minecraft-java-editionminecraft-redstone
I have been trying to get an row of 7 pistons to fire when a block has been pushed in front of the middle one. Every technique I try is not firing them. This is a Cobblestone floor maker. Here is an above view of the layout:
P = Piston
B = Block (I am using stone)
A = AIR SPACE
W = Water
L = Lava
X = Trigger SpaceBBBBBBBBBBBBB
BLBPPPPPPPBLB
PAAAAAXAAAAAP
BwBAAAAAAABwB
BBBAAAAAAABBB
This is a bug in the 1.9 pre-release (not sure if just pre-release 3, or all of them).
As you can see here:
It's working as you intended it to in 1.8.1
Come with me on an adventure in redstone optimization!
You can place Redstone Repeaters behind each of the pistons as shown below. This will direct the input into the piston and prevent those annoying loops that usually don't accomplish anything. This will take up much less space, but uses a total of 18 redstone dust.
A more redstone efficient design would be this. It uses only 11 redstone dust. Other players not required. This method works because a piston can be powered by an adjacent powered block.
This design (courtesy of Tristan) uses a minimalistic 7 redstone. The lever powers both the block that it occupies and the block it attaches to. The hole on the right is required to keep the signals going to the two pistons separate.
Finally, this uses a measly 4 redstone. Since you're powering 4 pistons, I think 4 redstone is likely as low as you're going to get.
Best Answer
If I am correct that this is your layout:
Then this solution should work:
Note that this is a sticky piston.