reasons.

You could try the one in reply #22, carefully following the instructions to replace the speaker (8 Ohm R2) with the piezo, but it won't be any louder than the direct output from an Arduino, because there is no voltage boost.