Swamp Cooler

     Back in 2003, I had gotten a swamp cooler and wanted a more automated control system for it, but I was on a very tight budget at the time. I wanted my swamp cooler to behave as a HVAC unit. My cooler is the typical one with the options for the unit selectable from the from panel, 'off', 'pump only', 'low vent', 'hi vent', 'low cool', and 'hi cool'. I started with a thermostatic switch and that worked ok, but it would only turn the cooler on and off, that worked best by leaving the cooler on 'hi cool'. This left the house too cold at night and having the cooler come on at night when you really didn't think it was necessary. I knew how plc's worked and it would be perfect to do what I wanted, but didn't have the money to get what I needed so I could start learning them.
     In 2011, I went to a new employer and found a whole new set of challenges. My next move with the plc was when I got my first plc. I played with that thing until I had fell over in my chair. I fell asleep at the 'wheel' multiple times just trying to learn everything I could about it. I started whittling away at a control program for my swamp cooler. This took me longer than most programmers because I was new at it, but determined. I got the cooler working with a time-proportional PID loop that would control low and hi speeds. This worked flawless for the last two seasons.
     I had been thinking about what more I could do with this. I was thinking of a 3-phase motor so the air flow could be adjusted by the pid directly and eliminate the time-proportional parts as there would no longer be low and hi speed options. I was scouring the web for a 3-ph motor that would fit in the cooler. I finally found one, but it was $400. A little more than I wanted to spend. But, I just might have to bite the bullet and get it. While I was thinking about this, I was also wondering what else I could control in/on/around the house with this plc. I ran a few wires to the garage door button and wrote some code for opening/closing/venting the garage door based on outside temperature and garage temperature. This was tested last summer with great success. This kept the garage from getting too hot during the hot parts of the day.
     One year later, I'm training another co-worker and was telling him about my plc controlled swamp cooler and what that I was wanting to put a 3-ph motor for precise fan control. He lit up saying that is what he needs for his house. He tells me that his old school house is over 5,000 sq.-ft. with three swamp coolers and that he'd like to have the control system that I was building. I got a part list together for him with prices and while I was looking for the motor I had found a year ago, I ran across another one for 1/2 the cost! I was excited. I got to work on a new version of the plc program to include the VFD control. I then found that motor on EBAY for even cheaper. I ordered the motor on eBay and now have it here in my house setup for testing. I'm working out any other bugs before the snow melts so I can get the motor installed and get the real-world testing done.
     Now that I have my control program written for the VFD and the 3-ph motor here waiting to be installed, I have started working on the same VFD control program, but for three swamp coolers. I told the co-worker that I would do the program for no charge, but he would have to get the parts to make it work. I would even help him install everything. Then there's training time on the new system.