skrenes
Posts: 7
Joined: Tue Jan 24, 2012 12:01 am

Raspberry Pi 4 power pin

Wed Aug 28, 2019 8:54 pm

The Raspberry Pi 4 official specifications state "5V DC via USB-C connector (minimum 3A*)" or "5V DC via GPIO header (minimum 3A*)". Is there any difference electrically?

I remember with the older Pi's, it bypassed safety circuitry. I'm asking because I will be using cheap (Ali Express) buck converters to produce 5v from 12v/48v/52v DC sources and rather than buy USB-C cables, cut them in half, then solder into the buck converters. I'd rather use wires with Dupont connectors that I already have to connect to the 5v pin directly.

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Imperf3kt
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Re: Raspberry Pi 4 power pin

Wed Aug 28, 2019 9:31 pm

The Pi4 has no polyfuse like previous models and according to the reduced svhematics the USB-C power in is directly connected to the 5v pin on the GPIO header
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davidcoton
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Re: Raspberry Pi 4 power pin

Wed Aug 28, 2019 9:41 pm

Consider wiring in your own polyfuse to protect the Pi if (when) the polarity gets reversed or the buck converter fails.
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LTolledo
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Re: Raspberry Pi 4 power pin

Thu Aug 29, 2019 6:15 am

the typical dupont jumpers are AWG28 with a rating of 1.5A.... so you might encounter undervoltage warning if used as power in connector on RPi2B and above.

better make you own connecting wire using AWG24, (3.5A) or better if AWG22 (7.0A) for your power connection to GPIO header pins #2 or #4 and pin #6.
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Come to me with 'problems' and I'll help you find solutions"

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andrum99
Posts: 800
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Re: Raspberry Pi 4 power pin

Thu Aug 29, 2019 11:21 am

LTolledo wrote:
Thu Aug 29, 2019 6:15 am
the typical dupont jumpers are AWG28 with a rating of 1.5A.... so you might encounter undervoltage warning if used as power in connector on RPi2B and above.

better make you own connecting wire using AWG24, (3.5A) or better if AWG22 (7.0A) for your power connection to GPIO header pins #2 or #4 and pin #6.
Thicker wires will have a lower voltage across them, which means less voltage dropped between the power supply and the Pi. That's just as important as their current-carrying capacity.

skrenes
Posts: 7
Joined: Tue Jan 24, 2012 12:01 am

Re: Raspberry Pi 4 power pin

Wed Sep 04, 2019 10:39 pm

Thanks everyone. I'll be using around 20-24 AWG wire that'll only be 10-30cm long. So it should be more than enough. I just wanted to make sure there weren't any electrical advantages to the USB-C port.

andrum99
Posts: 800
Joined: Fri Jul 20, 2012 2:41 pm

Re: Raspberry Pi 4 power pin

Thu Sep 05, 2019 11:28 am

skrenes wrote:
Wed Sep 04, 2019 10:39 pm
Thanks everyone. I'll be using around 20-24 AWG wire that'll only be 10-30cm long. So it should be more than enough. I just wanted to make sure there weren't any electrical advantages to the USB-C port.
For reference, the official Raspberry Pi micro-B power supply outputs 5.1V and has a 1.5 metre 18 awg cable. Obviously your PSU needs to have as stable an output voltage as possible - it's no use doing 5.1V under no load, then dropping to 4.5V at max current output.

andrum99
Posts: 800
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Re: Raspberry Pi 4 power pin

Thu Sep 05, 2019 11:31 am

skrenes wrote:
Wed Sep 04, 2019 10:39 pm
Thanks everyone. I'll be using around 20-24 AWG wire that'll only be 10-30cm long. So it should be more than enough. I just wanted to make sure there weren't any electrical advantages to the USB-C port.
Compared to the micro-B connector, the type C connector can handle slightly more current, which is why the Pi 4 uses it. But you should be able to pump more current into the GPIO connector since it has relatively large pins. It obviously depends on the track sizes on the PCB as well. It is designed so that you can power the board off the GPIO header, but you need to do your own protection circuitry if you do it that way.

arminf82
Posts: 2
Joined: Thu Sep 05, 2019 11:46 am

Re: Raspberry Pi 4 power pin

Thu Sep 05, 2019 11:58 am

At the moment I am powering my Raspberry 4 via USB-C from this

Step-down DC-DC Converter Module for Raspberry Pi

https://www.sunfounder.com/step-down-dc ... ry-pi.html

. Input is a 2-4S Lipo. A PCA9685 is connected through the 5V pins of the Step-down DC-DC Converter. The 2A are enough to power the raspberry when no USB decides are connected (I want to switch to a more Amp converter). The raw input from the lipo also powers a Sainsmart Roverbot Motor Protoshield.

I want to power the Pi via GPIO. As it is said, it should be safe now with the Raspi4, compared to the Raspi3, where this was not possible?!

Is the connected safe for the raspberry and PCA9685, if there were back-currents from the motors on the Protoshield?

Is there a small and simple device that would protect the whole circuits and provide more amps, to change tot current Stepdown converter?

StepDownDCDC_02.jpg
StepDownDCDC_02.jpg (92.32 KiB) Viewed 711 times
StepDownDCDC.jpg
StepDownDCDC.jpg (117.15 KiB) Viewed 711 times


I have one PCA9685 16-Channel 12-Bit PWM Servo Driver

https://www.sunfounder.com/pca9685-16-c ... river.html

powered by the 5V pins of the Step-down DC-DC Converter Module that is also connected to the Raspberry.

PCA9685.jpg
PCA9685.jpg (144.32 KiB) Viewed 711 times
This wiring was suggested in the Smart Video Car from Sunfounder.

I actually want to power my Raspberry from the Step-down DC-DC Converter Module 5V pins into the 5 V GPIO pins.

“According to the reduced schematics the USB-C power in is directly connected to the 5v pin on the GPIO header”. So is it safe on the Raspi4 to used this setup to wire everything?

Is this wiring correct or can I skip the V+ from the Raspberry GPIO to the PCA9685, as it already gets power from the Stepdown converter?

I am new to electronics!

How does a polyfuse would look like to protect the Pi?

Can someone provide a link of a ready to use Stepdown converter with a fuse/protection circuit to connect my boards, that provides at least 3A output to power the PI via GPIO?
Moon Pi

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