I wanted to use the cigarette lighter receptacle of a car as the power supply for the Arduino Mega. From 12 V, I will convert it to a 7 V supply, but my problem is, what must be the minimum current or electrical power to be fed into the Arduino Mega?

And are there any things I have to do to the Arduino Mega 2560 for it to function well in supplying it a 7 volts supply from a car?


1 Answer 1


The Arduino's voltage regulator is rated for a suggested input range of 7 to 12 volts. Automobile power will range from slightly below 12 volts to over 13 volts, so stepping it down to 7 volts is a good idea.

Looking at the data sheet it doesn't say how much current it draws. Since it uses a linear power supply it will likely draw the same amount of current regardless of the input voltage, and simply waste the power from a higher input voltage as heat.

The power from a car cigarette lighter should have plenty of current, so your proposed setup should work just fine. Is your 7 volt supply regulated?

Note that you could also use a "buck" style switching power supply to feed 5 volts directly into the 5V line. There are several buck style power supplies on the market for less than $10 US that will provide up to 3A of regulated 5 volts.

  • Recommended voltage is 7-12V, maximum is 6-20V. So 13V would still be fine (though wasteful).
    – Gerben
    Commented Sep 20, 2014 at 20:59
  • Is stepping down the 12V to 7V and limiting it to 2Amperese already sufficient for the Arduino Mega 2560? Can it run 4 different UARTS, where these 4 different shield also get its power sources from the 5 V of the Arduino?
    – weyhei
    Commented Sep 24, 2014 at 11:54
  • @Gerben - automotive power is not limited to 13v. In fact it's notoriously variable (lower and much higher) and electrically grungy, for example when the engine is running (or worse, starting). Commented Oct 21, 2014 at 15:46
  • The input filter caps are rated for 16V, so putting an Arduino on the automotive supply directly is a very bad idea. Commented Dec 19, 2014 at 23:01

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