Power Pi 2 with a 5.1V 700mA charger and using a powered HUB

[Alan_]

Hello there.

I would like to know if this is going to work in theory:

Powering the Pi with a 5.1V 700mA phone charger (high quality), and using an old USB2.0 HUB that has 4 ports and two connections, by disconnecting the power pins of the plug that is going to be connected to the Pi and connecting the other plug to a 5V 1000mA charger, in order to use an external HDD (850mA) and perhaps a logitech nano receiver (100mA) and a USB Flash Driver (100mA).

Here's a plan I did using some highly specialized and pofressional software:

prostuff.png (3.01 KiB) Viewed 1845 times

"HUB C." stands for HUB Connector (USB male plug). The hub has 2 male plugs. Their power pins are connected together but I'm going to cut the power wires of the plug that's going to be used for the data.

Any ideas? Will any USB HUB work?

[mikronauts]

You still have to connect the GND of the USB cable between the hub and the Pi (but do not connect the 5V)

As long as your 700mA charger has enough power for the Pi, it should work.

[Alan_]

You still have to connect the GND of the USB cable between the hub and the Pi (but do not connect the 5V)

As long as your 700mA charger has enough power for the Pi, it should work.

Thanks, so the GND of the 1A power supply is going to be connected to the GND of the USB Port in the Pi 2?

[mikronauts]

You are welcome

Yes.

You still have to connect the GND of the USB cable between the hub and the Pi (but do not connect the 5V)

As long as your 700mA charger has enough power for the Pi, it should work.

Thanks, so the GND of the 1A power supply is going to be connected to the GND of the USB Port in the Pi 2?

[Alan_]

You are welcome
Yes.

Thank you Mikronauts, please let me know if I understood it correctly:

- The plug1 of the HUB is connected to the wall charger (1A)
- The plug2 of the HUB is connected to the Pi, and only the 5V pin of that plug2 is disconnected

Is that correct? Is there no problem in connecting two GNDs from different supplies?

[gkreidl]

Why?
Use a good 5V2A power supply for the Rpi, add
usb_max_power=1
to /boot/config.txt
and connect everything to the RPi directly.

[drgeoff]

You are welcome
Yes.

Thank you Mikronauts, please let me know if I understood it correctly:

- The plug1 of the HUB is connected to the wall charger (1A)
- The plug2 of the HUB is connected to the Pi, and only the 5V pin of that plug2 is disconnected

Is that correct? Is there no problem in connecting two GNDs from different supplies?

It is essential to connect the GNDs together. (But do not join the positives of the PSUs.)

[Alan_]

Why?
Use a good 5V2A power supply for the Rpi, add
usb_max_power=1
to /boot/config.txt
and connect everything to the RPi directly.

Thank you for your reply.
Because I don't have a 5V2A power supply.

It is essential to connect the GNDs together. (But do not join the positives of the PSUs.)

Thank you. I've once connected the HDD of a desktop computer to a netbook using only a long SATA cable, so I assumed it was the same thing. Perhaps I should've connected the grounds in that case too.

[3corey2]

i used a 3200 mA battery, so thats the amount on the charger i used after realizing that that would do it. everything works fine on my pi2. as long as its 5v (and not 4.7 like several that say 5) it should work.