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The recommended input voltage for Arduino is 7-12V. Given that both 7V and 12V power supplies (AC-to-DC converters) are available, which voltage will be more suitable/practical? Could be in terms of factors like energy efficiency, costs, heat generation etc...

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  • \$\begingroup\$ The real answer? Use a usb charger on the usb port, for a stable 5v with no heat issues on the board, higher capacity (must usb chargers are 1+ Amp at this point), and pretty cheap (5 dollars retail, and you can buy them everywhere to boot) \$\endgroup\$
    – Passerby
    Mar 16, 2014 at 16:50
  • \$\begingroup\$ @Passerby, would that kind of charger fall into the category this user describes? : "it must be a real stable 5V (not some wacky unregulated wall-wart)" \$\endgroup\$
    – brasofilo
    Jun 11, 2019 at 0:46

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The Arduino uses a linear regulator to convert the input voltage to 5V to run the logic. Any excess voltage gets converted to heat in proportion to the current being drawn (P = ΔV × I), therefore, you want to use the lowest acceptable voltage.

The regulator is physically very tiny, and has little if any effective heat-sinking to help it manage power dissipation, so the current that it can handle is very limited — basically the needs of the Arduino itself plus a few 10s of mA to operate external circuitry. Reducing the input voltage as much as possible allows you to get a few more mA out of it before it shuts down.

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