Arduino Mega LED_BUILTIN always on unless I write it low

I just started working with a Mega. When I first powered it up LED_BUILTIN was blinking.

My first thought was that possibly it comes with the 'blink' sketch loaded as a check to see if it functions.
I uploaded an empty sketch to clear out anything that may be running.

Now it is no longer blinking, but it is on steady.

I can easily digitalwrite it low in each sketch to turn it off, but I am concerned this is possibly a symptom of something else.

I have read others saying they have it light dimly, mine lights bright.
I did notice that when I try to measure the voltage between 13 and gnd (about .3 volts) they LED does turn off, but turns right back on when I remove the multi meter.

Any thoughts?
Any reason for concern?

No reason for concern. If you look at the schematic of the Mega (R3), the LED is driven by a LM358 (connected to pin 13).

If the input of the LM358 is not driven (which is the case when pin 13 is an input), it will pick up noise and that will light up the led. That's my understanding with my rusty electronics knowledge.

And Arduinos come preloaded with the blink sketch, so that was the initial blink that you observed.

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.