by NewtonRob, published
More pieces are being developed.
C-Spot is a simple robot that that will move towards a "Spot" of light when it "C"'s it. Thus the name. Or if you like C Spot run. The original was made of wood, a wipes container, and rubber bands (plus the electronics).
I have uploaded a Bill of Materials. The total cost is about $110 ($42 if you shop around). I did not try to find the best prices. Also consider that the Arduino might be useful for other projects. You might already have some of the stuff as well. But this is the worst case.
UPDATED BOM - Two tabs. The second cuts the price way down. But you have to make the servos continuous rotation yourself. Also use solid core wire instead of jumpers. Little things.
Wheel - 100mm wheel with a grove for a rubber band. Glue to servo horn. Has a screw hole so that you can remove it from the servo.
The wheel with the built in servo arm was derived from pilotjunki servo arm http://www.thingiverse.com/thing:38228
Robot deck. Designed for use with a 4 AA battery holder and a 9v battery. It also has holes for an Arduino UNO. Use 4" zip ties. Use one zip tie to go through the holes and use the head a second one to tension it down. No screws. Use the zip-plate spaces to space the Arduino from the deck. Note: I had to cut the top 2/3's of the zip-tie head for the AA battery holder. Otherwise it was too big and the batteries did not fit.
The CdS feature connects to the front of C-SPOT. You put CdS cells through the holes. I had to drill the holes out a bit with a 1mm bit (or something small).
Short YouTube video: http://youtu.be/j9fov7pS8wI
I've added quick build instructions. I'm working on a more detailed set.
I have also included the Arduino code. NOTE: Continuous rotation servo's might not all be "Stopped" at the same number. I will work on a software calibration tool to help you determine the right number to stop the servo.