What you'll build
A street lamp that switches itself on at dusk and saves power.
Before you start
You'll learn: analogWrite() on a ~ pin to fade an LED smoothly, instead of just on/off.
You'll finish: A model lamp post that fades on at dusk and fades off at sunrise, using your light sensor.
Real world: Real street lights, dimmable house lights and car dashboards all fade with this same signal.
Then try: Make it fade brighter as it gets darker, or add a second lamp that only comes on at midnight-dark.
Who does this: Municipal electrical technician — TVET electrical engineering, or an electrician's trade test.