When I connected a ground and a 4V input to arduino GND and Analog pin 0 without USB or external power supply to the board, the onboard LEDs are turned on. Also the LEDs on the Xbee (connected to my board) are on.
Why? Is it I should avoid doing this? I found something about ESD protection diode but cannot understand.
Thanks for your help!
kesikesi:
When I connected a ground and a 5=4V input to arduino GND and Analog pin 0 without USB or external power supply to the board, the onboard LEDs are turned on. Also the LEDs on the Xbee (connected to my board) are on.Why? Is it I should avoid doing this? I found something about ESD protection diode but cannot understand.
Thanks for your help!
Not sure what 5=4V is, but applying any voltage to an arduino pin when the board has no power applied to it will also current to flow through those clamping diodes, which can easily damage the chip as the clamping diodes cannot handle much current at all. This is sometimes called finding a 'backdoor circuit' and should be avoided.
Lefty
Oh sorry, 4V. Thanks!