arduino mega board voltage of I/O pins and what is the use of 3.3v in that board


I want use mega board in my project with 5V supply. But 3.3V supply on board making confused. Please explain the role of 3.3V in mega board

The 3.3volt pin is an auxiliary 3.3volt/150mA power supply output, not used by the Mega itself.

You can use it to power 3.3volt sensors etc.