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I have two Adapters, one is rated as Output 12V 500mA (used to power an old modem) and another one is rated as 5V 1A (old mobile phone charger).

My question is can use any of these to power my Arduino UNO with a barrel connector?

What does it mean when any adapter is rated as Output DC 5V 1A, Does it mean maximum we can draw 1A of current through it? What will happen if I draw more current than that.

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  • You can't draw more than 1A, thats adapter specification maximum. – Junior Dec 3 '15 at 7:31
  • You can use a clean 5v supply through the USB connector, but not through the barrel jack. The 12v supply would probably work (if it is DC) through the barrel jack but the regulator may get hot - something around 8v is better there. – Chris Stratton Dec 3 '15 at 7:39
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    An Arduino will not consume 1A of current, far from it, it will use less than 0.1 A of current even with a couple of LEDs lighting up. So don't worry about the current rating of the adapters, it is OK. The Arduino will only take as much current as it needs. – Bimpelrekkie Dec 3 '15 at 7:51
  • I'm guessing your other adapter is 500mA, not 500A. – immibis Dec 3 '15 at 8:36
  • The answers are here. – Nick Alexeev Dec 3 '15 at 8:48
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If we look at technical specifications, it is recommended to supply voltage from 7-12V so use your adapter 12V/500mA (never go above 20V). 5V/1A adapter is not enough when connecting via DC barrel jack according to technical specifications.

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    And that is valid if you use the DC jack on your Arduino board. You can make the Arduino work on the 5V/1A adapter but then you need to connect it directly to a +5V connection or a USB input (these are also 5 V). – Bimpelrekkie Dec 3 '15 at 7:49
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    Since the arduino only draws a few mA, the unloaded voltage on the power supply might be considerably higher. It depends on the quality of the supply. It is probably a good idea to measure the unloaded output voltage before connecting it directly to the board. – Robert Stiffler Dec 3 '15 at 7:58
  • What does it mean by measuring unloaded output voltage? Does it mean measuring voltage without connecting it through any device? If so, I've measured - it is perfectly 5.0V – palash Dec 3 '15 at 8:56
  • @palash it means that power supplies or regulators are rated to give out let's say 5V, but it is only guaranteed when you draw at least a certain amount of current. If there is no draw, the (unloaded) voltage may be higher. – jediz Jan 28 '17 at 14:54

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