Redstone has exactly one number: signal strength, from 0 to 15. Redstone dust carries a signal and loses 1 strength per block travelled, so a line of dust dies after 15 blocks. A repeater resets it to 15. A comparator measures it. Every circuit in the game is built out of those three facts.
The second number to know is the redstone tick: 0.1 seconds, or 2 game ticks. A game tick is 0.05 seconds and the game runs at 20 of them per second.
Signal strength
- A lever, button or redstone torch outputs 15.
- Dust adjacent to that source is 15, the next block 14, and so on down to 0 after fifteen blocks.
- A block of redstone is a permanent power source of 15 and can be pushed by pistons, which makes it the basis of many compact circuits.
Some components output variable strength, and those are what make redstone interesting:
| Source | Output |
|---|---|
| Daylight detector | 0–15 by sky light; invertible with a right-click |
| Target block | 1–15 by how close an arrow lands to the centre |
| Weighted pressure plates | Light (gold): 1 per item, Heavy (iron): 1 per 10 items |
| Comparator reading a container | 0–15 by how full it is |
| Comparator reading a composter | 0–8 by fill level |
| Comparator reading a cauldron | 0–3 by water level |
Strong and weak power
This is the concept that catches everyone out.
- A block is strongly powered when a redstone torch sits beneath it, or a repeater or comparator points into it. A strongly powered block transmits its power onward to adjacent dust.
- A block is weakly powered when dust simply sits on top of it. A weakly powered block activates components attached to it — a piston, a lamp, a door — but does not power adjacent dust.
If your circuit works when you place a repeater but not when you place dust, weak power is why.
Repeaters
A repeater does four jobs:
- Restores the signal to 15 regardless of the input strength.
- Delays it by 1 to 4 redstone ticks — right-click to cycle. Default is 1 tick (0.1s).
- Acts as a diode: signal passes only in the direction of the arrow.
- Locks when powered from the side by another repeater or comparator, freezing its current output. This is how a redstone latch is built.
Two repeaters set to 4 ticks give 0.8 seconds of delay in two blocks — the standard way to time a sequence.
Repeaters are 3 stone, 2 redstone torches and 1 redstone.
Comparators
A comparator has a rear input, two side inputs and one output, and two modes toggled by right-clicking the front torch:
- Compare mode (front torch unlit): output equals the rear input, unless a side input is stronger, in which case output is 0.
- Subtract mode (front torch lit): output equals rear input minus the largest side input, floored at 0.
Its other job is reading containers. Place a comparator against a chest, barrel, hopper, furnace, brewing stand or dispenser and it outputs a signal proportional to how full it is. A single item in a double chest gives 1; a completely full container gives 15.
That single behaviour underpins item sorters, storage-full indicators, and automatic farm shutoffs. Comparators cost 3 redstone torches, 3 stone and 1 nether quartz.
Comparators have a fixed 1-redstone-tick delay and, unlike repeaters, they do not restore signal strength in compare mode — they pass it through unchanged.
Observers
An observer watches the block directly in front of its face and emits a short pulse — 2 game ticks — whenever that block changes state. Crop growth, a piston extending, a door opening, water flowing: all of these are detected.
The observer is why automatic sugar cane, bamboo, melon and pumpkin farms are so simple. It also produces a clean, very short pulse, which makes it useful as a timing component in its own right.
Note that an observer emits its pulse from its back, not its face.
Pistons
- A piston pushes up to 12 blocks in a line.
- A sticky piston also pulls one block back when it retracts.
- Neither can move obsidian, bedrock, or blocks with an inventory such as chests and furnaces.
- Slime blocks and honey blocks drag adjacent blocks with them, which is how flying machines and large doors are built. Slime and honey do not stick to each other, which is the trick that makes them useful together.
Quasi-connectivity
A Java-only quirk: pistons, dispensers and droppers activate not only from a directly connected signal but also from power in the block space above them. Many compact Java designs rely on this deliberately, and many accidental "why is this piston firing" problems come from it. It does not exist in Bedrock, which is why some tutorials do not transfer.
Timing components
| Component | Timing |
|---|---|
| Repeater | 1–4 redstone ticks, adjustable |
| Comparator | 1 redstone tick, fixed |
| Observer | 2-game-tick pulse |
| Stone button | 1 second (20 game ticks) |
| Wooden button | 1.5 seconds (30 game ticks) |
| Hopper | 1 item per 4 game ticks (2.5/second) |
A redstone torch inverts its input: powered block below means torch off. Chaining torch inverters builds clocks, but a torch that toggles more than eight times in 60 game ticks burns out and stops until the circuit settles. Use repeaters for fast clocks instead.
Input devices
- Lever — toggles, stays where you left it
- Button — short pulse; stone buttons cannot be pressed by arrows, wooden ones can
- Pressure plates — stone triggers on players and mobs, wooden on any entity including dropped items and arrows
- Tripwire hook — a line of string across a corridor
- Daylight detector — day/night switching, invertible
- Lightning rod — emits a signal when struck
- Sculk sensor — detects vibrations, and a calibrated sculk sensor filters by vibration type
Frequently asked questions
Why does my redstone signal stop after 15 blocks?
Because dust loses 1 strength per block, so a signal starting at 15 reaches 0 on the sixteenth. Place a repeater every 15 blocks or fewer to reset it to full. Repeaters also add a delay, so a long line of them is noticeably slower than the signal itself.
What is the difference between a dropper and a dispenser?
A dropper ejects an item as a loose item, or pushes it into an adjacent container. A dispenser uses the item where it can: it fires arrows, places and picks up water and lava, shears sheep, plants some seeds, and applies bone meal. If you want an item moved, use a dropper; if you want an item used, use a dispenser.
Do I need quartz for redstone?
For comparators, yes — one nether quartz each. Quartz is common throughout the Nether from Y=10 to Y=117 and breaks with a wooden pickaxe, so a single short trip supplies a lifetime's worth. Daylight detectors and observers also need quartz.
Why does my piston fire when nothing is connected to it?
Almost certainly quasi-connectivity: the block space directly above the piston is powered, and in Java Edition that is enough to activate it. Either move the power source, or place a solid block above the piston to break the interaction. This behaviour is Java-only.
How fast is a redstone tick?
0.1 seconds, or 2 game ticks. The game itself runs 20 game ticks per second, so a game tick is 0.05 seconds. Repeater delays are counted in redstone ticks (1–4, so 0.1s to 0.4s), while observer pulses and hopper transfers are counted in game ticks.
