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How is the power via USB filtered in an Arduino Nano

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SolarTrap

Computer
May 5, 2014
89
Hello all,

I have an issue with the 5V input to the Arduino Nano. I noticed that when I power (using a power bank) my Nano via the USB port I get a clean ADC reading from my microphone but using the same power via the Vin pin I am getting noise. This makes me think there is a filter in the path. I have attached the schematics, can someone identify what that filter is?

Thanks,
Markus
 
 https://files.engineering.com/getfile.aspx?folder=452cd2ee-bf57-486e-a9e3-762828ae4f7c&file=Nano-reference.zip
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In that schematic, the USB adds C8 and C9 to C2, C3, and C10 via the Schottky diode D1, so ~50% more capacitance, but you do lose 0.1-0.2V through that diode.

But the noise could come from elsewhere, since a power bank is essentially pure DC. It may be that the FT232RL might be generating noise that's suppressed when it's connected to your power bank.

TTFN (ta ta for now)
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How about hooking it to a scope and seeing what this so-called noise looks like... that will probably give a gigantic clue as to where it is coming from.

Dan - Owner
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