How does an Arduino circuit work

1 channel relay with Arduino Uno R3

I have already written that the circuit works, because I had previously connected a piezo buzzer to data pin 12, where the relay is now, (which I have already described). The only difference was that LOW and HIGH were swapped.

PIR at PIN 2 movement registered -> HIGH at PIN 12 Piezo gives a signal, wait 5s LOW at Pin 12 Piezo gives a signal.

I have, so to speak, recreated this example:

Here is the sketch of the piezo example: And here the circuit diagram: .

I've already posted that too.

Now I just replaced the piezo buzzer with the relay (ttp: //

The photo is from me, as you can see there is only one on_LED on the board, which ONLY lights up when the signal comes, i.e. the control LED. Otherwise I have no POWER_LED there and I have not connected any other LED. The complete relay is built as it can be seen there with a transistor, a resistor, an LED and a diode.

I don't hear any noises, but see that the control_LED lights up when a signal comes, but ONLY when GND and PIN12 are connected. If GND, VCC and PIN 12 are connected, garnix lights up. And that's since the beginning, since I bought it.

The only difference, I didn't know about the HIGH and LOW and that's why instead of sending a LOW signal, I sent a HIGH signal, nothing more.