LCD PC Monitoring Shutdown an Boot up.

If you hook up your raspi on a usb port on your motherboard it should turn on and off with your PC but AFAIK it might happen that your raspi doesn't get enough juice through that, if it has a screen attached. I don't know if someone already tried a molex to micro usb cable, but that might work I think.

Hi I use Molex to micro USB….but same thing…raspberry pi wont off even when the pc already shut down. 

I am also interested in a solution. I prefer not to keep the raspberry and screen running all the time, but since i am building it into my pc, i reckon it's not so easy turning both on and off. I did read that connecting to PC usb or molex does probably not provide enough power and might even corrupt the image. Maybe there are plans to at least control the raspberry (start and stop)  from mobro on boot and shutdown? [feature request] :)

I have solved that with a master slave socket.

There are plenty of those on amazon. 

https://www.amazon.es/Brennenstuhl-1159490966-Regleta-Autom%C3%A1tica-Antracita/dp/B00C255EQG/ref=sr_1_3?dchild=1&keywords=enchufes+master&qid=1627209172&quartzVehicle=93-1247&replacementKeywords=enchufes&sr=8-3

Connect your PC to master and the pi to slave. I use it with a 2.1A and it goes just fine.

I am all new to this (particular to raspberry). Is there a way to remote shut it down? So perhaps it would be possible to trigger that on the shutdown of the pc...

It doesn’t cut off the power of the PC.

it detects when it is at sleep or shutdown and cuts the power.

if you want a trigger you could try and write a script that sends the ssh sudo shutdown to your pi.

Well that's easier said than done.
Triggering a shutdown of the Pi when the PC is shut down could be done via script, like @magnificent3 suggested.

But starting it back up on boot is another story.
You can't just start it from software. After all it's turned off and therefore not reachable over the network.
You need to power cycle it.

Just another idea:
If you power it through your power supply (e.g. Molex) you could also turn off said power supply after you shutdown the PC.
This will then also cut the power to the Raspberry Pi. Once you turn the power supply back on (and the Pi gets power again), it will boot again.
Basically the manual version of what magnificent3 suggested with the use of a master slave socket ^^

"Seraksab

Well that's easier said than done.
Triggering a shutdown of the Pi when the PC is shut down could be done via script, like @magnificent3 suggested.

But starting it back up on boot is another story.
You can't just start it from software. After all it's turned off and therefore not reachable over the network.
You need to power cycle it.

Just another idea:
If you power it through your power supply (e.g. Molex) you could also turn off said power supply after you shutdown the PC.
This will then also cut the power to the Raspberry Pi. Once you turn the power supply back on (and the Pi gets power again), it will boot again.
Basically the manual version of what magnificent3 suggested with the use of a master slave socket ^^"

Ok, but as op mentioned, the cable to go from molex to micro usb is hard to get. Besides, from what i read that might not give enough power for a pi 4b and a screen connected. Specially with a lot of graphs running and also a heatsink with 2 fans on the pi. Or perhaps you have tried that solution? 

I read this and found the part that thagrol wrote interesting: https://www.raspberrypi.org/forums/viewtopic.php?t=295420#p1782861

So, is it possible with mobro to at least do this to prevent damage to the image: “use a readonly root and boot filesystem (both can be set via raspi-config, you want the overlay enabled for the root partition)”

As i said, i am all new to this and eager to learn, but i don't want to fry my new pi and screen on the first try… :D

Edit: i just watched the tutorial video again and there it's suggested to power the pi using a “usb header to micro usb cable”. So would that actually do the trick? there they use a 3b, i will use a 4b.

@pcvdbroek 

Starting from v12 our current image already uses OverlayFS for the root partition, while the boot partition is mounted read-only ;)

As for the “USB header to micro usb cable”: 
Most USB headers are only rated for 0.5A, while the recommendation for a Pi 4 is at 3A. So that will almost certainly not be enough

@pcvdbroek I have tried making my own molex cable and did that successfully. But it doesn’t get the power it needs to get the pi working with the LCD. So I ditched it and got a dedicated power adapter and a master slave socket solution. 
And now with overlayFS is safer ?

@pcvdbroek I have tried making my own molex cable and did that successfully. But it doesn’t get the power it needs to get the pi working with the LCD. So I ditched it and got a dedicated power adapter and a master slave socket solution. 
And now with overlayFS is safer ?