Lego servos on minibot?

after reading about the LEGO servos I am wondering this: according to rule 92 we are allowed to use LEGO sensors and associated cables, since the servos are also rotation sensors, are they legal?

Edit: I followed links on USFIRST to this address . If you look under NXT sensors the servos are listed there.


This would be question best answered by the GDC in Q and A but I would hazard a guess.

The guess would be that you are allowed to use them as an encoder for your minibot but you may NOT use them as a source of climbing power.

the power for the Lego Servo/Motor comes from the battery for the NXT brain…and could not be used to provide power to climb…

that being said… why would you WANT to use them? You don’t really need encoders… and you would need to have the NXT onboard your minibot to read the encoders…

Claiming the Lego motor is a sensor seems dubious…

We bought the NXT for the minibot so we do intend to use it. I think that we probably won’t use the Lego servos (after further thought I don’t think they will be needed). I did not intend to use them for climbing purposes but tohelp us clamp around the pole. On another note, do you know if it is possible to hardwire motors to the NXT? I’m saying without having to spend $80 on the HiTechnic converter.

Why? The FLL rules specify that the NXT motor has an internal sensor. The old RCX motors did not; if you were still using RCX you could have additional sensors to compensate for the ones that weren’t in your motors.

You might be able to hack that but I wouldn’t advise it…You wouldn’t get much current and it would only be at 5 volts or so…

More importanly, you cannot use the NXT battery for anything more than powering the NXT…

The minibot rules specify the battery and the motors that must be used…

I’m not saying to use the NXT to power the motors. Sorry if I made it sound like that. I’m refering to the piece where you plug the cord from port 1 (on the NXT) to to the $80 piece that tells the motors to go. I’m totally new to the FTC thing (I didn’t even know that the NXT was the c-rio of FTC :)) so I’m wondering if there is a way to work around the $80 piece.


Because they only allow Tetrix motors and servos. The lego motor is more of a motor than a sensor, even if it has both. But what I think doesn’t really matter - if you want to use a lego motor post a q&a and see what the game design comittee thinks.

The sensors in a Lego motor are encoders, so saying that a Lego motor has a sensor is vague to people not as familiar as others to the subject. Lego Motors also feature PID Control algorithms.

I believe it’s impossible to hardwire TETRIX motors to the NXT without the controller, and the TETRIX motors need a lot of power, and once the NXT battery runs out it takes 3-4 hours to recharge them back to full. The 10-cell battery needs only 20-30 min to recharge back to full.

In regards to the $80 HiTechnic controller, they are pretty expensive for what they do. But if you can get a FTC team to buy TETRIX parts for you they will receive a 30% discount so it costs only $55.

Finally, I want to point out that TETRIX motors have encoders as well, but a NXT and HiTechnic motor controller is needed to use it and the encoder cables are REALLY fragile anyway

The HiTech controller is connected to the NXT as a sensor by way of one of the numbered ports 1,2,3,4. The battery pack and the motor are connected to the controller which responds to signals sent to it from the NXT. Robots that are required to do more sophisticated movements than go and stop can make good use of this four component setup. Minibots are looking like go and stop are all they really need, so some designers are thinking switches are the only control needed. Good thing the designers of electric cars are using controllers. There are no minibot passengers to get whiplash out of the starting gate at deployment.