Hello. So I reread the rules and am going to pose my dillema as specifically as I can. I've been researching it for a couple weeks and am still stumped, so please bear with me...I'm just a beginner.
Here is the problem I am trying to solve, posed metaphorically.
What sensor exists, that would allow you to detect a particular tennis ball being dropped into a bucket, only that tennis ball, and no others? What would I have to attach to the bucket AND that one tennis ball that could detect and alert me it just passed into the bucket?