Why does extended piston become stuck if air above it is powered? [duplicate]
![Why does extended piston become stuck if air above it is powered? [duplicate] - White Clouds and Blue Sky](/assets/images/why_does_extended_piston_become_stuck_if_air_above_it_is_powered_duplicate_0.jpeg "Why does extended piston become stuck if air above it is powered? [duplicate] - White Clouds and Blue Sky")
To reproduce this problem make layout like this and then power the piston. Once the piston is extended, removing the power source will not retract it:
Since piston head block is transparent, I see no explanation for this. Also, even if it wasn't transparent, it still wouldn't power a piston. For example this doesn't power the piston:
But if I place redstone and THEN place the piston, it's powered:
It also remains powered no matter what, as long as there isn't a block update event:
I suppose this behavior can be used to make a block update detector, but in my case this sucks. I wanted such setup for automatic smooth stone generator (without any clocks):
But due to this bug, it won't work - the piston will be always extended.
Best Answer
The piston act this way due to a minecraft feature called the BUD, or block update detector. When some blocks have a powered block diagonal or above it Figure 1, they will become powered when its updated and will stay powered even if the power on these blocks are removed and will only unpower if the positions are unpowered and the powered block is updated.
Figure 1
_ Air
M Machine
P Powered Block
_P_
P_P
_M_
If any of the Powered block is powered, the machine will be a bud. This is rotatable along the y axis.
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What activates a sticky piston?
Pistons can be activated by several methods. For example, a Button, a Pressure Plate, a Lever, Redstone Torch, or few other Redstone methods. Including a Slimeball will make a Sticky Piston.What makes a sticky piston?
Add Items to make a Sticky Piston To make a sticky piston, place 1 slimeball and 1 piston in the 3x3 crafting grid.Why does piston stay extended?
In your examples, the redstone wire powers the granite block below it, which powers the air block above the piston, causing it to extend. Placing the piston causes it to check for power, which is why it extends in the first place. However, removing that power does not update the piston.Can a piston push an extended piston?
Sticky pistons can't move certain blocks, such as extended pistons.3 Deadly Command Blocks (Minecraft PE)
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