So a little while ago we covered BUD switches, but there's only so much you can show in one tutorial.
In this tutorial, I'll be showing you how you can use a combination of water and BUD switches to make a mechanical to kinetic power transfer, and then go back again. In case you don't know what that means, we're going to turn redstone power into water, and then turn it back into redstone again!
I'll be showing you two different ways to do that, both techniques of which are fundamentally the same, and are just adaptations of the same principle.
Here's a video of one of them in action (don't mind the weirdness).
In this case, we'll be using a waterfall to transfer the power. It's an easy way to affect objects below you without creating big spires of wire or torches.
The heart of this technique is the BUD switch. I won't go into detail about BUD switches, so I suggest that if you're confused or want to know more about them, check out our earlier tutorial on BUD switches.
The one I used is a non-self-resetting version, but you can use whatever type of BUD switch you like.
For this type, you're going to dig a one-block hole next to your piston, either behind it or next to it. BUD switches don't work diagonally, though, so make sure your hole is directly adjacent. In this case, I put my hole behind it.
All you need after that is a toggle-able water source above it. For that, I just made a simple container that I blocked off with a piston.
When the piston is turned off, the water flows downward, triggering the BUD switch. The switch is triggered again when the water is shut off.
Simple! Your power has gone from mechanical (redstone) to kinetic (water), and back again!
Using the same principle as above, you can use horizontally-flowing water in exactly the same manner.
Start out by making a little canal for your water, and make sure that your BUD switch piston lines that canal, like so:
Then lift the piston, and voilà! Power!