Arduino Robot for Lowest Cost

SEE ME AT THE NYC MAKER FAIRE!

It all started with this:
 Arduino Robot Challenge: How inexpensively can you create a robot using an Arduino for 5th Graders?

 I hope that this instructable has a certain elegance to its simpleness and will convince you to build your own and get some kids excited about technology with it!
Video of robot in Action!
 
Video -  Beta version:  improved front swivel (works on various floors better) and ENTER the pug named Mabel!

NEW - Wixel version in wall following mode!
 

<a href="http://www.makezine.com/go/makerfaire"><img src="http://cdn.makezine.com/make/makerfaire/newyork/2011/banners/mf_newyork_150X60_seeme.gif"See me at Maker Faire!" width="150" height="60" border="0" /></a>

The lightbulb moment in this project was when I realized that I could use the DC motors within the K'nex Flash Robo Battlers for my robot drives.

- K'nex are familiar to kids. 
- They are inexpensive and readily available at the big box retailers (no shipping charges).
- The motor comes with a clutch and is a very durable and kid safe module to build a robot around.

So the BOM:

- 2 K'nex Flash Robo Battlers, $10 each at Walmart, Target, etc.
- Arduino Uno, approximately $30 at the MakerShed.
- Breadboard, switch for collision detection and jumpers from Radio Shack, less than $20.
- BOM from the H-bridge driver project at ITP. (the H-bridge driver chip cost about $3 plus shipping...wish I could have found this close by)

Ok, first objective is to get a right and left drive motor for the robot:

1. Remove 5 screws.
2. Slice through the K'nex label so that you can split case open.
3. Open case with the "top" up, fewer things will fall out.  I have a video of the innards...this was a challenging part of this project...pay careful attention.
4. Now you can take out the motor, battery contacts, and circuit board.
5. Solder leads onto the motor, and to the battery post.

It was hard for me to show this.  You will need to remove plastic wherever the wires get in the way.  You can route and tuck the wires in similar places to the originals.  Goal is to get the 4 wires out the opening that had the switch of forward/off/backward.

Using the battery contacts was a later inspiration, allowed me to eliminate the need for a battery case.  It also means the weight distribution is good.

Open source means a mechanical engineer like me can cannibalize from the smart electrical people out there.

I tested my motor using this project.

AND

This project at ITP, they have great tutorials on Arduino's, and basic electronics.

Build a robot!  However you want...and add sensors...I used a Sharp IR sensor for distance measurement to follow a wall.

I then used Scratch 4 Arduino (S4A) to control the robot in a tethered mode. You will need a specific patch of Citilabs S4A.

I tried a bluetooth link that was no good and then I tried Xbee and my challlenged brain couldn't get it to work.  Then I found the Wixel product at Pololu.  It was a piece of cake with their documentation.  I would suggest using this.

 So now I have a robot for not much money that can be "created" by the students using the building blocks of a K'nex kit.  Then they can program in a drag and drop mode in Scratch!

Sweet!

Thanks for checking this out...shouldn't I win a Makerbot for this?  It would be an incredibly helpful part of our afterschool program!