Micrologix 1100 Solar Tracker design questions

[mmarti91 0]

Hello! First off, I want to state that I am a student working on my senior project looking for some general advice about Allen Bradley PLCs and have very little knowledge about them. In short, I am looking for a way to use a Micrologix 1100 PLC to control a solar tracking system. I would like to mimic what this controller does with a PLC. I know there are algorithm-based programs that move solar arrays based on the time, day of year, and location of the array but I am looking to build a closed loop system that reads sensor inputs and moves the array accordingly. Most solar tracking designs use inputs from standard photoresistors, but I want to build something that will track the sun accurately and last for years without service. I was thinking of using two Apogee SC-230 Pyranometers in place of photoresistors, but have no idea if this would work. The theory is that the PLC reads the voltage from the two pyranometers and adjusts the actuator until they both read approximately the same values. The actuator is 12 volts and draws 15 amps peak, they have built in potentiometers and adjustable limit switches. The easy thing would be to buy the off-the-shelf unit and call it a day, but there wouldn't be much of a project in that! Do you think this sounds reasonable at all to accomplish? Thank you!

[JRoss 84]

In terms of the hardware you have selected, I think you're on the right track. What kind of signal do the pyranometers give you? The ML1100 should be up to the challenge. Did you pick a PLC over something like an embedded controller for a reason? Your drawing only shows one axis of motion, but the kit you reference is dual axis. If you hadn't considered it, I would strongly recommend looking into doing two axes of motion so that you can also track the sun's position in the sky during the day. That would give a much greater boost to the output of the array, and make an automated system actually pay for itself. Not to mention meet your stated goal of duplicating the functionality of the kit.