Ok very puzzled. I have Arduino UNO driving a Back light LCD (16x2) for simple hello world message. Remember back light is ON. Power to LCD is from arduino board 5vheader pin.
Now i have 3 power sources.
1- Wall power adapter output 5VDC, 3.0A 2- Wall power adapter output 12VDC, 1.5A 3- USB Cable to PC for arduino for programming
and here is whats going on.
When i connect just USB cable to arduino, the LCD back light lits fine and i can see the message. All is fine but this is not feasible because i cant keep the PC always on to power my circuit. So i disconnect USB after programming.
When i connect 12VDC,1.5A source to UNO, everything works fine but regulator on the board become dangerously hot and i cant run more than a minute.
So i say to myself, great 5VDC, 3.0A power adapter would be great choice. I connect it, the UNO ON LED lits up but LCD is off and nothing on the screen, the program is not running. 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???
What makes me pull my hair out is when i connect the same 5VDC, 3.0A power adapter to Arduino MEGA+Ethernet Shield it is running fine a separate piece of software.
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?
Sorry for long post. Thanks all.