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I want to get a raspberry pi a+. I am trying to figure out how I can power it. I will use it with a USB Bluetooth WiFi Combo Adapter. The power consumption of the combo adapter is less than 1.5W.

As I understand things, it uses the mini usb socket as a power input. This is the same as the socket on my phone.

I am reluctant to buy a power supply specifically for the pi because so far I have boxes full of power supplies for various things and I'd rather not get another one to add to pile.

Can I use a USB A to micro B cable, and plug that into a computer, a phone charger or other usb power source to power the pi a+? Is there any danger of damaging it if I try to power it using any of those sources

The type of cable I'm talking about is like the one in the following picture:

usb a to micro b

  • That kind of cable is exactly what you want. – goldilocks Jan 5 '15 at 14:58
  • Note that the Raspberry supports a "more than 5W adapter" to give more power to its USB-ports. That might be a good idea as it may also allow you to attach e.g. a USB-harddisk without having to use a powered hub. – Thorbjørn Ravn Andersen Jun 17 '15 at 7:28
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Based on power rating specified for the adapter, 1.5 W (300 mA), plus 200mA for the pi, you should just be able to power up your pi a+ w/ adapter from a computer USB. Device connected to a computer USB will be able to draw out a maximum of 500 mA.

However, that is really tight, and you won't be able to plug in anything else to it. On the other hand, USB ports sometimes aren't properly regulated and may deliver in excess of 500 mA.

  • Hi, sorry, where did you get that power rating? – Bex Jan 2 '15 at 7:53
  • en.wikipedia.org/wiki/Raspberry_Pi under specifications – badrul Jan 4 '15 at 0:42
  • According to the table, the A+ has a power rating of 200 mA, equalling 1 W. I'll edit your answer. – Bex Jan 5 '15 at 14:27
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    @Bex I'd presume the 300 mA referred to the adapter from the question, so I've edited your edit somewhat. – goldilocks Jan 5 '15 at 14:56
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The cable that you show is the correct one. With your desired setup, you can use pretty much any USB power supply that you can find. If the supply is too weak, then the worst that can happen is an unstable Pi, and/or SD card corruption. The Pi won't break if this happens.

Only if there is a lot of load expected on the USB port of the Pi (such as a USB powered hard disk drive) then more care must be taken with the power supply.

To be on the safe side, look at the power supply and check if it delivers 1A or more

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Not sure about model A. I have a model B+ and I use the same type of USB cable to power it up from my computer. I don't see what wold be different on your Raspberry model. Also, since the USB cable have a Vcc wire, it will power your raspberry.

As I know, is a problem if you power your Raspberry from 2 sources in the same time, for example from the computer USB and also via serial cable or charger.

Don't risk to take my answer as a good one, I'm not really sure for model A+!

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To meet USB 2.0 requirements, ports must give at least 500 mA of power, and you would be very thight with your requirements

If we're talking about a desktop computer, normally the rear (directly on mainboard) USB ports give out a bit more than that, sometimes even 1000 mA; you can check the current power consumption under Windows:

  • In the Start menu search field, type: Device Manager and press the Enter key
  • In the Device Manager window, expand the node Universal Serial Bus controllers
  • Double-click on one of the USB Root Hub entries.
  • Click the Power tab.

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