Minecraft delay trap

Question

Im making a trap so that when an object is removed from the pressure plate it blows up but im a bit stuck. The pressure plate does not change the state of the redstone torch on the endblock. I need it to be on when an item is removed from the pressure plate, thus blowing up the player.

Asked by mrminecraft3000

Answer

You can remove the top torch and replace it with redstone to do what you want. In fact you can even remove the first two wood blocks and replace them with redstone.

This design has a serious flaw, though: the dropped item will despawn after 5 minutes, causing the trap to activate even if there is no player around. To work around that, you can use a dispenser and a long timer. After e.g. 4.5 minutes measured by the timer, the dispenser would drop another item on the pressure plate, so when the first item despawns, the pressure plate will still be on.

Answered by Kcats

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How do I make a piston go up and then down?

Question

I'd like to make a piston go up and down just once (then I'll make this thing repeat forever), how do I do that? How do I give the piston the order to go down after it went up in a single tick?

Asked by Jeffrey

Answer

You want to use a monostable circuit. This turns any input pulse into a pulse with an exact length (in ticks). Hook this up to your clock and you can pulse the piston on for 1, 2, or however many ticks you want.

By tweaking your clock speed and monostable circuit you can get very precise piston pulses, e.g. 1 tick on, 5 ticks off; 3 ticks on, 7 ticks off etc.

sethbling, noted redstone genius, gives a very good guide to monstable circuits, as well as other redstone components in this video:

Answered by fredley

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How do redstone torches (circuits) work in Minecraft?

Question

I tried reading the minecraftwiki page on the subject, but without an understanding of precisely how the torches work, none of it makes sense. I have a lot of questions, so even an article explaining only a few of the answers would be helpful.

• How is it possible for the torches to work as both input and output to a circuit?
• What if two torches are both acting as output to the same redstone-wire?
• What if one torch is outputting positive/on/true to a redstone-wire but another is outputting negative/off/false to the same wire?
• Is there a practical difference between torches on the ground and torches on the wall?
• When people talk about 'the redstone-torch's block' (ex. wires only carry power 15 blocks from the source block), do they mean the block the torch is attached to, or the block of space the torch is occupying?
• How do I read the diagrams on the minecraftwiki page?

Thanks for any help understanding all of this!

Asked by BlueRaja - Danny Pflughoeft

Answer

Bob's Minecraft Tutorial, linked by Billy ONeal, is a useful resource, but I'll try to put the basics into words.

How is it possible for the torches to work as both input and output to a circuit?

Is there a practical difference between torches on the ground and torches on the wall?

Depending on where the torch is placed, neighboring blocks will be inputs or outputs, but each neighboring block is EITHER an input or an output - no blocks are both.

• A torch on the ground (in other words, on top of a block) outputs power in the 4 cardinal directions, and also outputs power to any block in the air above it.
• That torch will only accept input from the level below it, so input wires must run straight into the block the torch is sitting on.

To summarize, torches on the ground output to their level and input from the level below.

• A torch on a wall (in other words, on the side of a block) outputs power in only 3 directions (it doesn't output back into the block it's mounted on).
• That torch will accept input from the top of the block it's mounted to, and from the other 3 sides of the block it's mounted to.

In summary, torches on a wall output onto the ground and take input through the wall block.

What if two torches are both acting as output to the same redstone-wire? What if one torch is outputting positive/on/true to a redstone-wire but another is outputting negative/off/false to the same wire?

This has been answered elsewhere, but: If any power source hooked up to that wire is on, the wire will be lit up.

How do I read the diagrams on the minecraftwiki page?

Again, I'll try to break down the basics:

• White squares are just air, nothing special
• Yellow squares are blocks
• Dark yellow squares are blocks a level below (that is, they're an abbreviation for "white on this level, yellow below")
• Grey squares are blocks on the current level with other items a level below

White and yellow squares can then have these items on them:

• Red lines are wires
• Red circles are redstone torches (which may be attached to the side of a block or sitting on one)
• Grey circles are levers
• Small dark grey rectangles are pushbuttons
• Large grey inset squares are pressure plates

So, for example:

• a red line on a yellow background is a wire on a block
• a grey circle on a yellow background is a lever on a block
• a red line on a grey background is a block over a wire
• a grey circle on a grey background is a block over a lever

Within the MCRedstoneSim program you can change levels and see the wiring and such on each level of the circuit, but these extended types of blocks exist so that the whole circuit can be communicated with one set of symbols and no need to show diagrams per level.

Answered by lilserf

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What's the largest size of “door” I can open with a single switch?

Question

I'm fairly new to using redstone, and I'm wondering what's the largest size of "door" that can be opened with a single switch?

I have a huge arena, and I'd ideally like to be able to hit one switch and open a large door to release the monsters. When I say "door", it doesn't necessarily need to be a door. For example, I once had a 2x3 door that opened via sliding blocks and sticky pistons.

Asked by Rachel

Answer

You could make a 5x5 piston door using stick pistons - but if you're new to Redstone this may not be for you.

There is also an option of making a "gravel door" (I am unsure if this works in the latest version of Minecraft).

A slightly easier piston door may be a 3x3 version.

Finally, you could use the design in my question here, the 2 high x 3 wide door, but make the door a lot longer - say 2 x 30 by wangling pistons and repeaters. If you wanted to "release" Endermen you'll need a bigger door, however.

Answered by tombull89

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How can I keep ghosts out of my machine?

Question

I've been building a number of redstone circuits lately, and to keep them protected I've been enclosing each entire circuit in obsidian. However, recently I noticed that a zombie managed to spawn in a dark 1x1x2 void within the redstone circuit. I fixed this by placing ceiling slabs to make these voids 1x1x1.5, too small for spawning.

Unfortunately, I came across a part of my design where I have a redstone torch in the top half of a 1x1x2 void, and a redstone wire on the bottom half. I can't fill the void in any way, and I'm afraid monsters can still spawn there. The only solution I can think of is to find a way to add another block of space to the 1x1x2 void where I can place a coal torch, keeping the light level in the void high enough to avoid spawning.

Are there any other tricks or design components that help keep redstone circuitry from becoming a breeding ground for baddies?

Asked by gnovice

Answer

You don't have to obstruct every area in your enclosed redstone circuits. You can easily place normal torches and/or Glowstone blocks throughout the enclosure. This will also aid in visibility within your ICs. Redstone can be placed on glowstone blocks, but they exhibit interesting properties, so be careful

Redstone can be put on glowstone, but being a transparent block signals can pass from one block to diagonally another with glowstone "blocking but not blocking" it, making possible nearly instant vertical redstone and new vertical logic gate designs.

Answered by OrigamiRobot

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How do you create double doors that open in sync from a 2-wide power source?

Question

I've got a double door which I power from below, using a T-flip flop triggered by a pressure plate on the inside so that when I walk out, the doors open before me and when I walk in, the doors close behind me. It's a very good design for me, but, while powering the doors from below, I usually have to put one powered from off to the side instead of both from the inside. I found the design in my image, which is only 2 wide (I uncovered it, it would usually be covered), on this site, used for something else. However, the two doors are a half-step out of sync, i.e. with the repeaters in this position, one opens before the other, and if I delay the first one with one click on the repeater, the behavior is switched. In this configuration (the delays are equal), the left door always opens and closes a half-step earlier.

How can I get the doors perfectly in sync?

Here's a screenshot:

Asked by Andrew

Answer

This is actually a very easy fix. Your design is something like this:

The extra delay comes from the raising of the signal on top of the block, which is actually unnecessary. Simply lower the signal, like so:

And there you have it. The doors will now be in sync.

Answered by Jake King

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Can I build a TNT cannon that fires the TNT directly upwards?

Question

I've successfully built a cannon that will fire the player upwards to above the clouds by using this design (found on YouTube). The player stands on the stone pad, it triggers the TNT and the "water compressor" pushes the TNT towards the player and detonates, sending the player flying.

I've tried replacing the stone plate with a half-slab and dropping activated TNT onto it but it doesn't work - the TNT launcher detonates but the "ammo" doesn't go anywhere and then blows up, destorying torches and redstone for the activiation circuit underneath.

Is this possible to do?

Asked by tombull89

Answer

Yes

First, build the base, add water:

Add a holder for the 'firework' tnt block one block above the center:

Wire it up. Two repeaters at full spacing will give a good delay:

Test at this point, make sure all the wires light up when you hit the button. If any fail to, you'll blow it all up. Next, load it!

5..4..3..2..1...

BOOM!!!

Answered by fredley

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When do redstone torches burn out?

Question

I know that if I make a redstone circuit that switches too often, my redstone torches will 'burn out' and stop working. Under what circumstances does this happen? Will a slow circuit eventually burn out? If not, what's the maximum 'clock speed' for a circuit such that it will never burn out?

Asked by fredley

Answer

The fastest clock that will not burn out is the 4-clock. A common design is this one:

- =wire
r =repeater- r -
r   r
- r -

I think all repeaters must be set to 4 to remain stable, but I've been fine setting them to 3 before.

Edit: I did some research, to investigate. I have found that a torch needs at least 8 ticks total delay between pulses to prevent burnout. So the repeater clock with 4 repeaters should be set to at least 2 ticks each.

My basic setup:

Basically, my experiment involved that basic repeater clock hooked up to 4 torches. I started with them each at 1 tick delay, and, as expected, all of the torches burnt out very quickly. I increased the delay on the repeaters one by one until the torches stopped burning out. This point came when each repeater was at 2 ticks delay (though the torches were probably pulsing too quickly for most devices).

Though it should be noted that torches can be extremely buggy sometimes; sometimes, pulling a lever will burn a torch out...

Answered by Unionhawk

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How can I get my redstone to activate adjacent pistons?

Question

I'm trying to create my first circuit in minecraft:

• a - pressure plate
• p - piston
• d - dirt
• - or | - redstone

 

a----dddd
     pppp

Pistons are placed over the dirt and there's water under the dirt.

I'm trying this but it doesn't work:

a-------
     ddd
     ppp

This also doesn't work:

----
a ||
  dd
  pp

This does work, but only if pistons aren't adjacent

a--------
    | | |
    d d d
    p p p

Here are two screenshots:

This doesn't work

This works:

Asked by Matteo Pagliazzi

Answer

There are actually a large number of different ways you can do this. Perhaps the simplest is using redstone repeaters, like so:

There's also the design proposed by StrixVaria, which uses elevated redstone:

But there are even more ways you can do this. Here are a few:

Take your pick!

Answered by Jake King

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Is there a more efficient way to wire a row of pistons?

Question

I want to create two sets of two adjacent pistons with a two block gap between them for a melon farm. It seems as though I'm using a prodigious amount of redstone for each section. This is my first redstone circuit, but is there a better way?

Asked by John

Answer

Yes, there a quite a few ways.

Come with me on an adventure in redstone optimization!

You can place Redstone Repeaters behind each of the pistons as shown below. This will direct the input into the piston and prevent those annoying loops that usually don't accomplish anything. This will take up much less space, but uses a total of 18 redstone dust.

---

A more redstone efficient design would be this. It uses only 11 redstone dust. Other players not required. This method works because a piston can be powered by an adjacent powered block.

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This design (courtesy of Tristan) uses a minimalistic 7 redstone. The lever powers both the block that it occupies and the block it attaches to. The hole on the right is required to keep the signals going to the two pistons separate.

---

Finally, this uses a measly 4 redstone. Since you're powering 4 pistons, I think 4 redstone is likely as low as you're going to get.

Science!

Answered by OrigamiRobot

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Redstone loop not working

Question

After building and exploring in Minecraft, I chose this sticky piston mob grinder to learn about redstone - which may have been a bit too ambitious, as I'm having problems with the loop which sends pulses to the sticky pistons.

I have set it up like this, and the circuit lights up when I step on the plate, and stays on constantly when I step off, until I break it by removing some redstone.

What I think should be happening when I step on the plate is that the circuit should activate, sending current round the loop, each time round sending a pulse out to the sticky pistons (which I'm fairly sure are wired up correctly, as they do move when they receive current) - and that this should continue, even when I step off the plate.

I've been fiddling around with this for 2 days, and just cannot figure out what I'm doing wrong. Any thoughts would be much appreciated!

Asked by Deiomene

Answer

The loop is called a "clock" -- searching for that might help. My guess would be try increasing the delay in repeater time and don't stand on the plate for very long. What you want is for part of the loop to be lit up so that moves through the repeaters and back around again. If it still doesn't work, try a different clock -- they're basically interchangeable.

Answered by Yamikuronue

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How can I create a “master” switch with redstone?

Question

How can I create a "master" switch with sub-switches all connected to the master switch? When then master switch is turned on, it allows power to go to all the sub-switch (when the sub-switches are on). When a sub-switch is turned off, its output cannot receive power.

Answer

It sounds like you want a lot of AND gates (sub-switches) with one common input (the master switch) in each gate.

Note: The piston is just an example of an output device.

Try constructing one AND gate for each sub-switch and connecting all the "A" inputs to a single lever and each "B" input to its own lever.

When connected properly, each AND gate will not be able to output power unless both the master switch is on and its corresponding sub-switch is on.

Be aware that redstone signals will only travel 15 blocks. A repeater can be used to extend this.

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How can I make a functioning piston elevator in SMP

Question

I've recently been trying to build a piston elevator in SMP from bedrock to the surface. However, every design I've tried (some of my own, and some from Youtube) results in me getting stuck in a block part of the way up. Are there any ways to get around this? If it's lag related would slowing the elevator down by adding an extra repeater or two between each level be sufficient?

Answer

To make a piston elevator I use the "staircase" design

The way this design works is by pushing you up stairs using pistons.

Here are some pictures of how this works:

Note: The first repeater is on 2-delay, and the second is on 1-delay.In the screenshots is different, sorry.

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Is there a way to keep a clock ticking with no players logged into SMP?

Question

I'm planning to build a clock tower for my SMP server; however, it's occurred to me that my plans have a gaping flaw: when nobody's online, the redstone clock won't keep time. I'm using vanilla, so Bukkit mods to keep chunks loaded won't work. Is it possible to use a different clock to count off hours, one that will keep running while I'm gone? Or better yet, somehow derive the time from the sun position?

Answer

The only solution I can think of is using a light sensor to manually correct the time displayed on the clock, but it would likely be very complicated, and depending on how the clock tower is built, it might not work. What you would do is build a light sensor and feed its output into a special reset line that sets the clock to a certain time. When the sun rises, it would activate the light sensor and set the clock to whatever time sunrise should be.

Ideally, you would also take the output of the clock, and give the clock a time range in which to ignore the light sensor, so that the clock wouldn't be changing times every morning (because the time at which the light sensor activates is slightly random). If, say, you wanted sunrise to set the clock to 7:30, you could create a signal that is turned on when the clock reads any time from 7:20-7:40, invert it, and connect it to one input of an AND gate (the other being the output of the light sensor). The output of this AND gate would be the signal to set the clock to 7:30. This way, if the light sensor activated and the time was already near 7:30, the clock would ignore it. (Now that I think about it, this would be a good way to implement error detection in the clock as well, in case the timing is slightly off).

Here's a video of a light sensor and how to build it:

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How can I get this redstone blast door to do what I want?

Question

I'm working on expanding my Minecraft Redstone experience and contraptions. Here, I have a 2 blocks high x 3 blocks wide section of a tunnel with a track approaching it that is meant to act as a "blast door" or "flood lock". The minecart arrives at the detector rail, the three pistons in the ceiling and floor retract, and the one in the side pushes the rail out, delayed slightly. Perfect.

The problem, however, is when the cart moves through the gate and the blocks return to their original location. The yellow block that the rail is resting on gets pushed up, taking the rail up with it (and both sides) immediately. Then, the side piston retracts, taking the yellow wool block sideways, snapping the rail into three pieces.

The wiring is fairly simple (which is probably my downfall).

This is the wiring for the "lower" pistions. The redstone torch (next to the detector rail) turns off, retracting the pistons.

The wiring for the upper section is equally simple. The redstone goes up and onto the area where the two glass sections are, hitting the repeaters and triggering the pistons.

Finally, the wiring for the track piston. Delayed and inverted this is most likely to be the issue.

What can I do (is it even possible) to get this to work?

Answer

I've made a video of a working example:

All you need are properly calibrated repeaters (4 ticks each), a "short-cut" for the door pistons and an inverter on one of the system parts.

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How can I generate a redstone signal when players are near?

Question

Is it possible to construct something that will run automatically whenever a player is nearby, say within a chunk's range, without that player having to trigger something like a pressure pad or detector rail ?

What I'm trying to do is get some pistons to move in this situation, so for example if someone was walking along something might light up on a distant hill

The only way I can think of doing this is to have a cavern underground with a load of pressure plates wired up to pistons on the surface, and an army of snow golems down there to wander around and hit the pressure plates. But they don't seem to spawn until you're pretty near.

Answer

Sethbling rigged up a Giant Self-Detonating Creeper statue that would only detonate when people were within a chunk or two of it.

https://www.youtube.com/watch?v=pHvWGTJ1Hsc

Sethbling's videos are very short and sweet, so I'll let him explain.

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Can I use Redstone underwater?

Question

Fairly simple question: Do redstone dust/redstone torches/switches/etc. work underwater?

Answer

Nope, you can't place them on tiles with water, they pop back up. If you have placed them already and water flows over them then they will do the same.

Bonus edit:

Here's a picture of me trying to place a redstone torch down, while a sheep looks on in bewilderment:

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How can I build a simple flip-flop with Redstone?

Question

I've been trying to learn more about Redstone after doing some research for another Minecraft question. I've never played Minecraft before, although I'm familiar with Terraria, which I believe is similar.

I'd like to build a simple flip flop using Redstone, but I'm not sure exactly how much time I'd need to sink into such a project, and what resources I'd require. Do I need to have played to a certain point in the game before I could start? Are there any tools or mods that would make this project easier?

Answer

You can start making basic "redstone" devices as soon as you have enough wood to make a door and a pressure plate: make the door and the pressure plate, and put them next to each other. Voila! Your first "redstone" device without needing any redstone.

If you want to start getting into more complex devices like flip flops, you need redstone dust: you can find it by mining redstone ore deep underground: 16 layers above bedrock or lower (sea level is at the 64th layer).

The best way to learn how to make redstone devices like flip-flops is to watch the myriad of tutorials on YouTube: figure out what you want to make, search for a tutorial on how to make it, and repeat it¹.

For example, Rolf-David's tutorial shows you how to build a basic T Flip Flop:

The basic flip flops (and most redstone devices) are pretty simple, but aren't very efficient because of the way redstone works: they take up a lot of space and because power doesn't travel instantly across redstone, larger circuits are incredibly slow.

So what people have been doing is exploiting buggy implementations of blocks not intended for redstone circuitry to make them smaller and faster. Etho is probably best known for exploiting what's called the "block update"; a quirk of Minecraft where blocks send power when they update their status:

For the most part, if you never got into advanced features like this, you'd still be fine.

^{Note 1}If you want a more comprehensive education on Redstone, there are couple of channels that focus on it pretty heavily: Etho's Lab and SethBling probably the two biggest ones. Etho's Lab is more "Let's Play"-ish (although he does do stand-alone tutorials from time to time), whereas SethBling is pretty heavily focused on tutorials.

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How to make pistons push back minecart tracks?

Question

I'm trying to make a door to my undergound house. The minecart passes over a pressure plate and it starts some pistons, which then open a hidden door in the wall. But my problem is, while the sticky piston pulls the stone bricks normally, the minecart tracks stay. So, my track has a hole in it everytime I close the door. I can't post pictures, because I'm a new user, sorry.

Is there a way to make the track come back with the blocks?

Answer

As far as I understand your question, you have trouble with the track going trough the door...

Here is a screenshot of my setup, first you switch over to the new track, then you go trough the 'door', but by going down under the door block the track doesnt break and just creates a slope whenever the door is open, this would work in both directions.

Also as often happens with these timed things, the doors or track switcher might not stay open long enough, here is a way to lengthen that. (This is my own design, not all that compact, but the only thing that makes sense and works for me)

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How to channel Redstone current vertically?

Question

I'm making a door with piston sliding sideways that reacts to pressure plates.
As the pressure plates are sending the current to redstone at a very low level, I need to raise it somehow, and this leads to awkward stairs of redstone.

So I'm wondering whether there are better ways of sending the redstone current up, maybe even vertically.

Answer

Going straight up is one of the easier directions to manage via redstone.

Just alternate torches and solid blocks, and you can send the signal up as far as you need.

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