Servo vs. stepper for camera mount

Question

I would like to make a camera mount where it can rotate automatically around the Z axis, and also make a variable angle against the ground plane.

The camera weighs about 500grams.

Is a servo motor adequate to make the camera make a variable angle against the ground, or is it a better idea to use a stepper motor and a worm drive?

For the vertical axis I believe that either stepper motor or servo will work adequately.

Also, could you suggest a good way to measure the actual rotation that takes place when using a stepper motor? For a servo I believe measurement is not necessary as it already has feedback from a potentiometer.

Answer 1

I would recommend a stepper motor plus worm drive. You will be able to keep this perfectly still, which is what you want for a camera.

A servo motor contains a circuit which actively tries to maintain the position of the motor. This system can be affected by external forces, electrical noise from the angle sensor, and poor tuning of the control algorithm. All of these things can lead to instability of the motor position, unless you spend good money on the motor.

On the other hand, if you want a stepper motor to stay perfectly still, you just stop stepping it. It will hold its position very accurately, and the worm drive will prevent you being able to back-drive it.

The other benefit of stepper motors is that you generally don't need to measure the rotation. If you're using it within spec, then you can be fairly confident that it has moved the number of steps you asked it to. So confident that many CNC milling machines use stepper motors without any kind of position sensors, and can machine parts for hours without loosing steps.