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Need help to identify type of buzzer

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ericgibbs

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Hi

Would like to know if the buzzer below is an external driven type or a self-driven(with built-in driver?) type :

http://www.mouser.com/catalog/specsheets/KT-400364.pdf

I am looking for the latter. Bought the wrong type previously and do not want to repeat the same mistake again. What I want to do is to apply a 5V to get a sound.

Much thanks!

:D
hi,
Its a poor datasheet, but as it says 5V pp and it gives a freq plot, I would say it requires a driver.
 

ericgibbs

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Last edited:

audioguru

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They are peizo transducers, not buzzers and not beepers. If you make an oscillator and tune it to the resonant frequency of the transducer then it will beep, not buzz.
 

Hero999

Banned
An oscillator can easilly be made using a 555 timer.

If you're using a microcontroller, then you might as well go for the transducer and send a squarewave to the port.
 

audioguru

Well-Known Member
Most Helpful Member
It is difficult to make a piezo transducer beep loudly. Its response is full of narrow resonances and nulls.
A piezo beeper that has a built-in oscillator has a special feedback terminal on the piezo that forces it to oscillate at its loudest resonant frequency.
 

Hero999

Banned
If you set the oscillator frequency to that specified on the datasheet and use a bridged driver (e.g. two I/O pin 180° of phase with each other), it will be just as loud as a unit with an internal oscillator.
 

Urahara

Member
As a newbie, I am actually quite confused with the definitions of a buzzer, piezo-electric buzzer, etc. Searching thru the internet for more information confuses me even more. :(

What I would like to do is to connect the buzzer/beeper/etc to a MCU pin and using PWM, control the tone/volume of the buzzer/beeper. Currently I programmed my PWM code to have a 4kHz frequency and I use duty cycles of 50%, 70% and 90% to vary the tone/volume.

In this context, do I need a externally driven buzzer/beeper or do I need a self-driven one? If you can go a step further, any good and cheap ones to recommend from Mouser?

Thks! :)
 

Urahara

Member
something like this, although my circuit does not include diode D1.

If diode D1 is not part of my circuit, I guess I should exclude those electro-mechanical ones and limit myself to piezo-buzzers/beepers (whatever!)?
 

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Boncuk

New Member
Hi Urahara,

The KT-400364 is a transducer requiring an external oscillator.

According to the spec sheet its operating criteria are 5V at 5mA for 80db.

You won't require PWM, just generate a rectangular wave at 4KHz (resonant frequency)

You also won't necessarily have to use a transistor for a driver. The MCU should be able to source or sink 5mA. Use a 100Ω resistor in series to measure the current flow and decrease the value of it step by step to have the maximum allowed current of 5mA across the transducer without killing the MCU.

Boncuk
 

ericgibbs

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Most Helpful Member
Morning Hans.

The 80dB is for 5Vp p, which suggests a push/pull drive.

The OP also wants to control the frequency.


Hope that things have quietened down in your location.:)
 

Boncuk

New Member
Morning Hans.

The 80dB is for 5Vp p, which suggests a push/pull drive.

The OP also wants to control the frequency.


Hope that things have quietened down in your location.:)
Hi Eric,

80db is quite some noise, which will apply only if 5Vpp at 4KHz is used. Varying the frequency off the resonance range will decrease the loudness.
PWM doesn't make much sense to me. It will produce strange noise at the most.

Things have calmed quite considerably here, after police and military decided to end the protests (having already reached a level of shooting and throwing "Mollies" (Molotow-Cocktails)), all initiated by Thaksin, who wants to regain power in Thailand, even for the price of a civil war.

My personal opinion: Thailand should have a secret service like the Mossad. :D
 

Hero999

Banned
I don't see why you'd want to use a seires resistor, a typical MCU can source/sink 20mA and the piezo only requires 5mA.

I don't know if PWM would be any help to reduce the volume, it might sound funny or it might work.
 

audioguru

Well-Known Member
Most Helpful Member
The 80dB sound level is rated at a distance of only 10cm.
So it is only 74dB at 20cm, 68dB at 40cm, 62db at 80cm, 56dB at 1.6m and 50dB (a whisper) at 3.2m.

A piezo beeper that has a built-in oscillator has an acoustical resonant chamber that makes the sound level much higher. I put a bottle cap behind a small piezo transducer and it became very loud after I tuned the frequency to the peak.
 

Sceadwian

Banned
Be wary of directionality too piezos aren't ominidirectional, so if it's not pointed directly at the listener you'll get even more power loss.
 
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