Stackable compact randomizer, bukkit, vanilla

As a request of my other post i made this, its a random pulse generator based on hoppers and droppers.

how it works: the dropper is pointing upwards to the hopper, and in the dropper are 5 items, iron spade, and some random blocks.

make SURE you have at least 1 non-stackable item (like the spade) inside if you want the pulse!

in the picture above it is stacked 10 times, and it works perfectly, i included a schematic

Additional Notes

I am not the first who made this, i am almost 100% sure of that.