Thanks for all the input folks! I appreciate it. Yes, full-timing in a RV is great! I'm still trying to put this project together.. Being retired, I don't get in a big hurry to do anything these days
So I now have a couple of ATiny85's ... one to practice with (and potentially let the smoke out of) and one for after I have the bugs worked out. I'm figuring on taking the RVs 12vdc and a 5 volt regulator (plus a couple of caps on the input & output) to bring it down to 5v for the ATiny.. I have relays that are for 12 vdc operation (both the coil as well as the contact side. I also have some small(-ish) arcade-style buttons that are backlit with some LEDs for the timer function. Again, I want to push one and have the fan run for a shorter time (10-15 minutes..?) and another one will turn it on for longer.. around an hour. No crystal since it really doesn't matter if it runs 15 minutes versus 16.5 minutes, etc. I'll breadboard this all up this weekend and see what happens. Next is the code for the ATiny.. I'm planning to use my Arduino Uno for that.. I have already found the code I can use to go that route. So.. any input on circuit configuration or components (instead of, in addition to what I have already mentioned).. would certainly be appreciated.