I've tried to figure this one out on my own, but every configuration I can think of has the piston re-triggering the observer, which re-triggers the piston, etc. Very noisy.

I've tried googling, but 95% of the relevant links are videos, and the videos inevitably either talk about Pocket Edition exclusively (not sure the same mechanics apply), are months old from when the feature was beta testing, or are aggrandizing where the machine is as large as possible.

Since the observer block and the piston will either be at right angles to each other, or facing one another, redstone dust wires seem inevitable (correct me if I'm wrong on that). Wires just delay the signal even more, making the problem worse, not better. Repeaters would seem to have the same issue.

I know I'm using these wrong (made the first one last night... scary run into the nether just to get the quartz with little armor/iron). What's the trick?

  • … What do you want the contraption to do? The whole point of the observer is to trigger when the piston changes, so what you want it to do differently is not clear. Could you edit to describe the exact beginning and end states of the contraption desired? – SevenSidedDie Dec 16 '16 at 19:18
  • Push the piston into the space that the observer is monitoring, without it going nuts. Past that, it needs do nothing else. – John O Dec 16 '16 at 22:04

I'm assuming you are doing something like checking whether a melon has grown, and pushing it out of the way if it has. When I was playing around with using an observer for this I used a pulse limiter with an input pulse longer than the time it takes for the piston to extend and retract so that the second trigger of the observer is effectively discarded.

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What you need is a reset delay. This can be done quite simply by building your favorite type of latch.

INPUT 1: Observer
OUTPUT 1: Piston [branch] Repeater string
INPUT 2: Repeater string This resets the latch
OUTPUT 2: nothing

If all works out, the latch should reset only after the piston has done its thing, so the observer's second signal will not get through. Depending on your exact purposes, you may also need to build a pulse former between the latch and the piston.

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