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The quick guide says that the power supply for my Raspberry Pi model should provide at least 700mA. How about the upper bound? Is it fine to use a power supply with an high output current, say higher or equal to 1A?

This is symmetric to my question: What happens if the power supply is 550 mA?

Community
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Alessandro Cosentino
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  • As long as the voltage is stable at 5, the Pi (plus the current-limited USB ports) will only draw what it needs. The standard power supply is 2.5 Amps at a stable 5 Volts. – SDsolar Jan 10 '17 at 02:28

4 Answers4

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Just because a power supply is rated (ie. capable of) a higher current does not mean that this is what the 'sink' (ie. Raspi) will take. This is different to voltage, where excess voltage can indeed damage a circuit that doesn't have sufficient protection (eg. voltage regulators).

Think of it with a battery. Most batteries are actually capable of quite high currents (albeit with a shortened life). However, something like a flashlight/torch will only take a current according to its design - and this is typically a lot less than what the batteries are capable of.

After saying all that, you should try to avoid a power supply with an extremely excessive current rating because such a set-up will prove to be inefficient in operation and uneconomic (relatively expensive to buy - although it might be one you have spare).

So 1 amp is fine and probably gives a healthy margin assuming you don't have many peripherals powered from it, but 5 amps would be excessive.

winwaed
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    +1 You merely need to supply enough amps. The device itself is responsible for drawing them. – Andrew Larsson Jun 14 '12 at 16:53
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    To clarify the answer's final statement, "5 amps would be excessive" to buy specifically for this application, but a power supply with a 5 (or 500) amp rating but otherwise meeting the requirements, that you happened to already have, would work perfectly and would not harm the Pi. – mlp Jun 15 '12 at 01:32
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    Also higher the current, bigger the zap if you were to accidentally short something out – varesa Jul 20 '12 at 22:58
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There is no upper bound, but anything above 700mA is unnecessary

You cannot supply current, you can only supply voltage. You provide the correct voltage and the Pi will take whatever current it needs. If your supply is incapable of supplying enough current then the voltage will drop, and if it drops too far unpredictable things will happen inside the Pi. You probably won't break it but it won't do what you expect.

So long as the voltage remains fixed the Pi will not take more than it needs, whether your supply can supply up to 1 amp or a billion amps.

http://en.wikipedia.org/wiki/Electric_current

David Sykes
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There's no upper bound, thanks to Ohm's law:

I (current) = V (potential difference) / R (resistance)

Your Pi has a constant resistance (it'll vary a bit with stuff like temperature, but let's call it constant) and you're applying a constant PD (5V), so the current will remain constant regardless of the maximum the power supply is capable of.

Simon Whitaker
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    I think this is stretching it a bit far. The Pi doesn't have a resistance, it will draw whatever current it needs for what it is doing at the time. This will not be constant, and may vary considerably. – David Sykes Jul 10 '12 at 02:37
  • @DavidSykes I think perhaps you're being a bit pedantic ;) The Pi does technically have a resistance, it just depends on the incredibly complex circuitry in play, and which way each of the hundreds of thousands of transistors involved are switched at any given nanosecond. The current draw may vary, but a reasonable baseline can be established that will be sufficient for the average Rπ user. – Doktor J Jul 31 '12 at 18:54

  • I (current) = V (potential difference) / R (resistance)

    Your Pi has a constant resistance (it'll vary a bit with stuff like

    temperature, but let's call it constant) and you're applying a constant PD (5V), so the current will remain constant regardless of the maximum the power supply is capable of. In this case what does change when we connect additional device which needs supple(mouse, keyboard, usb devices etc.)?

     – Kvach Dec 23 '13 at 22:04
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A 750mA current is sufficient to drive a Raspberry Pi. The exact amount of current to the Raspberry Pi also depends upon the count of devices you want to hook up with it. There is no upper limit but a current of 1.2 A is mostly enough and is ample to run external devices with it.

It is generally preferred to avoid supply of more than 1.2 A current as it will be ineffectual until you want to use high current rated devices with your Pi. As external peripherals are connected , current requirements can reach to any higher value as per the requirements of device(s) connected.

Ghanima
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Yadwinder Singh
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