I have an Arduino UNO. It has VoltageIN on a pin. Is there any difference between powering my UNO through VIN or powering it through the DC port?

The docs only say this,

5V.This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

So it seems to imply VIN/USB/DC in all go through the voltage regulator? Is there any difference then?

Is there any advantage to running a variable power supply through an adapter like this: DC-in

Or should I just go through VIN?

  • 1
    What do the technical documents (data sheet) say? If you haven't found one, do try.
    – Andy aka
    Oct 9, 2015 at 23:02
  • @Andyaka just updated the question 12 seconds after you said that.
    – Evan Carroll
    Oct 9, 2015 at 23:03
  • Instructions seem clear enough but I have no idea what relevance the picture is. Hint - I don't need to know.
    – Andy aka
    Oct 9, 2015 at 23:09

2 Answers 2


DC Jack has a Reverse Protection Diode, that drops 0.7V at usable currents. The VIN does not. Both go through the on board LM7805 or similar linear regulator. The USB does not, but it does go through a P-Channel Mosfet used to switch between USB and DC/VIN power before connecting to the 5V rail. The 5V pin bypasses the regulator, Diode, and P-Channel Mosfet completely.

The advantage of the DC jack is that the Reverse Protection Diode is used, preventing reverse voltage problems if you wire it wrong.

  • It's odd/cheap that they didn't put a MOSFET-based reverse polarity solution. I guess they had to cut corners somewhere to meet the target price. Oct 10, 2015 at 0:53

If you have a "variable power supply" just set it to 5.00v and connect to the 5v pins. Eg like the this http://blog.unixbigot.id.au/2015/10/make-5-volt-battery-supply-for-any.html?m=1

  • 1
    The post you linked to seems to be talking about batteries and a voltage regulator, rather than connecting a variable power supply.
    – Nick Gammon
    Oct 10, 2015 at 20:35
  • @NickGammon yes, but it's the same connection point. Oct 10, 2015 at 22:25

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