Turning keyfinder into a simple buzzer

[pjgfi]

Hello,

I bought a cheap whistle keyfinder I'd like to turn into a simple buzzer for dog training. I simply want it to buzz when I press the button (instead of turning LED on).

I thought I could bypass the mic but I know next to nothing in electronics, I just can solder. The circuit board is so simple there's only so much you can do (the core is the white blob!).

Playing tune when pressing button would be great but a simple buzz sound would do.

Can you help?

Thanks.

 

[audioguru]

The beige round "blob" is the entire circuit of the whistle keys finder. You would need to re-design it to do what you want.
Instead, buy a piezo buzzer that works from a DC battery and add a pushbutton to activate it.

 

[pjgfi]

Thanks for your answer!

So the buzzer would not be not self working like old electromagnets buzzer did (connect battery then electromagnet attracts blade > circuit open > blade freed > circuit closed > repeat!).

If it does, what if I connect buzzer in place of LED?

And as the buzzer also acts like a mic that detects sound, is it possible to trigger this by injecting some current into the buzzer wires? Because what I really need is "just" to trigger the mic, no?

 

[JimB]

is it possible to trigger this by injecting some current into the buzzer wires?

You could do that, but, there is just as much effort required in making a circuit which creates the correct frequency simulated whistle, as there is just making a circuit which drives the buzzer.

To be quite honest, your keyfinder is not a good starting point for a dog training buzzer.

JimB

 

[pjgfi]

Thanks. I understand, I thought it would be as simple as injecting 3v in the wires but it's smarter than this!

So if I understand correctly, those flat piezos need an external oscillating circuit while the black cased (button) ones might be self working, right?

 

[JimB]

those flat piezos need an external oscillating circuit

Yes.

while the black cased (button) ones might be self working,

Maybe, but I would not want to guarantee it without seeing the datasheet.

JimB

 

[audioguru]

A piezo buzzer has a transistor oscillator inside it so it produces a beeeeep when it is powered with DC. The transistor in it will prevent it from being a microphone. So the "blob" on the circuit board switches the piezo transducer from being a microphone to being a speaker that is driven with a tone.

 

[pjgfi]

Thanks both for your answers, I've learned a lot about buzzers!
I'll let you know about the updates on my project.

 

[pjgfi]

I found three buzzers from various devices :
- rdi-dmt-1206-i from a PCI Modem card
- htc1205g from a mobo
- no reference one from a... frog moisture meter

NONE of them beeps ! They all make a low "crrrr", no continuous sound. I fed them with 3v, 4.5v, 6v, 9v. The frog one croaks OK in its own circuit.
Shouldn't they at least make a continuous sound ?

 

[audioguru]

You and we don't know if the buzzers you found are piezo or electro-magnetic and if they are transducer speakers needing an AC voltage or if they need a DC voltage.
You also did not say if you fed then AC or DC.

 

[pjgfi]

Here are the datasheets I found :

HTC1205GElectromagnetic buzzer_ChangzChangzhou Dragon State Electronic Co.,LTD

http://www.gravitech.us/acbuzzer4v8v.html

Says AC on the RDI datasheet...

I fed them DC because I want my device to run on batteries.

 

[audioguru]

Do you put water in your car's gas tank because you want it to run on water??
The "electromagnetic buzzer" is simply a speaker that is driven by 6VAC at its resonant frequency of 2.4kHz. Since it is Chinese then its seller has a translation error about AC or DC.
It will run on batteries if you make a power oscillator that outputs 2.4kHz.

 

[pjgfi]

I don't say I want them to run on DC, I just need them to run on DC. I like to reuse part I've got lying around but this won't be possible this time.
I might go to my local electronic shop and buy a DC one (they told me they have some)...
I'll let you know.

 

[Nigel Goodwin]

I don't say I want them to run on DC, I just need them to run on DC. I like to reuse part I've got lying around but this won't be possible this time.
I might go to my local electronic shop and buy a DC one (they told me they have some)...
I'll let you know.

The ones you have are essentially small 'loudspeakers', so if you connect DC across it you get a click and nothing else. A 'DC'one will have an oscillator inside it to drive the disc and make the noise.

 

[pjgfi]

Done! I bought a HYDZ buzzer (a real DC one, don't trust the + sign on the others!) and wired and glued it in place of the LED.
It works perfectly! Thanks everyone for your help and advice.

 

[JimB]

Always good to hear a success story.

JimB