PLC help for very basic implementation

Hello everyone,

I'm really hoping I can get some advice on selecting a cheap PLC unit. It is for my Senior Design Project for Mechanical Engineering at the University of Portland.

First off, my experience with PLC use is minimal. My project consists essentially making a motorized Dolly track to attach a camera to. It will have a DC motor that I hope to vary the speeds by varying the voltages applied to it. The dolly would move about 3 feet over the course of hours (so high speed and smoothness, and therefor a need for motion controllers, are irrelevant) and gears will be used to make the motor's voltage range suitable for the range of motion.

This is where I need help. I don't want something more than what I need. If I'm not mistaken, I don't need the extra add-ons or do-dads if they're just going to be sitting there not being used. I have access to a lab with PLC programming, but would I need a separate module for portable value input? For instance, I'd like to be able to on the go input a number that would signify the velocity the dolly would move down the track.

If anyone has advice or insight, I would greatly appreciate it.

Thanks, Wren