Description:LineRider1 is a two wheeled differential steering line following robot that follows a black line on a white surface.Its built from just electronic components.Its motors are a twin gear box from www.robotstore.com set at a gear ratio of 203:1 for more tourqe.LineRider1 uses relays to control its motors.The circuit board,batteries for the interval timer,and the interval timer are held on by a rubber band.Its body is a project box. Problems:The only problem I had was the photocells because when they recieved light reflected off the floor they just kept running even when they got on the black line but I fixed this by adding a interval timer. Time to build:About a year on and off dew to the photocell problem but i fixed it. Parts: 1 Twin Motor Gearbox Kit $19.95@www.RobotStore.com 1 Narrow Tire Set (pair)$9.95@www.RobotStore.com 1 Interval Timer Kit $9.95@www.AllElectronics.com 16 AA's $4.00 From The Dollar Tree 1 Rubber Band $Free 22 Gauge Wire $Free 1 Pc Mount DPDT Switch $0.25@www.AllElectronics.com 1 Panel Mount SPST Switch $Free 1 Grid-Style PC Board-356 Holes $1.79 From Radio Shack 1 Grid-Style PC Board-750 Holes $3.29 From Radio Shack 2 Metal Standoffs With Screws $1.59 From Radio Shack 3 4 AA Battery Holders 3 Times $1.69 From Radio Shack 2 2 AA Battery Holders 2 Times $1.49 From Radio Shack 2 5 ohm light,20 ohm dark photocells $Free 1 Krypton Bulb $2.59 From Radio Shack 2 5vdc DPDT DIP Relay $1.50ea.@www.AllElectronics.com 1 6x3x2" Project Enclosure $3.79 From Radio Shack Email Me At:Botnerd@aol.com My Web Page:http://hometown.aol.com/botnerd/StevensRoboticsindex.html Email: Botnerd@aol.com