(Solved) Buzzer won't buzz.

[thehardwareman]

I got into a strange problem.

I got a buzzer and a LED driven by a 2N2222 connected to a MEGA 2560 as shown below.

The problem is that it will not buzz. I just hear a low clicking sound when it is being activated and deactivated. The LED lights up as it should.

When testing the circuit on a breadboard and connecting the resistor (that normally goes to A7) to Vcc, it work fine.

Why does it behave like this?




Here is a link to the image in case you don't see it here.

[larryd]

Make R6 220Ω

[groundFungus]

Lower the value of R6 to 330 Ohms, or so.  7.5K Ohms on the base is going to severely restrict the collector current.

[thehardwareman]

I can try that but I still wonder why it works when connecting the R6 to Vcc instead of A7 on the Mega.

[larryd]

Let's see the actual wiring.

[missdrew]

Because you are letting too small a current flow!

[groundFungus]

What is  the part number of the buzzer?  What is its operating current?

[thehardwareman]

Well, it worked with 330 - thanks.

Guess the combination of the buzzer and the LED was too much with 7k5 (I did not had the LED connected when I tested this circuit on a breadboard).

Part number? Do not know - cheap buzzer from Ali Express

[JohnRob]

I can try that but I still wonder why it works when connecting the R6 to Vcc instead of A7 on the Mega.

Best guess is;  Vcc is 5V the output of A7 is likely to be 4.5v maybe less.


In general for switching applications the base current should be no less that 10% of the collector current.

[Wawa]

I can try that but I still wonder why it works when connecting the R6 to Vcc instead of A7 on the Mega.

Did you set the pin with pinMode to OUTPUT.
Leo..

[Southpark]

I got into a strange problem.

Why does it behave like this?

Avoid calling things 'strange' unless even the 'experts' become puzzled.

It behaves like that because that's how it is expected to behave (or should behave) with that particular setup.

Take a look at Jim Fischer's post at this link here.

[TomGeorge]

Hi,
For those of us that can't see the circuit;



Best to attach the image file.

Tom...