Wednesday, May 03, 2006

NXT to NXT Communications (updated)

Here is an interesting video by Steve Hassenplug on NXT to NXT communications (he is probably one of the few people on the planet that has more than one NXT set!). He has constructed a "remote control" using one NXT brick, and a "car" using another NXT brick. The remote control drives the car using the Bluetooth link between the NXT sets. The software to do it is rather straight forward.

Click picture to play video

This looks like an excellent challenge to have two kids do in class or as a home assignment! Not too hard, great fun to play with, and excellent to learn about the wireless communication link.


If you look closely, you'll notice that Steve actually used the motors as input channels. By turning the motor, and measuring the angle, he measures how much the user has turned the dials on the remote control.

Here's what Steve said about this on LUGnet:
The motors offer little resistance when used this way. However, there's something else which I think is kind of cool. If you look close, when I let go of the controller, the paddles return to the middle, and the car stops. Using just one block at the start of the program, I set the motor to "stay there" so when you push the paddle forward, it springs back. The steering wheel does the same. Actually, in the latest version of my program, when you let go of the steering wheel, the car's wheels straighten out. The more you turn it, the more the wheels turn.

He also mentioned that stability of the Bluetooth was excellent, even in a room crowded with other NXTs, like at the First Lego League World Festival.


At May 05, 2006 4:29 PM , Anonymous Anonymous said...

What are those rolling things in the rear axle for? (I heard someone calling them "differential gearing" or something, but what does it do?) Is it there to add some stability, or something else?

At May 05, 2006 7:03 PM , Anonymous Filip said...

When the robot turns, the rear wheels turns at different speeds relative to each other. However, the rear wheels also drive the robot forward. A differential gear is a special gear that allows both wheels to turn independent from each other, but still allows to drive the wheels forward. Most new vehicles in Lego Technic have a differential gear inside.

At May 07, 2006 11:37 AM , Anonymous m. said...

Is it possible to stear NTX with mobile? If so, this should work with only one NTX set ?

At May 07, 2006 12:39 PM , Anonymous m. said...

I see the post with this topic down in the page now. :)

PS: I can hardly wait to buy NXT !

PPS: Very nice blog.

At May 08, 2006 12:51 PM , Anonymous Filip said...

Hi M.,

Thanks for the compliment.

As you discovered, I did write a bit on the how to control a NXT robot with a mobile phone. To the second part of you question, "only one NXT set", that depends on your setup.

In principle, it is certainly possible to control multiple NXT robots using a single mobile phone, and there are various ways to do it. But if you use the simple menu-generating method I explained before, you may have to choose: either have use one NXT robot communicates with with the mobile phone and other NXT robots, or have multiple menu's on your mobile phone, which would require some menu switching on the phone.


At November 13, 2007 3:21 PM , Anonymous Anonymous said...

I am making the robo arm and im trying to make a remote for it using another NXT brick could someone show me how?
P.S. Im only 11


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