How can I get dual tone from a 12v buzzer ?

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DickCappels

Joined Aug 21, 2008
9,105
What are you referring to as a "buzzer"? Are you looking for a way to tell the buzzer which tone to produce or do you want the buzzer to warble?
 

DickCappels

Joined Aug 21, 2008
9,105
Yes, but changing the frequency by electrical signal is not easy. Just about anything that makes a 50% duty cycle square wave would work.

Here are some circuits from a MuRata Piezo sounder datasheet.

1645173126164.png

Circuit #2 is probably the easiest to make into a two tone oscillator.

In that case you would need an enable signal ("Input") and a tone select signal. One more transistor would need to be added to select the tone.

Alternatively, you can build two different oscillators both feeding the same transistor -after all you would probably be using a 4 NAND gate package.

1645173548175.png
This is a typical frequency response plot. You would get the loudest output at the resonant frequency and one of its harmonics or sub-harmonics.

What power supplies are available?
How do you want to control the tone (variable voltage, Hi/Low digital signal, Two control inputs, etc)?
 

AlbertHall

Joined Jun 4, 2014
12,122
There are several different things which all get called buzzers.
Some just need a DC supply and they generate a tone which can't be changed.
Some are like a small loudspeaker - may be piezo or electromagnetic - and these need to be fed with an alternating voltage and will produce sound at the frequency of the applied voltage (within limits).
 

Thread Starter

rafiec14

Joined Dec 14, 2019
71
Thank you. Screenshot_20220218-112211_Chrome.jpg
In the above fig. The buzzer sounds as per the RGB LED. Can any changes be made to the above so as to get dual tone?
 

AlbertHall

Joined Jun 4, 2014
12,122
This circuit looks as if it is providing (or not providing) a DC voltage to the buzzer. The internals of the buzzer generate the frequency of the sound so this cannot be changed.

You need the other type of 'buzzer' - more like a loudspeaker - and a circuit to oscillate at the tones you want as shown in post #5.
 

MisterBill2

Joined Jan 23, 2018
12,740
With the circuit shown, and the internal oscillator piezo sounder, NO, the frequency is fixed.
In my vocabulary a buzzer is an electromechanical device, with an electromagnetic arrangement to open a contact that removes the voltage from the coil, (mechanical feedback.)
 

Ya’akov

Joined Jan 27, 2019
6,289
With the circuit shown, and the internal oscillator piezo sounder, NO, the frequency is fixed.
In my vocabulary a buzzer is an electromechanical device, with an electromagnetic arrangement to open a contact that removes the voltage from the coil, (mechanical feedback.)
I also had a little trouble with “buzzer” for piezos when I first started seeing it but it is standard terminology now. The schematic symbol doesn’t distinguish, and the designation is “BZ”. I think it has come to mean ”a self contained device that produces and audible signal when voltage is applied”, which seems fair enough.
 

MisterBill2

Joined Jan 23, 2018
12,740
I did create a beeper for a continuity checker using a CD4049, with 2 parallel inverters on each side of the sounder, driven out of phase. It was not like the common continuity beepers in that accidentally applying voltage would not damage it at all.
 
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