FLL - The Power Puzzle 2007 Presentation by V. “ CyberGranny ” Greene Brics-2-Bots Lab To RCX or To NXT: That is the Question!

RCX (with RL 2.9)NXT Number of Motor ports 3 3 Number of Sensor ports 3 4 Rechargeable Battery SystemNoYes IR Compatible Yes No Hard-wire link to computerNoYes Motor speeds Sounds 6 beeps infinite Drive straightNoYes On-board variables Display control numberstext, images, numbers Number of stored programs5Infinite w/memory limit On-brick programming NoYes Uses new and old sensors (No)*Yes *Can use the NXT Touch and Light sensors in RL and all 4 NXT sensors + servo motor in RL 2.9

+ Plus + If you have been using it, then you can focus on the new challenges rather than learning a new system. The design of the RCX makes it more adaptable to adding sensors/motors which are smaller. You can build a sturdier robot - reinforcing it is easier than the NXT. You can “piggy-back” your outputs & inputs, this frees up additional ports. (2 touch sensors w/same program instructions 2 motors running the same) Programming - Easy drag & drop. Fairness Bonus??? - On non-perfect scores. RCX Sensors Rotation Light Touch

- Negatives - Uses alkaline batteries - Some rechargeable batteries do not fit properly so it loses contact & turns off. If the robot is not balanced it will tend to drift, BUT that can be compensated for in the programming. Using the IR transmitter you can pick up stray signals (So cover the robot when downloading & turn it off when not downloading or running the programs). Battery strength affects performance when you use timing. Program wiring is sometimes a problem, but troubleshooting will show you where the broken wire is. The RCX will soon be discontinued.

NXT + Plus + Interactive Servo Motor offers 3 options of measurement control: timing, rotation, & degrees which can easily be switched for the best performance. Ultrasonic sensor for measuring distance & movements of objects. Programming is similar to The RCX - Drag & drop, however, wiring assigning values, conditions, etc. is easier. You can use RCX motors, touch, & light sensors with the NXT. Uses batteries or a battery pack that makes recharging easier. No stray transmission pick-ups. Sensors Ultrasonic Sound Light Touch Rotation/Motor

- Negatives - The NXT has extras downloaded, taking up memory that you might have to erase in order to fit all your programs on. The robots aren’t as sturdy as the RCX & reinforcing is a bit more of a challenge. You can’t “piggy-back” sensors/motors, except maybe with the conversion cable when using RCX sensors/motors. The Ultrasonic sensor might react with other ultrasonic sensors. Turning on, finding, & running programs is not as easy as the RCX - it involves extra button pressing (a slight time issue at the FLL tournament). The display can be hard to see, because of light reflection.

Excellent manuals for the RCX & NXT Video tutorials for the NXT Book LEGO Mindstorms NXT-G Programming Guide by James Floyd Kelly - Apress

So which one is better RCX or NXT???? That will depend on what you need the robot to do!