I need to be able to rotate a servo or stepper to any of four positions (+/- 45 and 135 degrees) and then lock in that position with power disconnected. Is there some kind of servo or stepper that does this? Is there a way to apply an external brake or locking pin?
Ideally the motor would be about a 1 inch diameter, it wouldn't need huge torque in the turning operation, but would need to resist occasional bumps or impacts without moving. (Or failing that, a way to read the position at the next update if it is forced off the intended angle.)