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This question already has an answer here:

This is Aakash. Student of Electrical Engineering in a University. I want to ask some information. Today I Purchased Arduino UNO R3 board. and facing some problem which are :

          "**Builtin LED at pin#13 is always ON on my board**".

Builtin LED is ON Is there any problem with the board ?

I tried to upload these sketches and got these results:: 1)...with empty setup(){} and empty loop(){}, Still LED is ON. 2)...When I uploaded these command "pinMode(LED_BUILTIN,OUTPUT);" in setup() and "digitalWrite(LED_BUILTIN,LOW);" in loop(), LED turned OFF 3)...If i touch pin13 and Ground both by a wet finger at back of board, LED turns OFF. 4)...but on uploading empty or any other code, BUILTIN_LED turns ON again and do not turns OFF.

Kindly reply me ASAP! So that if i have got faulty Board then i might go for claim.

marked as duplicate by Maximilian Gerhardt, Juraj, jfpoilpret, gre_gor, jose can u c Feb 19 '18 at 19:48

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This is a normal thing. All my arduino boards do the same. The reason for this is that the micro controller don't care about the pins that aren't defined in the code. When they aren't defined they all have a HIGH on them. Here is my board with this code:

void setup() {
}
void loop() {                
}

enter image description here

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