If your just looking to fit one robot, try Goodwill, Salvation Army, etc.
Get yourself some old Poloroid cameras with the ultrasonic rangefinder built
in.  There is sites with the pinouts on how to hook them up (but I don't know
where they are).

Werner Soekoe wrote:

> Hi
>
> Can anyone help: I'm looking for a circuit to be used to sense walls and
> solid objects with for a mobile robot. I though of using optics, but what
> will happen when you paint your
> walls black???
>
> Any help/circuit will be appreciated.
>
> Thanks
> Werner Soekoe
> wsoekoe@global.co.za