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Arduino sketch for controlling music amp power (via relay) from audio signal
/*
* 2020 Jon Robinson
* MIT License
* Arduino sketch which using envelope/peak detector circuit output signal to detect if music playing.
* Opens/ closes a relay accordingly - relay intended to switch amp on and off.
*/
// Two analog pins connected to envelope detector circuits
// one for left channel, one for right channel
int _aSoundPin = A5;
int val = 0; // variable to store the signal read from pins
const int _onoffPin = 7; // manual switch to turn function on and off
/*
* LED show status:
* - green only: music playing (relay closed)
* - red only: no music (relay open)
* - green and red: no musuc playing, will open relay in X seconds unless music detected again
*/
const int _redPin= 4;
const int _greenPin = 5;
const int _relayControlPin = 2;
const int SILENCE_THRESHOLD = 5;
const long SILENCE_TIME_TO_TRIGGER_POWEROFF = 1000*10; // 10 secs of silence turns off amp
const long TIME_TO_TRIGGER_SILENCE = 1000;
const long AFTER_RELAY_CHANGE_DELAY = 300; //ms. To address noisy ground relay seems to cause.
const int STATUS_MUSIC = 0;
const int STATUS_SILENCE = 1;
const int STATUS_POWEROFF = 2;
const int STATUS_UNDEFINED = 100;
int _status = STATUS_SILENCE;
int _oldStatus = STATUS_UNDEFINED;
int _onoff;
unsigned long _lastSilentStartTime = 0;
unsigned long _lastNotSilentTime = 0;
unsigned long _lastRelayChangeTime = 0;
void setup()
{
// Serial.begin(9600);
pinMode(_onoffPin,INPUT_PULLUP);
// rgb led
pinMode(_redPin, OUTPUT);
pinMode(_greenPin, OUTPUT);
// relay
pinMode(_relayControlPin, OUTPUT);
}
void loop()
{
_onoff = digitalRead(_onoffPin);
if (_onoff == LOW){
// Turn off/by-pass control function
digitalWrite(_relayControlPin, HIGH); //open relay
_lastRelayChangeTime = millis();
_oldStatus = STATUS_UNDEFINED;
digitalWrite(_greenPin, LOW);
digitalWrite(_redPin,LOW);
}
//read enveloped sound value on soundPin
if (millis() - _lastRelayChangeTime >= AFTER_RELAY_CHANGE_DELAY && _onoff == HIGH){
val = analogRead(_aSoundPin);
if (val>SILENCE_THRESHOLD){
_lastNotSilentTime = millis();
_status = STATUS_MUSIC; // debug value
} else {
if (_status==STATUS_MUSIC){
unsigned long dt = millis() - _lastNotSilentTime;
if (dt >= TIME_TO_TRIGGER_SILENCE) {
_status = STATUS_SILENCE;
_lastSilentStartTime = millis();
}
} else if (_status == STATUS_SILENCE) {
unsigned long dt = millis() - _lastSilentStartTime;
if (dt >= SILENCE_TIME_TO_TRIGGER_POWEROFF){
_status = STATUS_POWEROFF;
}
}
}
if (_oldStatus!=_status){
switch(_status){
case (STATUS_MUSIC):
digitalWrite(_relayControlPin, HIGH); //open relay
_lastRelayChangeTime = millis();
digitalWrite(_greenPin, HIGH);
digitalWrite(_redPin,LOW);
break;
case (STATUS_SILENCE):
digitalWrite(_greenPin, HIGH);
digitalWrite(_redPin,HIGH);
break;
case (STATUS_POWEROFF):
digitalWrite(_greenPin, LOW);
digitalWrite(_redPin,HIGH);
digitalWrite(_relayControlPin, LOW); //close relay
_lastRelayChangeTime = millis();
break;
}
_oldStatus = _status;
}
}
}
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