I have an Arduino Pro Mini 3.3v and the voltage is too small for my buzzer to ring loudly. I want to add a 9v battery to power the buzzer.

This is my current circuit:
Arduino (pin 9) => Buzzer +ve
Arduino Gnd => Buzzer -ve

I want to power the buzzer using an external 9v battery but I have no idea how to implement it in the circuit. All I know is that the ground should be common.

What next?

2 Answers 2


You can use an NPN transistor for this purpose.

All you have to do is connect it this wayenter image description here

Obviously use a buzzer instead of the motor and pin 9 instead of 4 :D

Arduino (pin 9)==>1k-10k Resistance==>Transistor base

Buzzer +ve ==> + 9V

Buzzer -ve ==> Transistor collector

Transistor Emitter ==> battery -ve ==> Arduino GND.

So now whenever you set the pin 9 to HIGH the transistor would allow current to pass through it from collector to emitter and your buzzer would work just as you wanted.

  • Sounds good... I was thinking of doing something similar!
    – YaddyVirus
    Commented Dec 30, 2016 at 11:57
  • Thnx :D you can upvote if this helped you :)
    – Manav
    Commented Dec 31, 2016 at 5:26

Use a MOSFET. They are like little electronic switches. They will work fine with the 9V that you want to use.


  • In this case a regular transistor will also work fine. Use an NPN transistor. The connect the 9V to +ve of the buzzer; -ve of the buzzer to the Collector of the transistor. - of the battery to both GND and the Emitter of the transistor. Connect the Base of the transistor via a resistor (e.g. 1kOhm) to an Arduino pin.
    – Gerben
    Commented Dec 28, 2016 at 18:51
  • I find a MOSFET just simpler. They are more reliable for beginners.
    – Dat Ha
    Commented Dec 28, 2016 at 18:53

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