Observer
Observer fires a one-tick pulse whenever the block in front of it changes — an indispensable trigger for compact farms and machines.
1.21
Description
Observer is crafted from six cobblestone, two redstone dust, and one nether quartz in a 3×3 grid. The device monitors the block directly in front of its glowing face: any state change — a crop ripening, a piston extending, water flowing into a square, a button being pressed — fires a single redstone pulse out the back lasting exactly two game ticks.
This simple behaviour makes it the most important automation primitive in modern Minecraft engineering. Wired with pistons, observers form flying machines and tile-based pulse extenders. Watching crops, they trigger automatic harvesters. Watching a daylight cycle change, they activate dawn-dusk lighting. Compact, predictable, and deterministic, the device replaced sprawling clock circuits as the standard trigger source. Crucially, observers do not detect entity movement — only block-state changes — which keeps their behaviour reliable across high-load servers.
This simple behaviour makes it the most important automation primitive in modern Minecraft engineering. Wired with pistons, observers form flying machines and tile-based pulse extenders. Watching crops, they trigger automatic harvesters. Watching a daylight cycle change, they activate dawn-dusk lighting. Compact, predictable, and deterministic, the device replaced sprawling clock circuits as the standard trigger source. Crucially, observers do not detect entity movement — only block-state changes — which keeps their behaviour reliable across high-load servers.
How to craft this block
Ingredients:
Cobblestone
x6
Redstone Dust
x2
Nether Quartz
x1
Cobblestone
x6
Redstone Dust
x2
Nether Quartz
x1
Crafting
1
