So you mean I can't hook up with a regular led and resistor to the 12V outlet (too much current), right?! Then I will use a 9V battery to light up the led. Just for curiosity, my last question was that if I cover up the display on the power supply, can you measure how much maximum current from the power supply? For example, I didn't know how much current from the 12V outlet, can I measure it?