Contents

Assembled Version of the 2WD Robot.

Building Your First Robot

Being the web and design guy at Acroname, I thought it was about time for me to make a robot.  I knew the actual building part would be a piece of cake for me, but the programming part had me scratching my head.  About the closet thing to programming I had done was some semi-advanced action scripting in Flash.  The question plagued me, "Can a guy with an art degree program a robot?" Well, lets take a look at how easy it was!

Parts List

I wanted to make this first robot simple and quick to build.  I started by modifying two Standard Servos for continuous rotation .  I added two black wheels , a Sharp GP2D12 IR Ranger , a 4-AA battery pack , four AA NiMH batteries and I topped it off with a BrainStem GP 1.0 controller .  Add to that a little double-side foam tape to stick things together, and a robot is born!

Building the Robot

I'll skip the detail of the servo modification since you can find that info in our ideas section or in the PPRK assembly section.  Or, you can simply buy a pre-made continuous rotation servo . 

Start by sticking a piece of double-sided foam tape onto each servo. 

The servos with foam tape.

After the foam double-sided tape is on the servos, you can stick the battery pack to them.  The pack fits nicely on the servos and you can use it as a guide to attach the servos squarely with the edge. 

Attaching the battery pack to the servos.

Next came the BrainStem GP 1.0 controller.  In order to have clearance to plug the servos and sensors into the controller, I raised it up about 3/4" with a couple spark plug boxes I had laying in my tool chest. 

The BrainStem is added to the stack.

Next came the wheels.  With these attached, you'll see why you needed to raise the BrainStem up to clear them. 

The wheels are attached to the servos.

Basic two-wheel drive robots need some sort of caster wheel or skid in the back to keep it from dragging the back-end.  Again, I grabbed some odd part from my tool chest, and made it into a simple skid for the back end. 

The skid in place.

Well, now that is about it for the simple robot design.  I plugged the battery into the Logic Power on the BrainStem GP 1.0, and then to power the servos, I "borrowed" some power from the IIC bus.  Here's how you do that.  On the IIC bus, next to the Logic Power, plug one end of your jumper wire into the third pin (as shown in the photo), the other end plogs into the power side of the servo power. 

Adding a power jumper wire.

Now, you can plug in the servos and Sharp GP2D12.  The servo pins are numbered 0 through 3.  I plugged my left servo into 0, and the right into 1.  The Sharp ranger can be plugged into analog port 0.  To attach the Sharp sensor, you can see in the photo that I just folded and taped a a piece of cardboard onto the front of the battery pack.  The sensor is aimed at an angle to sense a wall.  Adjusting the angle will be needed to get the best reading.  Trail and error, that seems to be the name of the game. 

Source Code

This is the part that struck fear in my heart.  (Well, not really.) I started off by reading Mark Whitney's Follow example .  I would recommed reading over this example, as it will help you to see how I modified the code to work with my wall following robot, and it has the instructions on how to configure the servos.  The servos will need to be configured first. 

If you are totally new to the BrainStem controller, you'll also want to read over the Getting Started Guides for the BrainStem GP 1.0, the Console, and TEA.  These guides will help you get started with the BrainStem, the GP application, and the Console. 

Ok, have you read all that other stuff I just directed you to? Good! Now I can explain how I modified the code from Mark's Follow example.  You might want to open a second browser window and have the the Follow example code in one window and the Wall Follow code in this. 

Source Code - TEA Include File

Source - TEA Program

Revision History:

• 2002-10-20: Idea Article Created