Sounds like fun, not.
Several years ago upgraded corn dryers and I added a third party auto controller for moisture. Continuously checks moisture content and is temperature corrected. First had to build a sampling chamber, originally you placed it on the bottom of an auger tube and cut a section of flight out, thats crap. The supplied sampling chamber uses a very small auger that two pieces of cob at the same time can plug.
Mounting it and getting a sampling chamber was the easy part, out of all the possible wiring options our dryer was mot listed in the third party manual, took a bit of research on that one.
So basically you turn the dial and set the desired moisture it discharges at, then it either speeds up or slows down the metering rolls fifteen percent if the moisture isn’t at the desired set point. Uses a bank of 3PDT relays, I changed those out and the sockets for 4PDT and off the fourth pole I ran wires to the control building and added LEDs that could be seen from the house. Green all is good, Yellow is running on slow mode (corn is too wet), White is on fast mode (corn is too dry) red if the dryer shuts down or if even on slow it’s 2 points wetter than set.
The relays control whether the juice that goes to the SCR is running straight thru or one of the POTS that speed it up or slow it down. I used the exact same make and model that came in it originally, 5V coils even but I’m just using ones with an extra pole. One of the problems known with this system is sometimes a relay just drops out, it will still close but it’s such low voltage and amperage even with closed contacts the circuit isn’t complete, sometimes if your careful you can find which is acting up by very gently opening the control panel and just touching it with a finger. Eventually started replacing them with a lot more expensive ones that are meant for micro voltage, if I shop around I can get two of the micro voltage ones for what I was paying for a whole box of the OEM’s. Thought about 5V solid state relays as well but those are single throws.