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buzzer amplify

Discussion in 'General Electronics Discussion' started by gatoulisss, Feb 2, 2015.

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  1. gatoulisss

    gatoulisss

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    2
    Jan 23, 2015
    hello, i want to use a piezo buzzer as syren but i dont know how i can amplify it so it would be enough loud the signal will come from an microcontroller.
    i have sean some sirens use a trasnporter to do that any advice? thank you!
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Fit it in an enclosure, or buy a siren.
     
  3. BobK

    BobK

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    Jan 5, 2010
    A piezo buzzer, if that is what you have, has an oscillator built in and makes a sound if you simply connect it to a battery. Using the highest voltage that it is rated for will give you the loudest sound. If you need louder, buy a buzzer that is louder. They normally come with a dB rating so you can compare.

    I have one from Radio Shack that is ear splitting when connected to a 9V rectangular battery.

    Bob
     
  4. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    no, in my case the driver circuit is from the pic microcontroller so is not playing if i just connect it to the battery. also the output is +5 from the pic how i can amplify it? the buzzer i want to use is somethink like the picture below

    Photo 1-2-15 - 9 11 22 μ.μ..jpg
     
  5. BobK

    BobK

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    1,686
    Jan 5, 2010
    Then it is not a piezo buzzer. It is a piezo transducer.

    Some of these will have a resonance frequency at which the sound will be maximized. You can also drive it with a higher voltage by using a transistor switch. Can you link to a datasheet for the one you have?

    Bob
     
  6. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    i dont have the datasheet but i have the ebay link wich is were i bought it http://www.ebay.com/itm/231141835644?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT
     
  7. BobK

    BobK

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    1,686
    Jan 5, 2010
    It does give a resonant frequency of 3.6KHz. What frequency are you trying to send to it? It might be a lot louder at the resonant frequency.

    Bob
     
  8. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    im giving to it 2900hz and 3200hz but if i connect it to the transormer then it sonds much more louder... i dont know how to amplify it and how to connect it to the transformer as i had the circuit in the foto ready made
     
  9. Arouse1973

    Arouse1973 Adam

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    1,081
    Dec 18, 2013
    That's because the piezo disc needs a higher voltage. This is what the transformer is doing. The other factor which allows overdrive and greatly increases the output is the resonant cavity. Two things running them in open air with a transformer is you risk over driving the piezo and much reduced output. I design a similar circuit several years ago using an auto transformer and resonant cavity. At 7.2 Volts I get about 100 dBA at 1m. It's very loud, but take it out of the cavity and it's not very loud at all.
    Adam
     
  10. BobK

    BobK

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    1,686
    Jan 5, 2010
    You can double the voltage from the microprocessor by using 2 output pins in a bridge configuration. I.e. You switch from pin1 high, pin 2 low to pin 1 low, pin2 high.

    Bob
     
  11. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    im using it on an plastic tube as speaker but again is not to loud... do yoy have any schematic how i can do this?


    im sorry i didnt understand how to do this can you be more specific?

    thanks a lot!!
     
  12. BobK

    BobK

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    Jan 5, 2010
    Okay.

    Right now, you presumably have one side of the transducer connected to ground and the other to a micro output pin. Then you toggle that pin between 1 and 0 to create a square wave.

    To get twice the voltage, connect each side to a micro output pin.

    The toggle the pins line this:

    First half period:
    pin1 high, pin 2 low

    Second half period:
    pin 1 low, pin 2 high

    So looking at it from one of the leads on the transducer, it used to go between 0V and 5V (or whatever voltage your micro is running at). With the two pin configuration it goes from -5V to +5V, giving you twice the voltage swing. This is the technique used by bridged amplifiers you find for car sound. A bridged amplifier gives you twice the voltage and 4X the power, because power is proportional to voltage squared.

    Bob
     
  13. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    yes ok but how i can programm it? im using for example this lines to play a continious bip-bip sound:

    sound_init (&porta,2);
    for(;;) {
    sound_play(3600,150);
    delay_ms(400);
    sound_play(3600,150);
    delay_ms(5000);}
     
  14. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    I guess the sound_play function is a library function?

    You will not be able to use it. You will have to manipulate the port bits directly.

    It looks like you are using RA2 as the output. If you make RA1 the other output, it would look like:
    (not sure of the syntax for your C compiler)

    porta.ra1 = 1;
    porta.ra2 = 0;

    for (i=0; i<10714; i++)
    {
    porta ^= 0b110; / this toggles both bits
    delay_us(14);
    }

    The loop is designed to run for 150 ms (10714 * 14uSec). You probably have to adjust the delay, or use buiting NOPs to get the right delay depending on your clock speed.

    Bob
     
  15. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015

    it is not working... its making a sonic sound but not louder...
     
  16. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    What is a sonic sound? (I guess one that is not sub-sonic or super-sonic)

    You probably have to adjust the delay to get it to come out to the 3.6KHz frequency. What clock speed are you running the micro at?

    Bob
     
  17. gatoulisss

    gatoulisss

    36
    2
    Jan 23, 2015
    4mhz i was thinking of amplify the output from the pic... is there any way? for example the 5v thats is the output to make them 9 or 12
     
  18. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    You can use a simple transistor switch to amplify a square wave from the PIC.

    But remember, you have already tried 10V p-p and that did not seem to help.

    Bob
     
  19. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Actually, after thinking about it for a bit, you need a push-pull stage to amplify for the piezo, because it is basically a capacitor.

    I cannot think of a reason why my idea of bridging 2 outputs did not give you a significant increase in volume, unless the code was incorrect. Can you post the code you tried?

    Bob
     
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