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I'm building a test circuit on an Arduino Nano that consists of a simple 220 Ohm resistor and an LED on pin D2 which is routed back to GND (ground).

It's as simple as this: Nano circuit

It's running a very simple program to blink the LED on and off. It all works while connected to the USB port. I know the USB port provides 5V.

Now I want to run it my Nano and circuit from a 9V battery. The datasheet says that you can run the Nano on 6V -12V by connecting it to pin 30 (VIN). Of course, I know I'll have to add a line from GND back to the (common) battery ground also.

When I do that, the voltage on the OUTPUT pin (D2) will never be higher than 5V though, right?
I should not expect any change in output voltage even though I'm changing voltage that is powering the Nano, correct?

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It looks like VIN connects to a LM2940, 5 volt regulator, so the voltage on the OUTPUT pin (D2) will never be higher than 5V.

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  • Side note: The actually used voltage regulator differs from board to board (with chinese clones etc) so you always need to look at the datasheet. For the LM2940x in the 5V version, the output is between 4.85 to 5.15V (given about 10V input voltage at 25°C). Other regulators (AMS1117,..) might differ. [ti.com/lit/ds/symlink/lm2940c.pdf] – Maximilian Gerhardt Jun 11 '18 at 20:29
  • That's a great, definitive explanation because you've also shown me how to discover this information on my own. Thanks very much and for the note about the clones. – raddevus Jun 11 '18 at 20:48

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