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Wu Qiufeng built this observer stabilizer on Youtube yesterday.

It looks really attractive and efficient but also confusing to me. Could someone tell me why the second pulse is prevented from firing the piston? Thanks.enter image description here

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I just did some further experiments on this contraption and placed under the observer a movable block instead of the melon. Now it gets stuck in this common observer piston loop. However, the fact that the sticky piston does not abort on the falling edge of the first pulse and pulls back the stone to its original position is unexpected and attracts my attention since I assume that observers always emit pulses of 1 redstone tick length, which theoretically would result in the abortion of sticky pistons (e.g. they leave the movable block on the off pulse and retracts itself without it). Does this suggest that the observer on the top layer contribute to the extension of the first pulse to at least 1.5 redstone ticks? If so, how does that happen? I thought the two horozontally placed observers would react simultaneously.


1 Answer 1


I did not confirm this myself, but I was told that a piston takes 3 game ticks (not the 2 listed on the Minecraft wiki) to retract. If this is true, then it can't react to the second pulse in time, because it is in the process of retracting when the redstone dust turns on. On the next redstone update the dust turns off, so the piston also doesn't extend.

  • Thanks. The 1.5 redstone tick long retraction explains it well, I think. I just found out that the first pulse activates the piston to a full extension (1.5 redstone tick long) rather than the expected aborted extension which lasts only 1 redstone tick. So a 1.5 redstone ticks long extension plus the 1.5 long retraction makes 3 redstone ticks, which makes the piston just miss the second pulse and therefore would not gets activated again. But I do not understand how the 1.5 redstone ticks long pulse occurs in the first place.
    – Ent L
    Oct 15, 2019 at 17:30
  • It's simply a bug. Oct 15, 2019 at 17:55
  • On pc it should take zero ticks, making zero tick sugar cane farms possible. Nov 21, 2019 at 13:01
  • 1
    No, that's a completely different area of redstone bugginess. Zero-ticks don't just happen simply from an observer or a piston. Nov 21, 2019 at 16:00

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