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My requirement is to sniff WiFi packets, for which I've heard that we need more current into the chipboard. I've figured out that around 1 A for raspberry and 1 A max for WiFi adapter should suffice.

However, if WiFi adapter is not in place, would supplying Pi with 2 A power damage it? How far should one go (in Amperes) before damaging Pi?

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    You can use 10A power supply without worrying about damage. The pi will only use as much as it needs. But it must be 5Volt. If it is 5.5V it could cause serious damage. – foibs Jan 17 '14 at 11:58
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    @foibs : You should turn that into an actual answer, because, well, just read this -- it helps to ensure this site's future in a small but concrete way. – goldilocks Jan 17 '14 at 13:23
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Firstly, you seem to misunderstand the power rating. This is the maximum the power supply can deliver without voltage drop - the actual current depends on what you are connecting to it.

Secondly, regardless of the rating of the power supply, the Pi can only supply a limited current to USB devices because it is limited by the polyfuse.

If your WiFi adapter needs 1A (which I doubt, since this exceeds the USB specification) or even 500mA, you will need a powered hub, because the Pi will not supply sufficient current.

Attempting to do so without a powered hub will drop the voltage to the Pi, causing erratic behaviour.

  • Indeed, the rating of the USB 2.0 was up to 500mA. – Xedret Jan 17 '14 at 23:45
  • You won't need a powered hub for a 500mA wifi adapter - the Pi's perfectly fine delivering that kind of current and lots of people are doing it. – recantha Jan 18 '14 at 14:05
  • @recantha: But as per raspberrypi.stackexchange.com/questions/13030/… we cannot get over 150 mA from USB. How would in that case 500 mA current reach WiFi? – Ouroboros Jan 18 '14 at 19:56
  • The Pi model B is not limited to 150mA, but there is still a limit (1A1 - whatever current the Pi and other peripherals use) so if you have a keyboard and mouse you probably only have 250mA left. – Milliways Jan 18 '14 at 23:22

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