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[randyshipp]

I'm about to lose it after my fourth scum save and a fortress that now requires a ton of babysitting to keep from flooding.

I feel like what I'm trying to do should be 0th-level, idiot-simple, Dorfish Engineering 101.  All I've done is dig out a cistern and dug a path from the surface to the cistern.  I didn't originally intend for there to be, since I thought flow control would be a lot simpler, but there's now also a 1-tile-wide tunnel leading to a fortification at the map edge as an ought-to-be-wholly-unnecessary cheat of a safety valve.  ALL I wanted to do was this:

- Create cistern
- Create fill tunnel with carved fortification for security and drawbridge for flow control
- Place pressure plate on floor of cistern
- Set pressure plate to min-0, max-3, since the best I was able to glean from the fantastically confusing wiki was that when the water level was between 0 and 3 over the plate, it would send an "open" signal down the line, then some number of ticks after the water level reached 4, it would send a "close" signal, and everything would work.

At no point did the pressure plate close the drawbridge.

Can someone tell me, step-by-step, how to do this?  I'm not interested in the depressurizer cheat.  Frankly, at this point I just want to make one stupid, simple contraption work as expected.

[Button]

Relax. Take a deep breath.

I suspect you're running afoul of signal delay.

A pressure plate with min 0/max 3 will have started its existence in an "on" state. It will not send an 'off' signal until it goes 99 continuous ticks with 4 water or more over it.

A bridge has a 100-tick delay between receiving a signal and acting on that signal, and an additional short (40 tick?) delay before it is open to receiving signals again. Signals sent during this period will be ignored. Since it sounds like you are attempting to fill from a high-pressure water source, I suspect your cistern is filling too fast.

If security is not a concern, I recommend replacing the bridge with a door or hatch cover, which can be destroyed by building destroyers but do not have signal delay.

If security is a concern, you're going to need to either enlarge your cistern substantially, or reduce the pressure of the water so that it fills slowly enough to not flood your fortress.

This information can be found at or is linked to by http://dwarffortresswiki.org/index.php/DF2012:Machine_component#Triggers , though I can't find a source for the additional 40-tick delay so I might be imagining that.

[GavJ]

To kill water pressure by the way, simply have it go through a diagonal only connection at the top level of the cistern, and it will then A) no longer insta-fill, and B) only fill up to the top of the cistern and not any higher, even if the fill source is higher.

[randyshipp]

After another hour or so of futzing around, I achieved my goal with the following sequence of actions:

1) build drawbridge in fill tunnel
2) build pressure plate on floor of cistern, set to min=4/max=7
3) connect pressure plate to drawbridge
4) release the krak...er...the water.
5) when water level reaches 4, the drawbridge closes.

I'd definitely tried to take in all the information in the wiki you linked to, but as you can see, I was obviously not able to puzzle out from that info that a pressure plate, once triggered, would *close* the drawbridge.  But now I've done it once and hopefully will be able to remember next time!  Thanks for the tips.

[GavJ]

Feel free to add to the wiki with clearer text, as long as you're sure it's still accurate, for the benefit of those with the same problem in the future.  It is a wiki after all.

[Larix]

The best explanation of how a bridge reacts to signals is found in the article on levers. I guess it could be helpful if something like that paragraph were added to the "bridge" article, considering it's a major aspect of actually using the potential of bridges.

[FrankMcFuzz]

This confusing crap is the reason I just conscript all my non-military dwarves to be bucket-slaves and carry it by hand, 1 painful drop at a time. Good work on sorting it out, Urist McRandyshipp, and congratulations on the !!Science!!