Arduino: motion-activated night security light
A real outdoor-style light: PIR triggers, an LDR confirms it is dark, a relay drives a 12V lamp. The AND logic that stops false triggers.
Tag
#ldr
2 tutorials
Arduino: build a light-following robot with LDRs
A 2WD robot that chases a flashlight beam using two LDR eyes and bang-bang steering. Phototaxis for twelve dollars of parts.