DIY follow focus for my camera.

Hello guys!

I've already done a double follow focus system for my anamorphic camera setup.
Here is the demonstration video: LINK

The thing is that it is too heavy, big and loud. I've used an expensive high torque KST servo. I've modified them by replacing pots with 10 turn Bourns pots so that it could make more turns as far as all lenses have an almost 360 degrees focus ring. I've chosen this servo because my retro lenses are quit stiff. So, the motor is heavy and big, the pot is placed outside and need a extra gear. All it makes everything very inconvenient.
Another thing is that it's very loud.

Now I'd like to find a way to make it smaller and lighter in order to use it on my gimbal.
something like this: LINK

How have they done it? Since all servos are very loud, do you think they use a step motor? But how does the controller know the beginning and end point of the focus ring? How does the controller know the position of the motor gear?

I've deleted your other cross post @Tofer.

Cross posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes writing a detailed answer on this thread, without knowing that someone else already did the same in the other thread.

Repeated cross posting will result in a suspension from the forum.

In the future, please take some time to pick the forum section that best suits the topic of your question and then only post once to that forum section. This is basic forum etiquette, as explained in the sticky "How to use this forum - please read." post you will find at the top of every forum section. It contains a lot of other useful information. Please read it.

Thanks in advance for your cooperation.