the fact that the servo power comes via Dupont connection from the breadboard into the servo connector plug.
Hi Tomgeorge, I think you have misunderstood my Fritzing diagram ? the servos are powered directly from my lab power supply, the arduino is powered via the USB or a 9v cell. Only the 2 grounds are connected.
My servo power supply and DMM show a maximum drain for one servo to switch is no more than 250mA.
SG90 stall current is given as 650mA +/-80mA at 5V. So 1A is overdoing it, but not by very much.Steve