Can you use a linear servo for eyelids?

Kelly Mahler

I just finished David's "How To Make An Eye Mechanism - Design, 3D Printing & Assembly" course. First of all- awesome! So incredibly information!

But I do have a few questions..

I know on his setup he was using multiple rotary servos, and attaching it to the eyelids, one per eyelid, to translate the motion. I was wondering though, is it possible to use a linear servo to accomplish the same thing? Could you use a linear servo to go in/out, and have the attachment on the eyelid(s) be able to pivot around a screw? Likewise, could you use one linear servo to control both eyelids? Perhaps with some kind of bar that splits into two (like an H or Y shape)?  Obviously, this limits the performance capabilities, but for my needs, I just need and easy open/close. I've even wondered if it would be easier to have the bottom lid be static, and only the upper lid move.

The biggest reason I ask is because I'm brainstorming on ideas for limited size and space uses- and wondering just how compact you can get a setup to be. (I'd like to have the eyes built into a mask, worn over the performer's face, and most likely, only one eye animated, instead of two side-by-side).

Chris Ellerby

Hi Kelly,

A linear servo would work good for eyelids as long as it can move fast enough to produce blinks at the rate you desire.

You can have a single servo control multiple lids as you suggested.  It's common to have 1 servo handle the top lids and 1 servo handle the bottom lids if you don't need the ability to wink.  Some setups use a single servo for all 4 lids, but then you lose the ability to mix in the eye up/down movement to impact the upper and lower lids individually, which makes eye movement a lot more realistic.

For compact spaces you can also use micro servos or have cable linkages so your servos can be located elsewhere (back of head, inside the torso, etc)

/Chris

Kelly Mahler

Good to know. I just haven't had any luck finding pictures or videos of anyone using a linear servo for eyes (if you know of any, please feel free to share!)

I did pick up two HS-55 servos today at any rate, so hopefully that will help me get started tinkering. 

Chris Ellerby

Liner servos just are not as common I think.  It's often easier to just keep a stock of regular servos and use mechanical linkages to make their motion linear when needed. 

/Chris