I might use this method. But first, I’d like to have a few more attempts with the relay, maybe using different pins or a different board.
Regarding the WOL method, I’ve used it before and it worked pretty well. But at the moment I don’t have a wired connection to the router on my PC, I’m using wifi connection.
I have a raspberry pi lying around, would it be possible to connect it via cabla to the pc and maybe use it as a server for WOL?
Wake up over Wireless LAN (WoWLAN) should be possible, and WoL doesn’t need a server, but there are security issues and many domestic routers don’t properly support static routing that’s needed for WoL. Even with the correct kit the magic packets seem to get randomly blocked by both of my ISPs, which makes it pretty useless.
Pete.
Well, when I used the WoL method I had anither PC that was on all the time, that why WoL was possible. I tought the raspberry would be a good alternative to that.
You obviously know more about WoL than me, so I’ll let you explore that yourself. The Sonoff solution works very well for me and I can’t see me changing from that anytime soon.
Pete.
I have set up my Raspberry anf I’mnstill trying to wrap my head around it as it’s the first time I’m using it. Using WOL to wake the PC via Raspberry is possible as I’ve read, like creating a batch file that sends a magic packetnto the PC. My question is: am I able to run that batch by using a Virtual Pin tied to a button widget?
Another approach…
Pete.
@PeteKnight seems like the problem with the relay method was the power source for the MCU. The USB ports I have used seem to power up slower. I have tried plugging it in directly to a socket with a 12v adapter and it works just fine.
So you were trying to power the MCU from the PC?
Pete.
Well, yes… and it does work if I power it directly from the motherboards ports. I also have another MCU hat I use for monitoring my plant that I have powered from the PC when off, so I tought there wouldn’t be a problem. Now, for the next part: is there any way to update the button widget state if I turn on the PC from the power button?
If you’d have shared that piece of information earlier then you’d probably have found a solution quicker.
I’d sense the state of the PC’s power LED via a pin on the MCU, but heed the warning I gave earlier…
Pete.
I did…kind of 
Tought about using a photosensitive sensor inside the case as my PC puts out a light show when powered up. But it’s kind of an “artificial” solution
I think the problem is with your pc motherboard [url to UK based commercial retailer site removed by moderator] first you have to check your motherboard.