When redstone (that is adjacent to the block the observer checks for updates) is updated the observer activates.
Note: it doesn't activate when the redstone is placed only when it is broken, powered, or the direction is changed in some way
Linked issues
is duplicated by 5
MC-108561
observer detects too much
Resolved
MC-108713
Observer triggered when redstone dust beside an observed block is removed
Resolved
MC-108916
Adjacent Observer triggered when redstone dust placed/broken on non-observing side
Resolved
MC-109018
Observer detects strange updates
Resolved
MC-109139
Observer detecting air blocks being powered
Resolved
Attachments
Comments 7
Duplicated by MC-108713. Affects 16w41a.
@G4me: there's a little more to that story: if you place redstone dust in front of the observer then it triggers due to the block update. If you then place another redstone dust in front it triggers again. Expected behavior because the initial redstone dust updated (changed from a round to a line). But if you then place a third redstone dust in front the observer triggers yet again. That shouldn't be happening because the block directly in front didn't update. However, the 2nd block did. So there's more to this than merely updating the block directly in front.
@ShelLuser To my knowledge, the block updates run from one side of the redstone wire to the other. So you are wrong. This isn't a bug. Only because it isn't visual, it doesn't mean nothing's happened
@Orell If we follow your reasoning then shouldn't the observer keep responding as long as you place redstone dust in a single connected line? Thing is: it doesn't, if you place the 3rd dust it'll respond (this triggers the "lower" or middle dust in the OP's picture) but if you then place a fourth then nothing happens anymore.
Seems to be fixed in 16w44a (see MC-109571)
Observers activate on a block update. The redstone dust in this case updates any block with a Manhatten distance (search it up, if you're confused) of 2