Published July 24, 2022 © LGPL

MAX9814 as Audio Switch

Simple binary on/off audio switch using an off-the-shelf microphone breakout board. Clapper?

BeginnerProtip1 hour472

Things used in this project

Hardware components

Espressif Wemos D1 Mini

Adafruit MAX9814 - Electret Microphone Amplifier with Auto Gain Control

Software apps and online services

Arduino IDE

Story

Motivation

Another project I'm working on includes an OLED display. I want the display to be off most of the time since they have limited lifespans (< 30, 000 hours). I'd prefer not to need to replace the display after a few years of operation.

So, I'm looking for a simple switch to turn the device on and off and I'm trying to use parts I already have. First I tried a piezo transducer as a "knock sensor" but that didn't seem to work.

Next I found an Adafruit MAX9814 breakout board: simple microphone and amplifier.

Solution

The MAX9814 is definitely overkill for making an audio switch, but hey, that's what I had lying around.

Hooking up the MAX9814 is super easy if you only hook up GND, VDD and OUT. I played with the 3 attack response (AR) options and the 3 Gain options (3x3 = 9 variants in total) so you don't need to: just leave both these pins floating (default options are fine).

I tried various sounds for throwing my switch: clapping, whistles, words, etc. In my case, I'm happy if any significant noise turns my OLED display on since it will be in the garage which is a fairly quiet environment for the majority of the time.

My demonstration code toggles an LED using a Wemos D1 Mini but it is fairly generic Arduino fare: just find yourself an analog input pin and a GPIO pin on any Ardiuno. I use some delay()s simply because it needs to behave the same way on faster MCUs (faster than the 16MHz Uno for example).

Circuit

Wemos D1 Mini and MAX9814

MAX9814 as Audio Switch

#define LED_PIN 5    // D1 on Wemos D1 Mini
#define KNOCK_PIN 17 // A0 on Wemos D1 Mini

// Start with a low value and test what works in your environment via the Serial Monitor
const int threshold = 805; 

// Comment this out once you've calibrated your threshold
//#define SERIAL_MONITOR

int inputFromMAX9814 = 0;
bool switchState = false;

void setup() 
{
  pinMode(LED_PIN, OUTPUT);
#ifdef SERIAL_MONITOR  
  Serial.begin(115200); 
#endif
}

void loop() {
  // read the sensor and store it in the variable sensorReading:
  inputFromMAX9814 = analogRead(KNOCK_PIN);

  if (inputFromMAX9814 >= threshold) 
  {
#ifdef SERIAL_MONITOR      
    Serial.println(inputFromMAX9814);
#endif
  switchState = !switchState;
    digitalWrite(LED_PIN, switchState ? HIGH : LOW);

    // this delay ensures that we only trigger our switch once per second ("debouncing")
    delay(1000);
  }
  delay(1);
}

Credits

Michael Cartwright

21 projects • 13 followers