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Power

Posted: Mon Feb 16, 2015 8:14 am
by sdcruze
Hi all,

I am new to Raspberry Pi.

I have been playing with electronics commercially for a few years but I'm taking steps to train myself up more in my own time on the technical side of things.

Are all Raspberry Pi boards USB powered, or are there any mains/battery powered versions?

Thanks.

Re: Power

Posted: Mon Feb 16, 2015 8:35 am
by BMS Doug
All models of Pi are designed to be powered through the microUSB power connector, this cannot be used as a data connection.

If you wish you can back-power the Pi through the GPIO but this is not recommended as it bypasses the Pi's fuse.

You can use a USB powerbank to supply the microUSB power, thus giving you a battery supply.

Alternatively you could use any battery you like and condition the output to provide a stable 5v to power the Pi.

Often the power is supplied from a "wall wart" (mains plug adapter which outputs 5vdc).

You choose which method of powering you wish to use.

Re: Power

Posted: Mon Feb 16, 2015 2:15 pm
by klricks
Many people use old 5V phone chargers. At least 1A output but the RPi B+ and 2B can use up to 2A depending on what is attached to the USB. Higher amps is OK but the RPi won't and can't use more than 2A.

Re: Power

Posted: Mon Feb 16, 2015 2:50 pm
by BMS Doug
klricks wrote:Many people use old 5V phone chargers. At least 1A output but the RPi B+ and 2B can use up to 2A depending on what is attached to the USB. Higher amps is OK but the RPi won't and can't use more than 2A.
I carefully avoided using the word "Charger" as these are not guaranteed to output 5v and a stable 5v input is necessary for the Pi.

Re: Power

Posted: Mon Feb 16, 2015 7:59 pm
by pluggy
Like it or like it not, putting 5V through a micro USB connector automatically brings it under the umbrella of charger. Many devices that will charge a phone, will not power a Pi, but most power supplies will also charge a phone. My 'holy' Swag store Pi 2A PSU is the best phone charger I have. For some reason my daughters tablet (a Tesco Hudl 2) won't entertain it but it will work with my Samsung 700mA charger, haven't quite fathomed that one yet. The swag store PSU is fairly generous on the voltage front (ideal Pi power supply ~5.2V) perhaps the Hudl is a bit picky voltage wise.

Re: Power

Posted: Mon Feb 16, 2015 8:31 pm
by klricks
pluggy wrote:Like it or like it not, putting 5V through a micro USB connector automatically brings it under the umbrella of charger. Many devices that will charge a phone, will not power a Pi, but most power supplies will also charge a phone. My 'holy' Swag store Pi 2A PSU is the best phone charger I have. For some reason my daughters tablet (a Tesco Hudl 2) won't entertain it but it will work with my Samsung 700mA charger, haven't quite fathomed that one yet. The swag store PSU is fairly generous on the voltage front (ideal Pi power supply ~5.2V) perhaps the Hudl is a bit picky voltage wise.
Some manufactures put bias on the data lines (pull up or down) in the charger as a way for the device to 'authenticate' the power supply. Some devices refuse to charge if the power supply does not match. I have an old phone that puts up a warning message about not having the proper charger but charges anyway.

Re: Power

Posted: Mon Feb 16, 2015 8:37 pm
by jimallyn
sdcruze, if you haven't yet purchased a Raspberry Pi, you might think about buying a kit containing the RPi, a power supply, a case, a wifi dongle, and so on. I bought one from Canakit, and the power supply is rated at 2.5 amps if I remember correctly, great plenty of power to run the Pi and any accessories you might have connected to it.