omarcolocci
Posts: 3
Joined: Mon Dec 17, 2012 11:07 pm

Power Supply and USB peripherals

Mon Dec 17, 2012 11:18 pm

Hello everyone.

I tried a search for such a question without success, so here it goes.

My Pi is still travelling to my home and I've got a Nokia AC-10x (5v, 1200mA) charger as a power supply.

My question is, since Model B requires 700mA, is it safe to add a small USB hub (no external power) to the Pi counting on the main power supply to handle, for example, a flash drive, Wifi Dongle and a remote control dongle?

What wpuld be a good option to supply power to the Pi and a powered HUB without having two different sources (and cords) on my setup?

Consider I'm intending on making a custom case both Pi and hub.

Thank you very much!

Wheel_nut
Posts: 136
Joined: Tue Sep 18, 2012 7:51 pm

Re: Power Supply and USB peripherals

Tue Dec 18, 2012 12:23 am

The problem with doing what you are planning to do is that ALL of the current to drive your peripherals will pass through the Polyfuse just inboard of the MicroUSB socket. This fuse is only rated at ~750mA and is the source of Voltage drop problems.

A better solution would be to power the Hub and back-feed the RPi through the upstream cable between the Hub and the RPi USB Port. This bypasses the Polyfuse and circumvents the problem.

omarcolocci
Posts: 3
Joined: Mon Dec 17, 2012 11:07 pm

Re: Power Supply and USB peripherals

Tue Dec 18, 2012 2:01 am

Oh, I see.

Thank you for the solution. Now you mentioned it sounded so obvious! Duhr! :oops:

Thanks again! :D

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