Greenhouse Controller Project

 We have 2 commercial greenhouse ranges on our farm. Each range is 1/2 acre gutter connected with a 12 ft. tall clear span of 120 ft. x 180 ft. Both ranges are 20+ years old and still in good working order. These ranges have environmental controls from Wadsworth Control Systems. The model Step500 controls have done a great job controlling the temperature and humidity through the years. The heart of the controller is the main board shown below.

Ten or so years ago we had a control board with problems so we bought a $900 replacement and had the bad board repaired and sent back for use as a spare. That was our only failure until last Spring (2020) when another board failed so I swapped it for the spare. I called Wadsworth to see about repairing a board again and was told that the Step500 was at "end of life" and they were not repairing or replacing the boards. I was advised to let them to design and quote a new system based on their newer controllers. I could not get a price over the phone but was told $3000 - $5000 would be in the ballpark. I still had 2 working controllers but knew something had to be done. 

With the Covid19 health crisis I had more time on my hands than I had money. Using the controller for 20 years I knew how it worked. The board in question basically controlled relays for 3 stages of heating, controlling 6 unit heaters and the relays for 5 stages of cooling, controlling contactors for the 10 - 1hp fans as well as position control of the vent wall. The board received temperature and humidity readings from a wired senor box in the middle of the range. 

I decided to get to work on this project. After about 120 hrs. of my time over several months I had the new system up and running. Since you have to get 5 boards made I decided to get 5 sets of all the parts as well. This will let me upgrade the second range as well once the first one finishes a shake down season and I will still have plenty of spare parts for the foreseeable future. The total cost of 5 complete systems was $450 or $90 per system. I wrote up a separate page going deeper into the decisions I had to make. I ended up with one large PCB and two smaller ones.

I consider this project a great success. It is a good feeling to be able to extend the life of this controller. It is not often for a hobby project to save you money but this one sure did. I would be happy to answer any questions on the project.