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I'm using an Uno to control NeoPixels LED strips (60 per metre). These are powered with a 5V DC supply. Now, when using USB to power the Arduino it works lovely. However I want to move the Arduino into a standalone "installation" where I'll only want one power supply.

I've already got a 5V DC supply which outputs about 5.2V. What is the best way to power both the Arduino and the LEDs? I understand the need for at least 7V at the Arduino's voltage regulator input. Would my best bet be to get a 12V supply (or similar) and use a buck converter to power the LEDs? The total current draw could reach 3.6A but will be 400mA for the majority of the time.

  • Just split the line coming from the 5v adapter. Have one 5v line connect the 5v pin on the arduino board, and the other to the led strip. That way you bypass the voltage regulator. – Gerben Dec 21 '14 at 16:14
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    My worry wasn't that. My worry was that the 5V from the adapter was potentially not stable enough. – CircularRecursion Dec 21 '14 at 20:56
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If your supply is regulated (put a 47ohm resistor across it and measure the AC voltage with a DMM; it should be almost nothing if properly regulated) then you can use it for both the Uno and the NeoPixels. The ATmega328P has a maximum input voltage of 5.5V, and the WS2812B has a maximum voltage of 5.3V, putting the supply within the proper range to run them.

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