0

On a Raspberry Pi 4, and I've noticed that the red idle LED light remains on even when the device is turned off. While I understand this might be a default behavior, I'm looking for a way to turn off the red idle LED light completely when the Raspberry Pi is powered down.

I've tried this:

{ crontab -l; echo "@reboot echo 0 | sudo tee /sys/devices/platform/leds/leds/PWR/brightness > /dev/null"; } | crontab -

which turns the led light off when the device is powered on, but the light is on when the devices is powered off.

user3607022
  • 103
  • 4

2 Answers2

1

Turn off the power supply.
The Red LED will light whenever 5V power is supplied unless you have running firmware to turn off the software.

NOTE It is possible to configure the Pi4 to enter a low power state when shutdown.
This was originally the default but changed (to prevent the PMIC from shutting down) as many vendors had produced hardware assuming 3.3V was always present (as was the case for all earlier models).

This won't affect the 5V power (and thus LED) as the Pi has no control over 5V power because 5V is connected to 5v input.

Milliways
  • 59,890
  • 31
  • 101
  • 209
1

As @CoderMike has pointed out in his comment, once your RPi goes into shutdown, it is no longer under software control. And since your method for extinguishing the light is in software, it simply can't work.

Also, you made a statement in your Q that reflects some confusion:

the light is on when the devices is powered off.

But your device is not actually powered OFF!! Here's the thing to know about all RPis:

Unless you have disconnected power from the RPi, it is NOT OFF.

Your RPi is not OFF - it is in shutdown; all that means is that the processor is no longer "processing". All of the circuitry on the RPi is still connected to the 5V supply, and it does draw some current.

It might interest you to know just how much power your RPi 4 is using when it is plugged in, but in shutdown. There was a Q&A on that about 3 years ago, and there are some actual measurements recorded here.

Seamus
  • 21,900
  • 3
  • 33
  • 70
  • Thank you for clarifying the distinction between shutdown and being powered off. It's interesting to note that the Raspberry Pi remains in a shutdown state, drawing some current. – user3607022 Feb 15 '24 at 20:04
  • 1
    @user3607022: Ya - it was a surprise to me also when I first learned of it. These RPis are designed to yield lowest manufacturing costs, and the power "shutoff circuitry" was eliminated. I think that's actually enlightening in a way :) – Seamus Feb 15 '24 at 21:04
  • sudo no pun intended. actually quite cool that they eliminated that circuit to keep cost down, it almost seems like a feature. Thanks – user3607022 Feb 17 '24 at 14:10