More details.

Originally the pulse width modulated signals from the radio receiver control the steering servo motor and the amplifier (speed control) which drives the DC motor.

My design has the PIC interrupting that service by controlling the multiple double pole double throw relay switches.

Channel 3 from the radio receiver be used to tell the PIC to toggle between autonomous control and radio control. This decision can be overridden with the toggle switch in the middle of the picture.

Once in autonomous control the car has two means of evaluating its environment. A narrow angle lense (the cardboard tube from a toilet paper roll?) light sensitive device and two sonic range control devices.

The light sensor could find a incandescent light bulb. Once found (by turning in a 360 degree circle for example) a simple line following algorithm should lead the car to the light source.

The front and right side mounted sonic range controls could guide the PIC counter clockwise around the inside of a room. This idea is on the WEB at:

http://letsmakerobots.com/node/928

Thanks all,

Ken