few issues regarding NXT

[amitbr]

Guys,

I am an electrical engineer and for a long time I think of getting into the NXT world which really seems amazing to me.
I learned about it form the web and saw people are doing great things with it.
But still few things bothers me and I would really like to get some information from the experts here:

1. If i understand correctly then the amount of memory in the brick is small (256K). isn't that a big limitation? Are there any options to expand that (via USB/...)?

2. The brick got 3 output ports for motors. I am sure that for many applications it is not enough (I guess that for a moving robot with an arm at least 4 motors are needed). How can one connect more than 3 outputs to the brick (external hardware/other/...)?

3. is there an option to connect two or more bricks together for a more complicated applications? How can they connect between themselves? What I mean is that event from one brick is connected as an input to a second brick.

4. Can the NXT brick communicate with the PC during work? For example collecting information and send it to the PC for processing during work?

Many thanks,
Amit

[mightor]

1. If i understand correctly then the amount of memory in the brick is small (256K). isn't that a big limitation? Are there any options to expand that (via USB/...)?

The limitation isn't really a problem. I've used the NXT for a few years now and I've never really run into this limitation, tbh.

2. The brick got 3 output ports for motors. I am sure that for many applications it is not enough (I guess that for a moving robot with an arm at least 4 motors are needed). How can one connect more than 3 outputs to the brick (external hardware/other/...)?

There are after-market devices for this. The HiTechnic Sensor MUX allows you to connected up to 4 sensor to each sensor port. To connect more motors, you could get the Mindsensors Motor MUX or the Holit Data Systems Motor MUX. I own all of these and they're all great.

3. is there an option to connect two or more bricks together for a more complicated applications? How can they connect between themselves? What I mean is that event from one brick is connected as an input to a second brick.

Yes, through Bluetooth you can connect multiple bricks together (4) and with RS485 you can connect even more (and at a higher speed, too). Pretty soon Dexter Industries will allow you to connect them via XBee as well (up to 16)

4. Can the NXT brick communicate with the PC during work? For example collecting information and send it to the PC for processing during work?

Yes, you can. Many have done this. Aswin made the NXT2Excel program which allows a ROBOTC program to push data straight into Excel.

Regards,
Xander

[amitbr]

Hi Xander,

thanks a lot for your detailed answer.
one more thing:
Should I start my study of the NXT with the NXT-G language or go directly to robotC? (I am new to robots but experienced in programing)?
Where can I get the robotC env and what do I need in order to connect to the NXT brick?

I guess the NXT-G is for beginners only? Correct?

Thanks,
Amit

[gloomyandy]

You may also want to consider NXC, or leJOS (or one of the many other languages available for the NXT)....

[mightor]

Amit,

I'm a big fan of ROBOTC, but like Andy said, there are many alternatives out there. I started off with NXT-G, despite knowing C, just to get the hang of how the system worked. I moved onto NXC fairly quickly after and to ROBOTC a short while later. I still use NXT-G and NXC to this day, but usually for testing purposes only.

- Xander

[linusa]

3. is there an option to connect two or more bricks together for a more complicated applications? How can they connect between themselves? What I mean is that event from one brick is connected as an input to a second brick.

4. Can the NXT brick communicate with the PC during work? For example collecting information and send it to the PC for processing during work?

You can connect up to 4 NXTs together via Bluetooth (1 master, 3 slaves) and pass string messages between them. Another way is to use a PC and connect up to 7 NXTs via Bluetooth to it and as many NXTs via USB cables as you want. In this case, the PC is the master. It can send string messages or so called "direct commands", which are instructions for motors and sensors that are carried out at once.

There are many packages for such "remote use cases" that you can use to do heave processing on the PC, for example using C, C++, Python, Perl, .net, Java, MATLAB, etc.

[amitbr]

thanks a lot for the wonderful answers. I now understand that I have a lot to learn.

One more thing. In Ebay i see two model of NXT:8527 and 8457. There is a big price difference between them.
Can you explain the difference?

Thanks,
Amit

[tabbycatrobots]

The robot JohnNXT in the book "Creating Cool Mindstorms NXT Robots" by Daniele Benedettelli may give you
ideas that will serve as starting points. The robot uses 6 motors, and 2 NXT bricks connected by the high speed
connection, using NXC. I use NXC and for the small amount of communications that I need between NXT bricks,
Bluetooth is adequate. When prototyping and debugging, I find Bluetooth is also much more convenient than USB
for downloading programs, i.e. download program, run robot for 3 minutes, find bug, edit program, download
program, etc. Regarding the amount of memory - using NXC, I have been able to write large, multitasking programs
without hitting any memory constraints. Memory is an issue for sound files. I volunteer in a 3rd grade, tutoring
reading and math, and built a robot that when the students swiped their nametag, would say their name and give
them an assignment. I could only fit one short assignment and about 15 first names in the memory. (Solved by
using Bluetooth to second NXT.)

[mightor]

thanks a lot for the wonderful answers. I now understand that I have a lot to learn.

One more thing. In Ebay i see two model of NXT:8527 and 8457. There is a big price difference between them.
Can you explain the difference?

Thanks,
Amit

Personally I would not buy an NXT 1.0 set (8527). Most examples and books on the market today assume you have an NXT 2.0 set. The 2.0 set comes with 2 touch sensors, an ultrasonic and colour sensor, the 1.0 set comes with a fairly useless sound sensor (volume only), 1 touch sensor, ultrasonic sensor and light sensor. The brick (the actual computer) and motors are the same for both sets. The 1.0 kit is OK if you have additional Technic Lego.

- Xander

[mattallen37]

In addition to what Xander said about the differences between 1.0 and 2.0, I would like to add that the 1.0 set has a much better selection of gears and some other stuff, IMHO. You can look at the parts lists for the 1.0 here, and the 2.0 here. To get started, the 2.0 has a nice amount of "different" parts (not very standard to the technic/mindstorms systems), but for additional parts, the 1.0 is cheap. Getting technic sets to supplement the NXT, is great for parts, but also for learning building technique (assuming you build the sets before using the parts for other stuff).