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.
Electronic – How to make active buzzer louder
piezo-buzzer
Related Solutions
I would recommend to use a transistor, even when the required current is low. A piezo buzzer is highly capacitive, and microcontroller outputs usually can drive only small capacitances.
For the speaker you also want the transistor. The reason why your setup only produces very low sound volume is that the resistor and speaker form a voltage divider, so that the speaker only sees \$\dfrac{8}{8 + 500}=1.5\%\$ of the microcontroller's output voltage. You have to place a flyback diode over the speaker.
Your NPN power transistor seems to be connected up wrongly.
I'd expect something like this ...
simulate this circuit – Schematic created using CircuitLab
where
- R1 limits base current and protects P1. \$R_1 = 5V - V_{BE(sat)} / I_B(20mA?)\$
- R2 limits LED current. \$R_2 = (18V - V_{LED} )/ I_{LED}\$
- Q1's collector is connected to the LED's cathode.
Perhaps your LED is actually an 18V LED module that has current-limiting built in?
Note: I believe piezo buzzers don't draw much current, you probably don't need a TIP31 to drive it. Check the specs and choose a more suitable transistor. To be connected as shown, the piezo buzzer should be rated for more than 18V.
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Best Answer
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).