abtekk
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What's the best PSU?

Tue Jul 31, 2012 12:51 pm

Hi

I should be receiving my Pi in the next couple of days, to power it i have an old samsung charger that has an output of 5v and 0.7a, is that optimal for this little device, or is there a better psu?

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RaTTuS
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Re: What's the best PSU?

Tue Jul 31, 2012 1:02 pm

that could work though your best bet is to get a
powered USB hub
and power teh RPI from that ans use the usb to power your peripherals
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mahjongg
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Re: What's the best PSU?

Tue Jul 31, 2012 1:06 pm

0.7A is a bit on the low side, the latest insights says you need something like 850mA or 1A.
But don't but any "e-bay specials" for $5, these are bound to be chinese garbage, and might actually be dangerous to use, and they do nothing like what it says on their labels. Adapters are sold that can barely supply 200mA and still have 5V 1A labels!
The wiki often has more specific "this works, this won't" info.

A powered hub is only needed if you plan to use the PI with more than just a plain simple wired keyboard and mouse.
Plain keyboard means, no USB ports or trackpads on them, and no backlit keys.

abtekk
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Re: What's the best PSU?

Tue Jul 31, 2012 1:41 pm

Thanks mahjongg, I'll see if i can find a better psu at a local store or something, i wont be using the usb ports for anything strenious to begin with.

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tvinzant
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Re: What's the best PSU?

Tue Jul 31, 2012 2:19 pm

I saw the following where Eben mentions he uses a Kindle Charger.
http://youtu.be/89sZvgI4AfU

So I purchased a Kindle Fire Charger - OUTPUT (DC): 5V, 1.8A
http://www.amazon.com/gp/product/B005CKAX82

I realize that the cost of the unit is 70% of the cost of the RPI, but bad power leads to problems.

Maarten
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Re: What's the best PSU?

Tue Jul 31, 2012 3:48 pm

Grab one of these;

http://www.ebay.com/itm/220804655748

Under 9 US bucks shipped to your door, its exactly what ive been using and its a great adapter!! Even tho it specifies that the voltage could be off by 5% under changing loads (possibly making it a bit tight for the Pis requirements) i have not been able to get it anywhere near that!

Not only will this power your Pi, it can also simultaneously be hooked up to power any 5V Hub while youre at it (thats in fact what this adapter is made for). 3A is alot!

Image
http://www.raspberrypi.org/phpBB3/viewt ... 5&p=137201

Maarten
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Re: What's the best PSU?

Tue Jul 31, 2012 3:49 pm

Oh, mind you that it does take some fiddling/tinkering/soldering to hook this up to the pi but its worth it ;)

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d1m15
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Re: What's the best PSU?

Tue Jul 31, 2012 5:10 pm

I've been using a sony ericsson charger rated @ 5v 850ma, it powers pi with usb wifi and keyboard n mouse dongle.

apple ipod 2 charger is 5v 2a, but i'm using that to charge the ipad.
RPI-1: Logitech mk260 wireless Keyboard&Mouse / Comfast Wireless USB ( Realtek 8188) New one ordered! :p / Sony Ericsson 5v 850ma charger...

abtekk
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Re: What's the best PSU?

Tue Jul 31, 2012 5:53 pm

tvinzant wrote:I saw the following where Eben mentions he uses a Kindle Charger.
http://youtu.be/89sZvgI4AfU

So I purchased a Kindle Fire Charger - OUTPUT (DC): 5V, 1.8A
http://www.amazon.com/gp/product/B005CKAX82

I realize that the cost of the unit is 70% of the cost of the RPI, but bad power leads to problems.
Thanks for the tip, luckily we have an old kindle laying around.

GeorgeWinter
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Re: What's the best PSU?

Thu Aug 02, 2012 7:28 am

I bought a cheap 5V charger with a USB-A socket in the bottom. Unfortunately it didn't come with a micro-USB cable, so I had to source that elsewhere. Anyone else in this situation should be aware that USB cables have fairly thin power conductors. At 700 mA a 6 ft (1.8 m) cable can lose you as much as 0.5V. Choosing the micro-USB as a power connector was, as Sir Humphrey would have said, "courageous".

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Re: What's the best PSU?

Thu Aug 02, 2012 11:16 am

abtekk wrote:Hi

I should be receiving my Pi in the next couple of days, to power it i have an old samsung charger that has an output of 5v and 0.7a, is that optimal for this little device, or is there a better psu?
depends how much you plan to use it. mobile phone chargers are usually linear and waste a lot of energy as heat. if you plan to use the pi a lot, or leave it on all the time you will want to pick up a switching power supply.

this is one I recommend: http://www.kenable.co.uk/product_info.p ... ts_id=5642
its 1000ma output @ 5v and doesn't double up as a radiator :D

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r4049zt
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Re: What's the best PSU?

Thu Aug 02, 2012 3:44 pm

Others have made valid recommendations but nobody has talked about testing.
Your 700mA rating sounds a bit borderline. For example, one 64GB usb memory stick draws an extra 200mA, so your rig might work fine until you plug one of those in.

If you can find 600mA worth of 6 volt torch batteries (eight in parallel) or an 8-Ohm power resister then you can try out the following tests of your power supply before your rPi arrives.

no-load voltage
========
unimportant, because the rPi never draws no power

10% load voltage
==============
With one torch bulb or a 100Ohm load or something which draws less than 200mA, what is your power supply output voltage?

Pass if 4.9 to 5.1 Volts
Fail otherwise

90% load voltage
==============
With at least six torch bulbs or an 8Ohm load or something which draws more than 600mA, what is your power supply output voltage ?
4.9 to 5.1V might work ok

I've been looking at the voltage across component D17 on the raspberry pi board, where I have soldered on wires for alternative power supplies. I don't yet have a recipe which works. 4.9 Volts there is the normal operating condition with an approved 5V 1A ac adapter to micro usb.
I can vouch that batteries at 5.3 and 5.45 Volts booted (so are 'safe' to try) but my PS2 keyboard did not work. Voltage at D17 was 5.0 to 5.25 Volts according to my cheap multimeter. So, power supplies above 5.3 Volts definitely do not work quite right, and I am seeking the right design targets for a solar power supply.

johnlane
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Re: What's the best PSU?

Thu Aug 02, 2012 4:09 pm

Just as an FYI, I am using a blackberry charger. It's working fine so far, which I'd expect given it's from the 'berry' family :lol: It's rated 750ma I believe (can't check now, it's plugged in!!!).
Raspberry Pi Utilities: https://github.com/johnlane/rpi-utils
For Raspberry Pi and Arch Linux

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r4049zt
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Re: What's the best PSU?

Thu Aug 02, 2012 6:45 pm

First, correcting an error in my previous post.
I meant eight 6V torch lightbulbs, but wrote something else by mistake.

Second, I can now advise that supply of 4.9 to 5.25 Volts seems to work.

This post was written from my raspberry pi,
running on only four NiCad 2000 mAh batteries,
charged from solar power and run down a bit to 5.25 Volts

I'm seeing 4.98 to 4.72 Volts at D17.

I don't entirely trust the calibration of my cheap multimeter so I'll continue on my own website. It might not be allowed to post links to there from here so email me if you need more info.

Terranigmus
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Re: What's the best PSU?

Mon Jan 21, 2013 8:40 pm

I currently have problems with network/keyboard not working although I am using a 2A power adapter from the Galaxy Tab 2. Could it be that the USB cable I am using is drawing so much power ?

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