I am just getting started with Arduino, so please forgive me if this is a stupid question.

I was searching for serial LCD displays, and found them in two variants: 3.3V and 5V. I looked on the Uno board to see which I should use, and found that it had power outputs for both.

So, which should I get? Or does it not really matter?


2 Answers 2


I'm not an Arduino user myself, but from what I read here all the time it seems that it works on 5V.

Confirmed here, see also this lousy schematic.

You need the 5V display.

  • \$\begingroup\$ Thanks. But then what is the purpose of the 3.3V pin? \$\endgroup\$ May 26, 2012 at 16:53
  • \$\begingroup\$ @G3n3ro - Sorry, no idea. I don't want to look at that schematic for too long :-/ \$\endgroup\$
    – stevenvh
    May 26, 2012 at 17:01
  • 1
    \$\begingroup\$ It's a convenience rail for powering 3.3v devices on Arduino shields - 50mA max, though. Possibly useful: LadyAda's hack to the Uno board to convert it to run on 3.3v by replacing its regulator. Presumably that would provide more current current at 3.3v. \$\endgroup\$
    – JRobert
    May 26, 2012 at 20:44

The uno has a regulator on board to provide a3.3v rail. All of the arduino i/o lines are 5v however. You can use either type of display BUT you must be sure to level shift your data lines if you plan to use 3.3v

I'm on a phone so it's a bit hard to get a diagram at the moment

  • \$\begingroup\$ So, it would be easier just to get the 5V? \$\endgroup\$ May 26, 2012 at 21:09
  • \$\begingroup\$ @G3n3ro - Yes, 5V is the obvious choice. That's the supply voltage of the microcontroller, and of what you want to connect it to. You'll have to add that extra logic if you want to connect 3.3V to 5V. That's why I said you want the 5V LCD. \$\endgroup\$
    – stevenvh
    May 27, 2012 at 4:30

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