Microphone preamplifier circuit not sensitive enough

Thread Starter

Amina96

Joined Sep 17, 2018
6
Hi everyone!

In my sound spectrum analyzer project, I'm using a MAX9812 mic preamplifier, an Arduino Nano and an OLED display. The mic preamplifier is powered with 3.3 V. Quite simple, but I'm having trouble because the microphone is not sensitive enough. Basically, I have to come very close to it, to shout in it to have some results on the OLED :/ It is not very practical, so if anyone could point out what I should do, I'd be grateful. I've tried to manipulate the code and to set the analogReference to external (the same voltage I'm using to supply the mic circuit) and it's a bit better, but still not satisfactory.
Is there a way to manipulate the code, or to add something to the circuit, or should I just buy a better microphone? If yes, which one?
If there are any other specifications you need, tell me.
Thank you all very much for the help.
 

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Thread Starter

Amina96

Joined Sep 17, 2018
6
The mic is fine. You need an extra gain of 10-30 after the MAX9812.

Do you have the correct DC bias on the mic?
Show us the circuit diagram of what you have now.
The mic is fine. You need an extra gain of 10-30 after the MAX9812.

Do you have the correct DC bias on the mic?
Show us the circuit diagram of what you have now.
I attached the diagram. The mic I'm using is MAX9812 (not MAX4466 as in the diagram). I also attached what I get on the serial plotter when I speak "normally".circuit schematic.png analogread.jpg
 
Hello Amina, as MrChips said, you either want to increase the gain of the mic to about 40dB, or you can try lowering your arduino's ADC reference voltage level. Not sure about this one, but in default, arduino's Vref is set to 5V. You could try lowering it to about 1V by supplying the 1V to REF pin.
 
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