This one uses LEDs as the light sensor and mosfets to drive the output to rotate on a single axis. He even reduced the duty cycle on the fets so no heatsink is needed. Mounting in a peanut butter ...

Case in point: an easy way to make your backyard, garage, or other outdoor spaces safer and more secure is with this ...

Or you can go back to basics and build this reflective RGB sensor from an LED and a photocell. The principle behind [TechMartian]’s approach is simplicity itself: shine different colored lights ...