Power supply confirmed as 5V micro USB

There has been a lot of speculation about the power supply design for the production Raspberry Pi devices. The alpha boards use a pair of switch-mode power supplies to generate 5V and 3V3 rails from a 6-20V input on a coaxial jack, and LDOs to generate the low-current 2V5 and 1V8 rails for the analog TV DAC and various I/O functions. This is a flexible and power-efficient design, but suffers from two drawbacks:

  • Expense. The two switch-mode parts and their accompanying inductors add roughly $2 to the cost of the device.
  • No support for 5V input. To correctly generate the 5V rail, more than 5V has to be presented at the input.

After a lot of experiments and spreadsheet work, we finally settled on an LDO-only power supply design, with a fixed 5V input, and the 1V2 core voltage generated directly from the input using the internal switch-mode supply on the BCM2835 die. We have chosen a 5V micro-USB jack to supply power to the board, for two reasons:

  • Ubiquity. Micro USB has been chosen as the GSMA’s Universal Charging Solution, so we expect AC adapters with this connector to be cheap and plentiful.
  • Voltage assurance. Unlike coaxial jacks, we know that we’ll be receiving 5V over this connector, which we can pass on unregulated to HDMI and USB devices.

Model B owners using networking and high-current USB peripherals will require a supply which can source 700mA (many phone chargers meet this requirement). Model A owners with powered USB devices will be able to get away with a much lower current capacity (300mA feels like a reasonable safety margin).


mdafbmm avatar

Great news, now I know what I need to buy (or dig out of my man draw) to be completely ready for my shiny new raspberry pi :)

Michael avatar

That is exciting to me, because I love the idea. You referenced your spreadsheet calculation, but I’m curious…

How much power does a Raspberry PI consume when doing a simultaneous 1080p encode and decode? I’m assuming that is close to worse case. You stated that the B version will require 700mA capable phone charger. According to Wikipedia, a USB 2.0 device may draw 500mA of current [1]. If someone plugs in just one USB 2.0 device into their Raspberry PI, that could leave only 200mA left for the Raspberry PI and whatever it is doing. That would be only 1watt of power (200mA * 5v) left.

As a workaround, anyone with a relatively power hungry USB device could use a powered hub, but that would be messy.

[1] http://en.wikipedia.org/wiki/Usb#Power

liz avatar

That’s basically right. Effectively, you have to negotiate for that power; the board will not repond to a device which requests more power than can be supplied. You wouldn’t, for example, be able to be able to plug in 2 USB hard drives, and have them both work. Instead, you’d have to use a powered hub.

hocares avatar

I think you are wrong about this.
Sure you won’t speak with devices that request more.
But (some if not all) devices will take the power without your ACK.

In desktop PC segment noone cares..
Motherboards can give 2A , you can’t configure, there is a piece of wire.
That means that device manufacturers have no negative feedback for exceeding the limit.

Plugging two usb HDDs in rabspi will probably break/pull down your power supply. And crash the RabsPI of course.

I once tried to run an USB HDD from my phone.. it drew ~700mA without a permission.

note: I have the Pandaboard, there are quite some problems when power management on USB is done according to the specs.. Devices don’t expect that.
Example: devices in my hub won’t enumerate when the hub is plugged into panda. It has only those 100mA to begin with.. It does not expect that.

liz avatar

I’m happy to be able to tell you that I’m *not* wrong – we just have cleverer people designing these boards than everybody else. (For those not familiar with the names and faces around here: I volunteer for the Foundation, so I’m perfectly confident that we don’t have a problem here.) :)

CtoZ avatar

I wouldn’t be so sure of that claim “Motherboards can give 2A , you can’t configure, there is a piece of wire.
That means that device manufacturers have no negative feedback for exceeding the limit.”

Pretty sure this is dependent on hardware and software. If I plug in a device that wants to draw more than 500mA from my motherboard via a single USB port, and it can’t provide it for one reason or another, the kernel deactivates the device and throws and overcurrent warning in the log.

hocares avatar

I am *not* sure about that.
I haven’t seen all motherboards.
Sorry if my post looks like that.

My first motherboard with USB had a fuse in place, the rest nothing.. no way to physically check the real current.

Sure that not speaking to device that asks for 550mA would work.

But what about devices that “forget” to ask you for more current and take it without asking? I had this category in mind

AVee avatar

@hocares: Devices which draw more the 100mA without asking are violating the USB spec. You won’t be allowed to even call them USB devices or use USB logo’s on them. And they will cause issues on netbooks and some laptops as well. I haven’t seen devices which do this in the wild.
Devices which charge over USB should (under the GSMA charging spec) check for shorted data pins, which indicate a dumb charger (or USB port in charging mode). Those ports should support up to 1.8A, so a decent mobile charger should support the Raspberry Pi plus two 500mA usb devices.

tomas avatar

As far as I know the USB host is allowed to cut off a badly behaving device (i.e. one drawing more current than allowed). I guess that’s what Liz is alluding to.

Just kick out the rascal ;-)

jamesh avatar

I don’t think its capable of doing that encode/decode simultaneously as some of the HW blocks are need for both, and they can only cope with 1080p30, not 1080p60 (as would be needed for both).

Figures for power are on the Wiki I think.

Lack Thereof avatar

I plan on using a powered hub with a Model B… and powering the Raspberry Pi with a cable from the same hub.

A micro-USB cable is even cheaper than a micro-USB charger

Jannis avatar

That idea is just awesome! Thanks for that great hint :D

Swiftek avatar

That is pure genius! (I think.) Can anyone think of a reason why this won’t work like a dream? I see a great default setup for a wide variety of applications. Thanks for a great idea.

Luchsen avatar

Quote from the Quick Start Guide:
“Micro USB power supply – make sure you use a good quality one, capable of providing at least 700mA at 5V. Do not attempt to power your Raspberry Pi by plugging it into a computer or a hub.”

Kenneth avatar

Can you please tell me why I can not use my Manhattan 5v 2 amp powered 7 port hub to power my Pi through it’s USB USB USB to micro USB ?
UASmicro usb ? it’ss

jamesh avatar

Just checked my Kindle charging plug which is USB, that pushes out 0.85A, so should run nicely off that!

asb avatar

Loads of cheap (as in a few £) supplies on ebay/dealextreme/amazon as well.

liz avatar

Ubiquity’s brilliant – Eben and I accidentally swapped hand luggage when we were going to different places last week. I charged my Kindle from his Blackberry charger, and he charged his Blackberry from the Kindle charger. He was not so happy about the underwear situation.

henry avatar

can we get a hydra charger?

a multi head cable off one maybe laptop psu in order to power many pi’s off one plug?

or would we use a powered hub to do this with many cables?

liz avatar

Do whatever you want – as long as you feed it 5V and it can source enough current, it’ll be perfectly happy. (Very few laptop psus provide 5V, though, so be careful – if you blow up your TV, I am not responsible!)

jamesh avatar

I dunno, brother of an ex girlfriend many years ago ran out of clean undies, and just used his wife’s. Methinks he liked it a bit too much.

Ken Pemberton avatar

oh thanks for that, Liz, you just made my day, I really needed a chuckle!

Dave avatar

so he says…

matthewtb avatar

So raspberry pi will run on a kindle charger??? but isnt there 2 different types of micro/mini usb . it would be really helpful if some one could give a link to amazon indicating what one i would need???

JamesH avatar

I think the Kindle charger will be OK – that uses MICRO USB.. Mini USB won’t work.

Doktor J avatar

There is only one micro USB connector (well there are two, but the “one” is like 99% prevalent); mini USB is a different animal entirely — often used on GPSes, some cameras, portable hard drives. If it says “micro USB”, chances are it will work.

Nick Dolan avatar

Perfect :-), a real use for a kindle in the UK

ffuentes avatar

I don’t understand well.

Will the R-pi include an AC adaptor or not? I have one with USB port but I don’t know if it will be useful.

liz avatar

You will to buy a separate AC adaptor if you don’t have one already.

vfrico avatar

What would happen if I use a micro usb B plug with 5v – 750mA for the B device? Would I damage the device?

liz avatar

Not at all – do you mean the A device? You certainly wouldn’t damage the model A – it’s the capacity, but nothing forces the device to take that current.

jojopi avatar

Surprising late change, but this is a smart simplification.

Also, many HDTVs now have powered USB ports (I have run a 2.5″ HDD off my LG). So some users may not need a separate power supply.

liz avatar

Well, it’s not late to us (it’s been in the works for a while), but there are a few reasons I can’t go into here which have meant that we haven’t been able to announce it yet. :)

Adam Riley avatar

So in theory, could I power the Raspberry Pi off one port of a powered USB hub? Then also plug that USB hub back into the Raspberry Pi and use it to power my external hard drive? So then I only have one power supply to plug into the wall?

But the circular nature or my wiring sounds like it could be asking for trouble…

liz avatar

That *does* sound a bit like it’s asking for trouble. Definitely not something we’ve experimented with – I’d be very interested if you can tell us whether it works when you have your own Raspberry Pi!

lightinthedark avatar

That’s exactly the question I was going to ask :-) I would guess that it would “see” itself as an attached device. What (if any) functionality would you get over the micro USB port? Is it a fully functioning USB port or just a power supply?.
It’d be nice if you lovely Pi people could see if it works and let folks know before an unsuspecting customer blows up their shiny new toy though.

liz avatar

It’s just a power port. And yes, we’ll get someone to test the horrible circular power hack before we ship!

Adam Riley avatar

Hey, less of the “horrible circular power hack”! ;-)

I thought it was quite an elegant solution (if it works…)

SeanD avatar

As the Pi is using just a power connector (no data lines connected) this should work. I have done with other USB powered devices. At the end of the day all you are doing is creating a parallel connection of the 5V bus.

b stone avatar

Electrically, this should not be at all ‘circular’.the hub should only draw power from from its own power supply and therefore has no need to connect to the host’s power supply.

James avatar

The powered usb hub should just cut off any power-in source other than the power adaptor. Circular power should therefor not be occurring at all.

So the data pins only will provide a little current into the othet devices to read/provide data (and will not affect the power for running a device).

If you want to be absolutely sure, you van disassamble a usb connector, cut off the 5v + and – poles, and reassamble.
This way circular power will absolutely be impossible, since the Pi will not connect the data pins of the USB power-in-cable to provide energy to the device (correct me if I’m wrong).

liz avatar

It was a joke.

Jared D avatar

Hypothetically, the power supply does share the ground over the USB so that the receiver and sender both know what the voltage difference is between 0 and 1…
It doesn’t relay the voltage [+5v] through it though on most devices…

Mikko Rauhala avatar

Yeah I wouldn’t go so far as to promise it’ll work, but there shouldn’t be any showstoppers necessarily. However, three considerations:

1) The hub will have to provide power to downstream ports even when upstream is not connected. (Sometimes called “Always-on ports”.)
2) The hub will have to provide power to a port with unconnected data lines, and therefore also without negotiation more than the USB minimum of 100 mA.
3) For model B, the hub will have to not mind the >500mA power drain on a single port.

I _suspect_ many cheap powered hubs would work. I’ve seen only one that seems to promise the necessary features: http://www.amazon.com/gp/product/B000I3XIE4/ (still, buy and try at your own risk, I’ve just looked at the specs). Costs almost as much as a model A though ;I

Michael avatar

If you are handy with a soldering iron and have a spare hub you can always modify your hub to put out 5V on the host side. I’ve done this to use USB host mode on a few phones (Motorola Atrix for example) and it works well. Granted you can never use that hub for a PC again :)

Michael avatar

That’s actually a pretty common setup for Beagleboard, so I would expect it to work for R.Pi also.

WASD avatar

You could also power the USB-hub from the R-pi usb-port. Infinite power!

Tom Cole avatar

Ah yes, but ‘asking for trouble’ = ‘asking for experimentation’ = ‘asking for a try’ = point of RaspberryPI!

DeatK avatar

this is the same question i have…
but i didn’t understand if it works (sorry maybe my english is not good enough)
cause i’d like to plug to the wall only one power supply
using the usb powered hub tu supply the power to the raspberry and to use the external devices
does this works or not?
it would be great!

liz avatar

There’s a discussion about this on our forums – have a search and see what you come up with!

seeingu avatar

This is how the NSLU2 is wired internally. To power external USB devices it draw power direly from the 5 volt input just like most cheep USB HUB’s will do it. Therefore the NSLU2 can alternatively be powered trough the USB port. If powered through power inlet and a there is a powered USB HUB connected the two 5 volt line are wired in parallel.

Guess this does not apply for the RPi as it sounds like it use real USB logic to handle power distribution.

Jorge G avatar

Well not rasberry PI, but I had done the same with a chinesse NAS…: having a powered HUB and pulling the power from it to the NAS, here the trick was use one of those Y-USB cables provided on some 2.5 HD cases. one of ends has connections only on the power line, but not on the data, and that reduces any change of a horrible loop (Vcc goes to Vcc and ground to ground… so it keeps cool)

hajj_3 avatar

very happy to see you went with micro usb instead of a psu brick. Much cheaper and available everywhere.

Do you know when you will have photos of a retail board yet, would love to see some high res photos :)

jamesh avatar

No photos, as no board yet! Not yet gone to manufacture – few final bits and pieces to sort out.

Yakovlev avatar

I just want to chime in that I consider this fantastic news.

I’ve been concerned about the power supply, so it’s great to hear that it’s something I already have laying around.

Now I have an excuse to go get that charger with a longer cord that I’ve been considering…

novelty2145 avatar

If my PSU can source enough current to power an external HD (in addition to the RPi of course), will the RPi hand it through to the USB ports?

Could I even power 2 disks provided my power supply has the required wattage rating?

chris avatar

kinda wondering this too, if your powersuply has enough current would you still need a powered usb hub?

liz avatar

Yes – the 5V in connects into the 5V out.

Bernhard Kuemel avatar

What’s the current rating of micro USB?

JamesH avatar

Supply or demand?

MDG avatar

How does this play into the OTG Device Mode board task? WIll the microusb used for power also be the port for the device mode, or am I just missing something? (Granted, putting OTG device functionality on the microusb “power” port will mess up the USB circular power idea from Adam Riley….)

fhtah avatar

There may be a catch with micro usb charging . I have N900 and most cheap chargers and also kindle charger cannot charge it without modification. It was said nokia sticked to specification about anything >500mA and dumb charging need to shortwire some pins.

AVee avatar

You need to short the datapins, as specified by the GSMA charging spec. I shorted the datapins on my car charger, to make my n900 (and other recent phones) draw more the 100mA when charging. Worked like a charm.

Before the EU forced phone manufactures to get their act together devices used there own ways of checking for dumb chargers, generally by checking for a manufacturer specific resistance on the datapins.

The Cageybee avatar

Would I be right in thinking that the USB mini-b port will only be connected to the power rails and not to any data lines?

If so they’ll be no problem with the looping USB. If they are connected, just take a standard cable and cut the data lines (green + white) and wrap them in some electrical tape ;)

mat80c avatar

Ok I’ve gone through the box of power supplies, 14 of them, and I have one that supplies 1 amp. What has everyone else got to hand already? (not currently in use)

Great choice of supply they are really cheap/plentiful online and you can get ones that supply more current too!

lwalthour avatar

I have two wall to USB adapters, 1A and .85A, plus my cheapo walmart Micro USB charger that outputs .8A.

covex avatar

Do not be fooled, the stamps on power supplyes may say anything, especialy the cheap ones, but there is no guarantee they really can supply this..

Delyan Kratunov avatar

In my experience, they usually *can* provide that much current but it’s not their maximum. Also, the cheap ones don’t have any protection from drawing too much current, they just burn out (some of the official phone chargers do have protection, however).

Ryanroll avatar

@ Raspberryteam, excellent choice! you guys Rock !

I guess plenty of us already got a usb charger like the Apple ones (iphone, ipod…) and if you don’t, you can purchase one very easily and cheap on ebay for instance.

Can’t wait to have one :)

[…] “After a lot of experiments and spreadsheet work, we finally staid on an LDO-only energy supply design, with a bound 5V input, and a 1V2 core voltage generated directly from a submit regulating a inner switch-mode supply on a BCM2835 die,” writes Upton on a official plan blog. […]

lobster avatar

What rechargeable battery power supply is recommended/available?

caminati avatar

I like this choice.
However, I was wondering if there are crappy power supplies around presenting Micro USB form factor on output and supplying low quality (e.g. rippled, or out-of-tolerance) DC signal.
This worry arises because the 5V goes directly to the board core, if I got things right.

liz avatar

There’s a polarity protection diode, a voltage clamp, and there’s a self-resetting semiconductor fuse onboard, so you shouldn’t have to worry about blowing your Raspi up. We’ll also be selling a tested and approved power supply from this website.

caminati avatar

Wow, exhaustive reply, thanks.

Brian Smith avatar

Do you know if the 5V in is available elsewhere on the board, maybe on a pin strip or solder pad? (for connecting batteries without having to mangle a micro-usb cable)

Gert avatar

Yes, there are two 5V pins on the GPIO connector.
But that will not have fuses, polarity etc.

Scott Sullivan avatar

Brian was asking about Vin, to supply voltage to the RPi. Your answer is informative but to me seems to address Vout.

I too would like to know about this as it would be interesting to directly wire a power source to the board, by-passing the MicroUSB connector.

Gert avatar

It is not Vout it is V (5V). In a power plane there are no ins our outs.

Michael K. avatar

The difference between the 5V (VBUS) from the USB and the +5V0 power plane is the Fuse (F3)! If any power supply behind the fuse rises over the limit of D17 it could be a problem for D17 or the power supply. Be careful

liz avatar

Gert is one of the Raspberry Pi’s hardware designers; I think he understands what he’s doing just fine. :)

Paul Burjwah avatar

This is absolutely FANTASTIC. 

Eben, thanks for sharing the details of this design decision and especially for making the job of powering the board so inexpensive and easy. 

Nice job cutting out the fat and coming to this very elegant solution. 


Andre_P avatar

This is an excellent solution, it also removes the scariness of getting the polarity wrong that can happen on a coaxial connection.
I have a sat nav that when in the car is powered via a micro USB so it means that I can go mobile when I get a board. Imagine an entire car running just to power a Raspberry Pi, there goes my eco values ! :)

csaba2 avatar

So could it handle a 2.5″ hhd(sata to usb adapter), keyboard, ethernet, hdmi with 1000mA adapter?(model B ofc)
Or I ask too much? :-)

Mike S avatar

Great, i’m so waiting for this to get out to test on some of my projects. Any change on getting my hands on some alpha boards ? ;;)

liz avatar

Ha! No. 8)

ukscone avatar

alpha boards are so last year. it’s beta boards that people want now

Chris avatar

Good news indeed, just need to find a good powered USB hub and Iam ready to go.

james avatar

Brilliant decision!

Bizzo avatar

Awesome. That’s a brilliant solution to the power issues. I can use my Kindle connector.
But here’s a couple of amazon links that are really very cheap if you don’t have any micro-USB cables:

USB 2.0 A to Micro B Data Cable – £0.71

Black Mains USB Travel Charger – £0.98

Not checked the P&P, so it might work out to be cheaper at your local electronics place, or even your local supermarket considering what it is.

WASD avatar

Thanks for the links. I will probably buy that cable and a http://www.amazon.co.uk/Neewer-Two-Pin-EU-USB-iPhone4G/dp/B0053WV9PU/ref=sr_1_1?s=electronics&ie=UTF8&qid=1319210078&sr=1-1 since we have that kind of power-plug here in Sweden.

I checked dealextreme too and the prices were about the same.

ausserirdischesindgesund avatar

What does this mean for supplying power by battery? Will there be an additional power supply or voltage regulator be needed to supply constant 5V?

Blars avatar

You may be able to get away with using 4 NiMH or NiCd cells in series without a regulator, but for most potential batteries you would need one. Boost dc-dc supplies with usb out are common on ebay, so you could use two alkaline cells or one lithium rechargable supplying the booster.

André avatar

4 NiCd/NiMH batteries would get 4.8 Volts. So… If this would be an acceptable input voltage, then I am wondering about the limits. How much under/over voltage does it accept.
Also, thinking about running on batteries, is it able to monitor it’s input voltage, in order to detect the batteries going empty, so it doesn’t just go dead without warning.

hajj_3 avatar

i realise this isn’t financially viable but would a usb3 chip onboard allow 1800mw rather than the current than 500mw to be used.

You would obviously need a usb3 cable and a usb3 charger too.

Just wondering if this is technically possible.

Blars avatar

I’m pretty neutral on this news. It means my pile of potential R-pi wall warts go to recycle (I think I get $0.25/pound) and I need to get some micro-usb cables. (I have pleanty of mini-usb, but no micro-usb at this point.) Since I need to supply 5v for other things (including the usb hub) anyway, the voltage isn’t a problem.

toxibunny avatar

same here…

Michael K. avatar

same here… ;(

I don’t really understand the decision to micro-usb? *ALL* my Gadgets need mini-usb. Some external HDs, Digicam, MP3 Player, USB (MIDI) Keyboard, Wacom Intuos, etc.

scep avatar

“I don’t really understand the decision to micro-usb”


Max avatar

I think this is a great solution, because seemingly everyone around here does appreciate it. I have to respect that and hence I think it’s good you made this decision.
However, as for me, I don’t like it, first of all, because obviously this (I’m talking about model B now) isn’t conforming to the USB (2.0) specification, thus there’s no reason to believe one could use an actual USB port (from another computer) to power the Pi. As far as I know, most host controllers provide some sort of overcurrent protection and if they don’t, trying to draw more than 0.5 A could seriously damage the controller. I never tried that, so I got no personal experience on that topic, but that’s what I think to have heard/read. Furthermore, I read several comments wondering about whether plain AC powered USB chargers really support those unspecified currents. Additionally, I never really liked the idea of powering the Pi off another computer, because the Pi itself is a computer and should thus not depend on any other.
On the other hand, I really love the idea of making the Pi portable (in any way), and obviously one needs batteries as a power source when doing so. I scanned through several forum posts discussing this topic, whose authors seemed to me to have found some solutions on this, and now I wonder whether these solutions will still work, e.g., just putting some batteries in series on the board and connecting them directly to the power input or if that will be endangered in any way because one has to make sure the input voltage is exactly 5 V (and not 4, 4.5 or anything like that; I don’t exactly know about the stability of the output voltage concerning batteries)?

In conclusion, I appreciate your decision because the majority does so. However, I’m afraid I won’t gain any benefits from it, because if I try to power the model B (which I am/was planning to buy) from a PC, it might damage it (you can never guarantee it won’t), the same applies to AC powered USB chargers. If you had sticked to the (proprietary?) AC adapter, I could be sure it would work. I guess, I now have to reconsider buying model A instead of B, because that one will be withing the allowed current range and thus at least safe to use.

PS: I didn’t even mention the fact so far, that as a passive USB device (i.e., no communication via USB), which I think the Pi to be, you’re technically not even allowed to draw more than 100 mA; however, there are enough USB gadgets out there who violate that rule, too, so that won’t be big of a problem.

max1zzz avatar

I’m not really very happy with this news, although i know allot of people have been asking for usb power, and i understand it will bring the price down, you loose the factor that everyone will have a adapter to power it, because it is now tied down to a specific voltage using a non stranded connector, i think if you are going to tie it down to 5v, use a coaxial or mini usb. the problem with micro usb is it is pretty non standard, i haven’t seen much that uses it, however everything uses mini usb, most people have boxes of them sitting around

liz avatar

Non-standard? I can think of a few standards bodies who’d argue with you over that one. They’re already pretty ubiquitous (as you can probably tell from the comments here), and we only expect to see more of them kicking around as time goes on.

Hernan Rodriguez Colmeiro avatar

At least here in south america mini-usb are far more common than micro-USB. I have at least 5 devices using it, while no micro-USB device.
But I see that if the micro-USB was adopted as the connector of choice, then using it for the R-Pi is a good choice, future-wise. Remember http://xkcd.com/927/ :)

max1zzz avatar

I was just going on what I have seen, but really i should quit moaning, 2 mins with some stripboard and a 7805 (with a cost of ~£3 inc postage) i can use pretty much any voltage i come across

Brian Smith avatar

Remember to add a big hunk of metal too to burn off the extra Watts without frying the regulator though.

André avatar

December 2011 was the first time I’ve seen a micro USB connector, when I got my new phone. All my other devices (including a BeagleBoard) use mini USB. At first I wasn’t even aware this to be a standardised connector, and suspected it to be another proprietary connector. Only when I started googeling to find an extra USB cable (so one can stay connected to my desktop computer and one for the laptop bag) I found out is was a standardised connector after all.

Tich avatar

Wierd… I’ve had a micro USB on my Samsung phone for the last 2.5 years and every Blackberry I have ever seen uses a microUSB for combined data and Charging (not to mention Kindle)

jamesh avatar

I believe every smartphone sold in Europe for the last year or two requires this connector…..that’s pretty standard (Europe, big place, to the right of the Atlantic)

Whilst mini are more common (or were), Micro is actually the standard as specified by the USB standards body.

Michael avatar

I would probably agree with you that right now mini-USB is probably more ubiquitous – especially when it comes to man drawers or odds buckets at your local radio spares shop.

However, this will change very quickly and if you can find a cheap mains to USB-A power adaptor, you can pick up USB-A to micro usb cables very cheaply online and fairly cheaply from your local high street.

Just today, a colleague pointed out to me that his external 2.5″ USB HDD had a micro-USB port on it, not mini-USB or USB-B as I was expecting. All the indications are that micro-USB is being used in place of mini-USB for new designs, pretty much regardless of the type of device.

Gert avatar

I think what was not so clear from Eben’s message is the litigation risk reduction. The 5V goes straight to the USB and HDMI ports. Suppose somethings happens to the supply or somebody plugs in 24V. There is a serious risk of blowing up $1000 HDMI TVs. As a charity we can not afford that!

caminati avatar

This raises the question: is the protection (clamp, fuse, etc…) Liz was talking about applied to the whole input signal or just to the portion going to the die, leaving out usb and hdmi?

liz avatar

It’s the whole input. :)

MG2R avatar

I must agree with Max on this one… Personally I don’t like this one bit. This makes it a bit more complicated and requires more space to make a battery powered r-pi, because of the external voltage regulator which needs to be provided.

Also, with an on board voltage regulator you can just plug in whatever AC adapter you want, now it HAS to be a 5V one.

But, given that the vast majority likes this decision, you made the right choice :)

liz avatar

We’re hoping to produce an add-on battery pack some time next year – not ideal for those who’d rather hack their own, I know, but for our intended market, it’s a better solution. I wish we could please everybody all the time, but we’re fast learning that it’s impossible!

MG2R avatar

No problem! As I said, you took the right decision! As far as I know your goal is not to make a computer to fit in hack projects of hobbyists but to make computing, electronics and programming accessible to less fortunate kids? In that perspective you guys did exactly what needed, hobbyists like me will figure out a way of getting this thing mobile anyway!

Keep up the good progress, can’t wait to get my hands on one (ore more) of these!

MDG avatar

A device you can model a battery pack on is the Tekkeon TekCharge:


It can even *charge* 2x or 4x AA NiMH batteries as well as providing 5V regulated output. I haven’t tried doing both at the same time, though. (And I haven’t been able to get mine apart without possibly destroying it yet, so I don’t know what’s inside….)

Ulrich avatar

I also am not very happy with this solution. I plan to use the ras-pi in some embedded applications where it would be much simpler to use unregulated input via a dc-jack (or direct input pins).

But I guess for the use case intended by you guys a USB powered solution is the most practical. Still I wonder if micro-USB is really as ubiquitous as you think. Looking at my personal “assorted cables” box I have more than 10 mini-USB cables in there and not a single micro one.

liz avatar

The move to micro USB as a standard for mobile devices only came into force early this year. You’ll see a sharp ramp in the ubiquity of the things – the various standards bodies say they expect the chargers to be “predominant” by the end of next year. And yes, they’re really as ubiquitous as we think; we do a heck of a lot of research into this sort of thing (along with every component on the board), and don’t just make these decisions frivolously or on the basis of what we see in our own houses and workplaces.

Ulrich avatar

I’m not suggesting that you do make those choices lightly. My apologies if my post came across as dismissive of your effort.

Sander avatar

I thought the micro-USB charger was already forced by the EU / EC (Neelie Kroes?) a few years ago (in 2009?), saying to the telco industry “define a common standard for telephone chargers, or … else we’ll make a standard”. A few months later, the telco industry came with the micro-USB.
All my phones for the past years have micro-USB: my HTC, my Nokia N97 (don’t know about my N95), and my Blackberry.

liz avatar

That’s absolutely correct – in Europe, at any rate, it was announced as the standard in 2009, with a deadline of the end of 2012 to comply – most companies are already offering micro USB already. In the US and elsewhere, there have also been moves towards consolidating, and it appears to be the way things are going – all this is nothing but a good thing, as far as we’re concerned.

Tom Slominski avatar

I think it is most imperative, that as the release nears, you release a “buyer’s guide”, eg. what will be included with the Raspberry Pi, if things like the charger aren’t included what would the Foundation recommend etc.

liz avatar

It’ll be very clear in the online shop what’s included, and what other bits and bobs you can buy – don’t worry!

brett avatar

Thank you!

mrlinux2u avatar

Found this on Amazon :


Seems to supply upto 1000ma – should be more than enough to power the RPi, and external 2.5″ HDD, and still have enough for a mouse/kb using an un-powered usb hub (please correct me if i’m wrong).



Cheap enough @ £2.99

Nigel Smith avatar

This really isn’t a USB powered device, it just happens to use the same connector COMMONLY found on micro usb devices, the only change this decision means for hackers is that you now need a regulated supply, that’s not much to ask for really, it’s as simple as one LM7805 attached to the same DC PSU you were thinking of using before.

Quit moaning and look for solutions, this is a learning tool, if you want small laptop power and a nice shiny power adapter all with a pretty fitted case, then buy a small laptop.

LM7805 will give you 1A of power at 5v with an input range of between 7-24vdc, that means you can use the RasPi in your car/truck/boat.

Andy Bisby avatar

Mr. Smith, I have to say that is a great answer.

Isn’t that the whole idea of the RPi? It’s a learning tool. Take it out of the box, see what else it needs to get going, and sort it out.

It’s unlikely there’s going to be any “Random HighStreet Store” PC support for it. The support for this is going to be here.

I reckon I’m going to be so far out of my comfort zone when I get mine, it’s going to be unreal. Exposed hardware, Linux etc, but I am so looking forward to it! It’s going to like being back at school for me, but at a really cool school.

Ken Anderson avatar

Typical 12v to usb car adapters make my car’s AM radio sound like “scorched earth” bombs are landing. Do they employ an LM7805 regulator? Or will one of these cheap little things leave me with pie all over my face?

And any thoughts on an hdmi audio to car stock 6 speaker stereo? FM transmitter? What level is hdmi audio? Do I need a preamp? fun stuff. yeah, I know I could google… I’m just expressing some excitement! :-)

Thanks & waiting on my ordered pie.

gz avatar

Still can’t wait. Seems that a $2 savings makes the advent of a $2 USB3 controller more likely! ( Sorry couldn’t resist. Version D board right? :) )

jamesh avatar

Except that the USB 2 controller is build in to the SoC…so you will need to respin the chip with a USB 3 controller. So that’s about $1M.

gz avatar

No, its an off the shelf chip. Runs about $2 in volume for the 2 port version. You’d never want to give up 2.0 just to add 3.0.

mahjongg avatar

Its an off the shelf chip… that cannot be used with this SoC.

Scott avatar

Could you please quit teasing us with how awesome this thing is and just sell it to us already?

bnolsen avatar

It seems to me that the only people upset about the move to microUSB for charging are the ones who actually have the knowledge to identify what they don’t like and definitely the ability deal with it.

The rest of us can just go buy a microusb charger that provides enough amps and go on with it.

If you were to have just pleased that small crowd you’d then have a whole bunch of clueless people having no clue what power supply to buy, where to buy one, and more than a few who would plug in the rpi with nothing happening (due to getting a wrong barrel, wrong voltage, wrong polarity, you name it).

reiuyi avatar

In a way I’m quite happy it ended up accepting 5v

The other side of the coin is that this makes my plans for a battery-supported device more difficult. Voltage regulators like LM7805 in TO-220 are a good choice I guess. Some can have input variances upto 35v without a hitch. Like the OP said, it’s about €1 or €2 for the voltage regulator.

Hope there won’t be any more big compromises in functionality!

Blars avatar

For battery power, it’s worth the slight extra complication and expense of using a switcher — something like a LM2595T-5 would do. (Requires an extra inductor and diode, and the input and output caps are less optional.)

reiuyi avatar

Thanks for the suggestion, I ended up getting something similar to:


It’s based on the LM2596, has a maximum of 3A (at 5v) and an efficiency of 80% when converting from 12v. To my understanding, that’s not so bad. Plus it has an input of like 7v to 40v! It’s way okay for my little battery-powered project

giammy avatar

Hi all,

I’d like to point – related to battery powered solution – which I will use – that there exist battery packs for smartphone with a micro usb output … elegant already present and common solution! I appreciate the micro usb choice.


WASD avatar

I don’t think the one for $1.99 will work. It says 500mA output and model B needs 700mA. This one says 1A ouput: http://www.dealextreme.com/p/usb-power-adapter-charger-for-iphone-4-white-100-240v-eu-plug-48615

ppcc avatar

Hi, mind that the first product is a MINI-usb connector not a MICRO-usb one, so it is no good. You can buy together your second and third products and get what you need ($1.99 + $1.20 = $3.19). The problem is that you only get 500mA with your adapter, enough to power your model A raspi but not enough for what’s recommended for your model B (700mA).
I’ve found a combination of adapter and retractable cable for $6.20 but with 2000mA. Probably you can find better deals.


With this I think you can even power a 2.5″ HD, for example a WD Scorpio Blue 750 GB (WD7500BPVT):

Electrical Specifications
Current Requirements
Read/Write 500 mA
Idle 400 mA
Standby 50 mA
Sleep 20 mA
Power Dissipation
Read/Write 1.6 Watts
Idle 0.65 Watts
Standby 0.20 Watts
Sleep 0.20 Watts
Electrical Specifications
Current Requirements
Read/Write 500 mA
Idle 400 mA
Standby 50 mA
Sleep 20 mA
Power Dissipation
Read/Write 1.6 Watts
Idle 0.65 Watts
Standby 0.20 Watts
Sleep 0.20 Watts


WASD avatar

So I wont have able to power an external harddrive directly from the R-Pi if I only have a 1A power adapter? That would be 1200mA total if r-pi + harddrive is 700mA+500mA.

Are you sure the R-Pi can handle the full 2A input from that adapter and give the harddrive what it needs?

My plan right now was to buy a 1A adapter I found and use a 2.5″ USB-harddrive that I have but maybe that won’t work. I’m not good at electronics.

covex avatar

The only problem with 5V supply is, you can not have a long cable to supply it as 5V is dropping quickly with the distance. Therefore you can not use a POE. What a shame.

liz avatar

In a peer reconfiguration you’d generate the voltage locally from the higher voltage on the ethernet line, so dropping over distance isn’t an issue. I do like to see you guys worrying about this stuff, though!

bense2k avatar

Would be interesting if the datalines were avaible on pins so you could use an usb to usb network adapter for connecting the raspi to a pc.

liz avatar

I’m sure it *would* be interesting, but I’m afraid it’s just a power jack. (This was one of the reasons we had to think hard about changing to USB power – we knew that a lot of people would look at the thing, think “but I’ve seen data come over those!” and make the obvious assumption. Just power, folks!)

Justin Stringfellow avatar

Agreed – I think it would be very good to be able to do power and console across a single cable. There’s an opportunity being missed, here, I feel.

liz avatar

There isn’t, I’m afraid; there isn’t any way to route anything other than power over that specific wire. The fact that it ends in a USB-shaped hole doesn’t imply data.

cait avatar

So the raspi B takes 700ma for itself correct?
Whats the amp draw with all ports filled?
Say i hook up a keyboard, mouse, and wireless adapter..whats the amp draw then? Have you guys even tested popular aftermarket accessories like these in different configs? If not…wow..i forsee alot of smokin usb chargers.

Liamthe1st avatar

I have spent over £100.00 on a new key board and mouse with a powered hubx4 way and an adapter after all this advice on here 0.7mA is too small for the Mouse and Keyboard 1000MA does nothing also and now there is no signal even with an adapter that is sold with a Pi kit from Maplin in the UK.
This leads me to ask where is the Poly fuse and do I need to had done a course in smd soldering to fix it?

James Hughes avatar

You won’t get any replies to tech questions here. Please post on the forum to get technical help.

Although I will say – I use a mouse/keyboard combo that cost about £10, and a Nook power supply that cost £5, and, when I need it a hubs that cost about £10 and it all works fine. You should not need to worry about any polyfuses, they were really only a problem on very early boards.

cait avatar

So the model B takes 700ma by itself or when all ports are loaded?
Whats the amp draw with say keyboard, mouse, wireless adapter, ethernet all hooked up? Have you guys tested various manufacturers of accessories like these for power usage? If not…i forsee alot of smokin usb chargers (most of which will only source 500ma)..i have 4 of them and all 4 say 500ma on em….

eben avatar

No, a good chunk of the 700mA requirement is to provide feed-through power for downstream USB devices. Most of the chargers I have to hand are in the 750mA range, but the GSMA UCS spec requires 850mA of capacity, so we expect to see chargers converge on this figure quite rapidly.

Jeff Hadow avatar

I have ordered along with a RaspberyPi B, a 550mA capacity charger. If I only connect a Hdmi cable, Ethernet cable and a USB from a powered Hub Will there be a problem with the shortfall os 150mA?

Abishur avatar

Time will tell I fear ;-) I know that 140 mA is dedicated per usb port (280 mA total), so in theory you *should* squeak by, but I’m waiting for real world experimenting before making too strong a response on the different power situations :-)

DaVince avatar

I have a notebook that has USB 3.0 ports – can I safely connect it to these ports?

petrus bitbyter avatar

The mini USB connector is used only to power the decvice. Many notebooks limit the USB current to the minimum of 100mA required. As the RaspberryPi requires more current you may not be able to power it from your notebook.

Roger Moe avatar

Would this be able to power the raspberry, if yes how long ?

Daniel avatar

16 amp hours at 400ma draw would be ~40 hours.

Burngate avatar

I seem to have lost the ability to post to the forum so I’ll put this here.
From the descriptions all around, I’ve come up with this:
(drew it, made a jpeg, posted it on facebook, hope you can see it!)
Only two questions : is it anything like reality? and does the 5V feed anything on the board bar the regulators?

Jeremy avatar

Can’t wait for this to come out. For those looking for clean setup check out this power supply set up. http://store.fastmac.com/product_info.php?products_id=458

Anthony Watts avatar

I’m totally OK with this solution, as there’s always a nightmare with coaxial power plugs in one way or another, size, polarity, goodness of fit. They tend to fall out a lot.

MicroUSB is indeed interchangeable – I charge my Android phone and my Bluetooh from MicroUSB, then plug it into my Android tablet. One size fits all.

I just hope the power is on one side (maybe the shorter board side) and the HDMI is on the opposite side. This allows for simple pass though wiring such as if I wanted to plug the board into the rear of the TV and power it from one of the TV USB ports.

Nothing worse than having cables come in/out at right angles.

The long thin version of the raspi (pre alpha) got me excited because of the form factor.

On another note – will there be any facility for installing a WiFi module daughter board of some type on header pins, so that we don’t have to hang it off a USB port?

Shadowww avatar

..which means Raspberry Pi will be able to work from AA batteries / Li-ion cell using MintyBoost! Awesome! Love you guys :)

Anthony Garoutte avatar

not sure how ambitious this is, but i found a usb solar charger that can output 5 volts and 5 watts if in good sunlight. if i can use that to constantly charge an external usb battery pack with a 5000 milliamp rating, is it safe to assume i can make this thing last on solar power if i only connect a usb keyboard, usb mouse, and an hdmi output?

the solar panels advertise being able to charge most devices even while the devices are being used. the battery pack claims to be able to handle 26 hours of movie playing on your device or something like that on one charge. can i use these to power the pi off solar alone? no external hdd, just keyboard, mouse, hdmi out.

liz avatar

That certainly sounds safe with an external battery, and I don’t seen any gaspingly obvious problem with it. We’d be interested to learn how it goes if you try it out – do come back and let us know!

Chris avatar

Post a link please, I want one!

Brandon avatar

How much power can the Pi handle going through it? Could it say handle 3+ usb devices that pull 200mah each? Obviously this would require a passive usb hub to connect 3+ usb devices but some projects like mine will only have a single 5v power source.

liz avatar

Lots of discussion on this in the forum – come and join in!

Marti avatar

I’ve got one of these that I use to keep my cell phone up when I’m travelling; it should be a perfect (if pricey) way to provide portable power to the R-Pi:


Some of their smaller units are more cost-effective (ie, cost less that the PC!) mobility solutions.

wrhii avatar

While they may be lower cost, many of them will not have the current to support the Raspberry, the 4001 does appear to be sufficient [at 2A max vs the 500 ma].

I found it on Amazon for ~$50, so the price is not that extreme if portable power is wanted. I would suspect it could power a Raspberry for quite some time too. Very nice find, thanks.

Serge Gilette avatar

Extremly good news ! keeping to low voltage will permit to use solar cells, low tech engine and plenty of other way.

I was looking for a simple low cost computer that works with little energy and i think i found it !

James avatar

I’ve ordered a few of these for use in 5V projects requiring decent current, you’d have to hack the cable off and put a micro usb end on it but at <$5 each they're a pretty good solution.


[…] http://www.raspberrypi.org/archives/260 GA_googleAddAttr("AdOpt", "1"); GA_googleAddAttr("Origin", "other"); GA_googleAddAttr("theme_bg", "ffffff"); GA_googleAddAttr("theme_text", "333333"); GA_googleAddAttr("theme_link", "0066cc"); GA_googleAddAttr("theme_border", "5581C0"); GA_googleAddAttr("theme_url", "114477"); GA_googleAddAttr("LangId", "1"); GA_googleAddAttr("Tag", "hardware"); GA_googleAddAttr("Tag", "islate"); GA_googleAddAttr("Tag", "phones"); GA_googleFillSlot("wpcom_sharethrough"); […]

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H avatar

Very interesting.

I’m currently researching photovoltaics as part of a PhD. Experimentation includes lifetime measurements and comparisons between current silicon PVs. The original intention was to log data etc. either with a small computer nearby, or down a wire to an indoor computer. It would be more convenient to log the data on a small nearby computer, however it would be quite interesting to also power the computer itself.

This may even show potential for uses in third world countries etc.

Jaga avatar

Are there any plans to have the board powered over LAN (PoE)?

liz avatar

No. It’s worth reading the FAQ if you have more questions like this.

[…] well as a TV with coaxial or HMDI input; the Raspberry Pi is capable of full 1080p video output. A power adaptor or batteries will also be required; a standard phone charger will work with the Raspberry Pi. The […]

[…] well as a TV with coaxial or HMDI input; the Raspberry Pi is capable of full 1080p video output. A power adaptor or batteries will also be required; a standard phone charger will work with the Raspberry Pi. The […]

… [Trackback]…

[…] There you will find 30555 more Infos: raspberrypi.org/archives/260 […]…

Jishnu Chakrabarti avatar

Hi, I stay in Oman…. can u let me know the shipping cost of model B to Oman…
thanks …. Jishnu

hal avatar

Can I swap out my nokia bl5 battery, and put it in a slot that can charge it for when the power is out, and this way allow its own latoppy ups?

Paul Richardson avatar

Looks good for the grandchildren, I have already given them Lubuntu on a very old Intel 86. Glad this project is Linux, I might have to buy 2!

demos4ever avatar

Hello guys.GREAT PRODUCT!!today,a new laptop cost about 300$,and you made it with only 25$,Well,I’m in greece,and just asking if we can buy it from england,or from stores here,in greece??And something else,what about a pre-made screen sell with the product,like an completed package,like a 11 inch screen,a power adapter and a case,so you can have a completed product!

[…] The device is powered by 5v micro USB. […]

MH Cornelissen avatar

Great project !

Paul_ArtCAM avatar

Micro-USB is an excellent choice for power.

BTW: The minimum spec for Universal Chargers is 850ma @ 5V

The challenge is to teach kids to work within a power budget (and not waste energy like their parents!)

Bjorn Andersson avatar

According to this article (in Finnish) http://www.tekniikkatalous.fi/ict/kannykkalatureille+kaksi+standardia/a562256, you have to license the micro USB connector from the USB Forum if the connector is not used for data as well, like on the Raspberry Pi. The article says this is the reason why many cheap phones that don’t does not have USB for data will not use the micro USB port for charging.

The article is my only source, and I have not verified the validity of statement. Is this statement not true, or have you not taken it into consideration?

liz avatar

It’s not true. Micro USB is now the EU standard for charging; it’d be a real racket if they were also able to charge a licence fee on top of that!

Bjorn Andersson avatar

Do you say it’s not true because you *know* it’s not true because you know the licensing terms, or because you *assume* it’s not true because it’s the EU standard?

The article is just about that very problem, that it’s the EU standard but in practise there will be two “standards” because of the licensing issue. The article title is translated “Two standards for mobile phone chargers”.

Note that I am not say that licensing is needed for non-smart phones or not. I’d like to see *facts* proving it’s either true or not. I did a quick search on usb.org, but did not find any licensing terms at all.

I just noticed that you have to be a registered user to read the whole article I am referring to. In the end it says (freely translated by me):

“The USB Forum licensing terms says that the connector can be used without licensing fees if you can transfer data through the connector in addition to the charging current. Therefore it would be against the licening terms to equip cheap basic phones with the micro USB connector”, says group manager Eero Sorri from the [Finnish] national electric and electornics standardization organization SESKO.

liz avatar

We know it’s not true. :)

Bjorn Andersson avatar

Reference to your knowledge source, please. ;-) Here’s a long article by the Finnish standardization organization about the subject and the history behind it. Unfortunately only in Finnish. My current understanding is that you are not allowed to use the micro USB for charging only, and that there is no specific licensing program for it either. For charging only you need another solution if you want to be strict. I guess the USB forum does not care if you use it for charging only, but the EU did not want to take the risk to run into trouble later and thereby added the 2mm barrel standard.

http://www.sesko.fi/attachments/sesko-lehti/sesko_410_matres_aukeamat.pdf (pages 8-10)

liz avatar

We were told this by our factory and suppliers.

Bjorn Andersson avatar

Also note the name of the EU standard EN/IEC 62684 is “Interoperability specifications of common external power supply (EPS) for use with data-enabled mobile telephones “. That is *data-enabled*. The standard does not apply to phones without data, i.e. basic mobile phones. For basic phones there is another standard EN/IEC 62637 “Battery charging interface for small handheld multimedia devices” that defines the 2mm barrel connector.

Note that I’m still not claiming that you have to pay a license fee for the micro USB to be used in the RaspberryPi for charging only, and think it would be ridiculous if you (or any one else) would have to.

Ross avatar

I would be interested to see the all up power consumption once a mouse, keyboard and a small low powered display are added. I like the slimline displays often found fitted to the national lottery machines in corner shops. Thin bezel and not to small. Would be a tad expensive though. A 12V car battery or a 12V alarm box battery should run it for a fair amount of time before needing a recharge.

johnd avatar

In all of this long thread, I can’t see a spec for current draw at idle and at some low/modest load level. (But maybe I missed it or it’s specified elsewhere). Seriously interested in RP but it would be for a solar-powered instrumentation application where real-life consumption under modest load would be an important parameter. Any numbers available please (ideally for both A and B types)?

JamesH avatar

At the moment, I think we only know the GPU characteristics, which a class leading (8mW at idle IIRC maybe less), but we don’t have specs for the Arm itself.

Nicholas Kingsley avatar

Does a power supply unit come with the device ?

JamesH avatar


Paul Tamm avatar

Micro USB comes in two flavors, Micro-A and Micro-B, which one will work on the Raspberry Pi B?

I’m currently buying some accessories for the Raspberry Pi that I will buy when it is available. I want to buy a power supply with the correct terminal.


Paul tamm

Chromatix avatar

A refers to the host-end, B to the device-end of the cable. The R-Pi will use a Micro-B connector, just like this year’s mobile phones.

Kevin avatar

To power the Pi, could a ‘dumb’ USB to micro USB cable be run from a powered USB hub connected to the R Pi itself? For example, a USB to micro USB with the data lines cut, so only the power wires are connected (much like the power only connectors on the cables for external USB)? This would use up one port on the powered hub, but you could always stack the Pi on the hub (or in the hub if it uses a sufficiently spacious interior) and would mean one power brick for both the Pi and peripherals.

[…] well as a TV with coaxial or HMDI input; the Raspberry Pi is capable of full 1080p video output. A power adaptor or batteries will also be required; a standard phone charger will work with the Raspberry Pi. The […]

Tim McCormack avatar

The GSMA UCS link doesn’t work anymore. This might be the replacement page:


Mick Farrell avatar

Looks good!

My son Leo is in his final year of his IT degree as University of Queensland.
We have a Farther/Son project going and the Raspberry Pi fits the hardware requirements.

You will see our orders when you launch.

Mick Farrell

sunny avatar

waiting to get my hands on this pi .

[…] Stromversorgung reicht ein Handy-Netzteil mit micro-USB Anschluss und mind. 700 mA […]

Robert Nix avatar

Your link on this page, to the “Universal Charging Solution”, is broken and goes nowhere. Just thought you’d like to know.

[…] Power to run the Raspberry Pi can come from a phone charger or even from 4 AA batteries. A 700 mA USB charger will be the power source for the Model B, and the Model A can get away with even lower power requirements (300 mA). At that low power level, solar powered options should be practical and not terribly expensive. […]

[…] Power to run the Raspberry Pi can come from a phone charger or even from 4 AA batteries. A 700 mA USB charger will be the power source for the Model B, and the Model A can get away with even lower power requirements (300 mA). At that low power level, solar powered options should be practical and not terribly expensive. […]

[…] Power to run the Raspberry Pi can come from a phone charger or even from 4 AA batteries. A 700 mA USB charger will be the power source for the Model B, and the Model A can get away with even lower power requirements (300 mA). At that low power level, solar powered options should be practical and not terribly expensive. […]

gromit avatar

I cobbled together what I call the largest portable media player (2TB media player running of a battery pack with LCD glasses also running of another battery pack), it was a bit big you couldn’t stick it in a jacket pocket you had to have a small ruck sack. I’m waiting to get my hands on the Raspberry Pi so that I can use the same solution and add a thumb keyboard maybe something like this or smaller http://www.amazon.co.uk/Wireless-Keyboard-Removable-Adjustable-Touchpad/dp/B004TQL3YS/ref=pd_cp_computers_3
This means that I don’t need to connect a mouse because of the touchpad or I could use a mini keyboard that has a track ball or a thumb stick (joystick).

Mark avatar

It would work if you gave it a battery with 9V or higher voltage for power in, it won’t be nearly as efficient as a switcher though (for example a switcher would be ~80% efficient, this would be ~41% efficient, off a 12V power source.) That’s why people like switchers :)

Barney Muckle avatar

Please indicate the potential use of the rasberrypi for solar powered pc labs in schools with only a 12v dc system available. Monitors running on 12v (like this one) are readily available. This is written from Kenya where many schools have a good signal but are remote and will never be connected to mains power.

T B Muckle

Ray_GTI-R avatar

I have briefly read the main FAQ and have a major concern about the power requirement quoted there specifically the amperage and also the way it is quoted.
If two physical disks are connected to the board e.g., directly or via an unpowered* hub with say a keyboard & mouse and each disk draws 500mA then the total power required will be greater than 1 amp plus whatever else the board is supplying power to e.g., card etc.
The way the FAQ is organised “hides” power requirements, inadvertantly or otherwise and makes only a passing comments about “powered” USB devices.
I know this is a chopped-to-the-bone board and the non-e.g., USB device power requirements would be adequately satisfied as described but I feel that the FAQ glosses over power pass-through from the supply point.
Then there is the heat issue. Anecdotal pre-release webchat pooh-poohs heat issues but are focussed primarily on the processor. I have very little practical electronics expertience but even I know tat a board passing 5v @ 1 amp+ continuously will have some components that need serious attention to cooling.
Just trying to be helpful!

Ray_GTI-R avatar

Thanks for allowing my previous message to be posted.

Minor clarification to my previous message:-
“5v @ 1 amp+” add … “unregulated input power requirement that must be regulated onboard in order to supply clean power to e.g., the processor etc”
Trivial clarifications …
“tat” = “that” (my typing problem, sorry)
“expertience” = “experience” (my typing problem, sorry)

Dave avatar

Any info on how much RF hash this generates when powered from you chosen power source? I have a potential application, a decoder for Morse signal part of a Morse based communication package for non-tech operators for use in disaster communications. Morse has the ability to punch through when ordinary coms are out. (dja.)

Paul Tabolinsky avatar

A great and worthwhile project that will surely decrease the computer, confusion, programing, hardware knowledge problem.
Thank You
BTW: What is an “LDO-only power …”

Hori avatar

Hi there..

What do you think about this one:

Jose R avatar

Would it be possible to power the raspberry pi directly from a 110V (standard US home cable) with no AC/DC power supply? For example if I want to hide it behind a light switch and power it directly from there.



JamesH avatar

No, you need to drop the voltage to 5v somehow, so you will need a transformer/power supply.

Suresh avatar

Can i build a torrent box which runs 24×7 , i guess if i provide sufficient exhaust it will not be a problem please suggest.

Claudio avatar

Hi, will the B model generate enough power from the USB port to drive an external harddisk connected on thar port?

Lynbarn avatar

No – check out the forums as there is lot about powering the USB ports and peripherals. Basically, You’ll need a powered USB hub.

artem avatar

can anyone tell for sure how much amp will the type A consume with an SD card, no display, or any other device attached. i would be interested to use it in a battery powered RC device as a central processing unit if the power draw is acceptable.

William Parkhouse avatar

I’m not very good with technical terms. Would it be able to directly run off 4xAA batteries or would it need a 5v regulator. If so does anyone know a link to buy one.

Doktor J avatar

You would need a regulator, as 4xAA (alkaline) is 6V — specifically, a 5V LDO regulator that has less than 1V forward drop. The LM2940CT-5.0 should suit your needs, it’s able to provide 5V at up to 1A. I’d recommend putting this on a tiny board with some degree of heatsinking, along with the other components it needs to regulate the output, then have a micro-USB pigtail coming off the board to get the power to the RPi.

Just bear in mind that the RPi’s draw @ 700mA will kill a set of ~2200mAh batteries in under 3 hours (higher drain = shorter life, beyond just the linear curve). If you’re running it without any USB devices or connected display, you might get 3-5 hours out of a set of batteries.

Also, NiMH/NiCD batteries only output ~1.25V, so at full charge an LDO regulator’s inherent 0.5V drop would bring the output down to 4.5V, and as the battery output decreases, voltage will continue to drop from there. If you plan on using rechargeables, you may want to consider using 5 (let the regulator deal with the excess, then as the battery output drops, you’ll still be getting 5V out until the batteries are nearly dead).

Christian Lehmann avatar

Would this external battery work? How long would a B-Model last with one of these? Would the B-Model just draw the “needed” juice? I’m no technician so please be nice ;)


Doktor J avatar

Voltage-wise, this would probably work; however, the connector is mini-USB rather than micro-USB, so you’d need an adapter or would need to snip the cable and add a micro-USB connector. You’d probably be better off looking at their HyperJuice offerings; while more expensive (starting at $69), they also have double (or more) the capacity, providing a ~5 hour runtime for the RPi model B (probably closer to 6 if you don’t have a keyboard/mouse/etc attached to USB).

Don Stewart avatar

You don’t say whether the power connector is Micro ‘A’ or ‘B’ type.
The socket looks from the 3D sketch to be a Micro ‘B’ type, can you confirm this?

Abishur avatar

Yes it is micro type b.

azur avatar

i was thinking on sticking some batteries, those ni-cd rechargeable ones to the B-type, and there are a coupe of questions i would like you to answer:
you say you can power it on with four AA, how long would it last? and some advanced electronics: if i were to recharge the batteries while using (and since you claim you have to input more than 5V) now about i use a 12V one? so i could charge batteries while using it.
thanks. :)

san avatar

Good Day,
Its really amazing, First of all, congratulations for the team’s hard work.
if i connect an USB cable with a laptop and Model B device, will it gets powered ? like my android devices do?

JamesH avatar

It will be powered, but the device does not connect via that USB.

Patrick Allen avatar

Am I right in thinking that a Raspberry Pi should run happy off a Morphie Juice Power Pack? (Especially a (red) one ;))

Doktor J avatar

If it has a standard USB port and can provide at least 700mA on that port, you should be okay — which this seems to meet. To figure out (a ballpark) runtime, divide the capacity (4000mAh in this case) by the average draw (700mA), resulting in ~5.7 hours. Real-world results will probably be closer to about 5 hours, but it gives you an idea :)

Stavros Dimopoulos avatar

Raspberry Pi is designed for educational use, not for cunsumer / ready to use out of the box use.

You have to calculate the estimated power consumption for your project before you chose the appropriate power supply.

You may use the specs of each device to do that.
Raspberry Pi Board: No specs available. I estimate 5V x 300mA = 1.5W
GPIO: 3V, 16mA max, 17 ports = 3 x 0.016 x 17 = 0.816Watt
USB: 5V, 500mA max, 2 ports = 5 x 0.500 x 2=5Watt
Estimated power supply needed: 1.5W + 0.816W + 5W = 7.316W~7.5W

A 7.5W (5V, 1500mA) power supply for the Raspberry Pi should be sufficient for every project.
However, if you use a powerd USB hub, a 5W (5V, 1000mA) power supply should be sufficient for the Rasbperry Pi.
A powered USB hub uses power for it’s own power supply and it only consumes a few (if not zero) mA from the raspberry Pi.
However, you also have to calculate the powered USB hub power requirements. I have a powered USB hub with 7 USB ports. It is supposed to support 7 High power USB devices (7 x 5V x 0.500A = 17.5W), but its’ power supply is only 15W.

HarryB avatar

The Blackberry Playbook has an ‘international’ psu which supplies 2 amps and costs about 10 quid from Amazon. Make sure you get the charger with a yellow micro USB tip rather than the ‘fast’ charger which uses a different type of plug altogether.

Martin Mcdonald avatar

I started programming on the old sinclair zx81 with a massive 1k of memory ! Firstly basic then moved on to machine code ! It`s about time someone came up with something to show not just kids but adults alike what really makes a computer work ! I can`t wait to get one so my kids will get a chance to better understand modern tech !!

Damhack avatar

Can you please confirm that a standard Apple plug with a micro-USB cable is okay.

It’s rated at 5V, 1A.

Doktor J avatar

I assume you mean an Apple USB power adapter (like for an ipod) but with a micro USB cable plugged in, in place of the ipod cable? In that case, yes it would work. It’s 5V, and over 700mA (0.7A) so you’re set.

Jotecnologo avatar

Hi everybody! Some days ago I found this interesting video about the power supply for the Pi: http://youtu.be/XX3kiRUf7mg
After I saw this video I was thinking that it’s really better if you could sell the right power adapter together with the Pi, it’s few dollars more but you would solve the problem that people don’t know what it’s the best power supply to use and the Pi won’t crash if you plug into too much usb device or in the case of overload. I know that everybody have a usb plug at home but we could use our phone charger, because we need to charge the phone while the Pi is on and I personally have a lot of usb charger (for mp3 players and a camera) but none of them is at 700 mA, so I guess a lot of people like me have to buy anyway an other usb power supply.

william warner avatar

ok, i got my raspberry pi. how do i power it in the United States? Do i get a USB to Micro USB Cable 2m (Raspberry Pi Power Supply) and plug it into my computer?
Can I plug it into a USB wall socket?

Not quite sure about this.


William Warner

Doktor J avatar

A USB to USB-micro cable is indeed what you’ll need. Plugging it into your computer *may* work, if your computer is willing to provide 700mA on its USB port to an un-negotiated device (the RPi’s USB port is power-only, no data and thus no negotiation) — in other words, YMMV.

A USB wall adapter is a better bet, as they list their output; anything over 700mA (0.7A) should do the trick. If the adapter has more than one port, be sure to divide the output rating by the number of ports, as many cheap adapters do just that, so a 2-port 1A charger will only provide 500mA (0.5A) to each port!

forumisto avatar

I have a kindle 4 charger. It says “5.25 V – 1000mA”.
Is it valid?

a.out avatar


Matthew Timmons-Brown avatar

Hello my pi is coming soon and I want to get everything ready. I think I have a power supply but I am not sure: can I use a kindle USB with ad adapter. The adapter says it is 5v however the mA is 850. Is this okay to run my beloved pi on without blowing it? Thanks

Doktor J avatar

Yes; devices will only draw the current they need, so the current rating (A or mA) only needs to meet or exceed the requirement. Voltage, on the other hand, must match exactly (well, usually +/- 5%)!

So a 5V 4,000mA charger is a much better choice than a 6V 700mA charger ;)

kaps avatar

not technical….so just was curious to know if it can run on or any plans to run it on lithium(cell-phone) re chargeable batteries.

Doktor J avatar

If said battery outputs 5V, or is run through a device like a mintyboost, yes, that should work. Be aware of the battery capacity though, as a 700mA draw will drain most cell phone batteries in 2-3 hours!

Thomas avatar

I have a 5V 2A micro usb power supply. Will this work?
Thanks, Tom

Doktor J avatar

Yes, 2A = 2000mA, and the RPi only draws what it needs, so you’ll be fine. You should even be able to connect higher-powered peripherals to the RPi’s USB port (such as a portable hard drive, or a wifi dongle) as your adapter has power to spare :)

Ryan Chapman avatar

If anyone is looking for a good power supply, the USB battery pack I bought for my Wi-Fi Pineapple should work just fine: http://hakshop.myshopify.com/products/usb-battery-pack-3200mah. Very nice unit.

Daniel Pérez avatar

I live in Costa Rica (Central América) and here the electricity has 110 V, 60 Hz, so the power adaptor for the Pi from your site will not work here.
Is it fine to use my cell phone charger to use it, understanding that it should have 5 V output and 1.2 Amp ?

Doktor J avatar

Yes, any micro-USB charger that outputs 5V and at least 700mA (0.7A) should be fine. 1.2 > 0.7, so you’re okay :)

J.J.Dawson avatar

“Should work well on 4xAA cells”
Surely 4 new alkalines could deliver nearly 6.5 Volts? Might this be a bit rich for the Pi? Ni-MH rechargables now, that would be a different story.

Sam avatar

What is the maximum voltage/ current/ power output that the HDMI socket can supply to a particular external peripheral? Thanks

ben sutherland avatar

hi, the raspberry pi looks amazing value! it occurs to me that your little computer could put many large expensive computer sellers out of business. given that for the price of a converter cable you are making a whole computer which can be a media centre and do many of the things an expensive computer does, are you anticipating any backlash from the large companies? i support you 100%…

Doktor J avatar

Actually, the RPi is rather underpowered for many of the tasks expected of a regular desktop computer; even a $400 low-end PC has more memory and storage space than the RPi (and probably more overall processing power). Not to mention, the RPi is intended as more of a teaching tool and experimental device than an “out of the box” solution.

I have many expensive computers at home (7 at last count), and now also have a Raspberry Pi… I think they complement each other well, and fill different niches :)

rocketero avatar

I have a 5V, 2000mA micro-usb (B) adapter, is this OK or too much Amperage?

scep avatar

that’s fine, the Pi will just take the current it needs

BrianAC avatar

Having just powered up my model B pi for the first time I can confirm that using a low power kb this will NOT work on a 500 ma phone charger, voltage dips to below 4 v and I get sync errors and ultimately it fails. All seems good on a 750 ma with kb, mouse, HDMI and ethernet.

Timothy avatar

I am looking at powering the Pi with a USB Hub, namely, the Targa ACH81US with 7 ports. “Two of the hub’s seven ports are high-power. These ports deliver twice the power of a standard USB 2.0 port. More importantly, they are always powered, even when the connected computer is off. This allows you to use them to charge a cell phone, iPod, or other USB device.” This sounds like it can power the Pi while running an external Hard disk, keyboard and mouse. Do you agree?

Doktor J avatar

I’d agree. A “standard USB 2.0 port” can provide 500mA (ostensibly once it’s been negotiated, but most will do it even without)… so a high-power port would be 1A, or 300mA over the RPi’s requirement. I think you should be able to find significantly cheaper hubs out there though that can do the trick… it’ll just take some searching :)

Danno avatar

Do the D+/D- lines need to be shorted? This is the USB standard to indicate the power supply is capable of more than 500mA. Or does RPi assume it can get what it needs?

Doktor J avatar

If I’m not mistaken, the D+/D- shorting is to tell the connected device that it’s okay to draw >500mA, rather than the charger (the charger should just supply whatever the attached device attempts to draw, up to its maximum rating). Since the RPi’s micro USB port is power-only, it pays no attention to what’s going on with the D+/D- lines and just tries to draw the power it needs.

Sten J. Pettersen avatar

Ordered my Pi two days ago. Waiting in agony and anticipation for the 11 week delivery time to pass…

From what I’ve gathered so far, I can without problems use my phone charger. It has 5V – 1A output. But what I wonder is this (pardon me if this has been asked before and I missed it): Will there be a problem if I decide to use the charger from my Asus tablet (5V – 2A)? Will the increase in Ampere just mean that I can plug more stuff into the USBs, or will a fuse somewhere interfere?

Doktor J avatar

It looks like each port has a 140mA polyfuse on its power line, and then there is a master 700mA polyfuse on the input power… so to run higher-power devices you’d need to rig some sort of power bypass, or just use a USB powered hub (and leave the extra current capacity of your charger unused).

This guy just bypassed the fuses with wires — not something I’d recommend, but it’ll get the job done in a pinch:

Doktor J avatar

You might look into replacing the polyfuses, too, if you’re so inclined. Digikey sells the Littelfuse 1812L200THPR (8V 2A fuse for the master) for 0.55/each, and Bel Fuse 0ZCB0075FF2G (8V 0.75A fuses for the ports) for 0.28/each… so a little over $1 (plus about $5 shipping, lol) for replacements.

Profesor Yeow avatar

It’s great work with 5V.
I will buy one for try to make a mix with this RaspberryPi and my Arduino.

Alex avatar

What kind of micro usb is required for the pi? Is it 5*2mm. 7*2mm or 7*3mm?

Doktor J avatar

I don’t understand your question; there is only one connector that can be referred to as “micro USB” (well okay, there’s micro USB A and B, but I have yet to see anything that uses A). To quote Wikipedia, “The micro-B connector is 6.85 by 1.8 mm”.

It’s the same connector that like 90% of smartphones today use… if you check http://en.wikipedia.org/wiki/File:Usb_connectors.JPG, it’s the first one on the left.

Trevor Palmer avatar

Because of the small size of the board I am concidering using it to convert the now digital TV signal to analog and fit it into my car which cannot now receive a TV signal. My questions are

1. Is this a viable use for the Raspberry Pi
2. If I have a mini USB connector from the Car battery (normally used to recharge an Android Phone) would it be able to provide the current for the Pi.

Many thanks

chris avatar

I bought a micros usb power supply as the little paper said it can handle 700-1200ma on the model b i can boot it have it connect to the network ok but when i hook up a keybored it does not see it ? I have tried all the image files on the site. please help shed some light thank you.

input:AC 100-250v~50/60hz
Yong Xing Tong 3


Can I use Samsung mobile charger with Micro USB as power supply to model B

Tim avatar

I am thinking of using an iPad solar charger to use as a power supply for my Rev B. Here are the specifications:

Output capacity: 18.5Wh(5000mAH)
USB output:5V,1.5A
Max output current:1.5A

Obviously this is at maximum capacity, but is this current too high? Will it cause damage?

Krishna avatar

I want to use a power source with 2.0A. Will it cause any damage to my pi?

David A. avatar

I’m looking to set up four (4) Pi boxes for network monitoring. I’d like to mount these to the back on the monitors and have them powered off of a single USB hub. I have looked around, but can’t find any solid information on which USB hub could power four of these devices simultaneously.

Can you recommend any products that would work in this situation?

Stephen avatar

I power my Raspberry Pi from a Belkin usb hub..The hub is self powered.. I plug the input of the hub into the Raspberry Pi usb port. Then I plug the Raspberry Pi power source (the micro usb port ) into the the usb port on the hub.. Then I plug in my mouse, keyboard and my 250 gb. usb hard drive made by Net Disk. Then I take the other empty usb port on the Raspberry Pi and plug in a 8 gb.usb drive in it so I can swap files from one computer to the other with out unplugging my usb hard drive … I have no trouble with this set up at all… The power plug on the usb hub dose not even get warm and the Raspberry Pi works as good as it dose just pluging it in by itself…

roger feldman avatar

A question about the mains adaptor in a Raspberry Pi kit from Maplin, with a Raspberry PI Model B, USP peripherals, and Cables

The box (still unopened) says it includes a “2.1 A dual USB Mains Adaptor.

Since bought it in London, the mains adaptor has a UK 3 pin connection, for the UK mains 220 volt supply.

I intend to give the Raspberry Pi to my grandson, in the USA. where I know they has an adaaptor to handle a 3 pin UK plug..

But does the adaptor work with 110 volts?

Rob avatar

There are micro-USB power-supplies which have on the label: 800mA, 4.5…9.5V.
Apparently these have a resistor in series so the voltage can drop as the current rises. Could be fine for charging, but is it OK for the Raspberry? The zener in the Raspberry will make it 5V.

Dinesh Bhaskar Ajgaonkar avatar

can i oprate 3.5inch color lcd up to7 inch colr lcd.on yuor board.

Ted Shaw avatar

To use a wifi dongle, the power supply need to be 1A

Larry avatar

PiHut sells USA power supply that puts out “1500mA” or 1 AMP. The 1 AMP is the ‘target’ per specs I’ve seen, but isn’t 1500mA 1.5AMP and will that then a) work fine or b) “fry my Pi” ? Sorry, but I’m in SOFTWARE and this is HARDWARE. Any help appreciated…

Prof. Michael P. Harris avatar

I had a 4-port powered hub attached to my Type 2 Raspberry Pi. I recently purchased a small compact 7-port powered hub off eBay. I’m powering the hub with a 5V 2.4A power supply. I’m powering the Raspberry Pi from one of the powered USB ports. I also connected the “host” cable from the powered USB hub to the bottom USB port on the Raspberry Pi. Now for the surprise…
When I unplugged the micro-USB power cable from the Raspberry Pi to swap it out for a shorter one… my Raspberry Pi stayed on! I unplugged the powered USB hub from the wall (to power down my Pi) then plugged it back in, my Raspberry Pi will power itself, boot and run from power from the powered USB “host” cable, with nothing plugged into the micro USB power port.
Is the normal? … with this damage my Raspberry Pi? -profharris

David B avatar

I want to create a super computer using several Raspberrys like they did at the University of Southampton.

I don’t want all those plugs. Anyone know if there are any adapters on the market I can use to connect a normal computer power supply to a wire harness to plug into the various raspberry boards?

javad avatar

Hello all.
I have a mobile charger that provide 850mA. Can I use it? Also, I have a laptop with USB2.0 and USB3.0 ports. Can I connect the board to my laptop? Which is better?


James avatar

Sounds like I’m only a couple solar panels and a voltage regulator away from a supply.

Penguin avatar

I got a weather station (connected via usb to raspberrypi [b]). It works great with debian and wview.
My power supply 1 A, 5 V.
But there is a problem:
If the battery in the station were discharged the pi gets unstable. How should I connect the station with the pi?

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