Redstone clocks are circuits which send a signal forever at specific intervals. The time between the signals can be set by the player, either roughly or very accurately. Clocks are useful for regulating mechanisms, like an automatic farm or perhaps even doors opening an area on you server for 10 minutes every hour.
All the clocks below can pretty much be used for the same purposes, though some have a higher interval between signals, which means they’re not really suited for jobs which require a lot of short term repetition. Other circuits could be expanded to make the intervals longer, but this will usually make those circuits unnecessarily long.
Single Torch Clock
This setup is technically a clock, though it will break within a second due to the fast turning off and on of the redstone torch. However, by adding a repeater in the circuit, the time between activating and turning the redstone torch off increases, which means it won’t burn out. You’ll have to use at least 3 ticks on the repeater to make sure the torch doesn’t burn out.
Multi Redstone Torch
To overcome the burnout of a redstone torch, multiple torches could be used, though you need at least 5 of them. This setup is a lot bigger, but it does allow you to set a specific clock time by either adding torches or repeaters to increase the time.
The repeater clock is pretty much a more stable and controllable version of the redstone torch clock. You can use as little as 2 repeaters, which allows for a very compact clock, however, this compact version will stop if you power it for too long when you activate it. As we’re only using repeaters, some form of power will have to be used to activate it quickly placing and destroying a redstone torch will usually work, but if the torch isn’t destroyed fast enough, the complete circuit will be powered and come to a halt.
By using more repeaters, very long times can be set for your clock, though there is a better option for really long (5 min+) clocks, which we mentioned later in this article.
A piston clock is another neat, controllable clock. The advantage of this clock is that you can turn it on and off. By simply providing the redstone torch with power, that torch will turn off and stop the clock from working.
This clock works by feeding power to the sticky piston, which will push a block over a redstone wire 1 block below everything else, which will cut of the signal to the piston, which will then retract. Rinse and repeat.
This clock takes advantage of the 5 minutes it takes for items to despawn. By simply connecting a pressure plate to a dispenser via an inverter, a signal will be send to the dispenser once every 5 minutes (when the item despawns) which will cause it to drop another item onto the pressure plate. Mechanisms could be powered for a short time once every 5 minutes or they could be turned off for a short time once every 5 minutes.
Cobweb Despawn Clock
Cobwebs slow items down if they fall through it, which means we can easily extend the time of our despawn clock by making the items fall through cobwebs first. A single cobweb will slow the item down by about 21-23 seconds, depending on how well it fell into the cobwebs. Sometimes the item will bounce off of the wall first.
While the time isn’t very exact, it will only be off by about a second or two, which isn’t much of an issue on timers of more than 5 minutes.
A blink device sends out at least 4 signals randomly and rapidly. This fast and random clock isn’t the most useful clocks, but it could be used for things like randomizing mob drops from spawn eggs in dispensers or shooting arrows at random intervals to make sure players can’t time their attempts to get passed.
Note that despite the fast turning on and off of the redstone torches, none of the torches will burn out.
By using detector rail and either powered rails with a normal minecart or simply a powered minecart, clocks can be made quite easily and fairly accurately. As seen in the image below, the minecarts will ride over the detector rail at a constant pace. Note that the powered minecart requires coal or charcoal to run, however, this can be use to deactivate the clock after a specific amount of time, as each coal or charcoal you add, 3 minutes are added to the total time the minecart will ride.