It seems my Arduino doesn't work

Question

I've got an Arduino Uno.

I was building a simple circuit with only one switch and it doesn't seem to work (I followed the Arduino project book from the Arduino starter kit).

This is my circuit :

Then I try again to move the switch and then it works (but I don't understand why).

So I tried to understand where the error is and I try to read digital input from the simple circuit with only one LED :

And this is my code :

int SWITCH = 13;

void setup() {
    Serial.begin(9600);
    pinMode(SWITCH, INPUT);
}

// the loop routine runs over and over again forever:
void loop() {
    int val;
    val = digitalRead(SWITCH);
    if(val == HIGH) {
        Serial.println("OKAY");
    }
}

I expect to see on the Serial Monitor "OKAY OKAY" and so on... but nothing appears on the Serial monitor.

Then I try to change the condition :

if(val == LOW)

And now I see "OKAY OKAY" and so on...

I think that there is something wrong with this Arduino... Can someone tell me something about what is happening? Am I stupid or there is really something wrong with this?

Answer 1

It looks to me like your arduino is working just fine.

In the first two images you use the arduino only to provide 5v power to the circuit on the breadboard. In the first image you haven't connected your button to properly function as a button. I don't know the exact pin layout of the button (which should be explained in a datasheet of that button), but it is also good to know exactly how to holes in a breadboard are connected. This picture shows why your button works on your second image but not your first:

This picture also shows how the breadboard holes are connected:

In your third image you have practically connected input pin 13 to GND, so it makes sense that digitalRead(13) in your code always returns LOW. Thus, the variable var is always LOW (or 0). Thus, the comparison (var == HIGH) is FALSE, which won't send "OKAY" to the serial monitor. And, the comparison (var == LOW) is TRUE, which will* send "OKAY" to the serial monitor.

I hope you can follow the logical steps and it is clear to you what is happening.