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How many NXT/RCX bricks are allowed?

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  • How many NXT/RCX bricks are allowed?

    I understand that the gap in the rules described below will likely be clarified so that only one NXT or RCX brick is allowed. However, the current reading of the rules must be interpretted as either no NXT brick is allowed or an unlimited number of NXT bricks are allowed.

    The current "Rule 4 - EQUIPMENT" allows for an RCX brick: “RCX” robots are allowed, but not an NXT controller brick: No other electric elements nor devices are allowed for use in any way in the competition area. I don't see much wiggle room here.

    The bullet You may not use more than one robot in any one match and other references to a robot are difficult to interpret, since a robot is not well defined in the rules. Certainly a controller brick does not constitute a robot, so this is neither an allowance nor a limit on controller bricks.

    If one makes the leap that we can indeed use an NXT brick, how many can we use? Again, one robot is no limit on the number of controllers the robot may use. Certainly if the definition of a robot is subject to interpretation, multiple controllers are more common than not.

    Of course, I'm not going to go out and buy 3 more NXT bricks for our robot. I'm just pointing out that, while the rules are meant to be taken literally, they are not perfect and as such do require some degree of common sense in interpretting them.
    Make things as simple as possible, but not simpler.
    - Albert Einstein

  • #2
    Re: How many NXT/RCX bricks are allowed?

    Begotus,

    Please read Rule #4 a bit more carefully, particularly the second bullet under "Electric Elements", which says: "You are allowed a maximum of three MINDSTORMS™ motors in the competition area."

    By default, when using either an NXT or RCX, these microcontrollers only accommodate up to three motors each. That means one NXT or one RCX is the deployed robot's design basis.

    I hope this clarifies your "interpretation" under Rule #3.

    DSE
    Tech Coach -- Team 7305

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    • #3
      Re: How many NXT/RCX bricks are allowed?

      Originally posted by Warpdrive View Post
      By default, when using either an NXT or RCX, these microcontrollers only accommodate up to three motors each. That means one NXT or one RCX is the deployed robot's design basis.
      You could even interpret the rules in a way that it allows no NXT bricks; there's another thread on that & it's obviously not correct. However, the number of motors wouldn't exclude using another NXT brick. One could control the third motor (which may or may not be driving a wheel) and the 6 sensors could be used all at the same time with a 2nd brick. Although since bluetooth isn't allowed, communication between the two would be difficult.

      Not that I think we're allowed more than one NXT brick. But Begotus is right; the rules aren't perfect. See rule 8; 16" does NOT equal 40 cm. I asked Scott about that one; his answer referred me to rule 25 (Benefit of the Doubt).
      Kansas City Region Head Ref 2014-present
      KC Region coaches and teams can ask FLL robot game rules questions at [email protected]

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      • #4
        Re: How many NXT/RCX bricks are allowed?

        Originally posted by Warpdrive View Post
        Please read Rule #4 a bit more carefully, particularly the second bullet under "Electric Elements", which says: "You are allowed a maximum of three MINDSTORMS™ motors in the competition area."

        By default, when using either an NXT or RCX, these microcontrollers only accommodate up to three motors each. That means one NXT or one RCX is the deployed robot's design basis.
        Warpdrive - you got the bullet right regarding the number of motors allowed. Your following conjecture is simply that - conjecture. The bullet regarding the number of motors allowed is deafeningly silent with regards to the allowance or number of controllers allowed. You could have 9 NXTs, 3 controlling a single motor and 6 controlling individual sensors.

        someonewhobikes is right that without bluetooth, coordination of these would be troublesome - but not against the rules.
        Make things as simple as possible, but not simpler.
        - Albert Einstein

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        • #5
          Re: How many NXT/RCX bricks are allowed?

          Originally posted by begotus View Post
          The bullet regarding the number of motors allowed is deafeningly silent with regards to the allowance or number of controllers allowed. You could have 9 NXTs, 3 controlling a single motor and 6 controlling individual sensors.
          Well, there are two problems with that. The Base is a finite space after all, it's all got to fit. And if you're going to do this, you'd better put a couple more NXT bricks on for weight; with only 9 it'd be so light it might bounce off the table when it runs over the base of one of the contamination stations.


          Kansas City Region Head Ref 2014-present
          KC Region coaches and teams can ask FLL robot game rules questions at [email protected]

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          • #6
            Re: How many NXT/RCX bricks are allowed?

            Originally posted by someonewhobikes View Post
            See rule 8; 16" does NOT equal 40 cm.
            Okay, so if you use the most precise conversion it's 0.64 cm off. There are 2.54 cm in one inch. If you have 16 inches, that's 16 * 2.54 = 40.64 cm. Using the easier to use conversion of 2.5 cm to one inch, you get 16 * 2.5 = 40 cm. That's close enough for me.

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            • #7
              Re: How many NXT/RCX bricks are allowed?

              Originally posted by Apollo1169 View Post
              Okay, so if you use the most precise conversion it's 0.64 cm off. There are 2.54 cm in one inch. If you have 16 inches, that's 16 * 2.54 = 40.64 cm. Using the easier to use conversion of 2.5 cm to one inch, you get 16 * 2.5 = 40 cm. That's close enough for me.
              We teach our kids to use standard metric units; we don't allow the use of the English side of a meter stick. If we have anything that's close to too high they'll be measuring for 40.64. Honestly, if the conversion isn't precise, I don't see how one could call the conversion "correct". Why would you teach the kids to use an "easier" conversion?

              A beam is a shade over mm thick (sorry for the approximation; I don't own a micrometer), so that's a significant enough difference that using the correct height could actually matter.
              Kansas City Region Head Ref 2014-present
              KC Region coaches and teams can ask FLL robot game rules questions at [email protected]

              Comment


              • #8
                Re: How many NXT/RCX bricks are allowed?

                Originally posted by someonewhobikes View Post
                We teach our kids to use standard metric units; we don't allow the use of the English side of a meter stick. If we have anything that's close to too high they'll be measuring for 40.64. Honestly, if the conversion isn't precise, I don't see how one could call the conversion "correct". Why would you teach the kids to use an "easier" conversion?

                A beam is a shade over mm thick (sorry for the approximation; I don't own a micrometer), so that's a significant enough difference that using the correct height could actually matter.
                Beams without studs are 8mm thick and 8mm high. The beams with studs are 8mm thick and 9.6mm high.

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                • #9
                  Re: How many NXT/RCX bricks are allowed?

                  Originally posted by Dean Hystad View Post
                  Beams without studs are 8mm thick and 8mm high. The beams with studs are 8mm thick and 9.6mm high.
                  Like I said; no micrometer. Thanks.
                  Kansas City Region Head Ref 2014-present
                  KC Region coaches and teams can ask FLL robot game rules questions at [email protected]

                  Comment


                  • #10
                    Re: How many NXT/RCX bricks are allowed?

                    This whole thread is just silly.

                    And anyway you can't use bluetooth, so even if you have multiple bricks, they can't directly communicate with each other.

                    I guess whoever wrote the rules (Scott), just assumed everyone understood it to be a given. But assuming does lead to this type of silliness.

                    Comment


                    • #11
                      Re: How many NXT/RCX bricks are allowed?

                      Originally posted by hastypete View Post
                      And anyway you can't use bluetooth, so even if you have multiple bricks, they can't directly communicate with each other.
                      With the option of using up to 6 sensors, I can think of several ways two NXTs could communicate with each other. Besides, if the two NXTs can't communicate with each other, it still is possible to envision a way where both NXTs could assist in completing a mission.

                      I'm not saying it would necessarily be very practical, or help a team accomplish more on the mission board, but it certainly is doable and could be a lot of fun.

                      I expect a Robot Game Update to clarify this issue. Since Scott has already devoted several entries to the farm animals, he probably will add an entry to let us know how many NXT/RCX controllers are allowed.
                      Last edited by timdavid; 09-08-2011, 09:33 AM.

                      Comment


                      • #12
                        Re: How many NXT/RCX bricks are allowed?

                        Originally posted by someonewhobikes View Post
                        We teach our kids to use standard metric units; we don't allow the use of the English side of a meter stick. If we have anything that's close to too high they'll be measuring for 40.64. Honestly, if the conversion isn't precise, I don't see how one could call the conversion "correct". Why would you teach the kids to use an "easier" conversion?

                        A beam is a shade over mm thick (sorry for the approximation; I don't own a micrometer), so that's a significant enough difference that using the correct height could actually matter.
                        Yes, in your case the .64 is very important, as you are using the metric system. However, for US competitions, the judges will probably be measuring everything with the English system, so they don't really care if 16" = 40 cm, 40.64 cm, or 400 cm. If you look anywhere where one system is measurement is used, but they provide the units of the other system for people who use that system, it is usually an approximation to 0 decimal places. That is the case in the robot game documents. They are operating under the English system, but provide metric measurements for a general reference.

                        As for 40 cm not being "correct", it is all a matter of terms. Accuracy is how close something is to the actual value, precision is how many decimal places a number goes to (check a chemistry book). 2.5 is an accurate representation of how many centimeters are in an inch, just not a precise measurement. Thus multiplying 16 inches (which for this example, we'll say it has a precision of two decimal places, making it 16.00 in.) by our 2.5 (which has a precision of one decimal place) conversion gives us: 16.00 * 2.5, which gives us an answer of 40 cm, which is accurate ("correct"), but not precise.

                        As for the merits, of using 2.5 vs 2.54 as a conversion, if you have a calculator or a pencil and paper, I say go ahead and do it. You will get the most precise answer you can that way. However, if you have no calculator, no pencil or paper, it is much easier to double a number and add half in your head than to double a number and add 0.54. Basically, if you can, go ahead and use 2.54. However, if it makes it much more difficult (like you're trying to calculate it in your head), just use 2.5.

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                        • #13
                          Re: How many NXT/RCX bricks are allowed?

                          At our tournaments in Minnesota the units for robot height measurement is "sticks". At the start of a mission no part of the robot, attachments, guides, etc... is not allowed to extend more than one "stick" above the surface of the mat. Between matches the measurement sticks are kept in an environmentally controlled container to keep them from being covered with snow. A stick is guaranteed accurate to within plus one thumb.

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                          • #14
                            Re: How many NXT/RCX bricks are allowed?

                            Back when we had light assemblies, I put a mark on the upright that was at least 16" or 40cm above the table. If the robot was not clearly above that mark, it was good.

                            I hope there's not too many kids reading here. We adults are having too much fun parsing angels and pins.

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                            • #15
                              Re: How many NXT/RCX bricks are allowed?

                              Originally posted by Apollo1169 View Post
                              Yes, in your case the .64 is very important, as you are using the metric system. However, for US competitions, the judges will probably be measuring everything with the English system, so they don't really care if 16" = 40 cm, 40.64 cm, or 400 cm.
                              When I asked Scott about this discrepancy, he said that rule 25 applies here. So if, for some reason, a US ref measured a bot with inches but it's 40.5 cm, and the kids point this out, it'll be ruled short enough, I'm sure. The kids would, of course, have to be able to explain why 16" isn't 40cm. This US ref will be measuring in cm.

                              I understand precision and significant digits, and I understand estimation & checking answers with approximations (I did my high school physics on a slide rule). 2.54 is *the* accurate conversion, and while 40cm is a reasonable approximation, that's exactly what it is -- an approximation.

                              otoh, I doubt any of this is important; I believe I only saw one robot in 4 tournaments last year that was even close to the limit; iirc it was only about 35cm. Nowhere near close enough to worry about, but it looked taller than it really was. We told the head ref we needed to just have a simple platinum/iridium bar of the correct length at each table. That would have solved any controversy about which system to use, but for some reason he wouldn't go for it.

                              Of course, none of this would be an issue if the US would join the rest of the world and stopped using a barbaric measurement system.
                              Kansas City Region Head Ref 2014-present
                              KC Region coaches and teams can ask FLL robot game rules questions at [email protected]

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