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
Have you tried running it through an LM386 audio amplifier?
no i did not try, is there any possible way of doing it without any external ICs ?
Why ? Isn't the AVR ouput strong enough ?
What is the inductor there for ?
A neat trick is to invert the signal used for the buzzer and connected to the 'other' terminal so you're doubling the voltage applied.
Graham
as I have read on news groupe that the inductor couses some pics which makes voltage over piezo higher (if you look into some old whatch with buzzer it is there)
avr output gives me 20mA, and the trick which you have describe do not work at all
any other idea ?
as I have read on news groupe that the inductor couses some pics which makes voltage over piezo higher (if you look into some old whatch with buzzer it is there)
avr output gives me 20mA, and the trick which you have describe do not work at all
any other idea ?
Only in a resonant circuit. Which you don't have. In fact it may be louder without the inductor. If you want a resonant circuit you'll have to do rather more than just add an inductor. A capacitor is needed too and you'll need to do some sums about their values.
In that case I doubt you need a transistor.
Then you've done it wrong.
Graham
i took an inductor and piezo from the watch, so I think that value of indcutor is in resonase with capacitanc of piezo.. isn`t it ?
i do use a transistor...
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
so all in all what is your sugesstions to make it louder ?
i took original piezo i tried many freq... still not loud enough ...
Drive the piezo from 2 gates / buffers / whatever ( including the PIC ) with the original drive signal on one terminal and an *inverted* 'copy' of it on the other terminal. You can get 10V ( assuming 5V logic ) across the piezo this way which should be loud enough.
Graham
i did it but it much worse ...
...than with transistor and inductor
You're not being very scientific about this.
Graham
I bet that transistor is still there isn't it ?
Graham
How loud are you trying to get it ?
Graham
David,
Making an effective piezo drive circuit is about 10% of the work. The resonant cavity design and mounting technique of the piezo is the other
90%. You need to know how the piezo will vibrate at your selected (resonant) frequency. The mounting points should be at the vibrational nodes of the piezo disc, which may be at the outer edge of the disc, or somewhere between the edge and the center of the disc. You need to know how your piezo disc will vibrate. The amount of airspace in your cavity is also an important factor, as well as the port aperture. In many ways, it is a lot like speaker enclosure design.Check out Goldmine Electric, they will send a free driver schematic if you buy one of their piezo discs:
They supply their driver schematic with other piezo discs they sell as well. I have not seen their schematic, myself. I would like to see it.
Take care,
-Chris
imagine you are drivie a motorbike 200km/h and the device is very near to your ear, then you need to here beeping ...
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Can you glue or fix a sounding plate?
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