I have enchanting table with bunch of bookshlves around (5x5x2 square with door). Now I want to make some level 1 enchantments. How to temporary disable bookshelves (preferably by some mechanism)?
If you don't want to set up a Sticky Piston system to retract and extend the Bookshelves, you can place a torch or place water in the area where the Bookshelves are. For some reason, this disables all of the Bookshelves and makes the Enchanting Table act as if there aren't any Bookshelves around it.
As Jake King suggested, you can use sticky pistons, and I've made a video to explain (made it before the first answer, but it was uploading too long).
It isn't that hard, you'll need a piston for every bookshelf, so it's 30 pieces. The tricky part is to get 30 slimeballs, but you can farm them. If you are okay to use an utility - you can find it here, but if you aren't - just explore some caves close to the bedrock and remember the place, where you have seen any slimes. They spawn in certain 16x16 chunks, so you'll have to dig out a big ~32x32 room somewhere between levels 10-40, they'll spawn there eventually. Good video tutorial and text tutorial.
UPD: I've upgraded my system. Nothing complicated, but it gives access to any enchantment level (not just the lowest and the highest). Still uses 30 pistons, but I'm an aesthete and I don't like how other solutions look/work.
A lot of people here presented some very nice designs and ideas that only fall short in one of two categories:
- not being a redstone-based solution, or...
- not being flexible in the number of bookshelves you may activate. (I.e., not allowing every possible number 0 through 15.)
I feel it's necessary to point out that you can, using ONLY 4 levers, activate any number of bookshelves desired. Taking inspiration from binary, try a design like this:
- Lever 1 powers a piston to activate 1 bookshelf.
- Lever 2 powers piston(s) to activate 2 bookshelves.
- Lever 3 powers piston(s) to activate 4 bookshelves.
- Lever 4 powers piston(s) to activate 8 bookshelves.
For every number n, 0 through 15, there exists some combination of the numbers 1, 2, 4, and 8 such that their sum is equal to n.