Servo vs Stepper Motor


I'm working on a traverse mechanism that only requires to lift and lower a pitot tube (very lightweight) for an experiment. Speed is of no importance, I only want precision and accuracy. It's an inexpensive project, so I was considering using a motor and belt pulley system to move up and down. My question is, is it better to use a stepper or a servo? The only advantage I'm seeing for the servo is that it doesn't require calibration for its zero, but its more expensive. Which one do you think is best for the application?

How far does it need to be lifted?

The cheapest steppers are slightly cheaper than the cheapest servos but you need a driver for the steppers so they actually end up being more expensive. The servos also come with a variety of horns whereas you will need to make or buy something to attach to the stepper shaft, which could cost more than the price of the stepper motor itself.

I don't see why this would need a stepper, so servo it is to me. Easier. Much easier.

The total height to be lifted is maybe about 12 inches. What I was concerned by using a servo is that they are limited to only 360 degrees of rotation (some only 180 degrees), which may not be enough to cover the whole distance.

The most common servos indeed just do 180°, but there are servos that can do multiple turns. They'll cost more.

Another cheap alternative is a DC motor + optical encoder (to tell you how far you've moved) + limit switch (for homing). Main difference with stepper and servo is that it will not hold position by itself, if that's needed you need to use a worm drive. Then you can hold position without needing any additional power even.

I'm not looking to building motor alternatives, it's either a stepper or servo. I was leaning towards stepper because this is a low speed application, which provides me with a lot of torque, and it has a strong holding torque compared to servo. My mechanism would resemble that of a 3D printer 9 (using a belt and linear bearings), but in the vertical direction.

For the purpose of the discussion, I'll assume that by "servo" you mean "R/C servo" since otherwise we can end up talking past each other :slight_smile:

A stepper is a better choice when you consider overall cost. For short, precise motions or longer, less precise ones, an R/C servo is lighter and costs less. However, for longer motions a stepper is a better choice because in order to get the precision you need, the shaft will have to make multiple turns. Depending on the mechanical assembly, a stepper can hold position quite well but it will consume a fair amount of current while doing so.

FYI, this "Gigs & Collaborations" forum section is for submitting job offers. So, unless you were looking to pay someone to answer your question, this is the wrong forum section. In the future, please take the time to chose the most appropriate forum section before you post. In this case, the "Motors, Mechanics, and Power" section is the obvious choice.