Dispenser

A Dispenser is a special redstone-powered block. When right-clicked, a menu allows you to place items inside it. Each time the block receives power from a redstone circuit, a random item from its inventory drops out. Dispensers resemble furnaces and droppers, but the three blocks have different uses and crafting recipes.

Crafting
Note: a damaged bow cannot be used to craft a dispenser.

Dispensing
The exact action of a dispenser on the items contained in it depends on the specific item.


 * Most items will simply be ejected as items and land 3 by 3 blocks away if on level ground, similarly to items dropped by a player.
 * Arrows, Fire Charges, Chicken Eggs, Snowballs, Splash Potions, Bottles o' Enchanting, and Firework Rockets are fired out like the right-click action of the items carried by a player.
 * Arrows fired from a height of 2 above level ground will go anywhere from 10 to 21 blocks away. When firing arrows, its optimal range for mob killing (if placed at eye level) is 1 to 5 blocks with a hit ratio of about 98% at the edge of the 5 block range on a target the size of a standard mob. Arrows will cause 3HP (1.5 hearts) of damage, and can be picked up, unlike those fired by skeletons.
 * Arrows fired from a dispenser at the top layer not facing up or down will travel a maximum of approximately 80 blocks (±7 blocks) away from the dispenser before hitting the ground on the bottom layer.
 * Arrows fired from a height of 1 block above level ground, can go anywhere from 6 to 13 blocks away. In some weird cases, the arrows, 9 blocks away from the dispenser can go to the left or to the right of a target.
 * Chicken eggs and snowballs break with most of the usual effects. Any projectiles shot by the dispenser do not knockback the mobs that it hits; it is unclear whether this is a bug or not.
 * Fire Charges will become fireballs of the same type as Blaze fireballs and will continue in a straight line (though the line may be at an angle from the dispenser). Upon being dispensed, the fire charge will make the same sound as Blazes and Ghasts when they launch their projectile. However if used by the player, it makes the same sound as Flint and Steel.
 * Spawn Eggs will result in the corresponding mob being created with its feet in the block directly in front of the dispenser, with no initial velocity.
 * Minecarts and Boats will be placed (as their entity form), but only if the dispenser is placed above water (for boats) or on a rail (for minecarts).
 * Water and lava buckets will place water and lava source blocks. Water and lava source blocks will also be taken if there is an empty bucket inside. Water won't be placed if the dispenser is in Nether though.
 * TNT will be placed and ignited with no obvious forward velocity. However, when they are dispensed, they may be moving at a very small rate in a random direction before falling straight down. Thus, if you try to drop TNT using a dispenser above a one block by one block hole, the TNT will have a good chance of narrowly missing the hole. Because of this, extra caution must be used in delicate machines requiring TNT and dispensers.
 * Flint and Steel will ignite fire in front of the dispenser consuming one durability.
 * Bone Meal will be used on the crops it is pointing at.
 * Armor will be equipped on a player from 1 block away.

All items which are fired out have a random variation in direction.

When a dispenser dispenses an item, it emits a clicking sound (unless the item is a projectile or a Spawn Egg) and a puff of smoke. If it is empty when activated, it emits a slightly higher-pitched click.

Triggering
Unlike most other redstone devices, it may be triggered by redstone wire placed up to one block adjacent to it as well as running directly into it; therefore a single redstone wire can trigger up to 5 dispensers in a cross pattern. This allows for easy creation of large walls of dispensers.

As of Snapshot 13w02a or higher, you can place redstone on dispensers by sneaking when placing. In versions previous to 13w02a, this can be easily overcome by placing redstone on the side of a block diagonal to the dispenser or on the bottom of a block two blocks above the dispenser. Another use for dispensers is delaying. Using a single water current and a wooden pressure plate, you can delay a signal up to 11 seconds. The equivalent of this is 28 redstone repeaters, which is quite expensive. For even longer delays, the item despawn time can be utilised. This can be done by using a dispenser to eject an item onto a pressure plate, which then has its current inverted and wired to the next dispenser. After 1.3, dispensing more than 1 item every 5 minutes will cause them to stack and no extra time will be added to the 5 minute despawn of the first item.

Due to the dispenser's ability to equip armor, it is also possible to make a set of four dispensers arranged around a one block space that will equip a full set of armor all at once when a button is pressed.

Dispensers are most effectively used offensively with a 5-clock or pulser hooked up to a pressure plate or switch.

A dispenser will work if it is placed underwater, even without any blocks touching it by placing a redstone torch underneath it. Also it can be properly wired by placing the redstone in a tunnel underneath the water.

A mob killed by something dispensed will not drop XP.

Placing a trapped chest adjacent to a dispenser and opening the chest triggers the dispenser.

Probability distribution
Currently each stack in the dispenser is picked with equal probability. That is, if there are x stacks in the dispenser, the probability that a particular stack is picked is 1/x. Beware that the distribution isn't weighted by stack size. That skews the distribution of individual items. For example, if there are two stacks in the dispenser, one of 18 dandelions and one of 6 roses, at first dandelions and roses are equally likely. Roses will run out rapidly, after which the distribution abruptly changes to 100% dandelions. Example output:

If each individual item were picked with equal probability, as if each item of a stack were in a different slot, the distribution would stay at roughly 75%/25% even over time. Indeed the output would be a uniform random permutation:

While such behavior is impossible to replicate for anything over 9 items, it can be approximated by splitting stacks such that each stack is fairly small and has the same number of items. For example, three stacks of 6 dandelions will neatly complement the stack of 6 roses. Splitting into stacks of 3 would be even better, since smaller stacks can't retain as much 'undeserved' probability.

Trivia

 * The texture the dispenser uses is similar to the one used by the dropper.
 * The Dispenser uses the same texture as the Furnace on all sides except the face, which has a unique texture.
 * You can use dispensers to delay Redstone circuits by intervals of five minutes, hook up a wooden pressure-plate to an i/o reverse then to a dispenser and put an item onto it. when the item vanishes then the Redstone charge will change state.
 * The texture file for the dispenser menu is named "trap.png", which suggests that it was originally designed for making arrow traps.
 * Pistons cannot push or pull dispensers, because they are tile entities.
 * It is now possible to design more compact and powerful cannons and traps with Dispensers since they can ignite TNT upon activation.
 * One can cause dispensers to drop items or fire projectiles at abnormally high speeds by powering it with an ordinary rapid pulsing circuit, with the addition of a single redstone repeater directly behind the dispenser.
 * An arrow dispenser with a stair in front of it will act as a homing dispenser, always hitting the player, but not dealing any damage.
 * If the player dies from fall damage after being hit by an arrow shot by a dispenser, the death notice will show as " was doomed to fall by arrow."