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Just in the nick of time, the day before Easter, I completed building a 4-colour
NXT Easter egg painting robot. I started building it several months ago, when I
thought I'd have plenty of time before Easter. Of course, at about the 85%
complete state, I let it sit until the week before Easter. :-)
And then even though it was finished mechanically, I was up until about 5 AM
writing little programs to colour eggs that I could hide for my son before he
woke up. Naturally I was too tired to be very creative at that point, but
they're not ending up in a museum anyway. They're for eating, so it doesn't
matter too much.
Originally I was going to have the entire pen-holder driving back and forth, but
it got too heavy; the inertia was too great to start and stop it reasonably. So
I ended up mounting the egg on a rotating platform (using the hailfire droid
wheels).
To use it, you open the egg-holder up, insert your blank (hard boiled) egg, make
sure that it's reasonably centered, and then fold it up to the pen unit and lock
it in place. Select your program, and run it. Two motors control the egg
position, one for rotating it about its long axis, the other for spinning the
egg on its side. The 4 pens are held in a rotating cartridge. The third NXT
motor controls moving the pens back and forth, as well as changing them. This is
accomplished by pushing an axle with worm-gears on it (that only act as a rack
here) back and forth with the motor. When the axle is all the way to the rear,
it engages another wormgear, which then causes the axle to spin. This spin is
transfered to the pen-cartridge. A touch sensor can tell when the pen is getting
close to being in place. Just as it releases, the pen is in position. A couple
of rubber bands put light force on some beams which lock the pen into position.
Of course you can only rotate through the colours in one order. Turning the
motor the other way will push the currently selected pen forward again.
Pictures, once moderated, can be found here:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=246207
Here's direct links to a couple:
http://www.brickshelf.com/gallery/David/Robots/EggArt/cimg7266.jpg
http://www.brickshelf.com/gallery/David/Robots/EggArt/cimg7356.jpg
http://www.brickshelf.com/gallery/David/Robots/EggArt/cimg7357.jpg
http://www.brickshelf.com/gallery/David/Robots/EggArt/cimg7361.jpg
http://www.brickshelf.com/gallery/David/Robots/EggArt/cimg7332.jpg
I also hope to have videos of EggArt in operation soon.
--
David Schilling
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Message has 3 Replies:
 | | Re: EggArt - a 4-colour Easter egg painting robot
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| (...) Congratulations on getting your egg painting robot done! Looks like you got your pen mechanism working exactly as you planned. Very nice! (...) What do you mean; I think the eggs are beautiful! But I think you should write "Happy Easter" on (...) (17 years ago, 9-Apr-07, to lugnet.robotics.nxt)
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