Getting started on the my autonomous robot

After a couple weeks of tinkering with my Raspberry Pi and wondering what to do with it, I've finally decided to build an autonomous robot.

After several days of browsing sparkfun.com and amazon.com, I've finally converged on a basic foundation:

Chasis
  1 x #989 Pololu Micro Metal Gearmotor Bracket Pair - Black = 4.99
  1 x #951 Pololu Ball Caster with 3/8" Metal Ball = 1.99
  1 x #1501 Pololu 5" Robot Chassis RRC04A Solid Black = 7.95

Motor

  2 x #992 100:1 Micro Metal Gearmotor = 31.90

Wheels

  1 x #1090 Pololu Wheel 42x19mm Pair = 6.98

Battery

  1 x #1155 6-AA Battery Holder = 1.75

Electronics

  1 x #713 TB6612FNG Dual Motor Driver Carrier = 4.95

  2 x RioRand LM2596 DC-DC Buck Converter Step Down Module Power Supply Output 1.23V-30V (1 Pcs-LM2596) = 8.00

Note those motors are the most expensive piece!!!

The idea is to build a small robot first, have it navigate on a table. I have yet to decide on what sensors to add (leaning towards camera). Also, still need to decide on how to power it, and mount it on the chasis.

1/22/14 Update: I just purchased another LM2596 step down for the RPi. The first one works great to step down from ~7.2V to 6.0V needed for the 100:1 gear motors.