maybe because of a 330uF capacitor thats used by the switching 5v voltage regulator?
A diode is also fine, but only when there is no voltage drop.
Is it posible to use the external 5v supply and still be able to use USB, without draining power from the USB?
Can this be dangarous to test?
Just to make it clear...when I use an external 5v power supply on the 5v pin (works that way, tested it, arduino runs fine).But Than I also plug in the USB cable, thats dangerous to test?USB alone gives to much of a current to be handled by the USB port, but with a external 5v power supply on the 5v pin, it can't be worst.I only hope the USB current is not used, the external 5v power supply on the 5v pin should be used.Will the load be on both power supplies paralel, or detect the arduino it already has power on 5v pin, and don't use USB power?Or will they both power, but when the external supply is turned on first, and charge the capacitor, the USB can handle it?
Is it posible to cut the pin 1 of the USB VCC 5v+ but still be able to use the arduino normally?pin 2 D-, pin3 D+ and GND are enough for communication?