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If I want to power up 6 normal 3mm LED with the appropriate series limiting resistor, do I need the 5V with 1A or 5A power supply? Same goes to the Arduino, if I want to power it externally, do I go for the 1A or 5A?

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  • Both will work, but using a 5A one is quite a bit of overkill. – Gerben Jan 24 '17 at 15:01
  • If I'm using 5A, will be voltage drop of the resistor be more or less? Should it be more since it needs to resist more current, hence more voltage drop – Kyle Nathan Jan 24 '17 at 15:07
  • @Jason "series limiting resistor" will limit the current. – Paul Jan 24 '17 at 15:40
  • The 5A refers to the maximum current it can supply. If you draw less, it will supply less. As long as the voltage is the same, there will be the same amount of current flowing through the led. – Gerben Jan 24 '17 at 15:57
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Depending on your led, it will draw 10 to 20mA for a standard led. Thats 0.010 to 0.020A. Multiply this by 6 and you see that a 1A power supply will be enough.

Your arduino, when driving those leds, will also use a few mA. So you can power everything with a 1A power supply.

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Both will work, but go with 1A!!!

It is more forgiving if a short happens.

A 5A short circuit will make sparks that might be dangerous.

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