First of all, thank you very much for everyone's replies. Actually, this is not a 'vanilla' buzzer im using here. What i did is, i bought a very cheap battery operated (3x1.5V cells) magnetic switch alarm module that operates to detect if there's an opening door/windows. I strip off the alarm module because i wanted to use the built-in very loud buzzer cicuit (which i believe is using a piezo diaphagrm (at least it looks that way to me because it is very thin in thinkness with diameter of a coin). And i also believe there's a pre-tuned oscillator circuit that came along with it. What i am trying to manipulate from this thing, is to take the input terminal of the alarm module and connect it to Vcc(+5V) instead of the battery.

Also for the note, the connection between the circuit to the piezo buzzer seems to be running very high voltage since i got a minor shock(electrocuted) when i accidentaly touched the 2 terminals connecting the buzzer.

I wanted to know, if this is the best method/convenient to get a very loud buzzer as alarm because i think it's troublesome if i am to get a 'vanilla' piezo buzzer and configure it from the scratch for maximum output, hence the idea of using existing alarm buzzer with built-in circuitry.

Oh yes, and about the current limiter resistor, i did not know the actual value to use since i did not know how much current does the whole "alarm module" actually draw (i have no datasheet or whatsoever), so i just insert an arbitrary 1k ohm resistor with the hope not to fry out the pin of the MCU in case anything went wrong.

I liked the idea of the transistor being a switching circuit instead of connecting the +ve and -ve terminal directly to the voltage supply and the P1.0 respectively. In conclusion, i am kind of lost here because i dont know what i did might/might not damage the MCU if something goes wrong.

Fortunately, i did not fried the P1.0 i have tested with during my first 'experiment' because i have tested driving LED using similar current sinking method and it works out fine.


I certainly need advice on this and please pardon my 'newbieness' about this. Thank you very much!