# Shut down Neopixels on external MCU when main MCU is powered off

**URL:** <https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658>\
**Category:** General Discussion\
**Created:** [April 11, 2024, 5:49am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658 "2024-04-11T05:49:33Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![akrto](https://avatars.discourse-cdn.com/v4/letter/a/f475e1/32.png) [@akrto](https://klipper.discourse.group/u/akrto)\
**Post date:** [April 11, 2024, 5:49am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658/1 "2024-04-11T05:49:33Z")

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Hi!

I am currently running a modified Sovol SV06, with X, Y and dual Z on the main board.  
Extruder stepper is running on a secondary Raspberry Pi Pico and so is two strings of NeoPixels.

Is there a way to make the secondary MCU shut down the NeoPixels when it is detected that the main MCU goes down when I flip the switch to the PSU?

Since this is more of a general question than a configuration specific question I didn´t post my Klippy.log.

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**Author:** ![TheFuzzyGiggler](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/thefuzzygiggler/32/12313_2.png) [@TheFuzzyGiggler](https://klipper.discourse.group/u/TheFuzzyGiggler)\
**Post date:** [April 11, 2024, 7:23am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658/2 "2024-04-11T07:23:29Z")

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> [@akrto](#):
>
> Is there a way to make the secondary MCU shut down the NeoPixels when it is detected that the main MCU goes down when I flip the switch to the PSU

You’re not powering both by the same PSU? Why would you want power to that secondary pico when the main board is offline?

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**Author:** ![akrto](https://avatars.discourse-cdn.com/v4/letter/a/f475e1/32.png) [@akrto](https://klipper.discourse.group/u/akrto)\
**Post date:** [April 11, 2024, 9:03am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658/3 "2024-04-11T09:03:27Z")

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Sorry, I knew that I probably left som information out

1. The Neopixels are powered by a separate 5V wall plug
2. The Pico is powered by the RPi 3B+ that runs Klippy.

The easy way to solve this would probably be to add a relay that is controlled by the 24V from the PSU to cut the 5V from the Wall plug but that was not my question 🙂

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**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\
**Post date:** [April 11, 2024, 10:14am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658/4 "2024-04-11T10:14:18Z")

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See [Configuration - Moonraker](https://moonraker.readthedocs.io/en/latest/configuration/#power)  
You can control GPIOs, external relays etc with Moonraker.

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/klipper/original/1X/64419bf2aac6639e6ef5cef200dcd456b0a01ac3.png) [@system](https://klipper.discourse.group/u/system)\
**Post date:** [June 10, 2024, 10:15am UTC](https://klipper.discourse.group/t/shut-down-neopixels-on-external-mcu-when-main-mcu-is-powered-off/15658/5 "2024-06-10T10:15:07Z")

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