Been searching for an answer, but I see lots of talk about it, but not clear answers. Can somebody clarify this? If I power the Arduino only via USB, can I put a small daughter board? and power it from the Power connector(5V)


Thanks for the answers I'm using a Genuino UNO and it does power the daughter board my meter was kaputt, got a good one and it is fine even hooked a breadboard circuit to the 5V and GND and it works!!!

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    Probably the reason there is a lot of talk, but no clear answers, is that everyone has a different idea of what a "small" daughter board is; there is a limited power margin, and every LED, sensor or other add-on uses some power. The only true answer is "it depends on your specific situation". – jose can u c Mar 6 at 16:40

Yes. USB is limited to 500mA, the Arduino like an Uno has a 500mA fuse to protect the USB source.

The Arduino itself can use 25-50mA of that, or more depending on what you have connected to the IO pins.

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    note that USB3 officially provides almost an amp, while most computers and virtually all mains-usb "chargers" provide more than 500ma. Both apple and samsung "wall worts" for example provide 2 amps. – dandavis Mar 6 at 17:21

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