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I am making a POV display. For that I am using an LED strip, a motor, and a Raspberry PI 3. All work with 5V. My motor consumes about 6 A, LEDs 4 A, and the Raspberry Pi 3 normally uses 2.5 A. Thus my system will consume about 12.5 A in total.

Instead of using 3 power supplies, I will use this made in China (5V-20A) power supply to power the whole system. The Raspberry Pi will be supplied through power header pins.

Is that safe or must I take some precautions to protect it?

enter image description here

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  • \$\begingroup\$ which GPIO pins are you planning to use for the power supply connection? \$\endgroup\$
    – jsotola
    Oct 25, 2021 at 2:43
  • \$\begingroup\$ GND and 5V . i will supply the raspberry pi though them \$\endgroup\$
    – 0ussama
    Oct 25, 2021 at 3:07
  • \$\begingroup\$ What is the reason that prevents you of feeding RPi from its regular micro-USB connector? You could wire the USB cable to the 5V power supply (just cut the USB B connector) \$\endgroup\$
    – mguima
    Oct 25, 2021 at 3:08
  • \$\begingroup\$ I know that , but i want the project to be organized as far as possible , So i am planning to make Main PCB that have one supply input , 40 pin header socket for raspberry pi and others sockets for sensors ... \$\endgroup\$
    – 0ussama
    Oct 25, 2021 at 3:32

2 Answers 2

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You can definitely power the Pi from pins 2 and 4 on the 40-pin header and some of the ground pins on that header.

Note: your question mentions GPIO pins. Pins 2 and 4 on the header are not technically "GPIO pins" - they are not general purpose input/output pins. Those pins on the header are for power and you'll need to pick some pins that are specified as ground pins on that header for your power.

But, the two 5v pins on the header are a perfectly fine way to power your pi if you don't want to use the MicroUSB power connector.

There are some suggestions from the Pi Foundation... https://github.com/raspberrypi/hats/blob/master/designguide.md#back-powering-the-pi-via-the-gpio-header

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Electrically, it's completely safe to power the Pi through the 5 V and ground pins on the header. However, you need to consider "safety" at the system level as well:

  • You are drawing a lot of power from an unspecified power supply. I would hazard a guess that it's not very high quality. You need to ensure that the supply to the Pi is clean and stable enough under the worst case scenario (switching at high load). Also be aware of ground bounce etc.

  • If you use the 5 V pin on the header, there is no overcurrent protection. You need to ensure you can't draw too much current through the header. If you do, you could cause damage to the power supply and/or the Pi.

  • As mentioned in GT Electronics' answer, make sure that there is no way for a user to plug in a power supply to the normal connector. If you can't ensure that, you need to include some protection against back power.

  • You need to ensure that the header can only be connected correctly, so there is no way for 5 V to be exposed to a 3.3 V or ground pin etc.

If the end user can do something wrong, they will do it wrong - it's just a matter of when!

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    \$\begingroup\$ This is not wrong, but a little overly cautious imo. Plugging usb power in while powering the pi through the header is not advisable, but I doubt anything would blow up if you did it. The voltages would be very close so little current would flow. The PSU noise could be a problem, but I wouldn't worry about it unless the pi starts acting weird. I have a prototype that's in use right now which is powered exactly like OP is describing. We haven't had any problems for more than a year. \$\endgroup\$
    – Drew
    Oct 26, 2021 at 0:50
  • \$\begingroup\$ @Drew - almost everything here is "free", so I would always engineer this protection in and assume others haven't. For e.g., USB is 5 V +/-5% so even in spec, you could have a full 0.5 V difference. That's enough to fry some supplies. If there's no chance that things could be abused, then you don't need a fuse etc, but my experience over the years is even when I've designed and used things only for myself, if it's possible to miswire it, it will happen. Fixing the problem after "the event" is orders of magnitude more expensive than designing it out. \$\endgroup\$
    – awjlogan
    Oct 26, 2021 at 8:10

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