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Help finding good power supply

Posted: Mon Mar 30, 2015 2:10 pm
by ludespeedny
Over my lunch today I am heading out to but a Raspberry Pi 2, and am wanting to get a good adapter that will work. Currently I have a RPi model B with the following plugged into a hub: Edimax Wifi, Rii KB/mouse dongle, usb tv tuner, external hdd.

I would like to power all these off the new RPi 2 if possible. What specs should I look for, or will the Pi not be able to power all these?

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 2:35 pm
by ludespeedny
related: I have a usb cable 6ft 28awg that seems to be causing issues on my B+ with a 5v2a adapter I already have. Should I look for a 5.1 or 5.2v adapter instead, or just get a "wall wart" with a micro usb on the end?

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 2:36 pm
by LeoJr2015
ludespeedny wrote:Over my lunch today I am heading out to but a Raspberry Pi 2, and am wanting to get a good adapter that will work. Currently I have a RPi model B with the following plugged into a hub: Edimax Wifi, Rii KB/mouse dongle, usb tv tuner, external hdd.

I would like to power all these off the new RPi 2 if possible. What specs should I look for, or will the Pi not be able to power all these?
The Pi will not power all that stuff on the usb ports. Each port is rated for 100milliamps. In order to avoid issues, you should plug all those devices, or at least the high power ones, to an external powered usb hub.

Also, here is a decent power supply:
http://www.amazon.com/Kootek-Universal- ... B00GWDLJGS

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 2:38 pm
by LeoJr2015
ludespeedny wrote:related: I have a usb cable 6ft 28awg that seems to be causing issues on my B+ with a 5v2a adapter I already have. Should I look for a 5.1 or 5.2v adapter instead, or just get a "wall wart" with a micro usb on the end?
I suggest you put a voltmeter on it and see. Shouldnt be less than 4.7 or 4.8

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 2:51 pm
by gkreidl
LeoJr2015 wrote:[
... Each port is rated for 100milliamps.
http://www.amazon.com/Kootek-Universal- ... B00GWDLJGS
That's wrong. All 4 USB ports together can deliver either 600 mA or 1200 mA, if the high current USB option is set.
But a HD+WiFi+DVB-T+keyb./mouse combo should be too much.

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 3:48 pm
by Jednorozec
This is a very good power supply https://www.adafruit.com/products/1995

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 4:03 pm
by ludespeedny
I like the idea of that one being 5.1v. I wonder how good this one is.
http://www.microcenter.com/product/4411 ... le_-_2_Amp

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 5:16 pm
by LitterBugs
ludespeedny wrote:I like the idea of that one being 5.1v. I wonder how good this one is.
http://www.microcenter.com/product/4411 ... le_-_2_Amp
I have this very power supply on one of my Pi2s with a DVB-T dongle, wireless, and keyboard. Have been using it for a week 24x7 with no problems. I intend to do some comparisons between all the different power supplies I have for rated vs. observed voltage and current. Also hope to look at how clean the power is coming out with a scope.

Cheers!
LitterBug

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 6:09 pm
by ludespeedny
Cool, I'd be interested in your findings. Do you get an actual 5v from it or more like a 4.75

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 6:23 pm
by ludespeedny
is the max that the Pi 2 can draw 2a?

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 7:55 pm
by W. H. Heydt
ludespeedny wrote:is the max that the Pi 2 can draw 2a?
IIRC, the polyfuse is for 1.8A.

Re: Help finding good power supply

Posted: Mon Mar 30, 2015 9:51 pm
by klricks
W. H. Heydt wrote:
ludespeedny wrote:is the max that the Pi 2 can draw 2a?
IIRC, the polyfuse is for 1.8A.
Per the B+ schematic and markings on the polyfuse part, I believe It is 2A (hold).

Re: Help finding good power supply

Posted: Tue Mar 31, 2015 12:28 am
by ludespeedny
so the 6ft cable I was using is giving me about a .5-.7v drop.
I am currently using my nexus charger (5v 2a) and cable with everything plugged in and get the square in the corner if it hits 4.8v, which is occassional.
I then swapped to my Galaxy charger (5.3v 2a) and am running at 5.14v with no flashing square.

My question is should I just stay with the Galaxy charger?

Also, what is the typical voltage drop for a usb cable?

Re: Help finding good power supply

Posted: Tue Mar 31, 2015 1:55 am
by kusti8
ludespeedny wrote:so the 6ft cable I was using is giving me about a .5-.7v drop.
I am currently using my nexus charger (5v 2a) and cable with everything plugged in and get the square in the corner if it hits 4.8v, which is occassional.
I then swapped to my Galaxy charger (5.3v 2a) and am running at 5.14v with no flashing square.

My question is should I just stay with the Galaxy charger?

Also, what is the typical voltage drop for a usb cable?

You'll be fine as long as it always gives less than 5.25 and more than 4.75.

It depends on the type of cable. Big short fat ones won't drop a whole lot if any while cheap China cables will drop a lot.