Problems with Electret Microphone MAX4466

[jeff009]

Hello,

I purchased an Electret Microphone MAX4466 and I'm having some issues with
getting it to work. I followed the wiring instructions at
https://learn.adafruit.com/adafruit-mic ... and-wiring

To test it, I created a sketch similar to the one at
https://learn.adafruit.com/adafruit-mic ... und-levels


Code is:
unsigned int minSample;
unsigned int maxSample;


void setup()
{
Serial.begin(9600);

minSample = 1024;
maxSample = 0;
}

void loop()
{
unsigned int sampleValue = analogRead(0);

if(maxSample < sampleValue)
{
maxSample = sampleValue;
}

if(minSample > sampleValue)
{
minSample = sampleValue;
}

Serial.print("Current: ");
Serial.print(sampleValue);
Serial.print(" Minimum: ");
Serial.print(minSample);
Serial.print(" Maximum: ");
Serial.println(maxSample);
}


With the gain screw turned all the way clockwise, I'm typically getting
Minimum: 223 Current: 337 Maximum: 550
* Ambient noise level is around 337
* When I clap (close to the mic) I was able to get up to 550 (but that's
out of 1024)
* Ambient noise level stays constant around 330-340. When I clap, I
noticed that the "minimum" went down (which I didn't expect)


With the gain screw turned all the way counter-clock wise, I'm getting
(with ambient noise)
Minimum: 307 Current: 321 Maximum: 361
After I clapped, I got:
Minimum: 197 Current: 339 Maximum: 421
so...
1) The max did go up a little bit it's still 421/1024
2) The min went down after I clapped


(these are pretty loud claps, fairly close to the mic).



Is there a problem w/my code, or do I have a faulty mic?

Thanks,

Jeff

[adafruit_support_mike]

If you've connected the microphone to the 3.3v pin on your Arduino, the highest ADC reading you can possibly see will be 676.. 3.3/5ths of 1024.

The 337 ambient reading corresponds to a quiescent voltage of 1.65v, which is exactly what I'd expect from a 3.3v supply.

[jeff009]

Thanks for clearing it up. This makes sense now.

Thanks!

Jeff

[awleonard1]

Thought this would be the best place to ask this since it is right in line with the same issue. My values at ambient noise are lower than 1.65/338 steps. Since they are scrolling so fast, it is hard to figure an average, but I'd say between 250 and 290. What might be the reason for that? Thanks for the help, I am still trying to learn about this stuff. The above reply helped me along quite a bit as I didn't think about the fact that 3.3 was the max.

Oh, the gain wire is loose at the moment. Attaching it to Vcc didn't seem to make much if any difference.

EDIT: I found that the DC bias is 1.25 according to the product description. That would put my ambient noise readings right in line at a little above "silence."

Thanks,

Tony