Powering the Pi from GPIO


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

Thanks for any input guys and gals :D
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by domesday » Fri Jun 22, 2012 10:01 pm
Yes, you can supply 5V to the 5V pin on the header, I would suggest a fuse on the supply though.
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by bluseychris » Sat Jun 23, 2012 10:15 am
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?
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by abishur » Sun Jun 24, 2012 3:15 am
I might try to emulate the Pi's circuit protection as closely as possible and throw a capacitor in the mix too
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by dukla2000 » Sun Jun 24, 2012 8:15 pm
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.
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by selsinork » Tue Jun 26, 2012 6:22 pm
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by selsinork » Tue Jun 26, 2012 6:23 pm
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 :)
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by abishur » Tue Jun 26, 2012 7:53 pm
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 ;-)
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by psergiu » Wed Jun 27, 2012 7:03 am
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.)
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by rasbeer » Wed Jun 27, 2012 9:15 am
What's the advantage or powering the Pi from GPIO? :oops:
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by psergiu » Wed Jun 27, 2012 10:01 am
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.
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by rasbeer » Wed Jun 27, 2012 10:04 am
Oh - I see... Thanks!
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by dukla2000 » Wed Jun 27, 2012 10:44 pm
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:
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by bluseychris » Thu Jun 28, 2012 11:29 am
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.
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by rurwin » Thu Jun 28, 2012 11:50 am
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.
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by repton » Thu Jun 28, 2012 8:52 pm
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...

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by pygmy_giant » Fri Jun 29, 2012 8:11 pm
If I stick 5.5v into the GPIO will my Pi vapourise?
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by psergiu » Fri Jun 29, 2012 8:23 pm
Not all of it. Just the esential parts. You can still use-it afterwards as a "mechanical sample"
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by pygmy_giant » Fri Jun 29, 2012 9:29 pm
how about if I shoved it in the micro usb socket?
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by Gert van Loo » Sun Jul 01, 2012 7:10 pm
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.
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by pygmy_giant » Sun Jul 01, 2012 7:31 pm
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 :?
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by mahjongg » Sun Jul 01, 2012 7:36 pm
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.
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by pygmy_giant » Thu Jul 05, 2012 11:49 pm
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-Protection-Circuit-Module-LiIon-LiPo-Battery-/220712755881?pt=LH_DefaultDomain_0&hash=item33638162a9 one instead)...anybody got any good advice about handling lipos based on experience...?
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by rjm27trekkie » Sun Dec 30, 2012 5:20 pm
Ran mine of the 5V out pin of an arduino uno suits me just fine.
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