can someone tell me why my L led on arduino uno glowing continuously I tried restarting my pc, changing USB port I also tried uploading an empty file and resetting the Arduino board but nothing seems to work. Does it mean I have to buy a new one?

  • What happens if you upload the example blink sketch? And what, if you try to blink an LED on another pin (you need an extra LED for this) – chrisl Nov 18 '19 at 12:58
  • … and a resistor – Michel Keijzers Nov 18 '19 at 13:00
  • 2
    Some Arduino boards drive that LED through an op-amp. If pin 13 is set to INPUT Then the input to the op-amp will be effectively floating. That can cause the LED to glow since it lacks further instruction on what to do. – Majenko Nov 18 '19 at 14:37
  • I ran a blink code using pin 13 and an LED both L and LED is now blinking. But if I ran an empty code the L led is on continuously also if I connect an LED with the empty code uploaded both the L Led and external LED goes out – JacksonPro Nov 18 '19 at 15:42
  • Does L LED glowing continuously mean something? bcuz the programs that I run seem to do the work – JacksonPro Nov 18 '19 at 16:25

Don't let that pin float undefined: If undefined (INPUT), pull it to GND to have the led OFF.

If ever possible, try to use the LED_BUILTIN pin as an OUTPUT pin.

And signal some information there. On an UNO (or other 328-based Arduino), this hint might collide with the SPI_SCK pin, which is D13 (PB5 on an atmega328). But as an SPI Master, this pin is at least OUTPUT (and thus will signal SPI activity).

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