Green led on promini


Can anyone please explain what it means if the red led on promini 3.3V glows when powered but not the green one.

Thank you

The red LED is the power indicator.

The green LED is an indicator on pin D13. It comes on when you make pin 13 HIGH.


I have a sd card breakout board and clk is connected to pin 13. Even though it is high , the green light doesn't glow .

There are a lot of Pro Minis out there, maybe yours needs a jumper to enable the LED on D13. Maybe they installed the LED wrong.

Try to trace out the connections going to D13.


The official datasheet shows an unbuffered green LED connected to pin13, that draws ~9mA when the pin is HIGH. Not sure why they used a 10k resistor for a red LED and a 330ohm resistor for the green LED. Seems like a dumb move to me. 9mA already used means you have to be careful connecting anything else to pin13.

Upload a blink sketch to see if the LED is working.