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I have this adapter (https://global.rakuten.com/en/store/denshi/item/55154/) powering a set of RGB screens that I picked up from adafruit. Essentially I completed their pi/rgb matrix project and want to enclose it into a frame (with easy access of course) but I was wondering if I can power both the pi and the screens with this adapter. I don’t really want to have 2 plugs going to the frame. If I could use just 1, that would be ideal.

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    Well, it's 5V at 10 A. If your RGB screens use 7 A or less, there's plenty of power. You should power the Pi through the USB connection, not through the GPIO pins because going the other way bypasses protective circuitry.
    – Bob Brown
    Feb 26 '20 at 0:23
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    I was thinking about taking an old usb cable and splicing it to take the red and black and connect it into the adapter
    – chollan
    Feb 26 '20 at 4:51
  • I don't see the problem here. Yes, you can connect the Pi to 5V, either via micro USB or the pin header. Feb 26 '20 at 13:54
  • It’s more a question of if I can splice a usb cable and feed it into the adapter without harming the pi or not having enough power to run the screens. The adapter plugs into another adapter that turns it into a black and red cable that runs to the screens. I want to tie a spliced usb cable into that adapter in addition to the screens.
    – chollan
    Feb 26 '20 at 13:59
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    @chollan If you can cut the end of a USB cable or buy one with the wires exposed then yes it should be perfectly safe to wire it into the adapter socket as you have described. But make sure the combined current of the screens and pi do not exceed the rated current of the adapter.
    – justinjt
    Feb 26 '20 at 19:17
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The Adafruit RGB Matrix + Real Time Clock HAT includes a 5V power output via the solder pads circled in the attached image.

power output

According to the Adafruit RGB Matrix + Real Time Clock HAT documentation, the HAT has onboard power protection circuitry:

Power protection circuitry - you can plug a 5V 4A wall adapter into the HAT and it will automatically protect against negative, over or under-voltages! Yay for no accidental destruction of your setup.

According to the Adafruit PCB layout and schematic, the 5V output pads are downstream of the protection circuit.

This means that it would technically be safe to wire this into the GPIO (MAKE SURE IT'S THE 5V PIN!!!) of your Raspberry Pi, but note as per Bob Brown's comment above you must be aware that you are bypassing the Raspberry Pi's protection circuitry and "trusting" the HAT's protection.

Another solution is to modify a micro USB cable by cutting off the end and wiring the 5V and GND wires from the miro usb cable to the HAT's power output and plug that into the Pi's micro USB port (Making absolutely sure you have the USB cable pinout correct).

Both of these solutions would allow you to power everything off the one power adapter and give a reasonably tidy end product.

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  • I’m not using the hat, I’m using the GPIO onboard. I was thinking about just stripping a usb cable or finding a red/black usb cable on amazon and just tieing it into the adapter.
    – chollan
    Feb 26 '20 at 4:40

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