An explanation of how a rain sensor works internally as a variable resistor and LM393 circuit, and details on wiring it to Arduino with a lifespan note.
Building a clap-activated switch using a sound sensor and a relay, with simple 25ms timing logic that tells a clap apart from stray noise.
Wiring the A4988 driver for precise stepper motor control via just the STEP and DIR pins, with a safety note on setting the current limit.
Wiring the L298N module to control a DC motor, with an important safety note on the 5V jumper when exceeding 12V.