Power supply question

[ffernn]

Would it be possible to power a raspberry pi (3 model b), a metro (mini) and a 12 neopixel ring off one power supply? What would the output have to be?

[adafruit_support_mike]

That should be possible.

The Pi3B uses up to 800mA without any USB peripherals, and each NeoPixel can draw up to 60mA for RGB, or 80mA for RGBW. That would put the worst-case NeoPixel load about 1A, though we've found that most NeoPixel projects run happily on an average of 30mA per pixel. That puts the probable load around 360mA.

A 2A @ 5V power supply should be able to handle both, though you'll get close to the 2A limit if you runthe RasPi and NeoPixels close to their upper limits.

[ffernn]

The pi will be running fairly intensive code, and I'm a bit confused about the power for the metro mini, as it seems you can power it from USB or a pin on the side? Which one of these should I use, and if I use USB can I just power the neopixels off the USB power out pin?
The neopixels are rgbw btw.

[adafruit_support_mike]

Ah.. I missed the Metro Mini in the list.. sorry. That uses around 50mA itself, plus any additional current for things like LEDs driven by the GPIO pins.

it seems you can power it from USB or a pin on the side? Which one of these should I use,

The Metro Mini is based on the Arduino Uno R3 hardware design, so powering it from USB is the first preference. You can also connect an external 5V supply to the 5V pin, and it should still hot-swap power from the USB cable safely. Powering through the 5V pin is more of a preference for embedded applications that will never see a USB connection to a computer once the board is installed.

if I use USB can I just power the neopixels off the USB power out pin?

Yes. Powering NeoPixels from the 5V line in a USB cable is the preferred method in cases where you want to make and break a USB connection for power, even if you only break the connection to swap in another battery pack.