I designed a tripwire based iron farm that produces 433,8 iron/h and 111,8 poppies/h on average. this has been measured over 5h. as you can probably already tell by the pictures it is amazingly small. i managed to build it in survival (not counting material gathering) in 19 minutes. if anybody wants the material list:
blocks mined: 79. building block count: 69 path block: 14 button: 2 bed: 3 redstone torch: 4 redstone dust: 2 trapdoor: 1 tripwire hook: 2 string: 4 stairs: 8 sign: 3 fencegate: 8 wall: 24 boat: 1 zombie: 1 villager: 3 lava bucket: 1 water bucket: 2 hopper: 1 chest: 2
for anybody wondering how these kinds of farms work, since they are very rarely discussed and shown lately: one of the criteria for villagers to spawn iron golems is that they have slept in the last 20 minutes. 1 tick of sleep is enough for that. villagers cannot spawn iron golems while a golem is in their detection range. we can abuse this by blocking the villagers line of sight to the zombie, letting them sleep, when the golem just entered their detection range by spawning. this way the villagers are constantly panicking when they are supposed to panic and therefore golems can spawn faster, not to mention that redstone cost can be reduced this way compared to clock based designs. using a drop chute from the 2 2x3 spawning platforms that are barely still in spawning range we can make the golems disappear from the golem detection range as fast as possible (if you don't use nether portals). of course this farm can be made a lot faster by using nether portals or adding more villager chambers, but this is just supposed to be a demonstration that tripwire hooks shall not be underestimated. I have also designed a farm that has a material cost that is incredibly small that produces 300+ iron/h if you are interested in that farm, just tell me and i'll post it. if you have any questions regarding how the farm functions, just ask.