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MAX9814 Microphone Amplifier Module with Auto-Gain Control for Arduino
MAX9814 Microphone Amplifier Module
Auto-Gain Control Electret Mic Amplifier for Arduino Projects
Introduction
The MAX9814 is a complete microphone amplifier with automatic gain control (AGC), featuring low-noise amplification and adjustable gain settings. This module provides clean audio signal conditioning for Arduino sound detection, voice recognition, and audio recording applications.
Key Features
Integrated Mic
High-quality electret microphone
Auto Gain Control
Adjustable AGC for varying input levels
Low Noise
1.5μV input noise (typical)
Low Power
0.4mA shutdown current
Technical Specifications
| Supply Voltage | 2.7V – 5.5V (3.3V or 5V compatible) |
|---|---|
| Gain Range | 40dB, 50dB, 60dB (selectable) |
| Frequency Response | 20Hz – 20kHz |
| Output Type | Analog (AC-coupled) |
| Current Consumption | 3.5mA (typical at 5V) |
| AGC Attack/Release | Adjustable via external capacitor |
Pin Configuration
| Pin | Label | Description | Arduino Connection |
|---|---|---|---|
| 1 | VDD | Power (2.7-5.5V) | 5V |
| 2 | GND | Ground | GND |
| 3 | OUT | Audio Output | A0 (Analog Input) |
| 4 | GAIN | Gain Selection | See gain selection table |
| 5 | AR | AGC Release Control | Optional capacitor to GND |
Gain Selection
| GAIN Pin Connection | Gain | Use Case |
|---|---|---|
| Left open | 60dB | Quiet environments |
| Connected to GND | 50dB | Normal voice levels |
| Connected to VDD | 40dB | Loud environments |
Basic Wiring (Arduino)
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// MAX9814 Connections: // VDD → 5V // GND → GND // OUT → A0 (Analog Input) // GAIN → (See gain selection table) // AR → (Optional 1μF capacitor to GND) // For best results: // - Keep microphone away from noise sources // - Use shielded audio cable for long connections |
Basic Sound Detection
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const int micPin = A0; void setup() { Serial.begin(9600); } void loop() { int soundValue = analogRead(micPin); // Remove DC offset (approx. VCC/2) int adjustedValue = abs(soundValue - 512); Serial.print("Sound Level: "); Serial.println(adjustedValue); // Simple threshold detection if(adjustedValue > 50) { Serial.println("Sound detected!"); } delay(50); } |
Advanced Applications
Audio Visualization
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// FFT analysis with Arduino #include "arduinoFFT.h" arduinoFFT FFT; #define SAMPLES 128 double vReal[SAMPLES]; double vImag[SAMPLES]; void setup() { // Sample audio at consistent intervals } void loop() { for(int i=0; i<SAMPLES; i++) { vReal[i] = analogRead(micPin); vImag[i] = 0; delay(1); // Sample at ~1kHz } FFT.Windowing(vReal, SAMPLES, FFT_WIN_TYP_HAMMING); FFT.Compute(vReal, vImag, SAMPLES, FFT_FORWARD); FFT.ComplexToMagnitude(vReal, vImag, SAMPLES); // Process frequency bins } |
AGC Timing Adjustment
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// Add capacitor to AR pin for: // - Smaller value: Faster AGC response // - Larger value: Slower AGC response // Typical values: 1μF to 10μF // Example wiring: // AR pin → 4.7μF capacitor → GND // (Better for music with dynamic range) |
Clap Detection
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// Detect sudden loud sounds unsigned long lastClap = 0; const int clapTimeout = 500; void loop() { int peak = 0; for(int i=0; i<10; i++) { int val = abs(analogRead(micPin) - 512); if(val > peak) peak = val; delay(1); } if(peak > 100 && millis() > lastClap + clapTimeout) { lastClap = millis(); Serial.println("Clap detected!"); } } |
Audio Recording
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// Record to SD card #include <SD.h> File audioFile; void setup() { SD.begin(4); // CS on pin 4 audioFile = SD.open("audio.raw", FILE_WRITE); } void loop() { int sample = analogRead(micPin); audioFile.write(sample >> 2); // 8-bit conversion delayMicroseconds(125); // 8kHz sampling } |
Troubleshooting
No Signal Output
- Verify power connections (VDD and GND)
- Check electret microphone is properly soldered
- Test with different gain settings
Constant High/Low Output
- Ensure proper DC bias (should be ~VCC/2 at idle)
- Check for shorts in the output connection
- Test with known good module if possible
Excessive Noise
- Add 0.1μF capacitor between VDD and GND
- Keep away from digital noise sources
- Use shorter wires between module and Arduino
