Mindboards

My friend will visit US next week and I want ask him to help take some sensors back for me(we're chinese), but my budget is really limited( <=100$), I looked at http://www.hitechnic.com, there're so many attractive sensors...
I'm new in NXT2.0 and play with NXC, do you have any recommend for me, which sensor or Multiplexer suits me best? i saw the 'self-balance' robot, it really awesome!
BTW, do i need to buy extra cables when i buy the sensors?
thanks lot.

HiTechnic sells some pretty nice sensors, but I'd like to point out that there are a couple other very popular companies that sell NXT sensors as well. Dexter Industries and mindsensors both have a very nice selection of sensors, and other NXT devices.

The sensor(s) you will benefit from most, depends heavily on what you want to build.

If you want to build a self balancing robot (like a segway), then you will need a gyro. HiTechnic sells a gyro for $55, and Dexter Industries sells a 6DOF IMU for $65. I would definitely go with the dIMU (Dexter Industries IMU), as it is a 3 axis gyro (with 16 bit resolution!) as well as a 3 axis accelerometer. The HiTechnic Gyro is only 1 axis, and it's analog (only 10 bit resolution).

If you want to do a lot of RC stuff, then I highly recommend the mindsensors PSP-Nx. It's an interface so that you can use a PlayStation 2 controller with the NXT.

There are so many choices, so you need to think about what type of ROBOTs you want to make.

You can use the cables that you have, but it never hurts to have extra (especially so that you have a nice selection of lengths).

Unbelieveable, Amazing! 'the dIMU: Inertial Motion Sensor is really really powerful, there's no reason to refuse it which much much better than HiTechnic one's except the packaging... and i think that's why the HiTechnic certificated by Lego.
I may need put this small stuff in a little case to avoid break.
so this is in my cart now.

how do you think about the multiplexer? anything need to be noted?

thanks.

Which Mux are you talking about?

The "Touch Mux"es are exclusively for NXT touch sensors (both the HT and mindsensors versions).

The HT active mux works with analog sensors, as well as most HT digital sensors (and maybe the lego ultrasonic sensor, but I'm not certain about this one).

Mindsensors' NXTMMX is very nice, and makes it easy to add 2 more motors to a robot (with encoder support!).

Mindsensors' MTRMX-Nx is, IMO, totally not worth it. This is the only mindsensors product that I am dis-satisfied with.

If you want to expand the input and output ports, I suggest you get another NXT. You can connect the two (actually, up to 32 NXTs) with RS485 (through sensor port 4), and have communication speeds of up to about 100 times the NXT I2C communication speed. I have done this a number of times, and it's fairly easy to program the "slave" NXTs as multiplexers. Using NXTs as multiplexers, you lose 1 sensor port on the main NXT, and gain 3 by the second NXT, but you also gain 3 motor ports (two NXTs connected with RS485 = 6 sensor ports, and 6 motor ports). If you want more inputs and more outputs, this is definitely the best option IMO.

thank you so much matt, i learned lot from you, i already place my order in Amazon for the dIMU Sensor, I'll give up the multiplex now, get another Brick is a better idea but when my budget is available.

You're welcome!

Come back with any more questions you have, and be sure to post about your robots