Help with simple motorized gear design


I’m looking to build a simple motorized gear in a stimulus application experiment I’m designing and am hoping someone here with more engineering intuition than I do might make some suggestions! The gear would need to be capable of moving a mounted load (e.g., a piece of food attached to a small glass pipette) at a slow speed in a single dimension (both forward and in reverse). The idea we’re going for is to be able to gently bring a small food stimulus up against the sensory organ of an animal, leave it in contact for several seconds, and then pull it back. We’re looking to mount the gear about 6" above the table using a magnetic stand and be able to advanced our load only a few inches forward/backward. An additional bonus would be finding or designing an apparatus with a DC motor that we could interface with a computer, thus being able to control the forward/reverse motion automatically and controlling the speed/distance over which to move the load; this is the least of my concerns though, as I can probably find software to do this on my own.

Can anyone suggest Pololu products that might fit the bill here? One possibility I’ve considered is an adaptation of the Tamiya 70121 Pulley Unit Set (, though I wonder if something a litter sleeker and more easily mountable might be available.

I really appreciate any help anyone can offer!



Hello, Jeff.

There are a variety of ways you could get that kind of motion with the products we carry. The pulley system you recommend might work, but it would probably be simpler to use an appropriately sized linear actuator. You could add a DPDT switch for manual control of extension and retraction. (ServoCity has an example of how to wire a DPDT switch to a linear actuator at the bottom of this page.) For controlling the position of a linear actuator with feedback, I recommend using one of our jrk motor controllers.

I suspect that the linear actuators we carry might be a little too large for your application. (You can see what we have by clicking here.) You might try Firgelli; they make smaller linear actuators.

By the way, your project sounds pretty cool!


Dear Jon,

I really appreciate your suggestions and references. I feel like I have a good place to start. I’ll let you know if I have any additional questions regarding design or purchase. Thank you for now!