Monitor a irrigation status
I have a hunter irrigation controller. I was thinking of building a binaryswitch as per the example with four switches to monitor the status of the valves. ie on/off.
The valves operate on 24v would this be posible without damaging the promini
Yes - but you have to protect the arduino from that high voltage. Best way is with a small optocoupler chip (I use EL817 chips which you can get for practically nothing). There is an excellent explanation in the first answer on this post on stackExchange. You may have to adjust the resistors because of the higher voltage. I've included the schematic below (it's a good idea to read the answer though).