Egg Plotter

Quick and dirty Easter Egg plotter out of parts and things I had lying around.

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My friend and I wanted to make an egg plotter for Easter, sort of like the EggBot, but a lot cheaper. I cannibalized a Lego set and got some parts on hand and we threw this all together in a couple days.

It's a bit remarkable how much you can do with things that are just lying around—especially when they're Legos and electronics parts! The only parts we purchased for this were some wooden tongue depressers ("craft sticks"?) and permanent markers.

The egg is held up between two rubber tires that have just the right combination of sturdiness and compliance (there is actually another ring-type tire stuff inside them so the contact surface is smaller, otherwise they swallowed the eggs). The whole structure is made of Lego parts from one kit I had gotten as a gift (plus a gear that I had to add), and the rest is just wooden sticks, hot glue and rubber bands!

The pen is mounted on a servo for moving back and forth, and its weight keeps it down on the surface of the egg. So far the pen just drags along, so it's not like this could draw anything complex (plus the resolution on the servo leaves something to be desired). Still, I've got no complaints so far.

The stepper motor is driven by a simple circuit made from a bunch of transistors that just selectively ground two of the four poles to the motor. It's very simple and I doubt it's original (I don't really remember when I drew the diagram the first time) but it works pretty well.

Right now the egg just spins steadily and the pen can be controlled manually, but that will change soon!

  • 1 × Lego 70808 Super Cycle Chase Believe it or not, all of the Lego parts came from this one set—except for an 8-tooth gear.
  • 1 × Small stepper motor I honestly have no memory of where I got it. It's not much bigger than a toy DC motor and is unipolar so it's not super strong, but it was pretty easy to cook up a driver circuit for it.
  • 1 × SG-5010 servo motor It's a standard large servo
  • 6 × 2N3904 NPN transistor
  • 4 × 1N4148 signal diode Electronic Components / Misc. Electronic Components

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  • It's alive!

    Kristian Sims04/06/2015 at 08:20 0 comments

    Well, we wanted to get at least something going by the end of Easter, and we made it (barely)! Right now all that it does is slowly crank the stepper forward and follow the potentiometer for side-to-side motion, but hey—it works! The next step is to get actual shapes and directives coming across—probably with a serial connection. I tried using my official Hackaday Trinket Pro, but an Arduino update killed whatever kext let me program it, so... we'll return to that later. Forgive the Leonardo for now, please ;-)

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  • 1
    Step 1

    There's no way anyone would want to duplicate this as is. Really? You do? Well, if you're sure, let me know in a comment or something, I guess!

    I could understand if someone wants the circuit diagram (though really, it's nothing), so let me know if you want that posted.

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Adam Fabio wrote 04/07/2015 at 16:59 point

Very cool project! I'm a fan of the EMSL's eggbot, and love seeing projects based upon it! Don't forget that eggbot is open source hardware - so you can build upon their control system:

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Kristian Sims wrote 04/07/2015 at 17:23 point

Cool, and thanks! I will definitely look through that! This project is also practice for us to figure out some of the steps to make a larger canvas-style pen plotter (but with real parts), so we might try to make some parts of it on our own, but the EggBot code should help a lot because we're both new to this.

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