Battery provides inconsistent power

[burning_toast]

When I use a USB cord to power my Arduino, the connected piezo buzzer provides a consistant noise.
However, when I use a 9V battery to power my Arduino (both using battery jack, and VIN), the buzzer is extremely inconsistent, making the buzzer sound like a geiger counter.

Piezo wiring is just a digital pin connected to the + end, and a resistor connected to the - end.
Also, the buzzer sounds normal when it it connected directly to 5V, instead of a digital pin.

The code just sets the pin to output, then uses tone() to play a noise.

[LarryD]

• Some piezo buzzers make sound by an internal circuit when connected to power.
  Are you saying your buzzer is like that.

• Please tell us you are not trying to use a 9v battery like this.

[jremington]

@burning_toast

Also, the buzzer sounds normal when it it connected directly to 5V

That sounds like an active buzzer, not a piezo disk, and it cannot be powered by a digital pin. Use a piezo disk buzzer instead.

9V block batteries are for low power devices like smoke alarms, and are generally not useful for Arduino applications.

[burning_toast]

Ok, thank you very much.

How would you recommend battery powering the arduino?

[LarryD]

• How long will it need to be powered ?

[PaulRB]

If you have NiMH rechargeable AA batteries and a charger for them, you can use 4 of these in a holder like those shown by @LarryD above. This will provide around 5V and so can be connected to the 5V pin on the Arduino.

[jonathanzcode]

Rechargeable AA batteries would be useful. However, be mindful of the run-time of the arduino. Different AA batteries have different capacities (measured in mAh).