Open a crafting table
Place 1 Dropper in the center
Place 2 Iron Ingots in the middle left and middle right
Place 1 Redstone Dust in the bottom middle
Place 1 Comparator in the top middle
Place 1 Iron Ingot in the top left
Place 1 Iron Ingot in the top right
Place 1 Iron Ingot in the bottom left
Place 1 Iron Ingot in the bottom right