An NXT Spitting Llama, created by Fay Rhodes
The story of this robot begins with ice cream.
I love ice cream, and in Perry, Oklahoma, that means I often visit the local Braums.
This particular Braums looks out over a field of llamas kept by my friends, Mary and Ed.
They acquired these creatures just to look at, and they have never domesticated them.
In other words, they are not used to people.
If I were to climb the fence and try to get close to the newest member of the herd,
the mama of that cute little llama would warn me off by spitting at me (just like a camel
What does this have to do with the NXT?
When I design animal robots, I start by observing. I not only observe the animals, I look
at my stash of LEGO shapes and colors and imagine how I might use what I have to
create the animals.
The first time I saw the Zamor Shooter in the NXT 2.0 kit, I instantly thought of using
it to create a spitting llama. It took me a while to figure out how to do it; but I kept at it,
and I’m pretty happy with the results.
How do you make the NXT llama act like a llama?
The new NXT 2.0 software offers me the option of using my computer as a remote
control. In this case, plug the motors that run the back legs of the llama into Ports B & C
Then configure the remote control to control Ports B and C.
That means I need only plug the third motor (the spitting motor) into Port A, and
configure the Ultrasonic Sensor to trigger the spitting action.
At first, I programmed the motor to move .25 rotations, but sometimes it couldn’t
actually move that far—which means the program got hung up, waiting for the motor to
finish its ¼ turn. Dave Parker gave me the solution to this problem by suggesting that I
use Time, instead of Rotations. This solved that problem. (Thanks, Dave!)
How can you design animal robots?
The most important thing you can do is observe animals. The second most important
thing is to take a good look at your stash of LEGO parts. (Remember, you aren’t limited
to the parts in your NXT kit.) Each animal has a unique shape or acts in a distinctive
way. Sometimes I will start working on one animal and end up with something
completely different, because the shape I was working with made me think of a different
There is no “right way” to build any robot, and you don’t need to be a genius to use
the NXT. You just need to persevere. When you have problem, don’t give up; just keep
trying different solutions—and asking questions. Ask people you know who use the
NXT, like the folks on the NXTStep forums or Ask the NXTperts.
You’re never too old or too young—and you don’t need an engineering degree. You
just need to start building and learning.
A special note to grandparents:
This is a great activity to take up with your grandchildren. (Just don’t tell them it’s
educational) Your “cool” rating goes off the charts; and, it’s a much more interesting way
to stimulate those “little gray cells” than crossword puzzles. (If you’re an artist, think
Please don’t say, “I’m too old!” You are never too old to use the knowledge of a
lifetime—or to discover a hidden talent. I’m proof of that.