Hi, I’m bit new to this word of ESP and WLED and tried my best but…
I guess i made one of this grounding problems in my project and do not know how to get it fix.
Maybe someone can help. Tried my best to skizz the project in the best way i can. 
*edit capacitor is wrong, he is currently between red and black not as shown
The Idea war to have the ESP running all time and switch on the big power supply only if needed. Did i made it that wrong or do i have to ground both circles together.
You have to connect all DC grounds together.
You have few errors on your diagram.
#1: Your fuse is on the ground and should be on the hot side.
#2: I would be more worried about putting a fuse after the 5v converter to the led strip.
#3: You don’t need to have the grounds going through that relay. Just wire all the grounds together.
#4: You don’t need two 5v converters. You could use just 1 and split off the + wire 1 to the esp and 1 to the relay common. Then from the relay NO to the leds/cap.
Sorry for the bad diagram rework lol. It was quick and dirty. You can also get rid of the data split going to the 2 relays as you only need to use the 1 relay.
Okay , about #1 - #3 my Apartment is old and the ground and earth is the same. I measured some wall outlets and the hot side isnt the same at all.
So i never no whats hot, if i turn the plug it changes…
@ #4 The Idea is to switch off the big power supply, dont want to have this running if not needed.
At the moment i use an 5v 20A for testing.
DO NOT MIX AC and DC grounds!
Where did i say to mix AC and DC?
i Just asked if i have to Connect the 2 Grounds from the 5v PS. otherwise i guess there is no reference for the PWM signal from the ESP what results in the crazy flicker?
All DC grounds (0V) need to be the same.
Yes your new diagram should work fine. I would still use just one 5v supply for the whole thing but I guess I can see your point in wanting to turn the large one off especially if it happens to have a built in fan. If no fan then I wonder if you would really be saving much. It’s not like its pulling 20A with the lights off just because it’s rated at that. When the lights are on I would bet you are using more power running 2 separate 5v supplies vs 1. Again different story if the big supply has a fan…
I would still think about sticking a fuse between the + out of the 5v supply and the + in of the led strip. If something were to short out that fuse could save you from burning your house down lol. Also if power injecting make sure that is tied in AFTER the fuse as well, if you choose to add a fuse.
I got the feeling that you do not know what are you building by the schematics you posted.
Sorry I never learned to draw electronic schematics. I just tried to make it easier to show on the picture than in a text
I want to power the ESP with an PSU with 5V 0,8A
and the Led strips with a different PSU one with 5v 10-20A
but want to switch it of if the light is off.
Thats all.
The general idea is fine, what’s got a few people worried is your comment:
#3 was talking about DC GROUNDS ONLY. Do NOT connect the “Earth” or “Ground” from the AC side to the DC side.
Having said that, some 3-Wire DC power supplies do connect the “AC Safety Ground” (the 3rd AC wire) to the DC ground and the metal chassis.
From your diagram it looks like all your AC wiring is 2 wire 230V. That’s fine, just make sure on the DC side your grounds are all common. That means the ESP32 and the strip use a common ground for all PSU’s. You can leave all the DC grounds connected all the time and only switch the +5V line(s) as required or as you originally intended, leave the DC ground connected and switch the AC power for the big PSU.
