I have an active buzzer connected to an Arduino and everything works fine but the buzzer is just not loud enough. I don't know any specs about the buzzer but I've tried connecting it to a 9v battery using a transistor with the collector connected to +9v, the base connected to the digital output pin of the Arduino, and the emitter connected to the buzzer. This did not seem to do anything different. I tried using a passive buzzer as well using a PWM pin, but I was not able to achieve the same results so I'd like to stick with the active buzzer. Thank you.

  • \$\begingroup\$ Active buzzers have specs limiting their maximum current and voltage and thus output power. If you want a louder buzzer look into a better hardware. \$\endgroup\$
    – nabulator
    Jun 17, 2018 at 4:54
  • \$\begingroup\$ Try 12V or get specs \$\endgroup\$ Jun 17, 2018 at 4:58
  • \$\begingroup\$ something like this maybe? ... youtube.com/watch?v=8zEH5GxPNO8 \$\endgroup\$
    – jsotola
    Jun 17, 2018 at 5:34
  • \$\begingroup\$ @jsotola I assume that guy lives alone. I would be flayed alive for making something like that. My iPad "old car horn" is bad enough (secondary alarm if the gentle first one doesn't work). \$\endgroup\$ Jun 17, 2018 at 6:01

1 Answer 1


Put the buzzer in the collector circuit and it should be about as loud as it is connected directly to the 9V source. If that's not loud enough, get another buzzer. Hopefully it's rated to work with 9V.


simulate this circuit – Schematic created using CircuitLab

You were connecting it as an emitter-follower which gives you about 0.7V less than the logic input voltage (4.3V with 5V logic) and the remainder (4.7V with a 9V supply) wasted in the transistor. A higher supply would just result in more wasted power. Depending on how much load the buzzer represents the emitter follower may result in a bit less loud than a direct connection or a bit louder (since the MCU output will be loaded significantly by most buzzers and you won't get the full 5V out).

  • \$\begingroup\$ 4.7V wasted, or 0.7? \$\endgroup\$
    – gbarry
    Jun 17, 2018 at 5:08
  • \$\begingroup\$ @gbarry 4.7 if you have the collector connected to 9V (as OP did). 0.7V if you have the collector connected to 5V. In both cases, the buzzer sees 4.3V. \$\endgroup\$ Jun 17, 2018 at 5:12
  • \$\begingroup\$ But why the diode? Are buzzers significantly inductive? \$\endgroup\$ Jun 17, 2018 at 9:02
  • \$\begingroup\$ @VladimirCravero Some of them are magnetic, some are piezo. If magnetic they may not have any bypassing so when they shut off the voltage might spike up. Probably not to the 60V that would begin to threaten a 2N4401 but putting a diode in there causes no harm and is cheap. \$\endgroup\$ Jun 17, 2018 at 12:54

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