Powering a RPi 3B+ through GPIO vs USB

[d1str0]

Hello,

Searching the internet, I have been unable to find an answer for this:
Which way of powering a RPi could source more current for the RPi itself and attached peripherals? Through the GPIO pins or the micro USB connector?

Is there any official documentation on this?
Thanks.

[Imperf3kt]

the GPIO will give you a tiny, tiny amount less resistance.
This is because you are avoiding some of the protection circuitry.

[davidcoton]

The Pi will draw what current it wants. Using microUSB or GPIO will not make any noticeable difference. The power used by the Pi itself is almost all converted through switching regulators, so the odd few millivolts are seldom significant, the regulator will compensate -- but see below.

Power for USB peripherals is limited by the USB supply circuit on board. You cannot easily change that (and should not).

It is important that your power supply (however it is connected) maintains the Pi's specified voltage (4V75-5V25) at the current you are using.

What is significant is that the microUSB feeds through a polyfuse, which together with a TVS diode protects the Pi from power mistakes. Using the GPIO bypasses this and means that faults that draw too much power are more likely to cause permanent damage.

[d1str0]

Thanks,
So far I 've had bad experience with low quality micro usb cables, they simply can't deliver enough current. Would anyone recommend a high quality micro usb supplier/brand to buy a lot of cables from?

[davidcoton]

I don't know specific manufacturers, but you need to specify 18AWG copper conductors for the power.

Good ready-made cables may have a marking like "28AWG/1P+18AWG/2C" where the first part indicates the size of the data pair (1P) and the second part the power conductors (2C).

[boyoh]

The Pi is not designed to be used as a power house. If you want to run power hungry
projects ,you must use buffer stages , and let the Pi control them with low power signals
The USB connection is the one to use . Using GPIO to feed the power to the Pi is asking
for problems ,and also bypassing the safety circuits

I suggest you do a course in basic electronics and Ohms Law, that then will answerer
all your future questions

Regards BoyOh

[d1str0]

I don't know specific manufacturers, but you need to specify 18AWG copper conductors for the power.

Good ready-made cables may have a marking like "28AWG/1P+18AWG/2C" where the first part indicates the size of the data pair (1P) and the second part the power conductors (2C).

Thanks, that's helpful. I'll look for those.

I suggest you do a course in basic electronics and Ohms Law, that then will answerer
all your future questions

Hahah
Relax mate, I'm a Certified Ohm's Law Lawyer @ Coursera

[HawaiianPi]

I doubt you'll find micro USB cables with 18 AWG power wires. Most I've seen is 19 AWG, and that was only from one brand (which I don't believe is still made). However, 20-22 AWG is pretty common, and in shorter lengths that should be fine.

The Official Raspberry Pi power supply does have 18 AWG conductors in its non-removable power cable. It also outputs 5.1V (instead of 5V) and up to 2.5A, so if you don't have one already, consider getting one. It's a proven performer.

What are you using for a PSU now?


EDIT
The ployfuse limits micro USB input current to 2.6A.

[LTolledo]

some HATs that require higher input voltage (like some DAC amps) power the connected RPi board thru the GPIO header, so its most likely pin2 and pin4 for the 5v and the GND on all ground pins.

so its better (and good practice) to power the RPi thru the GPIO headers.

am actually making one to power the RPi4B-2G using DC12v (and up to 36v) input so it can share the same power brick as the RAID box am planning to use it with.
I'll post pictures when am finished and tested it.

[davidcoton]

some HATs that require higher input voltage (like some DAC amps) power the connected RPi board thru the GPIO header, so its most likely pin2 and pin4 for the 5v and the GND on all ground pins.

so its better (and good practice) to power the RPi thru the GPIO headers.

That is not a logical conclusion. It is more convenient to use the GPIO header when the power source is a HAT. In the general case for Pi1,2,3 it is safer to use the microUSB. Providing a polyfuse for GPIO header power input overcomes the safety deficit; and for Pi0,4 there is no onboard polyfuse, so you should provide one anyway if the PSU limit is over 3A. (Note the Pi0 doesn't have a TVS diode either, so don't get the connections wrong.) Once that issue is dealt with, it is purely a matter of convenience as to where the power is applied (assuming the points chosen are the correct +5V and GND rails ).

[d1str0]

What are you using for a PSU now?

These step down switching regulators:

serveimage.jpg (35.82 KiB) Viewed 1251 times

Input Voltage: 3 to 40 V
Output Voltage Range: 1.23 to 37 V
Output Current: 3A

Through the GPIO port
These work ok most of the time, but I would rather be on the safe side and use the micro usb port.
I can't use a wall socket PSU because of reasons. All I have is a stable 12V supply with almost no noise and plenty of power (10A)

[drgeoff]

These step down switching regulators:
serveimage.jpg

Input Voltage: 3 to 40 V
Output Voltage Range: 1.23 to 37 V
Output Current: 3A

Make sure that the output voltage is not more than 5 volts before connecting to a RPi. Else the magic smoke is given an opportunity to escape.

[Imperf3kt]

What are you using for a PSU now?

These step down switching regulators:
serveimage.jpg

Input Voltage: 3 to 40 V
Output Voltage Range: 1.23 to 37 V
Output Current: 3A

I have several of these.
their rated output current is not quite as cut and dry as it looks.
according to their datasheet, they output up to 3A yes, but it depends on the input voltage and output voltage.
the datasheet I have, also states that they are only good for 2A continuous current without additional cooling. They will thermally shutdown if you try to draw 3A from them without some form of cooling.

[LTolledo]

am using the same one to provide power to my RPi4B-2G NAS build, also on my Rock64-1G NAS build.

RPi4B-2GNAS-topOpen.jpg (201.03 KiB) Viewed 1200 times

but am powering the RPi4B via connection to TP1 and TP7 pads.
a heatsink is attached to the regulator IC though....
never failed me yet..... just lucky I guess...

[emma1997]

These step down switching regulators:
serveimage.jpg

Input Voltage: 3 to 40 V
Output Voltage Range: 1.23 to 37 V
Output Current: 3A

I am fond of those cheap chinese converters myself but realize are not capable of rated current. 60%-70% at best depending on in/out differential and air flow. Cutting corners with small inductor and heat sink severely limits. The one you posted will not sustain even 2 amps. Here's a pic of the ones that were tested and only the last on the right would be technically capable of supplying a Pi4 with drives or anything else attached. More expensive. They run about a dollar each as apposed to middle one like yours at 2 for a buck or the little ones 5/$1.