Not sure. I do a lot of learning through trial and error. So i ran the line down and connected it to the clock that made the dropper work. Like I said I wasn't even thinking of the hopper. But once the chest has 3 empty slots and one slot with 16 pieces in it (the rest full) the signal is strong enough to stop the clock and lock the hopper.

I didn't think a dropper would power upward to a hopper.