This all started out as a project to demonstrate the Open Computers mod. Obviously, then, this post will not tell you anything about the Open Computers mod.
For some reason, that’s just the way I work. My PhD thesis followed essentially this same four-step pattern, just on a much grander scale.
- I get an idea.
- I research the idea.
- In researching the idea, I discover more fundamental ideas that must be researched before I can get back to my original idea.
- I pursue the new idea and never get back to my original idea.
You can actually chain multiple instances of this pattern together. In researching the new idea, it often happens that you discover yet even more fundamental ideas. My problem is that I am a big picture guy who nevertheless wants to nail down all the details. I just don’t see the details from the get go. So I am capable of coming up with ideas/projects of unimaginable complexity, thinking the whole time, “This should be doable.”
My wife, who was genetically engineered to be the perfect project manager, greets each new idea with a carefully controlled expression I have come to understand as a blend of interest and terror.
Fear not, however. I shall return to the Open Computers mod. For now, however, I want to talk about secret passages, piston extenders, and redstone pulse generators.
The Goal: A Secret Room With a Secret Door
The purpose of this build is to create an undetectable secret door whose opening mechanism is not visible. The means that I have to use pistons, and it means that the blocks being moved by the pistons must be flush with surface that surrounds them (so it is not obvious that they are a door). Now, you can, using six sticky pistons, make a door where two blocks retract and then move to the side. But for this project, I wanted to build a secret passageway into a staircase.
I want to give a shout out to YouTuber MrCubey for an outstanding instructional video on just this kind of staircase hidden door. MrCubey’s design makes conceals the triggering mechanism by making it so that you have to place down a button on a particular square. If I have one point of constructive criticism, it is that even with a wooden button, the window of time you have to pass through the door seems a little short. But that’s a minor point and one that many players wouldn’t have any problem with at all.
My design (which I worked out independently) works a little differently from MrCubey’s, so the dimensions end up being a little different. I think my Redstone setup is a little simpler, and it seems to be modestly more compact. Also, my larger design (which is, admittedly, not at all more compact than MrCubey’s) makes it possible to adjust the length of time the door stays open, AND you trigger it with a key item. I even went to the effort of making an amateurish video on my underpowered computer to demonstrate it.
An entrance like this requires the use of a piston extender (two pistons on top of one another)[picture]. This is easy enough to do, and I’ll show you below how it works. But this secret door also requires a single piston adjacent to the piston extender (we are retracting two diagonally adjacent stair blocks to make a two block high entrance we can walk through). Unfortunately, many of the piston extender designs I come across use all the space around the two pistons in order to keep the design compact (meaning we have no place to put one more piston). Two examples of this kind of piston extender can be seen in videos by TheRealMisterBam and Mumbo Jumbo. These are both fine designs, but they don’t serve our needs, in part because of their compactness. I feel that I have produced a design that solves this problem compactly and elegantly.
To solve the problem of the piston extender not fully retracting the second stair block, we have to add another part, which is essentially a pulse generator. There are lots of ways to do this, but this pulse generator is compact and serves our needs. Check out http://minecraft.gamepedia.com/Pulse_circuit for a very in depth article about pulse generators.
The problem at the moment is that this mechanism is “off” by default, meaning the door is opened. That can be changed simply with a NOT gate (a.k.a., a redstone torch).
Now, however, we need a way to trigger this door open. My larger project has you toss a key item onto the floor in front of the staircase. If you toss the wrong item, it simple spits it back out at you. If you toss the correct item, the door opens, and you receive your key item back inside the hidden room. But explaining all that is going to require a second post. So for this post I am going to show you how to use MrCubey’s button trigger with my piston setup.
In the next post, we will look a little more closely at how piston extenders work (retracting correctly usually involves what is called a redstone pulse generator). Plus, we will implement the key item triggering mechanism, which is, if I do say so myself, pretty darn cool.