This little bot can only ride and go round obstructions. For all the time it sending infrared beam. When he close to obstruction, beam reflect and go streight to photodiode. Simple electronic circuit detect it and stop one of the motors. It makes that bot turning. When beam will be stoped reflected then stoped motor starts and bot go ahead. To built this bot I used only one integrated circuit CMOS 4093 and couple of parts (transistors, resistors, etc.) The only problems which I encountered that the IR beam was to short and bot didn't menage to stop and turn. I changed frequence to high of generator. I was building this bot for 2 days. It cost about 3$. If you want to see exact schematic, go to this site: http://www.dudi30.republika.pl/galeria/selfrider.html or if you want see more then just go to http://www.dudi30.republika.pl Email: dudi_elektr@op.pl