The default angle of the servo is 0 degrees (that is when no voltage is applied). So, it can rotate only in one direction from the starting position.
For my project, i need servo which can oscillate in both the directions from the initial position. How is this possible?
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faced this problem while making a robotic arm(im a newbie, my first robotic arm)
From my experience with a radio controlled airplane...
With power off, the servo stays where it was when you last shut off power.
When you power up the servo, it immediately obeys the control signal. It will move to a middle position, if your control device is sending that command.
If there is no control signal, the servo does not move.
If there is noise in the signal line, it may respond to that, making jittery movements.