Voltage and Current and Arduino I put a LED into 3.3V of the arduino and Ground, and it blew my LED violently, smoke was everyone, the whole half top of the led blew up across my room.

However, when i program the arduino with Pin13 HIGH per say, it will not blow up. Will be lit brightly. (Both using no resistors). However, if I plug mroe stuff in the board, for example, a lcd screen, rotary switches, and pushbuttons for my program, the LED dims to such a low brightness I cannot see.

Why is this? How Do I fix it?

Schematic:


Note, that i am using a mega, and some of it is slightly changed, and LED is being powered from A0 (Or Pin 54 on Mega)
You must use a resistor. See The care and feeding of LEDs


  How Do I fix it?


Use a current-limiting resistor.