Here’s the Spinner Assembly Locking Stabilization Arm.

It prevents the spinner assembly from coming off the top of the paddle knob under normal circumstances.  Under extreme cases (such as reaching the extreme edge of the potentiometer range of the knob), the spinner will push itself off anyway.  This arm can swing out of the way when inserting or removing the paddle, then it locks into place.  So far, it works well.

Of course, letting it run for as long as I did to test out the arm revealed another problem.  The paddle wildly thrashes about, causing the entire robot to dance.  I may need to install inertial dampeners on the paddle to prevent the whole thing from dancing off a table.  Even if it doesn’t pirouette to destruction, the stresses from repeatedly bashing the paddle into the beams may eventually cause a catastrophic structural failure.

I just hope I’m recording it when that happens.

Miscellaneous Failures In Robotics

Unfortunately, no explosions.  However, parts do fly.  If you pay close attention, you’ll see a gear get thrown during the first attempt, just before everything goes wrong.

Looks like I need to be able to lock the arm in place, or it’ll keep popping up.

The clicking was the motor moving.  I fixed the serial port reading issues, so now it doesn’t hang after the first command.

Unfortunately, the clicking is the motor turning on and turning off very rapidly.  I can send commands and see the servo turn.  Very very slowly…  I think it’s reading the command in one cycle, so it’s sending the command to the motor, then in the next cycle, there’s no command, so it shuts the motor down.  Gotta take care of that.

It’s clicking.  My robot is clicking.

Well, okay, it only clicks once, then it stops responding altogether.

But still, that click means it’s doing something, right?

Right?

I mean, it should be rotating the paddle spinner left or right until I press stop, and it’s obviously not doing that, but a click means that the command is getting to the NXT over Bluetooth, so at least something is working right.  That is progress, isn’t it?

I guess I should actually be reading the return message.  And maybe I shouldn’t be closing the serial port every time.

Whatever.  I’ll look at it in the morning.

Looks like it’s just another serial port.  Not that I’ve ever used the SerialPort class, but the fact that it’s a built-in .Net class (prior to .Net 3.0) makes me happy.  (Most built-in .Net classes in >= .Net 3.0 make me unhappy.)

Here’s someone who has apparently done this sort of thing already:

http://www.codeproject.com/KB/cs/nxtBluetooth.aspx

On top of that, Lego even has some technical documentation that should be useful:

http://mindstorms.lego.com/Overview/NXTreme.aspx

I forgot that the Mindstorms NXT base unit takes 6 AA batteries.  Now I’ve got to charge up a whole boatload of batteries.  Looks like it can’t be USB powered, either.  I knew I should have bought the power kit/battery pack.  I wonder if it’s worth  trek to the Lego store tomorrow to see if they have it.  Is the Lego store even there?

At any rate, while that’s going on, might as well start looking at Bluetooth programming.

Well, okay, it’s only stylish if you close your eyes.

And as far as functional, I don’t know.  I haven’t hooked it up yet.

But it looks like it fits the paddle!  Which, of course, means that it’ll break into pieces as soon as I try to make it go…

Gears!  That’s the key!

The Atari 2600 Paddle has a series of ridges and grooves around the spinner knob.  I was trying to get things to grab onto those grooves, but for some reason, I didn’t try the gears in the kit.

Until now.

Groovy.

I’ve been working at the robot for the better part of an hour and a half, and I still don’t have anything that looks like it’ll work.  The main problem is that I have to work with Lego parts, so it’s hard to get anything that will fit the paddle.  They’re also the crazy Mindstorm/Technic pieces that are more like a plastic Erector Set than Lego pieces, so they’re hard to connect in the way you want them to go together.  I almost got something, but it doesn’t want to hold on to the paddle.

Back to the drawing board…