paracha3:
So i say to myself, great 5VDC, 3.0A power adapter would be great choice. I connect it,
Connect it where?
paracha3:
WHAT???? Here is what is confusing, how come USB (supposedly 5VDC, 500mA sourcing capacity) can drive LCD and program runs fine but the adapter 5VDC,3A cant turn on anything???
Because the USB port doesn't go through the on-board regulator. The DC-Jack does.
paracha3:
Secondly, even thought the arduino website says input voltage 6-12v, how come 12V makes the regulator so hot? what is good voltage adapter to but which can drive LCD and alike accessories for my circuits?
It runs hot because the on-board regulator is a linear regulator. That means the more current you draw through it and the higher the input voltage, the more power the regulator itself dissappates. The only heat sink is the PCB.
Your term "dangerously hot" may not actually apply. Assuming the current is relatively constant (not spikes) then the regulator will go into thermal shutdown when it becomes "dangerously hot." ICs can stand much higher heat than human beings.