B
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- Jan 1, 1970
- 0
it seems to be impossible what I want :/
it seems to be impossible what I want :/
imagine you are drivie a motorbike 200km/h and the device is very near
to your ear, then you need to here beeping ...
no I do not have any datasheet it has 24mm
For what you seem to need the piezo for, why not consider an led at the edgeHi 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
funny but i couldn`t find any datasheet ..Why don't you try to find a datasheet for a similar part? That will at
least give you a starting point.
no I do not have any datasheet it has 24mm
bout 50m/s and belive me it is very noise in there ...
funny but i couldn`t find any datasheet ..
imagine you are drivie a motorbike 200km/h and the device is very near
to your ear, then you need to here beeping ...
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
... but don't lose sight of the fact that, with the NPN buffer, it
won't work at all without the inductor (no DC path). Maybe instead
connect from AVR through inductor to piezo to ground (assuming the
AVR's protection diodes are OK)? With this arrangement, the piezo
voltage can exceed the supply by many times if driven at resonance,
but it will still work well at any lower frequency.
But the other important thing is the acoustic loading on the piezo.
Most loud piezo alarms also have a cavity in front of the piezo, and
the self-oscillating circuit uses the resultant acoustic resonance
(reflected as an electrical impedance) in order to oscillate, thus
keeping both acoustic and electrical systemes near resonance, and thus
working efficiently. It would be very hard to achieve anything like
this when generating the signal in an AVR.
Tony
The size of the hole in the cavity is important. A simple open-ended
tube probably has too low a Q.
Best regards,
Spehro Pefhany
... but don't lose sight of the fact that, with the NPN buffer, it
won't work at all without the inductor (no DC path).
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 ...
Mark said:From reading the whole thread I finally got enough information to
hazard an opinion.
Go find the watch you took the piezo and inductor out of and put the
piezo back in (I'll assume it came from the back of the case, which is
usually where they are). Back it up with something with audio properties
similar to the watch guts (you're basically using the "speaker
enclosure" designed around the piezo by the watch manufacturer, and
since they did all that work, you might as well take advantage of it)
and install the inductor appropriately.
Sorry to be late to the party.
To make the piezo louder, you want more voltage across it--so the
inductor goes in series, not in parallel.