# Green Flash on Startup

**URL:** <https://wled.discourse.group/t/green-flash-on-startup/6434>\
**Category:** Questions\
**Created:** [November 21, 2022, 6:30pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434 "2022-11-21T18:30:57Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Walfy07](https://avatars.discourse-cdn.com/v4/letter/w/839c29/32.png) [@Walfy07](https://wled.discourse.group/u/Walfy07)\
**Post date:** [November 21, 2022, 6:30pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/1 "2022-11-21T18:30:57Z")

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Hello,

Does anyone have any insight as to why my LED’s (WS2815’s) very briefly do a green flash once on startup?

It seems like they flash when they get 12V and maybe the ESP32 has not started sending data to the LED’s yet?

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**Author:** ![divsys](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@divsys](https://wled.discourse.group/u/divsys)\
**Post date:** [November 21, 2022, 9:40pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/2 "2022-11-21T21:40:51Z")

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Does it occur if you power up the LEDs with no MCU attached to Data IN?

Some GPIO pins will briefly output serial or PWM data on power up.  
You could try a different pin for data.

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<div class="post-metadata">

**Author:** ![Walfy07](https://avatars.discourse-cdn.com/v4/letter/w/839c29/32.png) [@Walfy07](https://wled.discourse.group/u/Walfy07)\
**Post date:** [November 21, 2022, 10:32pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/3 "2022-11-21T22:32:09Z")

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Yes.

I have a ESP32 dev board hooked up to a SN74AHCT125.

When I turn on the +12v with the DATA lines unplugged I see **some** of the LED’s do a very brief green flash. (~5%).  
On another setup I have they all do the brief green flash and it appears brighter/longer. Still prob less then 250 ms.

Could it have to do with the rise time of the 12v?

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<div class="post-metadata">

**Author:** ![tonyno](https://yyz2.discourse-cdn.com/free1/user_avatar/wled.discourse.group/tonyno/32/242_2.png) [@tonyno](https://wled.discourse.group/u/tonyno)\
**Post date:** [November 23, 2022, 3:17am UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/4 "2022-11-23T03:17:23Z")

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That is why a relay is supported. It keeps LED power off until the ESP boots.

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<div class="post-metadata">

**Author:** ![divsys](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@divsys](https://wled.discourse.group/u/divsys)\
**Post date:** [November 23, 2022, 6:36am UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/5 "2022-11-23T06:36:46Z")

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Yah possibly one way to check would be to use a 12V Gel cell as your power source and no data.  
Should have huge startup current capability.  
Do you have any capacitors in parallel with the strip?

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<div class="post-metadata">

**Author:** ![Walfy07](https://avatars.discourse-cdn.com/v4/letter/w/839c29/32.png) [@Walfy07](https://wled.discourse.group/u/Walfy07)\
**Post date:** [November 23, 2022, 3:10pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/6 "2022-11-23T15:10:08Z")

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Thanks for the replies. I think The latest version of LED chip may fix this issue.  
Backup plan will be to add a small relay.  
Does the relay only come on after DATA is being sent out?

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<div class="post-metadata">

**Author:** ![tonyno](https://yyz2.discourse-cdn.com/free1/user_avatar/wled.discourse.group/tonyno/32/242_2.png) [@tonyno](https://wled.discourse.group/u/tonyno)\
**Post date:** [November 23, 2022, 11:58pm UTC](https://wled.discourse.group/t/green-flash-on-startup/6434/7 "2022-11-23T23:58:05Z")

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It comes on when the brightness is over zero.