Redstone circuits/Clock

A clock circuit is a redstone circuit that produces a clock signal: a pattern of pulses that repeats itself.

Introduction

Clock generators are devices where the output is toggling between on and off constantly. The period of a clock is measured in game ticks (gt), redstone ticks (rt) or seconds and can be calculated by adding together the lengths of the on-pulse and off-pulse of a single cycle. The frequency is measured in Hertz and can be calculated by dividing 20 by the period of the clock (in game ticks).

With most redstone components, only even game tick timings can be achieved. In Java Edition however, pistons can be used to create odd game tick clocks.

Creating long clocks can be difficult, as adding repeaters to increase delay eventually gets unwieldy. There are multiple possible approaches to this issue, which are discussed in the long-period clocks section of this page.

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 too high eventually stops the clock, but the output may not respond until the current pulse has made its way through the loop. Whether the output gets stopped high or low depends on the clock and where in the loop players 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 a block of redstone to supply it.

Redstone Torch clocks

Rapid pulsar

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz

By burning-out two redstone torches with the same piece of redstone dust will result in a "Rapid Pulsar" clock. This clock

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

Redstone Torch loop

• (5 redstone torches version)
  • Period: 20gt (10rt, 1s)
  • Pulse length: on-pulse: 10gt (5rt, 0.5s), off-pulse: 10gt (5rt, 0.5s)
  • Frequency: 1Hz

The basic torch pulser is the oldest clock circuit in Minecraft. It can be made by joining multiple redstone torches in a loop. The design has been mostly replaced by repeater-based clocks, but still works. Its pulse length can be extended by adding pairs of redstone torches, while the inclusion of repeaters would turn it into a torch-repeater clock. Designs B and C show redstone torch 10gt clocks with a smaller footprint, while design G is a vertical version of the 10gt clock.

• (4 redstone torches version)
  • Period: 16gt (8rt, 0.8s)
  • Pulse length: on-pulse: 8gt, off-pulse: 8gt
  • Frequency: 1.25Hz

Design D uses a different method to produce a 16gt torch-only clock. Here, each redstone torch's output is fed into two other torches, instead of only one as in a basic torch loop. It resembles a pair of interconnected RS-NOR latches.

Repeater clock

A clock signal can be generated by introducing a pulse into a loop of repeaters.

4gt Repeater Loop Clock

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz
  • 2×3×2 (12 block volume)
  • flat, silent

The simplest repeater clock is simply two repeaters connected with redstone dust in a loop.

The tricky part is introducing a 4gt(2rt) or shorter pulse into the loop. If the pulse is too long, the repeaters are powered permanently and the only way to fix it is to break and then fix the circuit.

A simple solution to this is to use a lever; flipping it on and then off 4gt(2rt) or less later. The most common method seems to be to place a redstone torch next to the clock, and 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 block of redstone or on powered block – the torch is on when placed, but turns off 4gt(2rt) later because it's attached to a powered block. The torch and powered block can then be removed, but stopping the clock later still requires 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 the shortest delay, the pulse remains only 4gt(2rt) long no matter how many repeaters are added. If the delay is increased on any of the repeaters, the pulse length increases to match the longest repeater delay.

Switchable 4gt Repeater Loop Clock

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz
  • 3×4×2 (24 block volume)
  • flat, silent (while running)

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 at gt0, the sticky piston begins to extend. At gt2, the torch turns off, but the left repeater stays powered for another 2gt(1rt). Also, the piston finishes extending and the moved block gets powered by the left repeater. At gt4, the left repeater turns off and the right repeater begins to output the power passed to it by the block. From here on, it just continues as a 4gt clock until the lever is turned off, breaking the loop.

Repeater Loop 2gt Clock‌^{[JE only]}

• Period: 2gt (1rt, 0.1s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 0gt (0rt, 0s)
• Frequency: 10Hz
  • 3×4×2 (24 block volume)
  • flat, silent

This clock produces a 10 Hz clock signal (10 activations per second) consisting of 2gt(1rt) 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 2gt(1rt) pulse (for example, 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. Update-instant components such as noteblocks, doors, trapdoors, and fence gates operate normally, but non-update-instant components such as pistons act as if constantly receiving power.

Torch-repeater clock

• (6gt repeater delay version)
  • Period: 16gt (8rt, 0.8s)
  • Pulse length: on-pulse: 8gt (4rt, 0.4s), off-pulse: 8gt (4rt, 0.4s)
  • Frequency: 1.25Hz

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. The on-pulse of such clocks can't be shorter than a 6gt (or the torch burns out), but they can be extended almost indefinitely (subject to space and material limits). However, once the loop reaches 9-16 repeaters (delays of 72-128gt(36-64rt)), a T flip-flop 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 redstone ticks OFF, then the same time ON. All have at least one potential input that turns the clock OFF within half a cycle (after any current on-pulse passes the output). (Feeding an on-pulse into the output also stops the clock) When the power turns off, the clock automatically restarts.

• (4gt repeater delay version)
  • Period: 12gt (6rt, 0.6s)
  • Pulse length: on-pulse: 6gt, off-pulse: 6gt
  • Frequency: ~1.7Hz

Design A shows a basic loop clock. The repeaters must have a total delay of at least 4gt(2rt), or the torch burns out. Powering the block turns off the clock. 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.

• (32gt repeater delay version)
  • Period: 72gt (36rt, 3.6s)
  • Pulse length: on-pulse: 36gt (18rt, 1.8s), off-pulse: 36gt (18rt, 1.8s)
  • Frequency: ~0.67Hz

Design E is an extensible vertical clock. Its minimum size is 1×5×4, but it can be extended indefinitely, adding 2 repeaters (up to 16gt(8rt) of delay) for each block of extension. As shown, it has a minimum delay of 10gt(5rt). This delay can be reduced 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-pulse passes the output).

• (4gt repeater delay version)
  • Period: 12gt (6rt, 0.6s)
  • Pulse length: on-pulse: 6gt (3rt, 0.3s), off-pulse: 6gt (3rt, 0.3s)
  • Frequency: ~1.67Hz

Design D is a tiny vertical clock, a compressed form of E that can modified by changing the repeater's delay.

Earliest Known Publication: June 30, 2011^[1]

The period in redstone ticks is 2 times the repeater's delay+1, but the repeater must be set to at least 2 redstone ticks or the torch burns out. This circuit is formally 1×3×3, 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 is forced "off" while the dust is 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 is out-of-phase, and dust does not light).
  • Output from the dust side is reverse phase.

Comparator clock

Comparators can be used to make fast clocks and slow pulsers.

Subtraction clock

4gt Subtraction Clock

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz
  • 2×2×2 (8 block volume)
  • flat, silent

A 4gt subtraction clock toggles on and off every 2gt(1rt). It uses a redstone comparator 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 redstone 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 2gt(1rt) later the comparator subtracts 0 from its input and the cycle starts again.

Only the redstone dust next to the comparator actually toggles between on and off — the comparator, the block in front of it, and the dust next to the block toggles 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 works even with an input strength as small as 2.

Variations: Players 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: February 9, 2013^[2]

8-20gt Subtraction Clock

• Period: 8-20gt (4-10rt, 0.4-1s)
• Pulse length: on-pulse: 4-10gt (2-5rt, 0.2-0.5s), off-pulse: 4-10gt (2-5rt, 0.2-0.5s)
• Frequency: 2.5-1Hz
  • 2×3×2 (12 block volume)
  • flat, silent

The period of this clock depends on what delay the repeater is set to. 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.

2×3 Super-compact design

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz
  • 2×1×3 (6 block volume)
  • flat, silent

The input can be any types of power sources from a lever to a redstone block. Output can be taken anywhere from the three redstone dusts placed in front of the comparator.

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.

18gt Fader Pulser

• Period: 18gt (9rt, 0.9s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 16gt (8rt, 0.8s)
• Frequency: ~1.1Hz
  • 1×4×4 (16 block volume)
  • 1-wide, silent

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 2gt(1rt), and the signal strength declines by 2 each time through the loop, so the fader loop remains charged for 16gt(8rt). The redstone torch then turns on for only 2gt(1rt) because it short-circuits itself (the torch does not burn out because it's held off most of the time by the fader circuit).

58gt Fader Pulser

• Period: 58gt (29rt, 2.9s)
• Pulse length: on-pulse: 54gt (27rt, 2.7s), off-pulse: 4gt (2rt, 0.2s)
• Frequency: ~0.34Hz
  • 2×4×2 (16 block volume)
  • flat, silent

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 4gt(2rt), and the signal strength declines by 1 each time through the loop, so the fader loop remains charged for 56gt(28rt). 2gt(1rt) later, the redstone torch turns back on, re-powering the fader loop (it stays on for 4gt(2rt) so it overlaps the fader loop's on time by 2gt(1rt)).

Variations:

• Add more comparators to increase the clock's period.

• Add redstone between the first set of comparators to limit the on-pulse to 4gt(2rt)

• Skip the redstone torch for a non-repeating version (pulse extender).

Alternating clock

Alternates between two different signal strengths every other redstone tick.

Can be used to compact circuits that require lockstep timing.

Hopper clocks

• (Single-item Etho Hopper Clock)
  • First cycle period: 9gt (4.5rt, 0.45s)‌^{[JE only]} | 16gt (8rt, 0.8s)‌^{[BE only]}
  • Following cycles period: 14gt (7rt, 0.7s)‌^{[JE only]} | 16gt (8rt, 0.8s)‌^{[BE only]}
  • First cycle pulse length: on-pulse: 4gt (2rt, 0.2s), off-pulse: 5gt (2.5rt, 0.25s);‌^{[JE only]} | on-pulse: 8gt (4gt, 0.4s), off-pulse: 8gt (4gt, 0.4s)‌^{[BE only]}
  • Following cycles pulse length: on-pulse: 5gt (2.5rt, 0.25s), off-pulse: 9gt (4.5rt, 0.45s)‌^{[JE only]} | on-pulse: 8gt (4gt, 0.4s), off-pulse: 8gt (4gt, 0.4s)‌^{[BE only]}
  • First cycle frequency: ~2.22Hz‌^{[JE only]} | 1.25Hz‌^{[BE only]}
  • Following cycles frequency: ~1.43Hz‌^{[JE only]} | 1.25Hz‌^{[BE only]}
• (Multiple items Etho Hopper Clock)^[3]
  • Period: [(n-1)*8+2]*2gt‌^{[JE only]} | [(n-1)*8+4]*2gt‌^{[BE only]}
  • Pulse length: on-pulse: (n-1)x8gt, off-pulse: (n-1)x8+4gt‌^{[JE only]} | on-pulse: (n-1)x8gt, off-pulse: (n-1)x8+8gt‌^{[BE only]}
  • Frequency: 5/[(n-1)*4+1]Hz‌^{[JE only]} | 5/[(n-1)*4+2]Hz‌^{[BE only]}

A hopper clock (a.k.a. "hopper timer") uses the movement of items between at least two hoppers to create a clock signal.

General aspects:

• flat/tileable
• noisy/silent

Go to #Hopper clock schematics for more details.

• 
  Hopper-Loop Clock
• 
  N-Hopper-Loop Clock Shown: 4-Hopper-Loop Clock.
• 
  Etho Hopper Clock (EHC) – Both pistons are sticky.
• 
  1-Wide Compact EHC
• 
  1-Wide Tileable EHC
• 
  1-Wide Upside-Down EHC
• 
  sticky piston-less EHC
• 
  Hopper Timer (self-locking EHC with trigger input)
• 
  RS NOR Latch Hopper Clock
• 
  1-Wide RS NOR Latch Hopper Clock
• 
  Hopper-Latch Hopper Clock
• 
  Sethbling's Hopper Clock
• 
  SethBling's Hopper Clock (Simplified)
• 
  SethBling's Hopper Clock (Amputated)
• 
  Multiplicative Hopper-Dropper Clock (MHDC)
• 
  3-Stage Vertical Multiplicative Hopper-Dropper Clock — 72 block volume, clock period up to 10.7 years

Hopper clock schematics

This sub-page contains ~24 schematics. Open it only if needed, or open the same page on its own.

Dropper-Dropper clock

• (Single-item Dropper-Dropper Clock)
  • Period: 32gt (16rt, 1.6s)
  • Pulse length: on-pulse: 6gt (3rt, 0.3s), off-pulse: 26gt (13rt, 1.3s)
  • Frequency: 0.625Hz
• (Multiple items Dropper-Dropper Clock)
  • Period: (n*8+6)*2gt
  • Pulse length: on-pulse: n*8-4gt, off-pulse: n*8+6gt
• 7×4×2 (56 block volume)
• Earliest known publication: Apr 24, 2018^[4]

A simple design that does not require iron, as it uses no hoppers or pistons. However, it does require quartz. Pulsing output can be taken from the long dust trails in the top-right and bottom-left corners, while stable output can be taken from the redstone dust at the top-left and bottom-right. The repeaters at the top and bottom are set to 3 redstone ticks. The clock may need resetting after reloading the world.

Despawn clock

A despawn clock uses item despawn timing to create a clock signal.

Merely approaching a despawn clock can interfere with its timing, because any player might accidentally pick up the despawning item.

Dropper Despawn Clock

• Period: >5 minutes (depends on the thrown item's vertical momentum and on the pressure plate's scheduled tick)
  • 3×3×2 (18 block volume)

Start the clock by turning off the input. The torch turns on, the dropper drops an item on the pressure plate turning the torch off. After 5 minutes, the item despawns (disappear) and the pressure plate deactivates, allowing the torch to turn on, causing the dropper to eject another item onto the pressure plate.

If completely filled with items, the dropper must be re-filled every 48 hours, or continually supplied with items from a hopper pipe. Two chickens constrained above a hopper can keep a dropper despawn clock supplied with eggs indefinitely.

Variations: Longer clock periods can be achieved by chaining multiple despawn clocks together, so that each torch triggers the next dropper instead of its own. When chaining multiple despawn clocks, the dropper must be placed so that it is activated only by the previous torch and not the previous pressure plate.

A dispenser can also be used, instead of a dropper, but is slightly more resource-expensive (and not advised with use of eggs).

Piston clock

Pistons can be used to create clocks with a modifiable pulse delay without the use of pulse generators. In Java Edition pistons can be clocked in a fashion that leaves the arm extended only for the time required to push an adjacent block. Piston clocks in general can be easily turned off or on by a "toggle" input. The main problem of piston-based clocks is that some designs can break when exiting and reopening the world, due to MC-89146.

Extendible Basic Piston Clock (A)

• Period: 6gt (3rt, 0.3s)‌^{[JE only]}
• Pulse length: on-pulse: 5gt (2.5rt, 0.25s), off-pulse: 1gt (0.5rt, 0.05s)‌^{[JE only]}
• Frequency: ~3.33Hz‌^{[JE only]}

Design A requires only a sticky piston and redstone wire, and is controllable. It runs as long as the toggle line (its power source) is on, and turns off when the toggle line is off. Repeaters can be added to increase its delay.

Dual Block Piston Clock (B)

• Period: 40gt (20rt, 2s)‌^{[JE only]} | 44gt (22rt,2.2s)‌^{[BE only]}
• Pulse length: on-pulse: 20gt (10rt, 1s), off-pulse: 20gt (10rt, 1s)‌^{[JE only]} | on-pulse: 22gt (11rt, 1.1s), off-pulse: 22gt (11rt, 1.1s)‌^{[BE only]}
• Frequency: 0.5Hz‌^{[JE only]} | ~0.45Hz‌^{[BE only]}

Design B requires two sticky pistons, and can be easily stopped by powering the right piston. The repeaters can be indefinitely extended to make a long delay clock.

Inverted Basic Piston Clock (C)

• Period: 6gt (3rt, 0.3s)‌^{[JE only]}
• Pulse length: on-pulse: 1gt (0.5rt, 0.05s), off-pulse: 5gt (2.5rt, 2.5s)‌^{[JE only]}
• Frequency: ~3.33Hz‌^{[JE only]}

Design C is a version of design A with inverted pulse length. For the clock to work, the block the piston moves must be placed last. The piston extends and retracts quickly. The clock can be turned off b providing a redstone signal (e.g. the lever shown on the block below it) to the piston.

This clock is 2 blocks tall, 3 wide, and 5 long. There is a solid block under the piston. The redstone torch between the repeater and the output line is at ground level.

Simple 4 game tick Piston Clock (D)

• Period: 4gt (2rt, 0.2s)‌^{[JE only]}
• Pulse length: on-pulse: 1gt (0.5rt, 0.05s), off-pulse: 3gt (1.5rt, 0.15s)‌^{[JE only]}
• Frequency: 5Hz‌^{[JE only]}

Design D is very simple and can be used to create rapid clocks. It can be stopped by powering the piston. Place a block of redstone on a sticky piston, then lay down redstone so that the block powers the piston. Then, once the piston is powered and moves the block, the redstone current stops, pulling the block back to the original position, which causes the block to power the wire again, and so on.

Self-Powered Piston Clock (E)

• Period: 6gt (3rt, 0.3s)‌^{[JE only]}
• Pulse length: on-pulse: 5gt (2.5rt, 2.5s), off-pulse: 1gt (0.5rt, 0.05s)‌^{[JE only]}
• Frequency: ~3.33Hz‌^{[JE only]}

Design E is the simplest and the only one used vertically; it takes advantage of quasi-connectivity and block update detection to activate the sticky piston repeatedly.

To make this design, place a sticky piston facing up with a redstone wire next to it on one edge. Next to the redstone wire but still 1 block away from the piston, place a solid block and place redstone wire on top of it. Then, next to that block, but still 1 block away from the piston, place obsidian two blocks up with a redstone wire on top of it. Above the sticky piston place a slime block. Finally, on top of that, place a redstone block. The clock activates immediately.

Players can also add on to this design and make it toggleable. To do this, simply place a lever next to the sticky piston.

0-Tick Pulse Piston Clocks

0-tick pulse clocks are clocks that create 0-tick pulses on a regular basis.

1-output 3gt clock

• Period: 3gt (1.5rt, 0.15s)
• Pulse length: on-pulse: 0gt (0rt, 0s), off-pulse: 3gt (1.5rt, 0.15s)
• Frequency: ~6.67Hz

Every 3gt, the redstone block is 0-ticked to left and then 0-ticked back, creating a 0-tick pulse. The clock can be toggled by cutting the redstone line on the right

2-output 3-gt clock

• Period: 3gt (1.5rt, 0.15s)
• Pulse length: on-pulses: 0gt (0rt, 0s), first off-pulse: 0gt (0rt, 0s), second off-pulse: 3gt (1.5rt, 0.15s)
• Frequency: ~6.67Hz

This redstone clock create two 0-tick pulses every 3gt(1.5rt). The 0-tick pulses are timed with the correct block event delay to allow the pulses to reliably chain two 0-tick pulses.

When the repeater is powered, the back sticky piston starts extending. This un-cuts a redstone wire below the block, causing the front sticky piston to be powered and extend, causing the back piston to 0-tick tick block. This then causes the top block to get 0-ticked back, cutting the bottom wire again, and outputing a 0-tick pulse on the left. This causes the front piston to get 0-ticked, which then gets 0-ticked back, creating the second 0-tick output on the right.

2gt clock

• Period: 2gt (1rt, 0.1s)
• Pulse length: on-pulse: 1gt (0.5rt, 0.05s),off-pulse: 1gt (0.5rt, 0.05s)
• Frequency: 10Hz

Although this clock does not produce actual 0-tick pulses, any piston connected to it will act as if it were being 0-ticked, due to pistons' start delay. This clock makes use of three modules that output a signal every 3gt(1.5rt); each module is offset from the next one by 2gt(1rt).

1gt clock

• Period: 1gt (0.5rt, 0.05s)
• Pulse length: on-pulse: 1gt (0.5rt, 0.05s), off-pulse: 0gt (0rt, 0s)
• Frequency: 20Hz

This clock is very similar to the 2gt clock, but it has two extra pieces of redstone dust next to the repeaters and outputs actual 0-tick (off-)pulses: in fact, the redstone dust stays unpowered for less than a game tick.

0 tick clock

• Period: 0gt (0rt, 0s)
• Pulse length: on-pulse: 0gt (0rt, 0s), off-pulse: 0gt (0rt, 0s)
• Frequency: ∞Hz

In normal gameplay situations, achieving a clock faster than 1gt(0.5rt) is impossible: due to the passage of time, eventually the game will move on to the next game tick, causing either the on-pulse or the off-pulse to be at least 1gt(0.5rt)-long. However, by using exploits present in older versions of the game, it was possible to schedule block events in a chain reaction, causing the game to get stuck in the block event phase of the tick, thus never advancing to the next game tick. This clock was invented by technical player Myren Eario.^[5]

Minecart clock

Minecart clocks are simple to build, but the timings of some designs can be unreliable. A minecart clock is made by creating a small track rails with one or more powered and detector rails, arranged so that a minecart can run forever either around the track (A), or back and forth from end to end (B, C). (These need not be sloped—properly placed powered rails lets a minecart "bounce" off solid blocks — but the player get some extra time as the cart slows down.) The redstone torch can also be placed in the center of the rails, making it more compact. A larger vertical track (design C) is claimed to produce an exceptionally stable clock. Note that the minecart never quite hits the top of the track.

When running an empty minecart on the loop or back-and-forth, the cart generates redstone signals as it passes over the detector rail(s). Minecart clocks can be extended or shortened easily by adding and removing track, to adjust the delay between signals. On the flip side, they are easily disrupted by wandering players or mobs, and a long clock can take a fair bit of space. Also, the exact period is generally not apparent from the design. The need for gold in the booster rails can also be a problem for some players.

• (Rail Clock B)
  • Period: 36gt (18rt, 1.8s)
  • Pulse length: on-pulse: 20gt (10rt, 1s), off-pulse: 16gt (8rt, 0.8s)
  • Frequency: ~0.56Hz
• (Rail Clock C)
  • Period: 55gt (27.5rt, 2.75s)
  • Pulse length: on-pulse: 20gt (10rt, 1s), off-pulse: 35gt (17.5rt, 1.75s)
  • Frequency: ~0.36Hz

Observer clocks

Observers can be chained together in a loop to create a clock. The core idea is that an observer can react to another observer's reaction, passing the "reaction" down the chain - ultimately leading back to the start, forming the loop. The 2gt(1rt) output from one of the observers in the chain can then be used as the output of this clock.

Single Observer 4gt Clock

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz

One observer - combined with redstone dust such that it is able to watch its own output - can form a 2gt(1rt) clock. Run redstone dust from the space in front of the observing face, around to the observer's output. Break and replace the redstone dust being observed. You can add repeaters for longer periods. To switch the clock on or off, a lever can power the redstone dust, or a piston can be used to move the observer.

Double Observer Clock

Two observers watching each other makes for a compact rapid clock. However, the clock's period will depend on how the observers ended up facing each other (even though the schematic would appear identical).

6gt Observer Clock

• Period: 6gt (3rt, 0.3s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 4gt (2rt, 0.2s)
• Frequency: ~3.33Hz

Manually placing each observer facing each other will set them in a state which will form a 6gt(3rt) clock.

• The first observer A (who is already in place) will react to seeing the second observer B being placed, and power on.
• B will then react to this and power itself on 2 game ticks later (A will power OFF the same game tick that B powers on).
• A will not see B powering on, and so will be idle for the 2 game ticks that B is powered. But this means A will then see B power OFF, and will power itself on 2 game ticks later, starting the loop again.

4gt Observer Clock

• Period: 4gt (2rt, 0.2s)
• Pulse length: on-pulse: 2gt (1rt, 0.1s), off-pulse: 2gt (1rt, 0.1s)
• Frequency: 5Hz

Using a piston to push one observer in place (rather than placing it manually), will set them in a state which will form a 4gt(2rt) observer clock which works identically to the Single Observer 4gt Clock.

N-Observer Clock

Any number of observers can be chained to form a clock. Once the number is 3 or more, it's period will be determined by the number of observers in the loop. Each observer in the chain will add a 2gt(1rt) tick delay, and so the period will equal N redstone ticks, where N = the number of observers in the chain. Put another way, the clock output is 1 redstone tick on, (N - 1) redstone ticks off. Note that it is possible to fit in multiple "observer reaction pulses" through these longer observer chains, which will alter the output of the clock. This is usually not desirable, so special attention should be paid to how the observer chain has it's "reaction pulse" started.

Odd numbers can be managed by combinations of well placed solid opaque blocks (to take strong power from the output of an observer in the chain) and redstone dust, depending on where the "gap" is. Powered rails may be used in place of redstone dust in many configurations.

Long-period clocks

Creating long repeater loops can be expensive. However, there are several sorts of clocks that are naturally quite long, or can easily be made so, and some are described above:

• Devices can send item entities through the world: Items flowing on a stream, falling through cobwebs, or just waiting to despawn (that's a 5-minute timer provided by the game). Droppers or dispensers, and hoppers with comparators, can be quite useful here.
  • Hopper clocks are very versatile and relatively simple.
  • Additional stages added to the multiplicative hopper-dropper clock each multiplies the previous clock period by up to 1,152, quickly increasing the clock period beyond any reasonable use.
  • A simple despawn clock is shown above. These do have a couple of liabilities:
    • If the pressure plates are not fully enclosed, the trigger item may fall to one side, stopping the clock.
    • The droppers eventually run out of items. A droppers full of (e.g.) seeds serve for 48 hours, that is 2 days of real time. If this is insufficient, hoppers and chests can be added to refill the dropper (12 days per chest's worth). Alternately, a pair of chickens can provide enough eggs to keep the clock going indefinitely. A small full-auto melon or pumpkin farm can also serve to fill the hoppers.
• Boats and minecarts can be used with pressure plates or tripwires.
• Pseudoclocks can even be based on plant growth. For these, timing isn't exact, but they can still be useful for getting occasional signals over long periods.
• "Factorial stacking" of clocks: Precise clocks (that is, repeater or repeater-torch loops) with different periods may be connected to an AND gate in order to generate larger periods with much less expense. One way to make a 60-second (1200gt, 600rt) would be to use 150 repeaters set on 4 redstone ticks of delay, or players could connect two clocks with the periods of 48gt(24rt) and 50gt(25rt) (that's 13 repeaters) to an AND gate. Note that if the input clocks' on state is longer than 2gt(1rt), they must filter them with an Edge Detector or Long Pulse Detector, to prevent overlapping on imperfect syncs. The disadvantages here are:
  • The circuitry can be fairly finicky, and players may need a circuit just to start all the clocks simultaneously.
  • The lengths of the sub-clocks need to be chosen to avoid common factors in their periods. This list of the first few prime numbers may be useful: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103. Any one of the clocks can be an integer power of a different prime, and they do not share factors or they occasionally "beat" together, causing an extra or missed pulse.
  • A cycle of 1 Minecraft day (24000gt, 12000rt) can be produced by stacking clocks of periods 125, 32, and 3. A multiplier (as described below) may be helpful for the longest of these.
• Then there's the obvious: the daylight detector acts as a clock with a period of one in-game day. The duty cycle can be adjusted by using comparators at different threshold values. Keep in mind that weather may interfere with this, and of course the phase is fixed. The daylight sensor does offer a unique feature: Since it responds to the actual progress of the game day, it does not lose time if its chunk is unloaded. Naturally if its chunk is not loaded, it can't actually activate any circuitry, but when a player comes by later, the clock remains in sync with the daily cycle. By comparison, suppose that (say) an multiplicative hopper-dropper clock with T flip-flops extending it to 20 minutes is started at dawn, but the chunk is then unloaded. When the player comes back to reload the chunk (say, at dusk), the clock continues counting its 20 minutes from wherever it left off.

There are also a couple of extension techniques that apply to any clock whatsoever, including irregular pseudoclocks:

• A T flip-flop can be used to double the period of any clock. This also converts the pulse to have the same length ON and OFF, if it didn't before. (Pseudoclocks are not completely regularized, but they get smoothed out.)
• Latched repeaters allow production of a general clock multiplier, detailed below. This can be used to multiply the period of any clock, and they can be used in series.

Clock multiplier

This nearly-flat circuit (also known as a ring counter) takes a clock input of period P and any pulse length, and outputs as a clock of period N×P, where N is the number of latches used; the output is on for a pulse length of P, and off for the remaining (N-1)×P. N is limited to 12 or so by redstone signal attenuation; however, the design can simply be repeated to multiply the period again, e.g. a 21-multiplier can be made by chaining a 7-multiplier and a 3-multiplier. This can be continued indefinitely, and unlike factorial stacking there is no restriction on the multipliers.

The build is somewhat tricky: The multiplier loop is in fact a torchless repeater-loop clock. This needs to be started separately, before the latches are engaged. The easiest way to start it is probably to add a temporary "startup circuit" starting 4 blocks from the dust part of the loop: Place a power source, then dust and a block for it to power. Finally place a redstone torch on the block, positioned to power the redstone loop. The torch flashes on for 2gt(1rt) before "realizing" it is powered, and this starts the loop as a clock, which cycles until the latches are powered. This startup rig can then be removed.

The latches are driven by an edge detector, which takes a rising edge and produces an OFF pulse; the pulse length must match the delays of the latched repeaters, so that the multiplier's pulse advances one repeater per edge. The delay/pulse length must also be no longer than the input clock, so it's probably best to keep them both at 2gt(1rt). Note that the delays of the latched repeaters are not actually part of the output period; the latches count off input edges. The circuit's output is ON while the last repeater is lit and lighting the dust loop.

This circuit need not be fed with a regular clock. With any varying input, it counts N rising edges and output HIGH between the (N-1)^th and N^th rising edge.

Variations:

• A T flip-flop can be used to "normalize" the pulse to half on/half-off, while doubling the output period. Design L5 from that page is suitable and compact.
• By separating the latched repeaters with redstone dust (to read their signals individually), this circuit could be generalized into a "state cycler", which can activate a series of other circuits or devices in order, as triggered by input pulses.
• The return line can be run underneath the clock, making the build higher but narrower, or the entire repeater-latch loop can be extended to run backward on a lower level, similar to Torch-Repeater Clock design E. If used as a state cycler, this also makes the dust between the steps more accessible.

Efficiency: An efficient approach to making long-period clocks is to start with a repeater loop of 9 to 16 repeaters (up to 128gt(64rt), then add multiplier banks with N of 7, 5, and 3 (bigger is more efficient). Doublings should be done with T flip-flops, as 2 of those are cheaper and perhaps shorter than a 4-multiplier. A couple of notes:

• Using two 7-multipliers (×49) is slightly more expensive, but shorter, than getting ×50 with 5×5×2, or getting ×48 with 3×4×4 or 6×8;.
• An 8-multiplier is slightly more expensive, but shorter, than separate 2- and 4-multipliers. However, two of them are both longer and more expensive than three 4-multipliers.

Earliest Known Publication: October 22, 2012^[6]

Redstone Repeaters with Feedback

By using a ring of redstone repeaters tapped at specific intervals and an OR gate set in a feedback loop extremely long durations can be created. Durations of minutes, hours, even days can be created using a minimal amount of parts.

Clock cycle time = 0.4 × (2ⁿ - 1) seconds.

Hence each time the player add a single redstone repeater, they can effectively double the cycle time. The same circuit can be used to create long duration clocks and delays of any duration in 0.4s increments.

Super Delay on YouTube [1]

Copy of working Minecraft save game [2]

Below is an example of a free running 10 element clock that takes 409.2 seconds (6.82 minutes) to cycle. It outputs from the XOR Gate a unique stream of 0's and 1's that repeats every 409.2 seconds.

To turn it into a clock all we need to do is add a 10-Input Decoder that looks for one of those unique sequences. A NAND gate goes low when all redstone repeaters are outputting high.

By adding a RS flip-flop, we can reset our clock.

Here is a version where the decoder resets the clock at the 3 minute mark.

In electronics this device is commonly known as a "Linear Feedback Shift Register" (LFSR), players can make them count up, count down, create psudo-random binary sequences for testing logic circuits. In TCP/IP a 32-bit 'Linear Feedback Shift Register' is used to perform data integrity checks ie CRC-32. LFSR's also create the codes for CDMA phones and GPS (Global Positioning System).

Note that the XOR gate takes it inputs (Taps) from redstone repeater 7 and 10. For simplicity sake, these have been listed 2 tap LFSR sequences. In Minecraft, one could make a 1-many delay line structure to create more complicated clocks.

References

Navigation

v t e Redstone
Redstone circuits & tutorials Redstone basics Redstone components Redstone mechanics Conductivity Redstone circuits Clock circuits Logic circuits Memory circuits Miscellaneous circuits Pulse circuits Transmission circuits Featured tutorials Advanced redstone circuits Block update detector (BUD) Comparator update detector (CUD) Mechanisms Piston circuits Quasi-connectivity Redstone music
Redstone components Power emission Block of Redstone Buttons Wooden Stone Polished Blackstone Daylight Detector Detector Rail Jukebox Lectern Lever Lightning Rod Observer Pressure Plates Wooden Stone Polished Blackstone Light Weighted Heavy Weighted Redstone Comparator Redstone Torch Sculk Sensor Calibrated Target Trapped Chest Tripwire Hook Tripwire Signal transmission Redstone Wire Redstone Repeater Conductive and non-conductive blocks Item and entity transportation Allay Boat with Chest Bamboo Raft Copper Golem Crafter Dispenser Dropper Hopper Minecart with Chest with Furnace with Hopper Rail Activator Powered Water Bubble Column Comparator-readable Barrel Bee Nest Hive Brewing Stand Cake Cauldron Chest Copper Chiseled Bookshelf Composter Copper Golem Statue Decorated Pot End Portal Frame Furnace Blast Smoker Item Frame Glow Respawn Anchor Shulker Box Observer-related Redstone Ore Deepslate Scaffolding Sculk Catalyst Sculk Shrieker Wall Pistons/related Piston Sticky Honey Block Slime Block Movable and immovable blocks Sculk sensor-related Block of Amethyst Wool Carpet Mechanisms/misc. Armor Stand Bell Big Dripleaf Copper Bulb Creaking Heart Doors Copper Iron Wooden Fence Gate Head Note Block Redstone Lamp Shelf TNT Minecart Trapdoors Copper Iron Wooden Creative or commands only Command Block Minecart Minecart with Monster Spawner Structure Block Test Block