I was playing around with those and they seem to work fairly nicely during night and day. However I was wondering if it's possible to somehow make them work when something is "blocking" sunlight? I tried with a tree but nothing happened when it blocked the sunlight on various levels. Maybe I should dig it down one block in the ground so that light from the sides doesn't affect it? Just about to go to bed so I'll try that when I wake up unless someone got a better idea 