I am using an MG946R Servo.
When I use the power directly from the Arduino (Uno) and do a sweep, it works as expected.
However, when I replace the Arduino power with external power, the Servo either doesn't move or it moves randomly.
I've tried this with both a multi voltage power adaptor, setting the power to both 4.5V and 6V, as well as with a 4 x AA battery pack.
When I use a multi meter set at 6V and check the pins going into the Servo (when it's moving randomly) the voltage keeps moving to anywhere between 5.20V and 5.70V.
It seems that the Servo doesn't move when using battery pack, even though the voltage on the pins reads 5.75V.
Is there something that I am missing here?