RPi Power Supply


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by Larry_Adlard » Fri Jun 08, 2012 9:18 pm
jbeale wrote:Is it better if you separate the power supply and the cable? There are lots of 5V USB power supplies, and the USB port <-> microUSB cable is also widely available.

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There are two points here. Do you understand the difference between a charger, a power supply, and a regulated power supply (I'm not suggesting you don't but you can't claim that a particular device is suitable without testing a representative sample of a particular device. The one you have may work for you but the same make/model may not work for someone else.)

The cable is a much simpler business. All wires have resistance and this resistance causes a voltage drop. A thinner wire has more resistance, also the resistance is proportional to length. A long thin wire will have a significantly larger voltage drop than a short fat one. In my experience the lead to the mains is fine but the output wire is miles too long and adds to the nest of wires effect. You could open up the device and shorten the supply wire. If you do that and all you find inside is a transformer and a thermal fuse then it's an unregulated power supply. These have wide variability. They probably only cost 50 cents to manufacture.

I note from your picture that it is a model for the US market and plugs directly into the socket so the best you can do is use a high quality short USB lead.

If there are plenty of MicroUSB supplies there must be a hundred times more 12v discarded wall warts that don't have a use, or a MicroUSB outlet. The spirit of RPi is to re use equipment. It defeats the object if you have to go out and buy peripherals. If you have to buy a power supply, a keyboard, a mouse and TV then it's cheaper to buy a refurbished laptop if all you want to do is Python programming.
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by rew » Sat Jun 09, 2012 2:05 pm
Larry, 1A at 5V is 5W. To "transform" 5W from 230V to about 5V, the transformer would need to be able to store that 5W for 1/100th of a second (half the time for the full period at 50Hz). This requires a certain amount of metal, which results in BULK and COST for the transformer. These transformers are bigger than the small/neat USB chargers that you find everywhere nowadays.

So most modern "chargers" and "powersupplies" are nowadays of the switching/regulated kind, i.e. in principle OK for the 'pi.

Still you can get the badly regulated ones. 5.5V unloaded won't kill a 'pi. 4.2V loaded won't kill a 'pi. The 'pi is reasonably tolerant for the 5V it gets.

Another story is the cable and the fuse. Both of these might cause a voltage drop. The fuse adds in 0.2V, which I presume is more or less constant across all 'pies. The cable can add in anywhere between 0 and 0.6V and things will still work (provided the power supply remains at 5.0V), but if the drop is more than 0.6V, things might start not-working even if you have a proper regulated powersupply. Bad cables that have too much resistance are common.
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by Puce » Tue Jun 19, 2012 7:06 pm
I have just received the Raspberry Pi.
SD card loaded, USB keyboard mouse and DIV with adapter connected.
Ready to power on.

What's that connector ? a micro USB ?
I have three childrens, with 4 generations of ipods, some ericson, nokia, samsung, acer and other gsm, psp & gameboy console, camera usb cables, powered USB hub and so on...
Mini USB everywhere, some A USB, B USB, small square USB and strange connectors

Not ONE micro USB at home. :o

Micro USB may be the best choice, but not for our family.
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by AndrewS » Tue Jun 19, 2012 10:21 pm
So, in all the time you were waiting for your Pi to arrive, you didn't think to check what powersupply it needs? ;)
http://www.raspberrypi.org/faqs
http://elinux.org/RPi_Hardware_Basic_Se ... _Will_Need
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by Puce » Wed Jun 20, 2012 3:46 pm
Not one second.
I really thought I had one matching.
Unless I see the micro connector.
Such thing just didn't exist for me until I received the Pi
:roll:
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by holmez » Sat Jul 14, 2012 10:23 am
AndrewS wrote:So, in all the time you were waiting for your Pi to arrive, you didn't think to check what powersupply it needs? ;)
http://www.raspberrypi.org/faqs
http://elinux.org/RPi_Hardware_Basic_Se ... _Will_Need


I was in the same situation. Primarily because I didn't realise that there were two different types of small USB connectors.

Ended up buying a 1A generic power adaptor from Sainsbury's which worked a treat. Although I was trying to work out if I could tap into the extra 300mA it provides that the pi doesn't require.

My pi has just done a rather interesting thing today though, when I plugged the power into my USB hub, and the hub into my pi, it booted up - taking it's power via the USB hub.
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by itimpi » Sat Jul 14, 2012 10:33 am
holmez wrote:My pi has just done a rather interesting thing today though, when I plugged the power into my USB hub, and the hub into my pi, it booted up - taking it's power via the USB hub.

Yes - many cheap hubs provide 'back-power' via the larger USB connectors. However the Pi polyfuses limit it so although it is enough to get the Pi to start booting it is not enough to power it properly.
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by AndrewS » Mon Jul 16, 2012 11:32 am
holmez wrote:I was in the same situation. Primarily because I didn't realise that there were two different types of small USB connectors.

USB, MiniUSB, MicroUSB http://en.wikipedia.org/wiki/USB#Connector_types
SD, MiniSD, MicroSD http://en.wikipedia.org/wiki/Secure_Dig ... sical_size
HDMI, MiniHDMI, MicroHDMI http://en.wikipedia.org/wiki/HDMI#Connectors

Anyone else spot a pattern? ;)

Ended up buying a 1A generic power adaptor from Sainsbury's which worked a treat. Although I was trying to work out if I could tap into the extra 300mA it provides that the pi doesn't require.

Discussed at length here viewtopic.php?f=63&t=8591

My pi has just done a rather interesting thing today though, when I plugged the power into my USB hub, and the hub into my pi, it booted up - taking it's power via the USB hub.

That's caused by a cheap USB hub, and is not recommended - discussed in detail here viewtopic.php?f=29&t=8261
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by ahi » Mon Jan 21, 2013 1:43 pm
I have not purchased my Raspberry pi yet, but I plan to do so.

But I believe that you can find a proper power supply for the Raspberry Pi here:

http://www.vanson.com.hk/?cid=84604&lan ... SB_Adaptor

IF Clas Ohlson operates in your country, they resell Vanson power products also.

I am currently using Vanson's 230V, 50 Hz Input, 5V, 2A total, 2 USB sockets -output plug-in power supply to replace Sony Ericsson's own 850 mA power supply to keep my XPeria Mini pro powered and fully charged while at the same time using the phone to provide WLAN internet connectivity top a PC. So far I have had no problems, even while charging another phone from one of it's ports and the mentioned Sony Ericsson XPeria Mini pro from another usb poert of the same USB charger.

If the Raspberry PI needs 700 mA, then 2A should surely be enough, in fact there should be 1300 mA extra available for USB devices connected to the raspberry pi, although you may need a special Y -cable to get power directly from the VANSON charger, while connecting the two DATA lines to the raspberry pi; this applies to, for example, an external USB hard drive connected to raspberry pi's usb port with an Y -cable to get power to the hard disk drive directly from the VANSON charger, due to the fact that the internal power path from Raspberry pi's DC input jack (micro USB) to the two usb peripheral device jacks are not designed to carry the full 500 mA maximum current specified by USB standard.

The only bad thing I have noticed so far about this VANSON product is that the blue superbright power on LED is irritating to the eyes, so I have just covered it by a piece of thick black sticky tape.

( IF someone from VANSON product design is reading this, please replace that blue led by a red one, and also: do not use superbright LEDs to increase light output; instead use it to reduce power consuption comared to a standard led ).

Clas Ohlson also sells another VANSON model with 2.1 A output, but unfortunately that one has only one USB output jack instead of two, so I do not recommend that, although that one comes with a nice "extra" accessories: a cable and several conversion plugs matching commonly used DC input jacks.
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by permaband » Tue Jan 22, 2013 8:15 pm
Hello my pi is running as a 24/7 server and I've been using this switching psu. Its totally cool under load and hasn't caused me any issues at all compared to the terrible inline sony erikson phone charger I had been using. ;) Its not cheap tho.

Link to product: http://www.kenable.co.uk/product_info.p ... ts_id=5642

Datasheet: https://www.distrelec.de/ishop/Datashee ... ng_tds.pdf
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by abishur » Tue Jan 22, 2013 9:02 pm
I've been using a blackberry 700mA charger 24/7 for a samba server, as well as a 1A HTC phone charger for my media center. Both were what I had lying around the house and both have been working excellently with no problems.
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by W. H. Heydt » Wed Jan 23, 2013 6:08 am
I've started using the Adafruit 5.25v unit...but I also use good cables.
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by sim_tcr » Wed Jan 23, 2013 6:21 am
Mine is running 24/7 (webserver) with Ethernet and 32GB Kingston pen drive with no issues. I am using Blackberry 8520 Curve Travel Charger 5V, 700mA.
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by Jim JKla » Wed Jan 23, 2013 8:00 am
Could it be there is a niche in the market for a Foundation approved possibly even Raspberry Pi badged PSU that has a quality regulated power supply that comes with a USB to Micro USB lead that is meaty enough to be say 1.5 metres without suffering a significant voltage drop.

It could also have a jack socket backed by the same power protection currently on the RPi supplied with a matching lead for GPIO connection. You could also supply a lead for powering via the standard USB for RPi's without poly fuses.

Note this would not exclude the RPi being powered by charger or by USB Hub from the verified list so a starter would still have a cheap solution.

Also rather than a wall wart solution a plug socket on this PSU that uses a standard power socket so that international wall connection would not be an issue.

I am thinking along the lines of the way most laptops are powered by the little black box that has your National standard plug lead for your country.

This is a niche primed for those companies that already produce universal replacement power supplies for laptops.

I am not talking cheap here but a solution that was set at a price point for those that were minded to buy a PSU that little bit extra.

An alternative solution would be a USB Hub of a similar specification.

There is maybe room for two classifications Verified as currently exists and Approved here Verified would stay as it is but Approved would imply that it had some margin of expanded capability that would guarantee it could handle a specified known load like some of the flashier Keyboards. ;)
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