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Topic: (Solved) Buzzer won't buzz. (Read 132 times) previous topic - next topic

thehardwareman

Jan 18, 2021, 08:21 pm Last Edit: Jan 18, 2021, 08:47 pm by 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

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

groundFungus

#2
Jan 18, 2021, 08:32 pm Last Edit: Jan 18, 2021, 08:33 pm by 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.

No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

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.

Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

Wawa

#9
Jan 18, 2021, 09:03 pm Last Edit: Jan 18, 2021, 09:03 pm by 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

#11
Jan 19, 2021, 02:01 pm Last Edit: Jan 19, 2021, 02:02 pm by TomGeorge
Hi,
For those of us that can't see the circuit;



Best to attach the image file.

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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