Sunflowers, solar panels, and you

Every morning, a sunflower faces east. Every afternoon, it faces west. It's tracking the sun — a behaviour called phototropism — and it's been doing this for millions of years without a microcontroller.

You're about to build the electronic version.

Your Light Chaser has two LDR sensors (light-dependent resistors) mounted left and right on its front. A servo motor sits in the middle. When more light hits the left LDR, the servo turns left. When more light hits the right one, it turns right. The robot always faces the brightest source — a torch, a desk lamp, a window.

This is exactly how solar tracking systems work in large-scale solar farms. The panels rotate on motorised mounts, following the sun across the sky to maximise energy collection all day. The physics is the same — just bigger motors and GPS timestamps instead of an Arduino and two LDRs.

Hardware: 2× LDR + 10kΩ resistors, Arduino Uno, SG90 servo motor.

Let's start with the sensor itself.