Increasing Piezo Volume

Mad Professor

Senior Member
Good Day All.

I have a PicAxe 18x project that I am wanting to use a Piezo Sounder.

I have connected the piezo sounder to pin3 and run the test code.

Code:
for b1 = 1 to 100
sound 3, (b1,25)
next b1
It works but the volume is so low.

My piezo has a max working voltage of 30v p-p.

What is the best way of driving it at grater then 12volts?

Thanks for your time.
 

BeanieBots

Moderator
Use a complemetary output and wire between them.
If you use something like a max232 inverter which give +/-10 volts, it will give you 40v differential from a 5v supply.
Just a simple 5v logic inverter will give 10v.
H-bridge with 12v supply would give 24v.
 

boriz

Senior Member
Put a 1k - 2k resistor in parallel with the piezo. It will might improve the volume some because the piezo is very much like a small capacitor, and the resistor helps it to be fully discharged between pulses.

For high volumes, I have had success with a simple flyback coil+transistor.

Do you know what back EMF is? Can you wind a coil? Can you select an appropriate transistor for a particular collector current/voltage?

If the answers are all yes, then you should have no trouble.
 

Mad Professor

Senior Member
Thanks for your replys.

I think I will try using a MAX232.

I do have a few MAX232CPE+ in my draw of parts.

How should I go about wiring up a MAX232 to my picaxe and piezo?

Is it just a case of adding the four 0.1uf caps, and connecting the picaxe output to pin10 or 11 on the max232 and then pin 7 or 14 to the piezo?

Thanks for your time.
 
Last edited:

hippy

Technical Support
Staff member
@ Mad Professor : Just wire your MAX232 up as you would for connecting 0V/5V SEROUT to RS232C, then connect the Piezo between it's output and 0V.
 

westaust55

Moderator
If you have some space, for a totally non electronic solution, try putting a cone in front of the piezo sounder with the sounder over the opening at the vertex (small end). Your own Megaphone! While increasing the volume it does however make the sound more directional.
 

bogbean

Well-known member
On a recent project I found my piezo passive transducer output a bit quiet too.
I did 2 things to squeeze a bit more volume out...
  • A bit of electrical tape stuck over the sounder hole - I suppose this changed the resonance
  • A 10uF capacitor in series with the sounder made an discernable improvement - perhaps because it is blocking some DC - i'm not sure of the reason
These suggestions could make small incremental improvements, you won't be needing earlugs with them but for me the extra dB or two made a difference.
 
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