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Powering the Pi from GPIO

Posted: Fri Jun 22, 2012 9:50 pm
by mkmiles
Is there anyway to power the device from the GPIO pins without using the usb adaptor?

Thanks for any input guys and gals :D

Re: Powering the Pi from GPIO

Posted: Fri Jun 22, 2012 10:01 pm
by domesday
Yes, you can supply 5V to the 5V pin on the header, I would suggest a fuse on the supply though.

Re: Powering the Pi from GPIO

Posted: Sat Jun 23, 2012 10:15 am
by bluseychris
Roughed out layman's theory based on that; appropriate female connector -> positive wire -> fuse ->gpio pin // gpio ground -> negative wire -> female connector

would that work?

Re: Powering the Pi from GPIO

Posted: Sun Jun 24, 2012 3:15 am
by abishur
I might try to emulate the Pi's circuit protection as closely as possible and throw a capacitor in the mix too

Re: Powering the Pi from GPIO

Posted: Sun Jun 24, 2012 8:15 pm
by dukla2000
mkmiles wrote:Is there anyway to power the device from the GPIO pins without using the usb adaptor?
Yup,+5V on pin 2, ground on pin 6 is how I do it using an old PC 3-pin fan female connector. I run with no other protection - among other things think where you are getting the 5V from bears some consideration. Mine is coming from my PC which in turn is running off a DC power supply fed from an 80W AC adapter - the setup has yet to fry my PC so I am happy to risk my Pi on it.

Re: Powering the Pi from GPIO

Posted: Tue Jun 26, 2012 6:22 pm
by selsinork

Re: Powering the Pi from GPIO

Posted: Tue Jun 26, 2012 6:23 pm
by selsinork
abishur wrote:I might try to emulate the Pi's circuit protection as closely as possible and throw a capacitor in the mix too
the idea is not to mimick the polyfuse, the much-too-thin usb cable, or the 99p ebay phone charger :)

Re: Powering the Pi from GPIO

Posted: Tue Jun 26, 2012 7:53 pm
by abishur
selsinork wrote:
abishur wrote:I might try to emulate the Pi's circuit protection as closely as possible and throw a capacitor in the mix too
the idea is not to mimick the polyfuse, the much-too-thin usb cable, or the 99p ebay phone charger :)
A capacitor is none of those things ;-)

Re: Powering the Pi from GPIO

Posted: Wed Jun 27, 2012 7:03 am
by psergiu
But is the pin 2 PCB trace thick enough to not get burned out when the max current is sourced by the CPU, USB ports & peripherals ?

(If my question is far-off, note that i'm emotionally scared by a failed Electricity lab experiment at the Uni for the "Current" class where, with a badly connected wire, we managed to vaporize all the thick cooper plug-cables on our experimental pegboard. 200 Amps are scary.)

Re: Powering the Pi from GPIO

Posted: Wed Jun 27, 2012 9:15 am
by rasbeer
What's the advantage or powering the Pi from GPIO? :oops:

Re: Powering the Pi from GPIO

Posted: Wed Jun 27, 2012 10:01 am
by psergiu
rasbeer wrote:What's the advantage or powering the Pi from GPIO? :oops:
If you are building you own 5V power supplies, you no longer have to use a micro-USB plug.

Re: Powering the Pi from GPIO

Posted: Wed Jun 27, 2012 10:04 am
by rasbeer
Oh - I see... Thanks!

Re: Powering the Pi from GPIO

Posted: Wed Jun 27, 2012 10:44 pm
by dukla2000
rasbeer wrote:What's the advantage or powering the Pi from GPIO? :oops:
You bypass the voltage drop of the 700mA polyfuse which is (IMHO) a good thing, you bypass the protection offered by same polyfuse which could be a bad thing if some magic smoke escapes from some component :lol:

Re: Powering the Pi from GPIO

Posted: Thu Jun 28, 2012 11:29 am
by bluseychris
abishur wrote:I might try to emulate the Pi's circuit protection as closely as possible and throw a capacitor in the mix too
Like this?

http://www.petervis.com/Raspberry_PI/Ra ... upply.html

Please bare in mind I only really have what I can pull from GCSE Electronic Products which was done 13 years ago.
dukla2000 wrote:among other things think where you are getting the 5V from bears some consideration.
I have two ideas

1 - is to use an old 5v nokia charger. I know I can get the sockets for the more recent 2mm jack, I really want the older (3mm?) that was on the 3210/3310 models.

2 - I have my old PSP and Iomega Zip drive power supplies, one of the zip drive power supplies works with the PSP. Both are 5v, but I don't use the zip drives any more. Well, I may break out one and pop that via USB just to use it, but that's the one with the different supply.

Personally I'd like all three sockets on there, namely because I have two micro usb cables for my mobile phones (used to have three at onepoint but) I gave that to a mate. Also I'm using one to hook up my old HTC so I can see if I can use that as a Wireless adapter. That leaves me one for my new phone.

Re: Powering the Pi from GPIO

Posted: Thu Jun 28, 2012 11:50 am
by rurwin
psergiu wrote:200 Amps are scary.
There's an apocryphal tale about a telephone exchange. When they used relays, telephone exchanges used some low voltage -- 24 or 48V or something similar, but an awful lot of it. The power was fed to the relay banks from the transformers through two thick copper bus-bars, and we are talking inches thick of solid copper. The bus bars ran parallel and about six inches apart. Because the voltage was so low, they were considered safe and so not covered. You could lick them and come to no harm.

Then one day the cleaner came in and put her glavanised bucket of water down on top of the bus bars. The bucket was vaporised and the poor woman was significantly injured. Since then the bus bars have been covered.

Re: Powering the Pi from GPIO

Posted: Thu Jun 28, 2012 8:52 pm
by repton
rurwin wrote:When they used relays, telephone exchanges used some low voltage -- 24 or 48V or something similar, but an awful lot of it. The power was fed to the relay banks from the transformers through two thick copper bus-bars, and we are talking inches thick of solid copper.
To this day telco kit still runs almost exclusively on 48VDC and those copper bus bars are still a prominent feature of even the most modern telco switch site. As you say though, one of them is insulated these days to prevent shorts...

Paul

Re: Powering the Pi from GPIO

Posted: Fri Jun 29, 2012 8:11 pm
by pygmy_giant
If I stick 5.5v into the GPIO will my Pi vapourise?

Re: Powering the Pi from GPIO

Posted: Fri Jun 29, 2012 8:23 pm
by psergiu
Not all of it. Just the esential parts. You can still use-it afterwards as a "mechanical sample"

Re: Powering the Pi from GPIO

Posted: Fri Jun 29, 2012 9:29 pm
by pygmy_giant
how about if I shoved it in the micro usb socket?

Re: Powering the Pi from GPIO

Posted: Sun Jul 01, 2012 7:10 pm
by Gert van Loo
pygmy_giant wrote:If I stick 5.5v into the GPIO will my Pi vapourise?
5.5V is a bit high. Where do you get the 5.5V from? If you measure that on your supply when it is not loaded you might get away with it as a lot of supply's voltage will drop when you start drawing current.

Re: Powering the Pi from GPIO

Posted: Sun Jul 01, 2012 7:31 pm
by pygmy_giant
I have 8x 3v3 lipos taped together and wired up in paralell to a 5v switching regulator - which for some reason is throwing out 5.5v - unless of course my £2 multimeter is wrong :?

Re: Powering the Pi from GPIO

Posted: Sun Jul 01, 2012 7:36 pm
by mahjongg
Maybe the Switching regulator is giving out 5.5 Volt if its completely unloaded, that isn't uncommon.

Load it with a quarter watt 100E resistor, and see if the 50 mA it draws will drop the output down to a more reasonable value.

Re: Powering the Pi from GPIO

Posted: Thu Jul 05, 2012 11:49 pm
by pygmy_giant
Didn't work - need a new regulator that does what its supposed to - have ordered one off of that there ebay.

I have become frightened of my charged up lipos - their internal resistance is so low that I darn near burned my fingures when discharging them through a resistor to see if it caused voltage drop.

Googling 'lipo' + 'fire' or 'lipo' + 'safety' causes me to loose sleep - think I will buy a lipo bag for them.

Hoping that the Pi will cut out before the lipo over-discharges...(just realised that I should have ordered thishttp://www.ebay.co.uk/itm/Boost-and-Pro ... 33638162a9 one instead)...anybody got any good advice about handling lipos based on experience...?

Re: Powering the Pi from GPIO

Posted: Sun Dec 30, 2012 5:20 pm
by rjm27trekkie
Ran mine of the 5V out pin of an arduino uno suits me just fine.