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I have two metal doors, side by side. Adding a pressure plate in front of one allows me to successfully open that door. However, adding the pressure plate or button to the other gets the door stuck in an open state. Is there a trick to getting this to work?
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Ah, thanks. So it is something I'm doing wrong, just not something that would be obvious.
I use the plates as a lazy exit, with buttons on the outside to let me back in, while preventing the mobs from getting in.
Thanks for drawing that out. What confuses me, though, is that in that design I wouldn't be able to have the doors on the outside wall of a building, since the space immediately above needs the red dust. Is that right?
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Yeah double doors wouldn't be flush with the outside wall, needing that space for redstone. However, they could comfortably sit just outside the wall, or they could sit one block inside the wall, hiding all the redstone components. I'll have screenshots of both shortly.
Outside of wall:
http://i54.tinypic.com/30cc604.jpg - redstone skips over the left door which will be powered by the button
http://i52.tinypic.com/jb7m6o.jpg - torch on side of button block
Within wall:
http://i56.tinypic.com/22l0ki.jpg - glass makes it hard to see, but this would be a three-thick wall, with redstone circuitry hidden inside
http://i53.tinypic.com/xnysxy.jpg - button opens the left door, also stops the redstone impulse to the other door
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Thanks for your help. I ended up going a simpler route. I used a single plate to open both doors from the inside and a button to just open the one door from the outside. Doing this, I was able to use just one red torch and one red dust, under the doors.
WoM Coins: 3
Doors are one of those objects that can be activated by a redstone impulse, such as the one that gets sent by a button or a pressure plate. Whether the door opens on a redstone 1 or 0 depends on which side its hinges are on. Opening away from you, a left-hinged door will open on a redstone 1 (and this is the default placement for doors all the time). A right-hinged door, like in a double door (not sure if it can be forced any other way), will open on a redstone 0, or in the case of your scenario, all the time because the impulse to close isn't sent.
To my knowledge, double doors cannot be opened by pressure plate unless that plate is far enough away that its signal does not directly hit the doors, and even then you have to invert the signal going to the right door.
On the Minecraft forums in the Alpha singleplayer section is a thread with a bunch of redstone designs. In there somewhere is the most compact design for a button-controlled double door set I've yet seen. I'd pull a screenshot from my constructions, but with Alpha kind of wonky at the moment I'm just waiting for things to be all settled again.
Essentially, the design calls for a stone button to be placed on the upper block of the two supporting the left door, on the side of that place a redstone torch. There needs to be a layer of blocks on top of both doors, and above the left door an extra block needs to be placed. Run dust across the top and the button should trigger both doors.
[_][_][r][_][_]
[r][r][X][r][r]
[X][X][X][X][X]
[T][s][D][D][X]
[X][X][D][D][X]
Where [_] is air, [r] is redstone dust, [X] is whatever border block you're using, [D] is the doors, [s] is a stone button on top of one of the x blocks, and [T] is the redstone torch (placed on the side of the s block). Another stone button would go on the other side of this arrangement on the same block.
The design overall uses 6 redstone, plus the requisite stick and materials for the doors and the border blocks. It's not pressure-plate based, but then at the same time no mob will be able to inadvertently open the doors, which is usually the point of them.