The "Kyzoy challenge" (redstone / BUD issue)

Discussion in 'Community Discussion' started by ShelLuser, Apr 18, 2016.

  1. Hi gang!

    A few days ago our own Kyzoy suggested a new flag to stop pressure plates from responding. Because I once made a redstone circuit quite a few months ago which does just that I talked to Kyzoy today, showed him my solution and he showed me the actual problem he was having. It immediately looked quite intriguing to me because I immediately spotted something weird:

    The problem at hand

    If you step on the pressure plate nothing happens, but once you move away from it the wooden trapdoor will close. At first sight this might seem logical: the trapdoor is a redstone power source after all so it probably powered the trapdoor which then got closed when the power went down.

    But here's where things become interesting: that can't be the case. In the above picture the only block which would get directly powered by the pressure plate is the block below it. This block gets a so called "strong charge"; this means that blocks in its direct surrounding can "pick up" this redstone signal (I won't explain here, if you want to know more you'll have to wait for my upcoming redstone tutorial). But the block to which the trapdoor is attached is way up in the air. There is no way that this charge could ever reach it!

    Here is a more obvious example:

    All the sandstone you see here are slabs. And slabs have a unique ability: they cannot provide a redstone charge to other blocks in the vicinity. I demonstrated as much with the redstone dust you see behind it. Would this have been a normal sandstone block then that redstone dust would get charged, and lit up the redstone lamp. Yet that doesn't happen.

    But even if it did: you'll also notice that the block with the trapdoor attached to it is waay up in the air. There is no way that the redstone signal can reach it.

    And it gets even better ;)

    If I place some redstone dust next to the pressure plate then the trapdoor also automatically closes:

    Block Update Detector

    Now... I'm decently experienced with redstone and I can conclude that this has nothing to do with redstone at all. So what is it?

    My theory: this is a crude BUD switch, aka Block Update Detector. A BUD switch remains idle until something in its vicinity changes, usually the placement of a block. When that happens the BUD switch will then "do" something.

    So far my theory. As said: I'm experienced with redstone but not that much with BUD switches.

    As such my post here: what do you think dear reader?

    If you'd like to see for yourself then you can visit 3544 (on SMP2). Behind the main stairs is a trapdoor (which will be open for the rest of the day, no need to donate) and you can see for yourself.
    Kyzoy and LtCaptainMe like this.
  2. I think the pressure plate IS powering the trapdoor.

    A pressure plare is powering all 6 blocks arouwd it, the block under it, the four sides and the top block, the only problem is that you normally aren't able to use a pressure plate while a block is on top of it. This only is posseble with trapdoors (correct me if I'm wrong) so indeed, the trapdoor's block isn't powered, but the trapdoor itselve is, witch works aswell :)
    I am sure this isn't a BUD for a very easy reason: If a pressure can activate, placing a block on the pressure plate's place should also activate it, since That isn't working, it should be redstone ;)
  3. I can proof that it's not. If you attach a redstone torch to the block its attached to then you'll see. Once you step on the pressue plate then the torch remains unaffected.

    Update: But I've been proven wrong as well :D It is indeed!

    You probably know this (I'm explaining for the others as well) but: a torch powers off once it detects a redstone charge. So if a charge was present then the torch should turn off.

    Even funnier: the moment I attach the torch to the block then the trapdoor immediately closes again. For no reason.


    Even more bizarre: replace the trapdoor with redstone dust. Nothing happens. Remove the redstone dust and... The trapdoor closes again.
  4. I think you didn't understand my Englisch, better said, my Englisch wasn't good enough ;)
    A torch can on,y be powered tough the block were it's hanging/ standing on. As far as I know is this posseble with trapdoors. I mean, you are able to open/close a trapdoor WITHOUT powering it's block the only other. so: I'ave set up a little experiment with I didn't do (I'm typing on a tablet) but whould show what's hepening:
    Make this:

    Openend trapdoor | sandstone

    Now replace the air with sandstone block (or something Like That)band remove it
    Now replace That block for an redstone torch and remove it

    If it closes after you'ave placed one of the things it IS an BUD-switch.
    If it only closes after removing the torch it's redstone.
    ShelLuser likes this.

  5. Whats the problem? Pressure plates affect the block above it... It's an intended feature...
    JesusPower2 and Jelle68 like this.
  6. I think that the Pressure Plate powers the block it is in like a Button does. Because the Pressure Plate occupies the block below the Trap Door, it powers the Trap Door when activated.

    I tried replacing the Button in the second picture with a Pressure Plate and taking out the top lamp then quickly replacing it after stepping on the plate to prove this but it powered off before I could place the block.

    I think that Pressure Plates, Buttons, and Levers all work this way but are activated differently.
    ShelLuser and Jelle68 like this.
  7. thank you very much :) that is wat I meant to say :p
    ShelLuser likes this.
  8. Yeah, another update guys. The problem is actually two-fold.

    First: I stand corrected! You guys are absolutely right: the pressure plate does indeed power the block above it, which is the trapdoor. That was an oversight on my part. Corq and me cooked up a test case where we replaced the stone pressure plate with a wooden one, closed the trapdoor and then threw items on the plate. The result: the trapdoor opened and closed again.

    But there is more to this story.

    The moment you place a redstone component close to the (opened) trapdoor it'll reset and close again. From redstone dust to an attached redstone torch: for some reason the trapdoor resets when you do that.

    SO there's also an issue with BUD activity whenever you place redstone components.

    But bottom line: Kyzoy's idea to block the pressure plate using a flag should indeed do the trick to keep this trapdoor from responding.

    Thanks a bunch for your comments guys!
    Uber_Corq likes this.
  9. If you don't mind me asking, what is the end result you are seeking?

  10. this?
  11. For the trap door not to respond to the pressure plate. However I think its safe to conclude that this isn't possible because the trapdoor is adjacent to the pressure plate (on top).

    Sort off. If I replace the pressure plate with redstone dust nothing happens, but the moment I remove the dust again the trap door will reset and closes.
  12. Yes but for what application?
  13. *cough* wooden pressure plates & items *cough*
    *cough* put a chicken or whatever on the pressure plate *cough*

    Pab10S likes this.
  14. Solution:

    ShelLuser, Pab10S and TomvanWijnen like this.
  15. Kyzoy's build. He has a few sections where he uses a pressure plate to do something (I assume teleporting) but if he uses the plate then the trapdoor closes as well.

    The only reason I got myself involved is because I became intrigued with the setup; I kinda overlooked the obvious and wondered if there wouldn't be an option afterall.
  16. I think in normal circumstances this would be the fix. Unfortunately, that block is already taken in my build. Hence why I was suggested a use;pressureplate subflag to nullify the output. :confused:

    Here's the dilemma:

    ShelLuser likes this.
  17. Just to be clear on the whole BUD-like behaviour thing, an unpowered (yet open) trapdoor will close if you do certain things around it. When a trapdoor isn't powered, it should be down, as far as redstone logic is concerned, but of course you can open the wooden ones manually and it'll "remember" to stay up until it gets powered and then unpowered. However it seems to also go down just from placing/breaking certain redstone-related pieces in the immediate area around it. Just as an example, take this trapdoor with a pressure plate below it:

    I've manually opened the trapdoor. If I break the pressure plate below it, it will go down automatically:

    It doesn't go down when I place the plate, mind you - just when I break it. However, it does go down when I place or break a piece of redstone dust next to the pressure plate:

    Not only will it react to redstone touching the plate, but it will even do the same with redstone one space further:

    Keep in mind that piece of dust is nowhere near touching the trapdoor, and I didn't power anything the whole time, yet it still caused the trapdoor to get updated.

    This doesn't work with placing/breaking a regular block. It's some kind of "Redstone Update Detector", or something.
  18. You could have the pulse go through a block. Make the block be pushed by a piston (or pulled) if you don't want it to be activated.
  19. Change the pressure plate into a piece of silver carpet and nobody will notice the difference... unless they look at it for more than a glimpse. ;) :p
    Jelle68, TomvanWijnen and Kyzoy like this.