Arduino and MAX4466 electret module example

In this article we look at an electret microphone which uses a MAX4466 op amp – you can buy these max4466 modules

Lets look at what Maxim say about the MAX4466

The MAX4465–MAX4469 are micropower op amps optimized for use as microphone preamplifiers. They provide the ideal combination of an optimized gain bandwidth product vs. supply current, and low-voltage operation in an ultra-small package. The MAX4465/MAX4467/MAX4469 are unity-gain stable and deliver a 200kHz gain bandwidth from only 24µA of supply current. The MAX4466/MAX4468 are decompensated for a minimum stable gain of +5V/V and provide a 600kHz gain bandwidth product. In addition these amplifiers feature rail-to-rail outputs, high A_VOL, plus excellent power-supply rejection and common-mode rejection ratios for operation in noisy environments.

The MAX4467/MAX4468 include a complete shutdown mode. In shutdown, the amplifiers' supply current is reduced to 5nA and the bias current to the external microphone is cut off for ultimate power savings. The single MAX4465/MAX4466 are offered in the ultra-small 5-pin SC70 package, while the single with shutdown MAX4467/MAX4468 and dual MAX4469 are available in the space-saving 8-pin SOT23 package.

Features

• +2.4V to +5.5V Supply Voltage Operation
• Versions with 5nA Complete Shutdown Available (MAX4467/MAX4468)
• Excellent Power-Supply Rejection Ratio: 112dB
• Excellent Common-Mode Rejection Ratio: 126dB
• High A_VOL: 125dB (R_L = 100kΩ)
• Rail-to-Rail Outputs
• Low 24µA Quiescent Supply Current
• Gain Bandwidth Product:
  • 200kHz (MAX4465/MAX4467/MAX4469)
  • 600kHz A_V ≥ 5 (MAX4466/MAX4468)
• Available in Space-Saving Packages
  • 5-Pin SC70 (MAX4465/MAX4466)
  • 8-Pin SOT23 (MAX4467/MAX4468/MAX4469)

Connection

arduino and max4466

Parts List

Here are the parts I used

Code

This is actually an adafruit example which uses sampling – you could also simply read the analog value in. This is better

[codesyntax lang=”cpp”]

const int sampleWindow = 50; // Sample window width in mS (50 mS = 20Hz)
unsigned int sample;
 
void setup() 
{
   Serial.begin(9600);
}
 
 
void loop() 
{
   unsigned long startMillis= millis();  // Start of sample window
   unsigned int peakToPeak = 0;   // peak-to-peak level
 
   unsigned int signalMax = 0;
   unsigned int signalMin = 1024;
 
   // collect data for 50 mS
   while (millis() - startMillis < sampleWindow)
   {
      sample = analogRead(A0);
      if (sample < 1024)  // toss out spurious readings
      {
         if (sample > signalMax)
         {
            signalMax = sample;  // save just the max levels
         }
         else if (sample < signalMin)
         {
            signalMin = sample;  // save just the min levels
         }
      }
   }
   peakToPeak = signalMax - signalMin;  // max - min = peak-peak amplitude
   double volts = (peakToPeak * 5.0) / 1024;  // convert to volts
 
   Serial.println(volts);
}

[/codesyntax]

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