I'm trying to teach myself some basic electronics and coding (eventually, hopefully) via a Mega 2560 Arduino kit. I've been working through some tutorials but i'm trying to understand the principles behind the circuits rather than just copying by rote. I discovered a tutorial for putting a tune through a passive speaker and noticed in the code that it also had active pins for LEDs (not mentioned in the accompanying description) and decided to attempt to wire them in.
It worked and they flashed with the music but then I noticed that I had forgotten to connect the wire i had in the negative rail to the ground on my board but the circuit was still complete and functioning. Is anyone able to give me any insight as to why this is please? I understood the ground to be like the negative pole of a battery so i'm unsure how the circuit is functioning without that connection. I've attached a circuit diagram I made on Fritzing and the code was as follows:
const int c = 261;
const int d = 294;
const int e = 329;
const int f = 349;
const int g = 391;
const int gS = 415;
const int a = 440;
const int aS = 455;
const int b = 466;
const int cH = 523;
const int cSH = 554;
const int dH = 587;
const int dSH = 622;
const int eH = 659;
const int fH = 698;
const int fSH = 740;
const int gH = 784;
const int gSH = 830;
const int aH = 880;
const int buzzerPin = 8;
const int ledPin1 = 12;
const int ledPin2 = 13;
int counter = 0;
void setup()
{
//Setup pin modes
pinMode(buzzerPin, OUTPUT);
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
}
void loop()
{
//Play first section
firstSection();
//Play second section
secondSection();
//Variant 1
beep(f, 250);
beep(gS, 500);
beep(f, 350);
beep(a, 125);
beep(cH, 500);
beep(a, 375);
beep(cH, 125);
beep(eH, 650);
delay(500);
//Repeat second section
secondSection();
//Variant 2
beep(f, 250);
beep(gS, 500);
beep(f, 375);
beep(cH, 125);
beep(a, 500);
beep(f, 375);
beep(cH, 125);
beep(a, 650);
delay(650);
}
void beep(int note, int duration)
{
//Play tone on buzzerPin
tone(buzzerPin, note, duration);
//Play different LED depending on value of 'counter'
if(counter % 2 == 0)
{
digitalWrite(ledPin1, HIGH);
delay(duration);
digitalWrite(ledPin1, LOW);
}else
{
digitalWrite(ledPin2, HIGH);
delay(duration);
digitalWrite(ledPin2, LOW);
}
//Stop tone on buzzerPin
noTone(buzzerPin);
delay(50);
//Increment counter
counter++;
}
void firstSection()
{
beep(a, 500);
beep(a, 500);
beep(a, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 650);
delay(500);
beep(eH, 500);
beep(eH, 500);
beep(eH, 500);
beep(fH, 350);
beep(cH, 150);
beep(gS, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 650);
delay(500);
}
void secondSection()
{
beep(aH, 500);
beep(a, 300);
beep(a, 150);
beep(aH, 500);
beep(gSH, 325);
beep(gH, 175);
beep(fSH, 125);
beep(fH, 125);
beep(fSH, 250);
delay(325);
beep(aS, 250);
beep(dSH, 500);
beep(dH, 325);
beep(cSH, 175);
beep(cH, 125);
beep(b, 125);
beep(cH, 250);
delay(350);
}
