KA2284 Op-Amp-Free Design, Minimal Circuit Realizes LED Level Visualization

				
					/*
  Arduino Audio Frequency Output (Using tone() Function)
  Compatible with: KA2284 module IN connected to Arduino D9, no additional components needed
  Effect: Outputs low → medium → high frequencies sequentially. KA2284 LEDs light up in varying numbers based on frequency/duration
*/

const int audio_pin = 9; // Connect to the IN pin of the KA2284 module
// Define common audio frequencies (in Hz)
int frequencies[] = {196, 262, 329, 392, 440, 523, 659}; // From low C to high La
const int freq_count = sizeof(frequencies) / sizeof(frequencies[0]);

void setup() {
  pinMode(audio_pin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Loop through and output different frequencies, each for 1 second
  for (int i = 0; i < freq_count; i++) {
    int freq = frequencies[i];
    Serial.print("Output frequency: ");
    Serial.print(freq);
    Serial.println(" Hz");
    
    // Output audio signal at the specified frequency
    tone(audio_pin, freq);
    // Sustain for 1 second. During this time, KA2284 detects the level and lights corresponding LEDs
    delay(1000);
    // Stop output, pause for 0.5 seconds
    noTone(audio_pin);
    delay(500);
  }
}