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I'm about to make my first RPi purchase (a B+) to be specific. I do not want to spend any more than I need to, and hence have looked around to see what power supplies I have that may already work with it. I understand that the RPi needs a power supply of 5V with a current of at least 1A.

As I said in the title, I have an ASUS MeMo Pad HD7, and I've taken a look at the power supply. It has a USB -> Micro USB cable (no information written on it, but I take it that any such cable could be used?). It also has a USB -> 3 pin plug (I live in the UK). The specs on the side are:

ASUS Switching Power Supply MODEL: PSM06K-050Q INPUT: 100-240V ~ 50-60Hz 0.25A OUTPUT: 5.2V = 1.35A

I take it the input is what is being drawn from the mains (does the RPi require anything specific here?) and the output is what is then converted and 'given' to the RPi, in which case there is an output of 5.2V. Would this break the RPi, or is 5.2V still safe to use?

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Unless you want to risk your RPi to emit a healthy puff of magic smoke, I'd recommend to stay within the recommended values of 5V 2A+. That is, 5V sharp. Not 5.25 or 4.8, but 5.0, and more than 2A of current.

Most RPi distributors have a proper power adapter sold next to the RPi itself, please, don't hesitate to buy it.

  • Can you trust a power adapter marked 5V to actually output 5V, sharp, though? – Bex Jul 22 '14 at 7:26
  • @Bex a power adapter marked 5V has better chances to output 5V than adapter marked 6V. you may extrapolate this to the other possible markings as well. – lenik Jul 22 '14 at 11:17
  • While I agree that is a reasonable assumption, the question here was about 5.2V, and your answer about the risk of ignition. Which I, in my turn, have to assume is quite low, since I have a feeling that many power adapters marked 5V will have an acutal output in the range of 4.8V to 5.2V. This is just a feeling though, until I have got a hold of my trusted multimeter. – Bex Jul 23 '14 at 11:03
  • @Bex adapters usually provide the voltages within 5% tolerance. one marked as 5.2V may easily reach as far as 5.4V, which is well beyond the acceptable for RPi (5.0V +/- 5%). – lenik Jul 23 '14 at 23:45
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I'm running two raspberry Pi's on different power supplies including a 5V 1A Apple iPhone adapter (that came with an iPhone 3G and also one that came with a 4S) and 2 Samsung chargers rated at 5V 2.1A and 5V 1A.

The adapter I have at work supplies 5.1V at 2.1A and this one powers a raspberry pi that's on 24/7. No issues.

Might be worthy to note that current (Ampere) ratings on the charger's output is a Maximum rating. Meaning, it can supply UP TO 2.1A of power for example, but the device which its powering may not necessarily be drawing 2.1A of power. For example when no USB devices are plugged into the Pi, it draws less power than when 2 hard drives are plugged in. But the Pi B+ is rated at 2A+ because it now has 4 USB ports and requires 2A+ in the event all 4 USB ports are used up to power devices.

  • So if I were to only use 2 USB ports, a 1A iPhone charger is sufficient? But in the case that I want to use all USB ports I should only do so if I invest in a supply with at least 2A? – Keir Simmons Jul 22 '14 at 13:51
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    @Keir Simmons: Depending on the power draw of your devices. I connect a thumbdrive and Logitech Universal Wireless Receiver on my model B and the 1A iPhone adapter works flawlessly – shrmn Jul 22 '14 at 13:53

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