Redstone circuits

Redstone circuits are structures you can build to activate or control mechanisms.

Circuits can be designed to act in response to player activation, or to operate autonomously -- either on a loop, or in response to non-player activity such as mob movement, item drops, plant growth, etc.

The mechanisms that can be controlled by redstone circuits range from simple devices such as automatic doors and light switches, to complex devices such as automatic farms, mini-games, or even in-game computers.

An understanding of how to build and use redstone circuits and the mechanisms they can control will greatly increase the range of things you can accomplish in Minecraft.

Redstone Dust
Redstone dust acts as a power conductor. A signal will travel through 15 redstone before dying out. To increase the range, place Redstone repeaters in the circuit. To place Redstone dust, right-click on a block while holding Redstone dust. You cannot place redstone on sides of blocks, but redstone wire will automatically connect to wiring one block lower than it. Note that Redstone can't be placed on glass. Also note that Redstone dust can't be placed on non solid blocks (e.g., leaves)

Powering Blocks
Some blocks in Minecraft may be powered or unpowered. Think of a "powered block" as any block or empty space (though not truly empty, an Air block can be powered) that is invisibly electrified but safe to touch.

Power may be transmitted from a powered block to one or more of the six directly adjacent blocks. To transmit power, a block must be one of the following: One must be careful to note that a Redstone torch placed on the side of a block of dirt is actually part of the block next to the dirt, not part of the dirt block itself. Similarly, Redstone wire that is placed on top of a block of dirt is part of the block above the dirt. However, if the block on which the Redstone wire is placed becomes powered in any way, so does the Redstone wire.
 * an active power source (a Redstone Torch),
 * the block to which a switch is attached (that is, the block under a pressure plate or the block on which a lever or button is mounted),
 * the block a switch is in,
 * a block immediately following a Redstone Repeater.
 * the block above a Redstone Torch
 * an active power conductor (Redstone Wire that is immediately adjacent to a powered block).

Each actively powered block transmits power in several directions, depending on the contents of the block:
 * A Redstone torch powers itself and the block directly above it, unless that block is air. Because of how Redstone wires work, this also activates adjacent power circuits or conduits(Redstone Wire).
 * A pressure plate activates the block it is physically located in, as well as the block below (on which it is placed).
 * A Detector Rail acts exactly the same as a pressure plate but will only be activated when a minecart of any kind rests on it.
 * A Lever powers the block in which it is located and the block on which it is placed.
 * A button powers the block in which it is located and the block on which it is placed.
 * Redstone Wire powers itself, the block below it, or the block it is pointing to.

Redstone Wire & Signal Strength
Whether a block is weakly or normally (strongly) powered affects how Redstone wires interact with it. Blocks are strongly powered by Redstone power sources; torches (from below), repeaters, levers, pressure plates etc. If a block is powered only by Redstone wire then it is weakly powered. Redstone wire which is adjacent to, on top of, or below a block that is strongly powered will become active. It will not become active if that block is weakly powered. Redstone wire can be implemented into many useful designs such as sliding doors, wiring multiple things such as lanterns together, make timers, and many more.

Powering Devices
A device, such as a door, a rail, a powered rail, a block of TNT, a piston, a sticky piston, a trapdoor, a redstone lamp, a dispenser, a note block or fence gate is activated when an adjacent block is powered. As a simple example, placing a Redstone torch next to a door will change the state of the door to on. Similarly, standing on a pressure plate immediately adjacent to a door will activate the door. However, standing on a pressure plate two blocks away from a door will not activate the door, because the power does not reach the block next to or under the door.

To power devices at a distance, the power must be conducted from the active power source to the device; Redstone wire is used for this purpose. As noted above, the Redstone wire is part of the block it is physically located in, not the block to which it is attached. Redstone wire, or dust, has two states: on (lit) and off (unlit).

The simplest way to activate Redstone wire is to put a Redstone torch or switch adjacent to the wire. It also works to have a torch or switch directly above the wire, attached to a wall.

A Redstone torch is itself a powered device; its default state is "on", but it will be turned off if it receives power from the block to which it is attached. This feature, along with the use of wire to transmit power in particular directions over distance, is the basis for the advanced Redstone devices and circuitry below.

Care must be taken to follow the power rules precisely, or one might see unexpected results. For example, consider a pressure plate. Activating the plate will power the block underneath the plate as well as the block in which the plate resides. Nevertheless, Redstone wire beneath this block will still be powered, because it is adjacent to the powered block above it. However, activating the plate will not turn off a Redstone torch placed beneath the powered block—in fact, placing a Redstone torch under the block under the pressure plate will power it continuously, effectively disabling the plate.

Specific Powered Devices
Certain devices act in specific ways, for example:
 * If a block is powered, then a Redstone torch attached to it will deactivate.
 * If a block is powered, then a door on top of it or adjacent to it will toggle its state from open to closed or vice versa. (The actual state will depend because doors were implemented unintuitively.)
 * If a note block or a dispenser is powered, then it will play or shoot once, respectively.
 * If a block is powered and rails are above it, then they will toggle shape (the player can still have the wiring power the rail directly).
 * If a piston is powered, then it will activate.

Signal Duration
Not only does it matter in some circuits if something gets powered, but also for how long something gets powered. The different Redstone power sources produce different signal durations. The four main sources produce signals according the following list:


 * Redstone Torches - produce in its burning state an unlimited duration signal.
 * Pressure Plates - produce signals for as long as they are activated.
 * Levers - produce in their 'on' state unlimited duration signals.
 * Buttons - produce a 10 tick (1 second) duration signal when pushed (with the exception of the Wooden Button, the duration lasts for 5 ticks (0.5 seconds) longer than stone buttons.

The duration of a signal can be changed by different circuits and is very important when different blocks need to interact with each other. A sticky piston, for example, needs one tick to push outward (should be changed to two ticks in 1.3.1; using a Pulse Limiter set to one redstone-tick the pistons still seem to push blocks though), but it seems to need a bit over a tick to attach again to something 1 block away from it. So it would not pull a block back if it only gets powered for 1 tick. If a block was standing apart from the piston, it would be pulled back if the sticky piston was only powered for one tick.

Problems with short signals Overall, very short signals seem to be prone to not correctly interact with the game world, as the update cycle on the blocks seems sometimes to lag behind. Rapidly changing signals seem to make it even worse. Pistons are very prone to make such problems visible, as they seem to react faster to power changes than their neighboring blocks seem to update.

Common errors to avoid
The following are common errors to avoid:
 * Placing next to TNT.


 * Placing next to Water or Lava.


 * Trying to transmit power through a block that doesn't have any Redstone wire on it. While a generic block (dirt, sand, gravel, etc.) adjacent to the end of a wire can receive power, it will not transmit that power to wire on the other side, because it is not one of the blocks that can transmit power. If you have a block that you cannot move, send wire around it (including on top of it). Alternatively, you can put a repeater on the side transmitting power, as repeaters can send power through blocks (see below).
 * Trying to transmit power through a block that is transparent or non-solid(e.g. Glass, Slabs, Stairs, Cake, etc.), as they will not allow redstone current to pass through.
 * If a block has Redstone wire on top and a Redstone torch on the side, then the block above the torch must be either air, glowstone, glass, farmland or a half-tile (unless you know what you're doing). If you place any solid block above the torch, it will create a feedback loop and the torch will probably burn out.

Mechanical to Redstone Conversion


Making use of a quirk involving the update function on blocks near a water or lava source, it is possible to convert the "mechanical" energy of updating a nearby block into a Redstone signal. To do this, create a water or lava rig that will shift when the desired block updates (for more info, read this thread [broken]). Then position a Redstone torch or powder trail so that the water/lava will wash/burn the torch or powder. Do this in such a way that the missing Redstone component will change the input signal of your circuit.

Once this setup has been rigged, the next time an update function is called in an adjacent block to the water/lava source, it will trigger your mechanism. Update functions include: an adjacent block is placed by a user, gravel or sand falls into an adjacent block, grass grows, wheat grows, an adjacent block receives power, an item resting on an adjacent block changes state (such as a door being opened), or Redstone ore is stepped on, destroyed, or right clicked.

This setup can only trigger once before needing to be manually reset.

See also: BUD switches which are more versatile.

Redstone to Liquid Kinetic Conversion
It is possible to use the same quirk described in the Mechanical to Electrical Conversion section to make water or lava flow as desired. In order to do this, simply follow the instructions in this thread[broken] and run a Redstone wire to the block adjacent to the water/lava source. Whenever the Redstone wire toggles state, the water/lava source will update. If arranged properly, this can be used to redirect water or lava whenever the desired input is given via Redstone circuit.

Alternatively, as of Beta 1.7, pistons provide multiple-use liquid control. The piston plate in its extended position blocks fluids from any direction, as does a block attached to the end of a sticky piston. It is far easier to use a piston (or multiple pistons) to control fluid flow using Redstone circuitry, especially since they do not need to be manually reset.

Glowstone, Stairs, and Slabs
Placing redstone dust atop these blocks has many uses, as the signal cannot go down from them. See the main article for details.

Piston doors
See Tutorials/Piston Uses

Tutorials

 * Advanced Redstone Circuits
 * Mechanisms
 * Traps
 * Piston Circuits
 * Basic Logic Gates

Real-life circuits

 * digital electronics
 * boolean algebra

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