Sound spectrum analyzer-difficulty detecting sound with a sound module

Thread Starter

Amina96

Joined Sep 17, 2018
6
Hey all! I'm very happy to have discovered this website.
So my project was to make a sound spectrum analyzer (circuit in the attachment) and the software part is fine, but I have a problem with the microphone. I should note that my microphone does NOT have adjustable gain like in the picture, I am using MAX9812 (also in the attachment). Even though the module has an integrated circuit, the OLED display only shows something when signal has a single frequency and is very intense (loud), and this is done by using a frequency generator on my phone and bringing it very very close to the microphone.
I have been trying to build a circuit on my own using an electret microphone, LM324 op-amp and some capacitors and resistors but have failed everytime.
Does anyone have any brilliant ideas?
Btw, sorry if I missed some essential information, just ask and I'll write it as soon as possible. The circuit that I built is also in the attachments (I took it from some previous post) but still doesn't work.
I hope someone can help :) I would really like to understand this.

Amina
 

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Thread Starter

Amina96

Joined Sep 17, 2018
6
Welcome to AAC!
What is the amplitude of the microphone output?
Welcome to AAC!
What is the amplitude of the microphone output?
I'm probably going to give a vague answer to this:
Since my supply is 3.3 V, a very loud noise (or a tap on the microphone etc. gives me peak-to-peak around 700 on the serial plotter (from 0 to 700 and the range is from 0 to 1023)
 

KeithWalker

Joined Jul 10, 2017
895
In your pre-amp circuit you show one end of the potentiometer R1 connected to ground. That is wrong. If the pot is at one extreme position, the output of the op-amp is shorted to ground. At the other extreme, the gain will be unity.
Disconnect the end of R1 from ground and leave it connected as a variable resistor between pins 1 and 2. You will then be able to adjust the gain correctly. from unity to about x 500 (depending on the open loop gain of the op-amp you are using).
 
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