Pinto80
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Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 9:33 pm

So I am very new to the Raspberry world and I am going to use one for my high school final project, I will use a power supply of 5V 1A for my raspberry and I would like to know if it is enough?

For now besides the ethernet cable I'm not using any more port.

Appreciated for your time.


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B.Goode
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 9:50 pm

Two suggestions:

One. Read the documentation provided by the Raspberry Pi Foundation: https://www.raspberrypi.org/documentati ... /#pi-power

Two. Try it and see.

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davidcoton
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 10:45 pm

Pinto80 wrote: I will use a power supply of 5V 1A for my raspberry and I would like to know if it is enough?
It depends what your code is doing. An active but not busy Pi3B+ with little peripheral load will run on less than 1A. But a heavily loaded Pi3B+ will use up to 1A3. You will have troubles testing your code if the load rises even momentarily -- it will be hard to tell if it is your code or the PSU causing problems. That is the last thing you want whwn rushing to meet your project deadline. You will also find that not all "5V 1A" PSUs maintain 5V at 1A load. The recommended PSU is 5V1 2A5 for a reason.

TL;DR -- Use an "official 5V1 2A5 PSU and avoid problems later.
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HawaiianPi
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 10:49 pm

No, a 1A power supply is not enough for a Pi 3B (much less a 3B+).

The Pi 3B+ itself can draw up to 1.3A, and the USB ports have a combined output of up to 1.2A. That's why the recommended PSU is rated for up to 2.5A. Even a headless Pi with no peripherals can exceed 1A using just the CPU (no GPU, no WiFi, no USB).

Imperf3kt wrote:
Wed Feb 06, 2019 9:58 pm
According to the documentation (not my 'advice'), the Pi3b+ typically uses 500mA, which is 0.5A as far as I'm aware.
That's 500mA at idle, for a bare board. It's not that hard to get a Pi 3B+ over an AMP (it can pull nearly and AMP just opening the web browser).
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davidcoton
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 10:54 pm

Imperf3kt wrote:
Wed Feb 06, 2019 9:58 pm
Is there something I have misunderstood or overlooked?
Yes. You must design for worst case conditions, which is peak load, not just active load. Granted that without knowing the particular code, load, environment and peripherals for a particular Pi then we don't know the actual peak load, so in giving advice we must take the standard worst case figure of 1A3 (recommended PSU minus max USB, which actually may not be the worst case, the figure for a Pi3B+ is missing from the FAQ, the figure for Pi3B is 1A34). In extreme cases even the "official" PSU may not be adequate, but in this case we are told there are no USB peripherals "for now".
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WillBoxOwO
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Wed Feb 06, 2019 11:50 pm

If you think, like me, that the official power supply is a little too costy, just buy the northpada one (its 5v3amps).
Its *really* robust, Im been using it for 2 years now. :)
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davidcoton
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Thu Feb 07, 2019 12:00 am

@Imperf3kt:

The answer to "will it work " without qualification of circumstance has to be "Possibly, but not guaranteed". In this case the circumstances don't change the answer. Your original answer was not wrong, but incomplete. The circumstances are relevant to refining the answer. Given that we still can't reach a definite conclusion, we can do two things:

One is to show what areas of doubt and uncertainty need a more rigid definition (done).

The other is to look at the consequences of a wrong decision (guess). In this case the application is relevant, and since it has been defined it is not only legitimate but helpful to to use that context. Hence my suggestion that using a PSU that later turns out to be inadequate may have an detrimental effect on the project.

When you answer a question, try and put yourself in the position of the person asking. Answer for their circumstances, if known. Give a more general answer if it is helpful. Ask more questions about the circumstances so we can all refine our answers. Re-read this thread -- look at which answers actually give useful information, and which do not. Remember that there are narrow answers and broader ones, both can be good. Even humourous non-answers may provoke thought. (I could give examples of all three but there are already many to be found just by browsing this forum.) I try to avoid "maybe" answers without showing how to resolve the remaining uncertainites, but that is my personal style.

@WillBoxOwO: Link?
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PeterO
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Thu Feb 07, 2019 8:45 am

Imperf3kt wrote:
Wed Feb 06, 2019 9:58 pm
PeterO wrote:
Wed Feb 06, 2019 9:56 pm
Imperf3kt wrote:
Wed Feb 06, 2019 9:45 pm
Potentially.
It depends on your "power supply" and the connected cable.
Please STOP trying to give advice about things you don't understand.
PeterO
What advice us there in "potentially"?
I stated it's possible, nothing more.
Yes, I've misworded some of my replies in the past. I'm more careful with my wording now, if you've noticed. I left out all detail and simply said "it can be done".

Having successfully done so myself, I see no reason not to.

According to the documentation (not my 'advice'), the Pi3b+ typically uses 500mA, which is 0.5A as far as I'm aware.
https://www.raspberrypi.org/documentation/faqs/
Grade school level mathematics tells me that 0.5 is less than 1.0, so it should work.

Is there something I have misunderstood or overlooked?
Although my post seems to have been removed, the subsequent answers make it quite clear why I said what I did.
You don't seem to understand that "It works for me" is not a valid basis for giving advice. Some engineering principles have to be applied, and the "worst case" approach is the best to take in this case where there are unknowns, and "mission creep" will often lead to extra load (both CPU load and USB and GPIO loads on 5V) being added to a project. In such cases starting off with a "barely acceptable" PSU will just incur extra expense when a better PSU is needed later.

PeterO
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Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
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Re: Is 5V 1A enough for Raspberry Pi 3 B+

Thu Feb 07, 2019 9:46 am

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