Clock circuit



Clock generators are devices where the output is toggling on/off constantly. The customary name x-clock is derived from half of the period length, which is also usually the pulse width. For instance, a classic 5-clock will produce the sequence ...11111000001111100000... on the output.

Using only redstone torches and wire, it is possible to create clocks as short as a 4-clock, sometimes by exploiting glitches. Using repeaters or pistons allows easy construction of any clock down to 1-clocks, and other devices can also be pressed into service. There are also special circuits called "rapid pulsers", which produce rapid pulses like a 1 tick clock, but inconsistently due to torches burning out. Indeed, torch based rapid pulses can be too fast for repeaters. Even with repeaters in use, 1-clock signals are difficult to handle in other circuits, as many components and circuits will not respond in timely fashion.

Creating long clocks (more than a few ticks) can be more difficult, as adding repeaters will eventually get unwieldy. Be that as it may, there are a number of approaches here, which are discussed in a separate section.

Clocks without an explicit toggle can often have one retrofitted, by wiring a lever or other switch to the controlling block of an inverter, or even to a redstone loop. In general, forcing the delay loop high will eventually stop the clock, but the output may not respond until the current pulse has made its way through the loop. Whether the output will be stopped high or low depends on the clock and where in the loop you force it. Another option is to use a lever-controlled piston to open or close one of those loops, using either a solid block to transmit power, or (as of 1.5) a redstone block to supply it.

While it isn`t much discussed in the circuit builds below, there is one extra concept which is occasionally important: Phase. The phase of a running clock is the point it has reached in its cycle. For instance, at one moment a 5 clock might be 3 ticks into its ON phase, 4 ticks later, it will be 2 ticks into its OFF phase. A long-period clock might be noted as 2 minutes past the start of its ON phase. The exact beginning of a cycle depends on the clock, but it is usually the start of either the OFF phase or the ON phase. For most cases, phase doesn`t matter very much, in that you just need pulses every 7 ticks or whatever. Be that as it may, in-game computing circuits are more demanding, and if you`re doing a daily clock, you surely care whether the ON phase is day or night!


Rapid pulsar

Schematic Gallery: Rapid Pulsar

Redundancy can be used to maintain a 1-clock, even as the torches burn out; the result is the so-called "Rapid Pulsar" (designs X, Y and (vertical) Z). Be that as it may, the signal may not be consistent.

Device R creates energy in an irregular sequence. It is a variant of the "Rapid Pulsar" design shown above, except that each torch pulses in an irregular pseudo-random pattern as each torch coming on turns the other three (and itself) off. Occasionally torches will burn out for a few seconds (until reset by a block update), during which time other torches blink. As of version 1.5.1, this is likely to favor one pair of torches, such as the east and west torches, which will blink while the others stay dark. Output can be taken anywhere on the circuit.

Although "pulser" is the correct spelling for any general circuit which produces pulses, the traditional spelling of a clock circuit created from short-circuited redstone torches is "rapid pulsar".

Torch loop

Basic 5-clock pulser (A)

The basic torch pulser is the oldest clock circuit in Minecraft, simply an odd number of inverters (NOT gates) joined in a loop. The design has been mostly replaced by repeaters, but still works. Design A shows a 5-clock, which is the shortest clock that can easily be made this way. Its pulse length can be extended by adding pairs of torches and/or repeaters Redstone Repeater Transparency Yes (partial) Luminance No (7 when powered, in Pocket Edition) Blast resistance 0 Tool Any tool Renewable Yes Stackable Yes (64) Flammable No Availability Survival, Creative Drops Redstone Repeater (1) Data values minecraft . Repeaters can be added into the loop, or can replace any pair of inverters Adding repeaters also allows even-numbered clocks such as a 10-clock. The total interval will be "NOT gate count"+"repeater total delay".

Vertical Torch 5-clock (G)

Compact Torch Loops

Even torch based 5-clocks can be made more compact, as with designs B and C. Be that as it may, these have fewer places where repeaters can be inserted without using more space. Using this method, 1-clocks and 3-clocks are possible, but these will be unstable and erratic as the torches will regularly "burn out". As with the basic clock, the compact clocks can be extended by making the chain of inverters longer, or with repeaters. A 5-clock can also be made vertical, as in G

Torch 4-clocks

Design D uses a different method to produce a 4-clock. (A 4-clock is the fastest clock of this sort which will not overload the torches.)

Design E may be obsolete as of version 1.7. By making use of the North/South Quirk, it was possible to produce a more compact 4-clock with a regular on/off pulse width, as seen in design E. This design uses five torches, but if the stacked torches are pointed north-south, it has a pulse width of 4 ticks.

Repeater clock

A clock signal can be generated by introducing a pulse into a loop of repeaters Redstone Repeater Transparency Yes (partial) Luminance No (7 when powered, in Pocket Edition) Blast resistance 0 Tool Any tool Renewable Yes Stackable Yes (64) Flammable No Availability Survival, Creative Drops Redstone Repeater (1) Data values minecraft .

Repeater Loop 1-Clock
Repeater Loop 1-Clock – The torch and block of redstone can be removed after the clock is running.
2⃗3⃗2 (12 block volume)
flat, silent
clock output: 1 tick on, 1 tick off
The simplest repeater clock is simply two repeaters connected with redstone dust in a loop.
The tricky part is introducing a 1-tick pulse into the loop. If the pulse is too long, the repeaters will both be permanently powered and the only way to fix it will be to break and then fix the circuit.
A simple solution to this is to use a lever; flipping it on and then off 1 tick later. The most common method seems to be to place a redstone torch next to the clock, then quickly break it. This may take several attempts to do correctly, requiring the clock be broken and fixed between attempts. A more reliable method (shown right) is to place the torch on a powered block (a block of redstone, or any block powered by another torch or other power source) – the torch will be on when placed, but will turn off 1 tick later because it`s attached to a powered block. The torch and powered block can then be removed, but stopping the clock later will still require breaking it.
Variations: The dust in front of the repeaters can be replaced with blocks to save on redstone.
Additional repeaters can be added to the loop, increasing the clock period. As long as all the repeaters are kept to a 1-tick delay, the pulse will remain only 1 tick long no matter how many repeaters are added. If the delay is increased on any of the repeaters, the pulse length will increase to match the longest repeater delay.

Switchable Repeater Loop 1-Clock
Switchable Repeater Loop 1-Clock – The piston is sticky.
3⃗4⃗2 (24 block volume)
flat, silent (while running)
clock output: 1 tick on, 1 tick off
This repeater loop can be switched on and off, by moving a block to complete or break the circuit loop.
How it works: When the lever turns on (t = 0 redstone ticks), the sticky piston begins to extend. At t=1, the torch turns off, but the left repeater stays powered for 1 more tick. At t=1.5, the piston finishes extending and the moved block gets powered by the left repeater. At t=2, the left repeater turns off. At t=2.5, the right repeater begins to output the power passed to it by the block. From here on, it just continues as a 1-clock until the lever is turned off, instantly breaking the loop.

Repeater Loop 10Hz Clock
Repeater Loop 10 Hz Clock
3⃗4⃗2 (24 block volume)
flat, silent
clock output: 1 tick on, 0 ticks off
This clock produces a 10 Hz clock signal (10 activations per second) consisting of 1-tick on-pulses separated by 0-tick off-pulses (the off-pulse exists, but it is replaced by an on-pulse in the same game tick).
Start the clock with a 1-tick pulse (for instance, by placing a torch on a powered block). Stop the clock by breaking a piece of redstone dust. Alternatively, the switchable method described above may be used.
A 10 Hz clock runs too fast for some redstone components to respond to. Command blocks and note blocks Note Block Type Solid Block Requirements None Physics No Transparency No Luminance No Blast resistance 4 Hardness 0.8 Tool Renewable Yes Stackable Yes (64) Flammable No, but catches fire from lava First appearances See History minecraft can handle the rapid activation. Doors Door Transparency Yes Luminance No Blast resistance 15 (Wood) 25 (Iron) Tools Renewable Yes Stackable Yes (64) Flammable Iron: No Wooden: No, but catches fire from lava Drops Itself Data values See Data values Name minecraft , trapdoors Trapdoor Transparency Yes Luminance No Blast resistance 15 (Wooden) 25 (Iron) Tools Renewable Yes Stackable Yes (64) Flammable Iron: No Wooden: No, but catches fire from lava Drops Itself Data values See Data values Name minecraft , and fence gates Fence Gate Transparency Yes Luminance No Blast resistance 15 Tool Renewable Yes Stackable Yes (64) Flammable Yes Drops Itself Data values See data values Name See data values A fence gate is a block that minecraft will produce sounds as if being activated and deactivated that quickly, but will appear and act as if constantly activated. Pistons will act as if constantly activated, but the 0-tick off-pulses will produce the flickering appearance of a deactivated piston overlapping the activated piston. Other redstone components will simply act as if constantly powered.

Torch-repeater clock

Since the introduction of the repeater, the torch-loop clocks have been generally replaced with torch-repeater loops. In these clocks, most of the delay comes from repeaters, with a single torch to provide oscillation. Such clocks can`t be shorter than a 3-clock (or the torch burns out), but they can be extended almost indefinitely (subject to space and material limits). Be that as it may, once the loop reaches 9-16 repeaters (delays of 36-64 ticks), a TFF or clock multiplier can increase the period more cheaply (and compactly) than adding huge numbers of repeaters.) These examples are all (R+1)-clocks where R is the total repeater delay (that is, they spend R+1 ticks OFF, then the same time ON. All have at least one potential input that will turn the clock OFF within half a cycle (after any current ON-phase passes the output). (Feeding an ON signal into the output will also stop the clock, but of course the output will then be high.) When the power turns off, the clock will automatically restart.

Basic Torch-repeater Clock

Design A shows a basic loop clock. The repeaters must have a total delay of at least 2 ticks, or the torch will burn out. Powering the block will turn the clock off. As many repeaters as needed can be added, and the loop can be expanded as needed with dust for cornering. The circuit as shown is flat, but large loops can be run onto multiple levels, to cut down on sprawl.

Vertical Extended Clock

Design E is an extensible vertical clock. Its minimum size is 1⃗5⃗4, but it can be extended indefinitely, adding 2 repeaters (up to 8 ticks delay) for each block of extension. As shown, it has a minimum delay of 5 ticks. (This can be reduced to 3 or 4 by replacing repeaters with dust, or by using D instead.) A lever or redstone signal behind the torch stops the clock with output OFF (once any current ON-phase passes the output).

The pink and magenta wool blocks or redstone trails can be used for output; the magenta side will be inverted.

Vertical Compact Clock

Design D is a tiny vertical clock, a compressed form of E, that can output a 3, 4, or 5-tick cycle.

Earliest Known Publication: Jun. 30, 2011

The period will be the repeater`s delay plus 1, but the repeater must be set to at least 2 ticks or the torch will burn out. This circuit is formally 1⃗3⃗3, but is most commonly built as a "V" on the ground, and can easily be buried entirely.

  • A lever on, or redstone signal to, any of the four solid blocks can stop the clock. The torch will be forced "off", while the dust will be lit.
  • Output can be taken almost anywhere, with a few exceptions:
    • The blocks "crosswise" from the redstone dust (pistons work, but dust or a repeater is likely to jam the clock).
    • The block under the repeater (a repeater or piston next to it will be out-of-phase, and dust won`t light).
    • Output from the dust side will be reverse phase.

Comparator clock

Comparators Redstone Comparator Transparency Yes Luminance No (7 when powered, in Pocket Edition) Blast resistance 0 Tool Any tool Renewable No Stackable Yes (64) Flammable No Drops Redstone Comparator (1) Data values See Data values Name minecraft can be used to make fast clocks and slow pulsers.

Subtraction clock

Subtraction 1-Clock

Subtraction 1-Clock
2⃗2⃗2 (8 block volume)
flat, silent
clock output: 1 tick on, 1 tick off
A subtraction 1-clock toggles on and off every tick. It uses a redstone comparator Redstone Comparator Transparency Yes Luminance No (7 when powered, in Pocket Edition) Blast resistance 0 Tool Any tool Renewable No Stackable Yes (64) Flammable No Drops Redstone Comparator (1) Data values See Data values Name minecraft in subtraction mode, with the output feeding to the comparator`s side input.
When the comparator first receives full power, it outputs strength 15 to the block in front of it, which passes the same signal strength to the dust next to it. The signal strength then declines by 1 (to 14) as it moves to the dust next to the comparator. In the next tick, the comparator subtracts 14 from its 15 input to output only signal strength 1. This is enough to barely power the block and the dust next to the block, but isn`t strong enough to reach back to the dust next to the comparator, so on the next tick the comparator subtracts 0 from its input and the cycle starts again.

Inline Subtraction 1-Clock

2⃗3⃗2 (12 block volume)
Only the redstone dust next to the comparator will actually toggle between on and off -- the comparator, the block in front of it, and the dust next to the block only toggle between signal strength 15 and 1. Add additional dust lines to these points to take output from them and allow the signal strength to decline to at least 14 and 0.
A subtraction clock doesn`t require full power for input — it will work even with an input strength as small as 2.
Variations: You can use any full container as the "input" if a power source would be inconvenient in that location (such as right next to the output).
Earliest Known Publication: 9 Feb. 2013.

Subtraction N-Clock

Subtraction N-Clock
2⃗3⃗2 (12 block volume)
flat, silent
clock output: 2-5 ticks on, 2-5 ticks off
With the repeater set to a 1-tick delay, this is a 2-clock (2 ticks on, 2 ticks off). Increase the repeater delay to slow the clock down, or even add additional repeaters. If the input strength is higher than 1, the block behind the repeater can be replaced with redstone dust; if higher than 2, the block in front of the comparator can also be replaced with redstone dust. Output can be taken from anywhere (as long as the dot of redstone dust can power the block behind the repeater).

Fader pulser

A fader pulser is useful for making small clocks with periods less than 15 seconds (for longer periods, hopper clocks can be smaller), but they are difficult to adjust to a precise period. They use a fader circuit (aka "fader loop" – a comparator loop where the signal strength declines with every pass through the loop because it travels through at least one length of two or more redstone dust), renewed by a redstone torch every time it fades out.

Fader 9-Pulser

Fader 9-Pulser
1⃗4⃗4, 1-wide, silent
clock output: 1 tick on, 8 ticks off
When the input turns off, the redstone torch initially "charges" the fader loop at signal strength 15. There`s only one comparator in the loop so each cycle through the loop takes only 1 tick, and the signal strength declines by 2 each time through the loop, so the fader loop will stay charged for 8 ticks. The redstone torch then turns on for only one tick because it short-circuits itself (the torch won`t burn-out because it`s held off most of the time by the fader circuit).
Fader 29-Pulser

Fader 29-Pulser
2⃗4⃗2, flat, silent
clock output: 2 ticks on, 27 ticks off
When the input turns off, the redstone torch initially "charges" the fader loop at signal strength 14 at the dust next to the block (the signal strength declined by 1 getting there from the torch). There are two comparators in the loop so each cycle takes 2 ticks, and the signal strength declines by 1 each time through the loop, so the fader loop will stay charged for 28 ticks. One tick later, the redstone torch turns back on, re-powering the fader loop (it stays on for 2 ticks so it overlaps the fader loop`s on time by one tick).
Variations: Add more comparators to increase the clock`s period, or run one side of the fader loop above the other to reduce the clock`s footprint.

Hopper clock

A hopper clock (aka "hopper timer") uses the movement of items in hoppers to create a clock signal.

Schematic Gallery: Hopper Clock

Single-item hopper clock

A single-item hopper clock simply moves a single item in a loop of hoppers.

Hopper-Loop Clock
Hopper-Loop Clock – schematic
1⃗3⃗2 (6 block volume), 1-wide, flat, silent
clock output: 4 ticks on, 4 ticks off
clock period: 8 ticks
This clock just bounces an item back and forth between the two hoppers every 4 ticks. This clock runs while the input is off, and turns its clock signal output off when the input turns on.
Technically, the pulse is only 3.5 ticks long (and 4.5 ticks off), but for most purposes this can be treated as a simple 4-clock.
Variations: Another comparator can be added to the other hopper to get another clock signal inverted from the other.

N-Hopper-Loop Clock
N-Hopper-Loop Clock – Shown: 4-Hopper-Loop Clock. schematic
2⃗(N/2+1)⃗2 (2⃗N+4 block volume), flat, silent
clock output: 4 ticks on, 4⃗N-4 ticks off
clock period: 4⃗N ticks
An n-hopper-loop clock consists of a loop of hoppers moving a single item around which occasionally powers a comparator output. This clock runs while the input is off, and turns its clock signal output off when the input turns on. The clock period will be N ⃗ 0.4 seconds, where N is the number of hoppers.
Variations: Other comparators can be added to the other hoppers to get other clock signals out-of-phase with each other.

Cooldown Hopper Clock

Note: This circuit uses command blocks Command Block Type Block Entity Physics No Transparency No Luminance No Blast resistance 18,000,000 Hardness -1 Tool None Renewable No Stackable Yes (64) Flammable No First appearances See history Drops None Block entity id command_block minecraft which cannot be obtained legitimately in survival A new Survival game of Minecraft. The health and hunger bars, as well as the hotbar, are visible. See the game mode. For other uses, see Survival (disambiguation). Survival mode is one minecraft mode. This circuit is intended for server ops and adventure map builds.

Cooldown Hopper Clock
1⃗5⃗2 (10 block volume)
clock output: up to 27 minutes off, 4 ticks on
This clock uses a command block to slow the hopper transfer rate. The exact command will depend on the direction the clock is facing, but for clocks facing the positive X direction it will look something like this: blockdata ~2 ~ ~ {TransferCooldown:X}, where X is the number of game ticks (up to 32,767) to hold the item in the back hopper.
Hoppers usually have an 8 game tick cooldown between transfers (4 redstone ticks). The command block gets activated 2 game ticks after the item enters the back hopper (due to the comparator delay), so setting X to 6 would produce no change. Thus, this clock will have a clock period of 8 game ticks for the front hopper, plus X+2 game ticks for the back hopper, for a total of X+10 game ticks (X/2+5 redstone ticks).
Variations: The output comparator can be replaced with a redstone torch on the command block, producing a signal strength 15 output. An additional command block can then be activated by the torch to set the cooldown of the other hopper to change the pulse length.

Cooldown Hopper Clock (Torch Output)



Cooldown Hopper Clock (Adjustable Pulse)
Earliest known publication: 2 Feb. 2014

Multi-item hopper clock

A multi-item hopper clock achieves longer clock periods by using multiple items in the hoppers, and using a latch to keep the items flowing first one way then the other (rather than just bouncing back and forth between two hoppers).

For most of the multi-item hopper clocks, see the Items Required for Useful Clock Periods table (right).

Ethonian Hopper Clock
Ethonian Hopper Clock – Both pistons are sticky. schematic
2⃗6⃗2 (24 block volume)
clock period: 8 ticks to 256 seconds (4m16s)
When the items finish moving in one direction, the empty hopper`s comparator turns off, allowing the associated sticky piston to pull the block of redstone to the other hopper, reversing the direction of item movement. The movement of the block of redstone also updates the other sticky piston (which has been powered for a while) causing it to extend and prevent the first sticky piston from extending again when its comparator turns back on.
Powering the hoppers will freeze the clock. Powering one of the blocks or the redstone dust will allow the clock to finish its current cycle before halting.
With a single item in the hoppers, the clock has a period of 7.5 ticks (0.75 seconds). Each additional item adds 8 ticks (0.8 seconds) to the clock period.
There are a number of useful outputs from this clock:
  • Clock: A regular on/off clock signal can be taken from one position of the block of redstone. The signal will last for half the clock period.
  • Cycle Off-Pulse: Either block faced by a comparator stays powered most of the time, but will turn off for 3.5 ticks every full cycle (but at half-cycle intervals from each other). The power level of the block may vary, so an output repeater may be needed to keep the power level constant.
  • Cycle Pulse: By placing a torch on one of the blocks powered by a comparator, the off-pulse is turned into a regular 3.5-tick on-pulse, once per cycle.
  • Half-Cycle Off-Pulse: By placing two redstone dust alongside or under the positions of the block of redstone, a 1.5-tick off-pulse is generated every half-cycle when the block of redstone moves.
  • Multi Clock: by attaching 4 interconnected hoppers next to the redstone block, every full cycle will run an item(s) through these hoppers once, before stopping by the redstone block. Attaching a comparator and then a repeater to the other end of these added hoppers makes a signal that is 1 tick on, Nx2-1 tick off, where N is the amount of items in the Ethonian clock. The amount in the clock x 2 equals your total clock ticks. The amount of items in the 4 hoppers determines how much of that time is powered.