Since the Zero W doesn't have a polyfuse, am I right in assuming that the 5V pin can safely supply whatever current the power supply puts out minus the draw from the Zero W board itself (and any attached items)?

I'd like to power 4x devices with a max draw of 500mA each. My power supply provides 2400mA. According to this, the typical bare board consumption is 150mA. I don't have any USB devices attached which means I end up with 2400-500*4-150 = 250mA overhead if all 4 devices are on full load.

Is this correct? Is there any reason not to do this?

  • 1
    Your calculation is OK. Who knows how much current the board traces can "safely" handle.
    – Milliways
    Jan 13, 2018 at 2:01
  • Right, I didn't think about that. I suppose it would be better to solder wires directly to the USB power connector, and use those wires to power the 4 devices? Jan 13, 2018 at 2:19
  • 1
    I guess there's also the option of powering the pi directly from the 5v pin and gnd Jan 13, 2018 at 2:29

1 Answer 1


I would power from the 5V pin to minimize the current flowing through the Pi traces.

For my experiments I would actually apply power to a breadboard rail and take power from there to a Pi 5V pin. I'd also power the external devices from the breadboard rail.

Of course the Pi and devices also need to be connected to a breadboard ground rail.

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