I have been using what I assume are Arduino clones, and I'm using both the external power, and the USB power.
I am expecting for the external power to be the priority power source, however what I am finding is that the USB supply is dominant. Both sources are being used.
If I just power the Arduino on the USB input, then the 5v supply is providing ~40mA, however when I then add the extenal supply, the 5V drops to 39mA, and the external supply is only providing 1 mA.
Does anyone know why I might be getting this problem occur, or how to correct it?