BlueBill
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Can the RPi be powered by 3.3V only?

Fri Nov 16, 2012 11:33 pm

Is it possible to bypass the 5V regulator and power an RPi from a 3.3V supply via the 26pin GPIO header?
Bill


BlueBill
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Re: Can the RPi be powered by 3.3V only?

Fri Nov 16, 2012 11:51 pm

Thanks, that kills that idea.
Bill

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joan
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Re: Can the RPi be powered by 3.3V only?

Fri Nov 16, 2012 11:53 pm

Dilligaf wrote:NO
Do you know why not?

I did an experiment feeding 3.3V from a USB dongle into the Pi's 3.3V pin. The Pi did boot and printed quite a lot out on the screen before rebooting. I wasn't sure if it was failing simply because the USB dongle couldn't supply enough juice.

Dilligaf
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Re: Can the RPi be powered by 3.3V only?

Sat Nov 17, 2012 12:18 am

The SOC has a 5V as well as a 3.3 volt input

BlueBill
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Re: Can the RPi be powered by 3.3V only?

Sat Nov 17, 2012 12:21 am

The BCM2835 has 5V on its pins so that might be an issue.

Anyways I'll put use an LM2675 5V & NCP1117 for 3.3V on my project. Even though I'm only using the 2675 to power the RPi.
Bill

myrcioch
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Re: Can the RPi be powered by 3.3V only?

Tue Mar 19, 2013 7:26 am

Actually, RPi works stable even at as low level as 2.9V. You need to connect this voltage to both 5V and 3.3V rail.

mattvenn
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 9:30 am

I can confirm that putting 3.3 and 5v into the pi works.

Joe Schmoe
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 10:37 am

mattvenn wrote:I can confirm that putting 3.3 and 5v into the pi works.
1) Just out of curiosity, where do you get a source of 3.3V?

2) I assume that everything works (including the serial port) - except for anything USB (e.g., the ethernet, keyboard, etc). Correct?
2a) What about the HDMI port? ISTR that that involves 5V levels...
And some folks need to stop being fanboys and see the forest behind the trees.

(One of the best lines I've seen on this board lately)

RoboJ1M
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 11:30 am

Yes you can apparently.
It involves removing the 5v regulator, fooling the power pin on the bcm and voiding your warrantee, but I did read a how to do it.

I'm looking at solar power and it's one of the ways to cut down power consumption. You can even run USB peripherals if they will run of of 3.3v

I'll see if I can find the guide link.

RoboJ1M
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 11:39 am

http://www.daveakerman.com/?page_id=1294

It's an article on battery power.

RoboJ1M
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 1:40 pm

Also this:

http://www.bitwizard.nl/wiki/index.php? ... spberry_Pi
However, it's probably much cheaper and easier just to buy a Model A, which (if power consumption is the issue) mostly solves all the issues

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mahjongg
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 3:05 pm

Yes, you can power the PI with 3V3 if you connect it to both the 3V3 as well as the 5V line. But do note that there might be a problem with reading out the EEPROM in the HDMI monitor, with SEC, and you cannot use any (5V powered) USB devices, unless you separate the USB 5V from the PI, and feed the USB devices directly with 5V +- 10%.

boyoh
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Re: Can the RPi be powered by 3.3V only?

Tue Apr 01, 2014 7:43 pm

This question is being answered with to many IFFs or BUTTs
The Pi was designed to to work with a regulated 5vdc in/put
The on board regulator stepped the 5v down to give you
3.3v for the GPIO in/puts & out/puts to interface with your
Projects. Back feeding the Pi causes to many problems.
The Pi was designed to learn programming and electronics.
So use the Pi within It's designed parameters
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

kamilon
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Re: Can the RPi be powered by 3.3V only?

Wed Apr 02, 2014 12:22 am

The Raspberry Pi has a fairly large hacker friendly community behind it too. Being design for educating doesn't mean it isn't more than adequate for other tasks as well. Actually, everything I do with the many RPis I own is nothing close to educational.

There is a post on this forum somewhere where a guy made a weather balloon using a RPi running with only 3.3v powering it.
My blog! Mostly about electronics projects (Raspberry Pi, AVR Microcontrollers, and Arduinos) http://blog.kamilon.com

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mahjongg
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Re: Can the RPi be powered by 3.3V only?

Wed Apr 02, 2014 12:50 am

a guy made a weather balloon using a RPi running with only 3.3v powering it.
exactly, and its very educational to try to do something that is supposedly impossible.

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daveake
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Re: Can the RPi be powered by 3.3V only?

Mon Apr 07, 2014 11:41 am

boyoh wrote:This question is being answered with to many IFFs or BUTTs
The Pi was designed to to work with a regulated 5vdc in/put
The on board regulator stepped the 5v down to give you
3.3v for the GPIO in/puts & out/puts to interface with your
Projects. Back feeding the Pi causes to many problems.
The Pi was designed to learn programming and electronics.
So use the Pi within It's designed parameters
What it was designed for, and what it will happily do anyway, are two different things. Just connect the incoming 3.3V to the 3.3 and 5V lines (e.g. on the GPIO header) and the Pi will boot and run normally. That includes the LAN on a model B, HDMI and at least some USB devices. I do this all the time.

Dave

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daveake
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Re: Can the RPi be powered by 3.3V only?

Mon Apr 07, 2014 11:44 am

RoboJ1M wrote:Yes you can apparently.
It involves removing the 5v regulator, fooling the power pin on the bcm and voiding your warrantee, but I did read a how to do it.

I'm looking at solar power and it's one of the ways to cut down power consumption. You can even run USB peripherals if they will run of of 3.3v

I'll see if I can find the guide link.
Although I generally do remove the 3.3V regulator, you don't have to. Doing so reduces current consumption a little, and the weight by a tiny amount, but unless these are important (which they are for me) then don't bother.

Dave

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