I place an LED in Pin 13 and GND,
Thanks Lefty. I've done a little breadboarding so was aware about the use of a resistor with an LED. I only used Pin 13 as an example because as I understood it that Pin 13 already has a in series resistor with the on-board LED.The on board pin 13 LED does have proper current limiting resistor but only for it's on-board led. That on board resistor protection does not reach out to the shield pin 13 connection that has it's own direct connection path to the chip's output pin, therefore requiring an external series resistor if powering an external led. A good learning lesson would be to look up a schematic drawing of an arduino board and trace the current path for the on board LED Vs what the current path would be for an external led connected to the shield pin 13.LeftyErdin. Thanks. It's good to hear that I won't be putting undue stress on the board by repeatedly unplugging and replugging the USB during my experimentations although your post suggests I should be okay with careful rewiring on the fly? I would only do that for basic changes anyway. If I was making more elaborate changes, then I'd definitely unplug first.I was just wondering how others typically operate when building really.