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I'm playing Minecraft: Java Edition, 1.11 on PC. The reason I'm playing this version is because of the lack of OptiFine releases for the current version. My question is concerning the behavior of Observers in this version.

I built a pumpkin farm as shown in the screenshot below. The farm works, but the Observer facing the pumpkin is only sending redstone pulses two times: First is when the pumpkin grows and the second is when the piston retracts.

My question is, why the Observer is not sending a pulse when the piston extends? Doesn't that count as a block update?

If that's right, then the observer should send a total of three redstone pulses, which would obviously break this farm. But that's not the case.

Automated pumpkin farm

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    I think it would help to see the farm from a few more angles. From this angle, I can't clearly see how the farm even works to begin with. – MBraedley Jul 16 at 15:26
  • @MBraedley, thanks for the comment. But I can't post screenshots as I'm in work. However I can detail its working. Whenever a pumpkin grows, the Observer below activates the sticky piston above which in turn pulls the Observer in front of it. This Observer activates the piston below and it breaks the pumpkin. When the piston retracts the Observer causes the sticky piston to push the Observer above, back to its original position. – SlayerDiAngelo Jul 16 at 15:37
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    On another note im pretty sure there is optifine for the current version. It's listed on their download page optifine.net/downloads – Reflexive Jul 16 at 15:53
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I did some testing and it seems like observers have a 1-tick cooldown time.

The observer detects when the piston extends and breaks the melon block, one tick later the piston retracts, which is not detected by the observer, because it is still within it's cooldown time.

Another tick later there is an air block in that spot, which doesn't have a block update.

I rebuilt your farm like this in 1.11.2 and it should be accurate:

recreation of the setup from the question

Note: This is from personal testing and not from any official source, it appears to be correct, but it may be wrong.

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    The lower piston seems to be powered by the upper observer by utilising quasi-connectivity. The piston is supposed to be powered by the observer, BUT it should require a block update to notice that it's beeing powered. Can anyone eplain how the piston knows that it's being powered by quasi-connectivity in this case? I tested this in 1.14.3 and it works there, too. – user232393 Jul 16 at 18:14
  • so does this imply that Observers had a 1 redstone tick cooldown? – SlayerDiAngelo Jul 17 at 2:59
  • @SlayerDiAngelo That's a much better way to word it. I didn't test 2 or more tick pulses, so it may be a longer cooldown. – user232393 Jul 17 at 5:34
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    @SlayerDiAngelo In an extreme case (because I'm currently not sure how quickly everything moves), the observer detects the melon and turns on. As long as it is on, the upper piston would be extended and it wouldn't retract until the observer turns off again. When the observer turns off, the piston retracts, this alone should take at least one more tick. Also: the lower piston does not extend at the same time as the upper piston retracts (Or at least I think so, it's not much time in between so there is a possibility that my judgement, or my memory from when I tested it is off) – user232393 Jul 17 at 14:45
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    I saw one design somewhere that uses a flying machine to break and collect the melons, it would be fairly expensive, but extending it would basically cost nothing except for dirt, hoes, and water. You can also make a time based solution, which would require one piston and a little redstone dust per block where melons grow. You can then use one clock for many melon spots. – user232393 Jul 17 at 15:36

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