Raspberry Pi Forums

Hello everyone,
did anyone try to powering raspberry directly from usb wall outlet?
I would like to mount a rasp zero w with lcd on the wall and connect it directly to a usb wall outlet without classic power supply,

but I'm not sure that these outlet are suitable for continuosly power or only to charge a mobile phone due to overheating.
My idea was the 4box (italian supplier) with output about 2.1A , considering that between zero and lcd I will not exceed the 700 / 800mA should heat up a little, but I would prefer to hear if someone already did it, thanks !!!

It does not matter what power source you use as long as it provides enough mA to run the RPi AND hold steady at 5.0 VDC +-5%
Not sure why you are worried about heat? The heat is the same no matter what power supply is used.

klricks wrote: ↑

Thu Nov 30, 2017 1:32 pm

Not sure why you are worried about heat? The heat is the same no matter what power supply is used.

because the outlet is inside the wall so no wam air gone
if i use the outlet to charge the phone after 2-3 hour the outlet gone off
with raspberry the outlet put out power forever and i don't want to burn the outlet for overheating

I think I understand what you are saying .

You want to use one of those socket outlets that have a built in USB charging point to run your pi zero and the display.

running it 24/7 even at 50% of it rated capacity might well lead to it getting hot as the wall surrounding the socket outlet will act as an insulator and as there will be no air flow over the circuity.

As you say when using it for phone charging you might only use it for 2-3 hours then it has a long time to cool before being used again.

I would say there is a risk of it over heating how much of a risk I don't know

I'm not sure that these outlet are suitable for continuosly power or only to charge a mobile phone due to overheating.

if i use the outlet to charge the phone after 2-3 hour the outlet gone off
with raspberry the outlet put out power forever and i don't want to burn the outlet for overheating

My advice is that this forum is not a reliable source of advice about this problem!

If you have concerns about the electrical safety of anything connected to your permanent mains electricity supply you should seek advice from a qualified electrician.

Reading the manual, instructions or data sheet for the usb wall outlet might be an acceptable substitute.

There are some variations in standards for building and electrical safety across the world, and local knowledge of what is safe and permitted is probably an important factor in getting you reliable advice.

[But like most respondents to these forums, I am just a volunteer and I may or may not know what I am talking about... ]

welverin wrote: ↑

Thu Nov 30, 2017 2:29 pm

klricks wrote: ↑

Thu Nov 30, 2017 1:32 pm

Not sure why you are worried about heat? The heat is the same no matter what power supply is used.

because the outlet is inside the wall so no wam air gone
if i use the outlet to charge the phone after 2-3 hour the outlet gone off
with raspberry the outlet put out power forever and i don't want to burn the outlet for overheating

IMO if the USB outlet cannot operate indefinitely at full capacity at normal ambient temperatures ~20C, then either the thing is defective or poorly designed and I would not use it at all for anything.

Given that Pis are generally rather more picky about their supply than a phone would be, I would be wanting to know more about what's behind the face-plate.

But it shouldn't be too much of a problem, since as I understand it, the wall outlet should not be mounted in a flammable wall material.
Though my only experience with Italian mains, in Rome many years ago, horrified me - the kettle was powered through two-core flex slung across the room on drawing pins.

Qualified electrician here -- but what follows is no more authorative than other answers, and I accept no liability if your socket catches fire.

I can't answer for Italian sockets and codes of practice -- and wouldn't even like to guess at an answer for UK equipment. You would need to ask the manufacturer for the maximum continuous current rating, given the particular mounting conditions of the socket (eg, solid masonry, hollow wall, hollow but insulated? Metal or plastic backbox?).

If I had to install such a system, I would monitor it for an hour or so -- long enough to reach thermal equilibrium. In the UK we assume a maximum safe operating temperature for wiring of 70C, but it must stay within that at the highest expected ambient temperature. So if you test at 18C, and expect maximum temperatures of 28C, and want some margin for error, then the socket should not exceed 55C. (Common sense suggests that even 55C could be too warm for unattended 24/7 operation.) Check periodically that the socket is not getting hotter due to a developing fault. Have a qualified electrician check that the socket terminals are tight -- heat will worsen any loose connections.

klricks wrote: ↑

Thu Nov 30, 2017 6:19 pm

IMO if the USB outlet cannot operate indefinitely at full capacity at normal ambient temperatures ~20C, then either the thing is defective or poorly designed and I would not use it at all for anything.

+1 for this ^

many thanks to all for the aid !
they are very usefully

Leo