I wanted to wait to see if it worked and how much light it gave off before I installed it (good advice). So far I have had it on my window sill for 5 days and when I wave my hand in front of it, it has not lit up once. It has a pin to turn it on but there is really no way to tell if it is on or off. So, I pushed it once and waited a couple of days then I pressed it again...so far no luck. As others have said, the directions really aren't very helpful either. It has a lettered diagram but no explanation of what the letters refer to. Lastly, what is a "set"? I only received one.